SERVER-41071 Replace NULL and 0 with nullptr

288 files changed, 1600 insertions, 1553 deletions

diff --git a/src/mongo/base/clonable_ptr.h b/src/mongo/base/clonable_ptr.h
index 135fd272fa0..42b0c63c1db 100644
--- a/src/mongo/base/clonable_ptr.h
+++ b/src/mongo/base/clonable_ptr.h
@@ -63,7 +63,7 @@ struct detect_clone_factory_type_member_impl {
     template <typename U>
     static Yes& test(U*);
 
-    static constexpr bool value = sizeof(test<Derived>(0)) == sizeof(Yes);
+    static constexpr bool value = sizeof(test<Derived>(nullptr)) == sizeof(Yes);
 
     using type = typename std::integral_constant<bool, value>::type;
 };
diff --git a/src/mongo/base/owned_pointer_vector.h b/src/mongo/base/owned_pointer_vector.h
index 199e172e4c3..929606ec520 100644
--- a/src/mongo/base/owned_pointer_vector.h
+++ b/src/mongo/base/owned_pointer_vector.h
@@ -157,7 +157,7 @@ public:
      */
     T* releaseAt(size_t i) {
         T* out = _vector[i];
-        _vector[i] = NULL;
+        _vector[i] = nullptr;
         return out;
     }
 
diff --git a/src/mongo/base/owned_pointer_vector_test.cpp b/src/mongo/base/owned_pointer_vector_test.cpp
index 5838785725e..c11bda6fb6f 100644
--- a/src/mongo/base/owned_pointer_vector_test.cpp
+++ b/src/mongo/base/owned_pointer_vector_test.cpp
@@ -290,7 +290,7 @@ TEST(OwnedPointerVectorTest, ReleaseAt) {
         holder.reset(owned.releaseAt(1));
         ASSERT_EQUALS(0U, DestructionLogger::destroyedNames().size());
         ASSERT_EQUALS(3U, owned.size());
-        ASSERT_EQUALS(static_cast<DestructionLogger*>(NULL), owned[1]);
+        ASSERT_EQUALS(static_cast<DestructionLogger*>(nullptr), owned[1]);
 
         // owned destroyed
     }
diff --git a/src/mongo/base/status.h b/src/mongo/base/status.h
index 52a46d0adb0..d3faa8fd0ec 100644
--- a/src/mongo/base/status.h
+++ b/src/mongo/base/status.h
@@ -312,7 +312,7 @@ inline unsigned Status::refCount() const {
     return _error ? _error->refs.load() : 0;
 }
 
-inline Status::Status() : _error(NULL) {}
+inline Status::Status() : _error(nullptr) {}
 
 inline void Status::ref(ErrorInfo* error) {
     if (error)
diff --git a/src/mongo/base/string_data.h b/src/mongo/base/string_data.h
index 4192ccd60f6..3a943348680 100644
--- a/src/mongo/base/string_data.h
+++ b/src/mongo/base/string_data.h
@@ -279,7 +279,7 @@ inline size_t StringData::find(char c, size_t fromPos) const {
         return std::string::npos;
 
     const void* x = memchr(_data + fromPos, c, _size - fromPos);
-    if (x == 0)
+    if (x == nullptr)
         return std::string::npos;
     return static_cast<size_t>(static_cast<const char*>(x) - _data);
 }
diff --git a/src/mongo/base/string_data_test.cpp b/src/mongo/base/string_data_test.cpp
index a1d9d7d7773..b0cfac8467a 100644
--- a/src/mongo/base/string_data_test.cpp
+++ b/src/mongo/base/string_data_test.cpp
@@ -42,7 +42,7 @@ using std::string;
 TEST(Construction, Empty) {
     StringData strData;
     ASSERT_EQUALS(strData.size(), 0U);
-    ASSERT_TRUE(strData.rawData() == NULL);
+    ASSERT_TRUE(strData.rawData() == nullptr);
 }
 
 TEST(Construction, FromStdString) {
@@ -60,10 +60,10 @@ TEST(Construction, FromCString) {
 }
 
 TEST(Construction, FromNullCString) {
-    char* c = NULL;
+    char* c = nullptr;
     StringData strData(c);
     ASSERT_EQUALS(strData.size(), 0U);
-    ASSERT_TRUE(strData.rawData() == NULL);
+    ASSERT_TRUE(strData.rawData() == nullptr);
 }
 
 TEST(Construction, FromUserDefinedLiteral) {
diff --git a/src/mongo/bson/bson_validate.cpp b/src/mongo/bson/bson_validate.cpp
index da7f1de0c1c..40edd405c9b 100644
--- a/src/mongo/bson/bson_validate.cpp
+++ b/src/mongo/bson/bson_validate.cpp
@@ -309,7 +309,7 @@ Status validateElementInfo(Buffer* buffer,
 Status validateBSONIterative(Buffer* buffer) {
     std::vector<ValidationObjectFrame> frames;
     frames.reserve(16);
-    ValidationObjectFrame* curr = NULL;
+    ValidationObjectFrame* curr = nullptr;
     ValidationState::State state = ValidationState::BeginObj;
 
     uint64_t idElemStartPos = 0;  // will become idElem once validated
diff --git a/src/mongo/bson/bson_validate_test.cpp b/src/mongo/bson/bson_validate_test.cpp
index 2c3a9b0d07b..94fb4ec269b 100644
--- a/src/mongo/bson/bson_validate_test.cpp
+++ b/src/mongo/bson/bson_validate_test.cpp
@@ -146,7 +146,7 @@ TEST(BSONValidate, MuckingData1) {
 }
 
 TEST(BSONValidate, Fuzz) {
-    int64_t seed = time(0);
+    int64_t seed = time(nullptr);
     log() << "BSONValidate Fuzz random seed: " << seed << endl;
     PseudoRandom randomSource(seed);
 
diff --git a/src/mongo/bson/bsonelement.cpp b/src/mongo/bson/bsonelement.cpp
index 2ad980eb957..d659f84ee13 100644
--- a/src/mongo/bson/bsonelement.cpp
+++ b/src/mongo/bson/bsonelement.cpp
@@ -160,7 +160,7 @@ void BSONElement::jsonStringStream(JsonStringFormat format,
                             s << "  ";
                     }
 
-                    if (strtol(e.fieldName(), 0, 10) > count) {
+                    if (strtol(e.fieldName(), nullptr, 10) > count) {
                         s << "undefined";
                     } else {
                         e.jsonStringStream(format, false, pretty ? pretty + 1 : 0, s);
diff --git a/src/mongo/bson/bsonmisc.h b/src/mongo/bson/bsonmisc.h
index 6baec67d7a6..cfc56a63ef2 100644
--- a/src/mongo/bson/bsonmisc.h
+++ b/src/mongo/bson/bsonmisc.h
@@ -212,7 +212,7 @@ public:
 
     void endField(StringData nextFieldName = StringData());
     bool subobjStarted() const {
-        return _fieldName != 0;
+        return _fieldName != nullptr;
     }
 
     // The following methods provide API compatibility with BSONArrayBuilder
@@ -236,7 +236,7 @@ private:
     BSONObjBuilder* _builder;
 
     bool haveSubobj() const {
-        return _subobj.get() != 0;
+        return _subobj.get() != nullptr;
     }
     BSONObjBuilder* subobj();
     std::unique_ptr<BSONObjBuilder> _subobj;
diff --git a/src/mongo/bson/bsonobj.h b/src/mongo/bson/bsonobj.h
index 2faa7c9cc09..c79615bbb94 100644
--- a/src/mongo/bson/bsonobj.h
+++ b/src/mongo/bson/bsonobj.h
@@ -697,7 +697,7 @@ public:
     explicit BSONObjIterator(const BSONObj& jso) {
         int sz = jso.objsize();
         if (MONGO_unlikely(sz == 0)) {
-            _pos = _theend = 0;
+            _pos = _theend = nullptr;
             return;
         }
         _pos = jso.objdata() + 4;
diff --git a/src/mongo/bson/bsonobjbuilder.cpp b/src/mongo/bson/bsonobjbuilder.cpp
index 7c64e35cac5..871dcdfb1c0 100644
--- a/src/mongo/bson/bsonobjbuilder.cpp
+++ b/src/mongo/bson/bsonobjbuilder.cpp
@@ -90,7 +90,7 @@ BSONObjBuilder& BSONObjBuilder::appendMinForType(StringData fieldName, int t) {
             appendArray(fieldName, BSONObj());
             return *this;
         case BinData:
-            appendBinData(fieldName, 0, BinDataGeneral, (const char*)0);
+            appendBinData(fieldName, 0, BinDataGeneral, (const char*)nullptr);
             return *this;
         case RegEx:
             appendRegex(fieldName, "");
diff --git a/src/mongo/bson/bsonobjbuilder.h b/src/mongo/bson/bsonobjbuilder.h
index ef28c9d828a..fe8c0a5b555 100644
--- a/src/mongo/bson/bsonobjbuilder.h
+++ b/src/mongo/bson/bsonobjbuilder.h
@@ -68,7 +68,7 @@ class BSONObjBuilder {
 public:
     /** @param initsize this is just a hint as to the final size of the object */
     BSONObjBuilder(int initsize = 512)
-        : _b(_buf), _buf(initsize), _offset(0), _s(this), _tracker(0), _doneCalled(false) {
+        : _b(_buf), _buf(initsize), _offset(0), _s(this), _tracker(nullptr), _doneCalled(false) {
         // Skip over space for the object length. The length is filled in by _done.
         _b.skip(sizeof(int));
 
@@ -85,7 +85,7 @@ public:
           _buf(0),
           _offset(baseBuilder.len()),
           _s(this),
-          _tracker(0),
+          _tracker(nullptr),
           _doneCalled(false) {
         // Skip over space for the object length, which is filled in by _done. We don't need a
         // holder since we are a sub-builder, and some parent builder has already made the
@@ -135,7 +135,7 @@ public:
      * into this constructor where possible.
      */
     BSONObjBuilder(BSONObj prefix)
-        : _b(_buf), _buf(0), _offset(0), _s(this), _tracker(0), _doneCalled(false) {
+        : _b(_buf), _buf(0), _offset(0), _s(this), _tracker(nullptr), _doneCalled(false) {
         // If prefix wasn't owned or we don't have exclusive access to it, we must copy.
         if (!prefix.isOwned() || prefix.sharedBuffer().isShared()) {
             _b.grow(prefix.objsize());  // Make sure we won't need to realloc().
@@ -386,7 +386,9 @@ public:
         @deprecated Generally, it is preferred to use the append append(name, oid)
         method for this.
     */
-    BSONObjBuilder& appendOID(StringData fieldName, OID* oid = 0, bool generateIfBlank = false) {
+    BSONObjBuilder& appendOID(StringData fieldName,
+                              OID* oid = nullptr,
+                              bool generateIfBlank = false) {
         _b.appendNum((char)jstOID);
         _b.appendStr(fieldName);
         if (oid)
diff --git a/src/mongo/bson/json.cpp b/src/mongo/bson/json.cpp
index a2bc9872c79..15661b0a456 100644
--- a/src/mongo/bson/json.cpp
+++ b/src/mongo/bson/json.cpp
@@ -1108,7 +1108,7 @@ Status JParse::chars(std::string* result, const char* terminalSet, const char* a
     const char* q = _input;
     while (q < _input_end && !match(*q, terminalSet)) {
         MONGO_JSON_DEBUG("q: " << q);
-        if (allowedSet != NULL) {
+        if (allowedSet != nullptr) {
             if (!match(*q, allowedSet)) {
                 _input = q;
                 return Status::OK();
@@ -1226,7 +1226,7 @@ inline bool JParse::readToken(const char* token) {
 bool JParse::readTokenImpl(const char* token, bool advance) {
     MONGO_JSON_DEBUG("token: " << token);
     const char* check = _input;
-    if (token == NULL) {
+    if (token == nullptr) {
         return false;
     }
     // 'isspace()' takes an 'int' (signed), so (default signed) 'char's get sign-extended
@@ -1264,13 +1264,13 @@ bool JParse::readField(StringData expectedField) {
 }
 
 inline bool JParse::match(char matchChar, const char* matchSet) const {
-    if (matchSet == NULL) {
+    if (matchSet == nullptr) {
         return true;
     }
     if (*matchSet == '\0') {
         return false;
     }
-    return (strchr(matchSet, matchChar) != NULL);
+    return (strchr(matchSet, matchChar) != nullptr);
 }
 
 bool JParse::isHexString(StringData str) const {
diff --git a/src/mongo/bson/json.h b/src/mongo/bson/json.h
index 38217fb7eef..45b08acd095 100644
--- a/src/mongo/bson/json.h
+++ b/src/mongo/bson/json.h
@@ -52,7 +52,7 @@ namespace mongo {
 BSONObj fromjson(const std::string& str);
 
 /** @param len will be size of JSON object in text chars. */
-BSONObj fromjson(const char* str, int* len = NULL);
+BSONObj fromjson(const char* str, int* len = nullptr);
 
 /**
  * Tests whether the JSON string is an Array.
@@ -410,7 +410,7 @@ private:
      * string, but there is no guarantee that it will not contain other
      * null characters.
      */
-    Status chars(std::string* result, const char* terminalSet, const char* allowedSet = NULL);
+    Status chars(std::string* result, const char* terminalSet, const char* allowedSet = nullptr);
 
     /**
      * Converts the two byte Unicode code point to its UTF8 character
diff --git a/src/mongo/bson/mutable/const_element.h b/src/mongo/bson/mutable/const_element.h
index 4b8d483095e..5346c56c52d 100644
--- a/src/mongo/bson/mutable/const_element.h
+++ b/src/mongo/bson/mutable/const_element.h
@@ -120,7 +120,7 @@ private:
     friend class Document;
 
     template <typename Builder>
-    inline void writeElement(Builder* builder, const StringData* fieldName = NULL) const;
+    inline void writeElement(Builder* builder, const StringData* fieldName = nullptr) const;
 
     Element _basis;
 };
diff --git a/src/mongo/bson/mutable/document.cpp b/src/mongo/bson/mutable/document.cpp
index fb75d2d008c..443c57cebf1 100644
--- a/src/mongo/bson/mutable/document.cpp
+++ b/src/mongo/bson/mutable/document.cpp
@@ -997,7 +997,7 @@ public:
         // inform upstream that we are not returning in-place result data.
         if (_inPlaceMode == Document::kInPlaceDisabled) {
             damages->clear();
-            *source = NULL;
+            *source = nullptr;
             if (size)
                 *size = 0;
             return false;
@@ -1077,7 +1077,7 @@ public:
     template <typename Builder>
     void writeElement(Element::RepIdx repIdx,
                       Builder* builder,
-                      const StringData* fieldName = NULL) const;
+                      const StringData* fieldName = nullptr) const;
 
     template <typename Builder>
     void writeChildren(Element::RepIdx repIdx, Builder* builder) const;
@@ -2647,7 +2647,7 @@ Element Document::makeElementSafeNum(StringData fieldName, SafeNum value) {
 }
 
 Element Document::makeElement(ConstElement element) {
-    return makeElement(element, NULL);
+    return makeElement(element, nullptr);
 }
 
 Element Document::makeElementWithNewFieldName(StringData fieldName, ConstElement element) {
diff --git a/src/mongo/bson/mutable/document.h b/src/mongo/bson/mutable/document.h
index 0feb056cc35..ac254b7ac21 100644
--- a/src/mongo/bson/mutable/document.h
+++ b/src/mongo/bson/mutable/document.h
@@ -476,7 +476,7 @@ public:
      *  The destination offsets in the damage events are implicitly offsets into the
      *  BSONObj used to construct this Document.
      */
-    bool getInPlaceUpdates(DamageVector* damages, const char** source, size_t* size = NULL);
+    bool getInPlaceUpdates(DamageVector* damages, const char** source, size_t* size = nullptr);
 
     /** Drop the queue of in-place update damage events, and do not queue new operations
      *  that would otherwise have been in-place. Use this if you know that in-place updates
diff --git a/src/mongo/bson/mutable/element.h b/src/mongo/bson/mutable/element.h
index 85756d1fea9..7438d97f186 100644
--- a/src/mongo/bson/mutable/element.h
+++ b/src/mongo/bson/mutable/element.h
@@ -724,7 +724,7 @@ inline bool Element::isValueMaxKey() const {
 }
 
 inline bool Element::ok() const {
-    dassert(_doc != NULL);
+    dassert(_doc != nullptr);
     return _repIdx <= kMaxRepIdx;
 }
 
@@ -745,7 +745,7 @@ inline Element::RepIdx Element::getIdx() const {
 }
 
 inline Element::Element(Document* doc, RepIdx repIdx) : _doc(doc), _repIdx(repIdx) {
-    dassert(_doc != NULL);
+    dassert(_doc != nullptr);
 }
 
 inline StringData Element::getValueStringOrSymbol() const {
diff --git a/src/mongo/bson/mutable/mutable_bson_test.cpp b/src/mongo/bson/mutable/mutable_bson_test.cpp
index fa13986ef12..58a46d04ce3 100644
--- a/src/mongo/bson/mutable/mutable_bson_test.cpp
+++ b/src/mongo/bson/mutable/mutable_bson_test.cpp
@@ -1017,11 +1017,11 @@ TEST(Documentation, Example2InPlaceWithDamageVector) {
 
     // Extract the damage events
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
     size_t size = 0;
     ASSERT_EQUALS(true, doc.getInPlaceUpdates(&damages, &source, &size));
     ASSERT_NOT_EQUALS(0U, damages.size());
-    ASSERT_NOT_EQUALS(static_cast<const char*>(NULL), source);
+    ASSERT_NOT_EQUALS(static_cast<const char*>(nullptr), source);
     ASSERT_NOT_EQUALS(0U, size);
 
     apply(&obj, damages, source);
@@ -2772,12 +2772,12 @@ TEST(DocumentInPlace, InPlaceModeWorksWithNoMutations) {
     mongo::BSONObj obj;
     mmb::Document doc(obj, mmb::Document::kInPlaceEnabled);
     ASSERT_TRUE(doc.isInPlaceModeEnabled());
-    const char* source = NULL;
+    const char* source = nullptr;
     mmb::DamageVector damages;
     ASSERT_TRUE(damages.empty());
     doc.getInPlaceUpdates(&damages, &source);
     ASSERT_TRUE(damages.empty());
-    ASSERT_NOT_EQUALS(static_cast<const char*>(NULL), source);
+    ASSERT_NOT_EQUALS(static_cast<const char*>(nullptr), source);
     ASSERT_TRUE(doc.isInPlaceModeEnabled());
 }
 
@@ -2876,14 +2876,14 @@ TEST(DocumentInPlace, GettingInPlaceUpdatesWhenDisabledClearsArguments) {
     const char* source = "foo";
     ASSERT_FALSE(doc.getInPlaceUpdates(&damages, &source));
     ASSERT_TRUE(damages.empty());
-    ASSERT_EQUALS(static_cast<const char*>(NULL), source);
+    ASSERT_EQUALS(static_cast<const char*>(nullptr), source);
 
     damages.push_back(event);
     source = "bar";
     size_t size = 1;
     ASSERT_FALSE(doc.getInPlaceUpdates(&damages, &source, &size));
     ASSERT_TRUE(damages.empty());
-    ASSERT_EQUALS(static_cast<const char*>(NULL), source);
+    ASSERT_EQUALS(static_cast<const char*>(nullptr), source);
     ASSERT_EQUALS(0U, size);
 }
 
@@ -2929,7 +2929,7 @@ TEST(DocumentInPlace, StringLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueString("bar").transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -2955,7 +2955,7 @@ TEST(DocumentInPlace, BinDataLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueBinary(binData2.length, binData2.type, binData2.data).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -2985,7 +2985,7 @@ TEST(DocumentInPlace, OIDLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueOID(oid2).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -3005,7 +3005,7 @@ TEST(DocumentInPlace, BooleanLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueBool(false).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -3031,7 +3031,7 @@ TEST(DocumentInPlace, DateLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueDate(mongo::Date_t::fromMillisSinceEpoch(20000)).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -3053,7 +3053,7 @@ TEST(DocumentInPlace, NumberIntLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueInt(value2).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -3079,7 +3079,7 @@ TEST(DocumentInPlace, TimestampLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueTimestamp(mongo::Timestamp(mongo::Date_t::fromMillisSinceEpoch(20000)))
         .transitional_ignore();
@@ -3103,7 +3103,7 @@ TEST(DocumentInPlace, NumberLongLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueLong(value2).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -3132,7 +3132,7 @@ TEST(DocumentInPlace, NumberDoubleLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueDouble(value2).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -3161,7 +3161,7 @@ TEST(DocumentInPlace, NumberDecimalLifecycle) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueDecimal(value2).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
@@ -3192,7 +3192,7 @@ TEST(DocumentInPlace, DoubleToLongAndBack) {
     mmb::Element x = doc.root().leftChild();
 
     mmb::DamageVector damages;
-    const char* source = NULL;
+    const char* source = nullptr;
 
     x.setValueLong(value2).transitional_ignore();
     ASSERT_TRUE(doc.getInPlaceUpdates(&damages, &source));
diff --git a/src/mongo/bson/oid.cpp b/src/mongo/bson/oid.cpp
index a4d2d901e61..0f08d6c56b6 100644
--- a/src/mongo/bson/oid.cpp
+++ b/src/mongo/bson/oid.cpp
@@ -135,7 +135,7 @@ void OID::justForked() {
 
 void OID::init() {
     // each set* method handles endianness
-    setTimestamp(time(0));
+    setTimestamp(time(nullptr));
     setInstanceUnique(_instanceUnique);
     setIncrement(Increment::next());
 }
diff --git a/src/mongo/bson/util/builder.h b/src/mongo/bson/util/builder.h
index ad890ceb074..d1cd0d53963 100644
--- a/src/mongo/bson/util/builder.h
+++ b/src/mongo/bson/util/builder.h
@@ -458,7 +458,8 @@ public:
         verify(z >= 0);
         verify(z < maxSize);
         _buf.l = prev + z;
-        if (strchr(start, '.') == 0 && strchr(start, 'E') == 0 && strchr(start, 'N') == 0) {
+        if (strchr(start, '.') == nullptr && strchr(start, 'E') == nullptr &&
+            strchr(start, 'N') == nullptr) {
             write(".0", 2);
         }
     }
diff --git a/src/mongo/bson/util/builder_test.cpp b/src/mongo/bson/util/builder_test.cpp
index 2dc2662e29d..8ceb8c2c5b8 100644
--- a/src/mongo/bson/util/builder_test.cpp
+++ b/src/mongo/bson/util/builder_test.cpp
@@ -48,7 +48,7 @@ TEST(Builder, StringBuilderAddress) {
     const void* longPtr = reinterpret_cast<const void*>(-1);
     const void* shortPtr = reinterpret_cast<const void*>(static_cast<uintptr_t>(0xDEADBEEF));
 
-    const void* nullPtr = NULL;
+    const void* nullPtr = nullptr;
 
     StringBuilder sb;
     sb << longPtr;
diff --git a/src/mongo/client/connection_pool.cpp b/src/mongo/client/connection_pool.cpp
index 643817aa9c6..dfe098e1c9d 100644
--- a/src/mongo/client/connection_pool.cpp
+++ b/src/mongo/client/connection_pool.cpp
@@ -273,7 +273,7 @@ ConnectionPool::ConnectionPtr& ConnectionPool::ConnectionPtr::operator=(Connecti
 
 void ConnectionPool::ConnectionPtr::done(Date_t now) {
     _pool->releaseConnection(_connInfo, now);
-    _pool = NULL;
+    _pool = nullptr;
 }
 
 }  // namespace mongo
diff --git a/src/mongo/client/connection_string_connect.cpp b/src/mongo/client/connection_string_connect.cpp
index 76844368edc..81e3bdaef4f 100644
--- a/src/mongo/client/connection_string_connect.cpp
+++ b/src/mongo/client/connection_string_connect.cpp
@@ -44,7 +44,7 @@
 namespace mongo {
 
 stdx::mutex ConnectionString::_connectHookMutex;
-ConnectionString::ConnectionHook* ConnectionString::_connectHook = NULL;
+ConnectionString::ConnectionHook* ConnectionString::_connectHook = nullptr;
 
 std::unique_ptr<DBClientBase> ConnectionString::connect(StringData applicationName,
                                                         std::string& errmsg,
diff --git a/src/mongo/client/connpool.cpp b/src/mongo/client/connpool.cpp
index d4d58addcfc..5901f695014 100644
--- a/src/mongo/client/connpool.cpp
+++ b/src/mongo/client/connpool.cpp
@@ -572,7 +572,7 @@ bool DBConnectionPool::poolKeyCompare::operator()(const PoolKey& a, const PoolKe
 }
 
 bool DBConnectionPool::isConnectionGood(const string& hostName, DBClientBase* conn) {
-    if (conn == NULL) {
+    if (conn == nullptr) {
         return false;
     }
 
@@ -642,13 +642,13 @@ void ScopedDbConnection::done() {
     }
 
     globalConnPool.release(_host, _conn);
-    _conn = NULL;
+    _conn = nullptr;
 }
 
 void ScopedDbConnection::kill() {
     globalConnPool.decrementEgress(_host, _conn);
     delete _conn;
-    _conn = NULL;
+    _conn = nullptr;
 }
 
 void ScopedDbConnection::_setSocketTimeout() {
diff --git a/src/mongo/client/connpool.h b/src/mongo/client/connpool.h
index 24e2cd70dd4..9fbf65214db 100644
--- a/src/mongo/client/connpool.h
+++ b/src/mongo/client/connpool.h
@@ -457,7 +457,7 @@ public:
     explicit ScopedDbConnection(const ConnectionString& host, double socketTimeout = 0);
     explicit ScopedDbConnection(const MongoURI& host, double socketTimeout = 0);
 
-    ScopedDbConnection() : _host(""), _conn(0), _socketTimeoutSecs(0) {}
+    ScopedDbConnection() : _host(""), _conn(nullptr), _socketTimeoutSecs(0) {}
 
     /* @param conn - bind to an existing connection */
     ScopedDbConnection(const std::string& host, DBClientBase* conn, double socketTimeout = 0)
@@ -488,7 +488,7 @@ public:
     }
 
     bool ok() const {
-        return _conn != NULL;
+        return _conn != nullptr;
     }
 
     std::string getHost() const {
diff --git a/src/mongo/client/dbclient_base.cpp b/src/mongo/client/dbclient_base.cpp
index dcf30fa1881..3c896123850 100644
--- a/src/mongo/client/dbclient_base.cpp
+++ b/src/mongo/client/dbclient_base.cpp
@@ -287,7 +287,7 @@ bool DBClientBase::runCommand(const string& dbname, BSONObj cmd, BSONObj& info,
 */
 bool DBClientBase::simpleCommand(const string& dbname, BSONObj* info, const string& command) {
     BSONObj o;
-    if (info == 0)
+    if (info == nullptr)
         info = &o;
     BSONObjBuilder b;
     b.append(command, 1);
@@ -532,7 +532,7 @@ bool DBClientBase::isMaster(bool& isMaster, BSONObj* info) {
     }
 
     BSONObj o;
-    if (info == 0)
+    if (info == nullptr)
         info = &o;
     bool ok = runCommand("admin", bob.obj(), *info);
     isMaster = info->getField("ismaster").trueValue();
@@ -543,7 +543,7 @@ bool DBClientBase::createCollection(
     const string& ns, long long size, bool capped, int max, BSONObj* info) {
     verify(!capped || size);
     BSONObj o;
-    if (info == 0)
+    if (info == nullptr)
         info = &o;
     BSONObjBuilder b;
     string db = nsToDatabase(ns);
diff --git a/src/mongo/client/dbclient_base.h b/src/mongo/client/dbclient_base.h
index 558cc3efa8e..a7cdfc43c3b 100644
--- a/src/mongo/client/dbclient_base.h
+++ b/src/mongo/client/dbclient_base.h
@@ -77,21 +77,21 @@ class DBClientQueryInterface {
                                                   Query query,
                                                   int nToReturn = 0,
                                                   int nToSkip = 0,
-                                                  const BSONObj* fieldsToReturn = 0,
+                                                  const BSONObj* fieldsToReturn = nullptr,
                                                   int queryOptions = 0,
                                                   int batchSize = 0) = 0;
 
     virtual unsigned long long query(std::function<void(const BSONObj&)> f,
                                      const NamespaceStringOrUUID& nsOrUuid,
                                      Query query,
-                                     const BSONObj* fieldsToReturn = 0,
+                                     const BSONObj* fieldsToReturn = nullptr,
                                      int queryOptions = 0,
                                      int batchSize = 0) = 0;
 
     virtual unsigned long long query(std::function<void(DBClientCursorBatchIterator&)> f,
                                      const NamespaceStringOrUUID& nsOrUuid,
                                      Query query,
-                                     const BSONObj* fieldsToReturn = 0,
+                                     const BSONObj* fieldsToReturn = nullptr,
                                      int queryOptions = 0,
                                      int batchSize = 0) = 0;
 };
@@ -118,7 +118,7 @@ public:
     */
     virtual BSONObj findOne(const std::string& ns,
                             const Query& query,
-                            const BSONObj* fieldsToReturn = 0,
+                            const BSONObj* fieldsToReturn = nullptr,
                             int queryOptions = 0);
 
     /** query N objects from the database into an array.  makes sense mostly when you want a small
@@ -129,7 +129,7 @@ public:
                Query query,
                int nToReturn,
                int nToSkip = 0,
-               const BSONObj* fieldsToReturn = 0,
+               const BSONObj* fieldsToReturn = nullptr,
                int queryOptions = 0);
 
     /**
@@ -368,7 +368,7 @@ public:
 
        returns true if command invoked successfully.
     */
-    virtual bool isMaster(bool& isMaster, BSONObj* info = 0);
+    virtual bool isMaster(bool& isMaster, BSONObj* info = nullptr);
 
     /**
        Create a new collection in the database.  Normally, collection creation is automatic.  You
@@ -390,7 +390,7 @@ public:
                           long long size = 0,
                           bool capped = false,
                           int max = 0,
-                          BSONObj* info = 0);
+                          BSONObj* info = nullptr);
 
     /** Get error result from the last write operation (insert/update/delete) on this connection.
         db doesn't change the command's behavior - it is just for auth checks.
@@ -583,7 +583,7 @@ public:
                                           Query query,
                                           int nToReturn = 0,
                                           int nToSkip = 0,
-                                          const BSONObj* fieldsToReturn = 0,
+                                          const BSONObj* fieldsToReturn = nullptr,
                                           int queryOptions = 0,
                                           int batchSize = 0) override;
 
@@ -605,14 +605,14 @@ public:
     unsigned long long query(std::function<void(const BSONObj&)> f,
                              const NamespaceStringOrUUID& nsOrUuid,
                              Query query,
-                             const BSONObj* fieldsToReturn = 0,
+                             const BSONObj* fieldsToReturn = nullptr,
                              int queryOptions = QueryOption_Exhaust,
                              int batchSize = 0) final;
 
     unsigned long long query(std::function<void(DBClientCursorBatchIterator&)> f,
                              const NamespaceStringOrUUID& nsOrUuid,
                              Query query,
-                             const BSONObj* fieldsToReturn = 0,
+                             const BSONObj* fieldsToReturn = nullptr,
                              int queryOptions = QueryOption_Exhaust,
                              int batchSize = 0) override;
 
diff --git a/src/mongo/client/dbclient_connection.h b/src/mongo/client/dbclient_connection.h
index dc2f9ae7f6c..5b2976a134f 100644
--- a/src/mongo/client/dbclient_connection.h
+++ b/src/mongo/client/dbclient_connection.h
@@ -154,7 +154,7 @@ public:
                                           Query query = Query(),
                                           int nToReturn = 0,
                                           int nToSkip = 0,
-                                          const BSONObj* fieldsToReturn = 0,
+                                          const BSONObj* fieldsToReturn = nullptr,
                                           int queryOptions = 0,
                                           int batchSize = 0) override {
         checkConnection();
@@ -227,12 +227,12 @@ public:
         return _serverAddress;
     }
 
-    void say(Message& toSend, bool isRetry = false, std::string* actualServer = 0) override;
+    void say(Message& toSend, bool isRetry = false, std::string* actualServer = nullptr) override;
     bool recv(Message& m, int lastRequestId) override;
     void checkResponse(const std::vector<BSONObj>& batch,
                        bool networkError,
-                       bool* retry = NULL,
-                       std::string* host = NULL) override;
+                       bool* retry = nullptr,
+                       std::string* host = nullptr) override;
     bool call(Message& toSend,
               Message& response,
               bool assertOk,
diff --git a/src/mongo/client/dbclient_cursor.cpp b/src/mongo/client/dbclient_cursor.cpp
index 3e049f786e5..16be475d4b0 100644
--- a/src/mongo/client/dbclient_cursor.cpp
+++ b/src/mongo/client/dbclient_cursor.cpp
@@ -490,7 +490,7 @@ void DBClientCursor::attach(AScopedConnection* conn) {
     }
 
     conn->done();
-    _client = 0;
+    _client = nullptr;
     _lazyHost = "";
 }
 
diff --git a/src/mongo/client/dbclient_cursor.h b/src/mongo/client/dbclient_cursor.h
index e5b69b10b50..ad3a2c89583 100644
--- a/src/mongo/client/dbclient_cursor.h
+++ b/src/mongo/client/dbclient_cursor.h
@@ -94,7 +94,7 @@ public:
     /**
      * peek ahead and see if an error occurred, and get the error if so.
      */
-    bool peekError(BSONObj* error = NULL);
+    bool peekError(BSONObj* error = nullptr);
 
     /**
        iterate the rest of the cursor and return the number if items
diff --git a/src/mongo/client/dbclient_rs.cpp b/src/mongo/client/dbclient_rs.cpp
index 033f39b0bef..b7e2044f93c 100644
--- a/src/mongo/client/dbclient_rs.cpp
+++ b/src/mongo/client/dbclient_rs.cpp
@@ -298,7 +298,7 @@ DBClientConnection* DBClientReplicaSet::checkMaster() {
     MongoURI masterUri = _uri.cloneURIForServer(_masterHost);
 
     string errmsg;
-    DBClientConnection* newConn = NULL;
+    DBClientConnection* newConn = nullptr;
     boost::optional<double> socketTimeout;
     if (_so_timeout > 0.0)
         socketTimeout = _so_timeout;
@@ -313,7 +313,7 @@ DBClientConnection* DBClientReplicaSet::checkMaster() {
         errmsg = ex.toString();
     }
 
-    if (newConn == NULL || !errmsg.empty()) {
+    if (newConn == nullptr || !errmsg.empty()) {
         const std::string message = str::stream() << "can't connect to new replica set master ["
                                                   << _masterHost.toString() << "]"
                                                   << (errmsg.empty() ? "" : ", err: ") << errmsg;
@@ -398,7 +398,7 @@ DBClientConnection& DBClientReplicaSet::slaveConn() {
 
     uassert(16369,
             str::stream() << "No good nodes available for set: " << _getMonitor()->getName(),
-            conn != NULL);
+            conn != nullptr);
 
     return *conn;
 }
@@ -493,7 +493,7 @@ void DBClientReplicaSet::logout(const string& dbname, BSONObj& info) {
      * needed when we actually have something cached and is last known to be
      * working.
      */
-    if (_lastSlaveOkConn.get() != NULL && !_lastSlaveOkConn->isFailed()) {
+    if (_lastSlaveOkConn.get() != nullptr && !_lastSlaveOkConn->isFailed()) {
         try {
             BSONObj dummy;
             _lastSlaveOkConn->logout(dbname, dummy);
@@ -536,8 +536,8 @@ unique_ptr<DBClientCursor> DBClientReplicaSet::query(const NamespaceStringOrUUID
         LOG(3) << "dbclient_rs query using secondary or tagged node selection in "
                << _getMonitor()->getName() << ", read pref is " << readPref->toString()
                << " (primary : "
-               << (_master.get() != NULL ? _master->getServerAddress() : "[not cached]")
-               << ", lastTagged : " << (_lastSlaveOkConn.get() != NULL
+               << (_master.get() != nullptr ? _master->getServerAddress() : "[not cached]")
+               << ", lastTagged : " << (_lastSlaveOkConn.get() != nullptr
                                             ? _lastSlaveOkConn->getServerAddress()
                                             : "[not cached]")
                << ")" << endl;
@@ -548,7 +548,7 @@ unique_ptr<DBClientCursor> DBClientReplicaSet::query(const NamespaceStringOrUUID
             try {
                 DBClientConnection* conn = selectNodeUsingTags(readPref);
 
-                if (conn == NULL) {
+                if (conn == nullptr) {
                     break;
                 }
 
@@ -588,8 +588,8 @@ BSONObj DBClientReplicaSet::findOne(const string& ns,
         LOG(3) << "dbclient_rs findOne using secondary or tagged node selection in "
                << _getMonitor()->getName() << ", read pref is " << readPref->toString()
                << " (primary : "
-               << (_master.get() != NULL ? _master->getServerAddress() : "[not cached]")
-               << ", lastTagged : " << (_lastSlaveOkConn.get() != NULL
+               << (_master.get() != nullptr ? _master->getServerAddress() : "[not cached]")
+               << ", lastTagged : " << (_lastSlaveOkConn.get() != nullptr
                                             ? _lastSlaveOkConn->getServerAddress()
                                             : "[not cached]")
                << ")" << endl;
@@ -600,7 +600,7 @@ BSONObj DBClientReplicaSet::findOne(const string& ns,
             try {
                 DBClientConnection* conn = selectNodeUsingTags(readPref);
 
-                if (conn == NULL) {
+                if (conn == nullptr) {
                     break;
                 }
 
@@ -647,7 +647,7 @@ void DBClientReplicaSet::isntMaster() {
 
 unique_ptr<DBClientCursor> DBClientReplicaSet::checkSlaveQueryResult(
     unique_ptr<DBClientCursor> result) {
-    if (result.get() == NULL)
+    if (result.get() == nullptr)
         return result;
 
     BSONObj error;
@@ -733,7 +733,7 @@ DBClientConnection* DBClientReplicaSet::selectNodeUsingTags(
     // that returning NULL means none of the nodes were good, which is not the case here.
     uassert(16532,
             str::stream() << "Failed to connect to " << _lastSlaveOkHost.toString(),
-            newConn != NULL);
+            newConn != nullptr);
 
     _lastSlaveOkConn = std::shared_ptr<DBClientConnection>(newConn, std::move(dtor));
     _lastSlaveOkConn->setParentReplSetName(_setName);
@@ -767,8 +767,8 @@ void DBClientReplicaSet::say(Message& toSend, bool isRetry, string* actualServer
             LOG(3) << "dbclient_rs say using secondary or tagged node selection in "
                    << _getMonitor()->getName() << ", read pref is " << readPref->toString()
                    << " (primary : "
-                   << (_master.get() != NULL ? _master->getServerAddress() : "[not cached]")
-                   << ", lastTagged : " << (_lastSlaveOkConn.get() != NULL
+                   << (_master.get() != nullptr ? _master->getServerAddress() : "[not cached]")
+                   << ", lastTagged : " << (_lastSlaveOkConn.get() != nullptr
                                                 ? _lastSlaveOkConn->getServerAddress()
                                                 : "[not cached]")
                    << ")" << endl;
@@ -780,11 +780,11 @@ void DBClientReplicaSet::say(Message& toSend, bool isRetry, string* actualServer
                 try {
                     DBClientConnection* conn = selectNodeUsingTags(readPref);
 
-                    if (conn == NULL) {
+                    if (conn == nullptr) {
                         break;
                     }
 
-                    if (actualServer != NULL) {
+                    if (actualServer != nullptr) {
                         *actualServer = conn->getServerAddress();
                     }
 
@@ -985,7 +985,7 @@ bool DBClientReplicaSet::call(Message& toSend,
                               Message& response,
                               bool assertOk,
                               string* actualServer) {
-    const char* ns = 0;
+    const char* ns = nullptr;
 
     if (toSend.operation() == dbQuery) {
         // TODO: might be possible to do this faster by changing api
@@ -998,8 +998,8 @@ bool DBClientReplicaSet::call(Message& toSend,
             LOG(3) << "dbclient_rs call using secondary or tagged node selection in "
                    << _getMonitor()->getName() << ", read pref is " << readPref->toString()
                    << " (primary : "
-                   << (_master.get() != NULL ? _master->getServerAddress() : "[not cached]")
-                   << ", lastTagged : " << (_lastSlaveOkConn.get() != NULL
+                   << (_master.get() != nullptr ? _master->getServerAddress() : "[not cached]")
+                   << ", lastTagged : " << (_lastSlaveOkConn.get() != nullptr
                                                 ? _lastSlaveOkConn->getServerAddress()
                                                 : "[not cached]")
                    << ")" << endl;
@@ -1008,11 +1008,11 @@ bool DBClientReplicaSet::call(Message& toSend,
                 try {
                     DBClientConnection* conn = selectNodeUsingTags(readPref);
 
-                    if (conn == NULL) {
+                    if (conn == nullptr) {
                         return false;
                     }
 
-                    if (actualServer != NULL) {
+                    if (actualServer != nullptr) {
                         *actualServer = conn->getServerAddress();
                     }
 
@@ -1068,7 +1068,7 @@ void DBClientReplicaSet::_invalidateLastSlaveOkCache(const Status& status) {
 
 void DBClientReplicaSet::reset() {
     resetSlaveOkConn();
-    _lazyState._lastClient = NULL;
+    _lazyState._lastClient = nullptr;
     _lastReadPref.reset();
 }
 
@@ -1089,7 +1089,7 @@ void DBClientReplicaSet::resetMaster() {
 void DBClientReplicaSet::resetSlaveOkConn() {
     if (_lastSlaveOkConn.get() == _master.get()) {
         _lastSlaveOkConn.reset();
-    } else if (_lastSlaveOkConn.get() != NULL) {
+    } else if (_lastSlaveOkConn.get() != nullptr) {
         if (_authPooledSecondaryConn) {
             logoutAll(_lastSlaveOkConn.get());
         } else {
diff --git a/src/mongo/client/dbclient_rs.h b/src/mongo/client/dbclient_rs.h
index 506a3cf6f16..92e2a93acb0 100644
--- a/src/mongo/client/dbclient_rs.h
+++ b/src/mongo/client/dbclient_rs.h
@@ -93,14 +93,14 @@ public:
                                           Query query,
                                           int nToReturn = 0,
                                           int nToSkip = 0,
-                                          const BSONObj* fieldsToReturn = 0,
+                                          const BSONObj* fieldsToReturn = nullptr,
                                           int queryOptions = 0,
                                           int batchSize = 0) override;
 
     /** throws userassertion "no master found" */
     BSONObj findOne(const std::string& ns,
                     const Query& query,
-                    const BSONObj* fieldsToReturn = 0,
+                    const BSONObj* fieldsToReturn = nullptr,
                     int queryOptions = 0) override;
 
     void insert(const std::string& ns, BSONObj obj, int flags = 0) override;
@@ -136,12 +136,12 @@ public:
 
     // ---- callback pieces -------
 
-    void say(Message& toSend, bool isRetry = false, std::string* actualServer = 0) override;
+    void say(Message& toSend, bool isRetry = false, std::string* actualServer = nullptr) override;
     bool recv(Message& toRecv, int lastRequestId) override;
     void checkResponse(const std::vector<BSONObj>& batch,
                        bool networkError,
-                       bool* retry = NULL,
-                       std::string* targetHost = NULL) override;
+                       bool* retry = nullptr,
+                       std::string* targetHost = nullptr) override;
 
     /* this is the callback from our underlying connections to notify us that we got a "not master"
      * error.
@@ -345,7 +345,7 @@ protected:
      */
     class LazyState {
     public:
-        LazyState() : _lastClient(NULL), _lastOp(-1), _secondaryQueryOk(false), _retries(0) {}
+        LazyState() : _lastClient(nullptr), _lastOp(-1), _secondaryQueryOk(false), _retries(0) {}
         DBClientConnection* _lastClient;
         int _lastOp;
         bool _secondaryQueryOk;
diff --git a/src/mongo/client/index_spec.cpp b/src/mongo/client/index_spec.cpp
index c5d3061d781..4562a8fe17f 100644
--- a/src/mongo/client/index_spec.cpp
+++ b/src/mongo/client/index_spec.cpp
@@ -46,8 +46,8 @@ namespace {
 
 const int kIndexTypeNumbers[] = {IndexSpec::kIndexValAscending, IndexSpec::kIndexValDescending};
 
-const char* const kIndexTypeStrings[] = {NULL,
-                                         NULL,
+const char* const kIndexTypeStrings[] = {nullptr,
+                                         nullptr,
                                          IndexSpec::kIndexValText,
                                          IndexSpec::kIndexValGeo2D,
                                          IndexSpec::kIndexValGeoHaystack,
diff --git a/src/mongo/client/query.h b/src/mongo/client/query.h
index c8adf396cfe..24444e853e8 100644
--- a/src/mongo/client/query.h
+++ b/src/mongo/client/query.h
@@ -131,8 +131,8 @@ public:
     /**
      * @return true if this query has an orderby, hint, or some other field
      */
-    bool isComplex(bool* hasDollar = 0) const;
-    static bool isComplex(const BSONObj& obj, bool* hasDollar = 0);
+    bool isComplex(bool* hasDollar = nullptr) const;
+    static bool isComplex(const BSONObj& obj, bool* hasDollar = nullptr);
 
     BSONObj getFilter() const;
     BSONObj getSort() const;
diff --git a/src/mongo/client/replica_set_monitor.cpp b/src/mongo/client/replica_set_monitor.cpp
index cca254b4007..d134f935070 100644
--- a/src/mongo/client/replica_set_monitor.cpp
+++ b/src/mongo/client/replica_set_monitor.cpp
@@ -1200,7 +1200,7 @@ std::vector<HostAndPort> SetState::getMatchingHosts(const ReadPreferenceSetting&
 Node* SetState::findNode(const HostAndPort& host) {
     const Nodes::iterator it = std::lower_bound(nodes.begin(), nodes.end(), host, compareHosts);
     if (it == nodes.end() || it->host != host)
-        return NULL;
+        return nullptr;
 
     return &(*it);
 }
diff --git a/src/mongo/client/replica_set_monitor_read_preference_test.cpp b/src/mongo/client/replica_set_monitor_read_preference_test.cpp
index 3f738d6cd41..374a3f5f9c5 100644
--- a/src/mongo/client/replica_set_monitor_read_preference_test.cpp
+++ b/src/mongo/client/replica_set_monitor_read_preference_test.cpp
@@ -589,7 +589,7 @@ public:
     virtual ~MultiTagsTest() = default;
 
     const TagSet& getMatchesFirstTagSet() {
-        if (matchFirstTags.get() != NULL) {
+        if (matchFirstTags.get() != nullptr) {
             return *matchFirstTags;
         }
 
@@ -604,7 +604,7 @@ public:
     }
 
     const TagSet& getMatchesSecondTagSet() {
-        if (matchSecondTags.get() != NULL) {
+        if (matchSecondTags.get() != nullptr) {
             return *matchSecondTags;
         }
 
@@ -621,7 +621,7 @@ public:
     }
 
     const TagSet& getMatchesLastTagSet() {
-        if (matchLastTags.get() != NULL) {
+        if (matchLastTags.get() != nullptr) {
             return *matchLastTags;
         }
 
@@ -642,7 +642,7 @@ public:
     }
 
     const TagSet& getMatchesPriTagSet() {
-        if (matchPriTags.get() != NULL) {
+        if (matchPriTags.get() != nullptr) {
             return *matchPriTags;
         }
 
diff --git a/src/mongo/crypto/sha_block_openssl.cpp b/src/mongo/crypto/sha_block_openssl.cpp
index c776985c3b7..be2e9a67db9 100644
--- a/src/mongo/crypto/sha_block_openssl.cpp
+++ b/src/mongo/crypto/sha_block_openssl.cpp
@@ -98,13 +98,13 @@ HashType computeHashImpl(const EVP_MD* md, std::initializer_list<ConstDataRange>
                                                                       EVP_MD_CTX_free);
 
     fassert(40379,
-            EVP_DigestInit_ex(digestCtx.get(), md, NULL) == 1 &&
+            EVP_DigestInit_ex(digestCtx.get(), md, nullptr) == 1 &&
                 std::all_of(begin(input),
                             end(input),
                             [&](const auto& i) {
                                 return EVP_DigestUpdate(digestCtx.get(), i.data(), i.length()) == 1;
                             }) &&
-                EVP_DigestFinal_ex(digestCtx.get(), output.data(), NULL) == 1);
+                EVP_DigestFinal_ex(digestCtx.get(), output.data(), nullptr) == 1);
     return output;
 }
 
@@ -117,7 +117,7 @@ void computeHmacImpl(const EVP_MD* md,
     std::unique_ptr<HMAC_CTX, decltype(&HMAC_CTX_free)> digestCtx(HMAC_CTX_new(), HMAC_CTX_free);
 
     fassert(40380,
-            HMAC_Init_ex(digestCtx.get(), key, keyLen, md, NULL) == 1 &&
+            HMAC_Init_ex(digestCtx.get(), key, keyLen, md, nullptr) == 1 &&
                 std::all_of(begin(input),
                             end(input),
                             [&](const auto& i) {
@@ -125,7 +125,7 @@ void computeHmacImpl(const EVP_MD* md,
                                                    reinterpret_cast<const unsigned char*>(i.data()),
                                                    i.length()) == 1;
                             }) &&
-                HMAC_Final(digestCtx.get(), output->data(), NULL) == 1);
+                HMAC_Final(digestCtx.get(), output->data(), nullptr) == 1);
 }
 
 }  // namespace
diff --git a/src/mongo/db/auth/authz_manager_external_state_local.cpp b/src/mongo/db/auth/authz_manager_external_state_local.cpp
index e3184bef814..7fa1f2ff5f0 100644
--- a/src/mongo/db/auth/authz_manager_external_state_local.cpp
+++ b/src/mongo/db/auth/authz_manager_external_state_local.cpp
@@ -574,7 +574,7 @@ private:
     void _refreshRoleGraph() {
         stdx::lock_guard<stdx::mutex> lk(_externalState->_roleGraphMutex);
         Status status = _externalState->_roleGraph.handleLogOp(
-            _opCtx, _op.c_str(), _nss, _o, _o2 ? &*_o2 : NULL);
+            _opCtx, _op.c_str(), _nss, _o, _o2 ? &*_o2 : nullptr);
 
         if (status == ErrorCodes::OplogOperationUnsupported) {
             _externalState->_roleGraph = RoleGraph();
diff --git a/src/mongo/db/auth/authz_manager_external_state_mock.cpp b/src/mongo/db/auth/authz_manager_external_state_mock.cpp
index 42ad4dd5b53..16cdd668604 100644
--- a/src/mongo/db/auth/authz_manager_external_state_mock.cpp
+++ b/src/mongo/db/auth/authz_manager_external_state_mock.cpp
@@ -90,7 +90,7 @@ void addPrivilegeObjectsOrWarningsToArrayElement(mutablebson::Element privileges
 }
 }  // namespace
 
-AuthzManagerExternalStateMock::AuthzManagerExternalStateMock() : _authzManager(NULL) {}
+AuthzManagerExternalStateMock::AuthzManagerExternalStateMock() : _authzManager(nullptr) {}
 AuthzManagerExternalStateMock::~AuthzManagerExternalStateMock() {}
 
 void AuthzManagerExternalStateMock::setAuthorizationManager(AuthorizationManager* authzManager) {
@@ -164,7 +164,7 @@ Status AuthzManagerExternalStateMock::insert(OperationContext* opCtx,
     _documents[collectionName].push_back(toInsert);
 
     if (_authzManager) {
-        _authzManager->logOp(opCtx, "i", collectionName, toInsert, NULL);
+        _authzManager->logOp(opCtx, "i", collectionName, toInsert, nullptr);
     }
 
     return Status::OK();
@@ -262,7 +262,7 @@ Status AuthzManagerExternalStateMock::remove(OperationContext* opCtx,
         ++n;
 
         if (_authzManager) {
-            _authzManager->logOp(opCtx, "d", collectionName, idQuery, NULL);
+            _authzManager->logOp(opCtx, "d", collectionName, idQuery, nullptr);
         }
     }
     *numRemoved = n;
diff --git a/src/mongo/db/auth/privilege_parser.cpp b/src/mongo/db/auth/privilege_parser.cpp
index 2cae5290649..7fb7ea38008 100644
--- a/src/mongo/db/auth/privilege_parser.cpp
+++ b/src/mongo/db/auth/privilege_parser.cpp
@@ -56,7 +56,7 @@ ParsedResource::~ParsedResource() {}
 
 bool ParsedResource::isValid(std::string* errMsg) const {
     std::string dummy;
-    if (errMsg == NULL) {
+    if (errMsg == nullptr) {
         errMsg = &dummy;
     }
 
@@ -273,7 +273,7 @@ ParsedPrivilege::~ParsedPrivilege() {}
 
 bool ParsedPrivilege::isValid(std::string* errMsg) const {
     std::string dummy;
-    if (errMsg == NULL) {
+    if (errMsg == nullptr) {
         errMsg = &dummy;
     }
 
diff --git a/src/mongo/db/auth/role_graph.cpp b/src/mongo/db/auth/role_graph.cpp
index 8093864dfe3..51f91a10ba8 100644
--- a/src/mongo/db/auth/role_graph.cpp
+++ b/src/mongo/db/auth/role_graph.cpp
@@ -132,19 +132,19 @@ Status RoleGraph::deleteRole(const RoleName& role) {
 
 RoleNameIterator RoleGraph::getDirectSubordinates(const RoleName& role) {
     if (!roleExists(role))
-        return RoleNameIterator(NULL);
+        return RoleNameIterator(nullptr);
     return makeRoleNameIteratorForContainer(_roleToSubordinates[role]);
 }
 
 RoleNameIterator RoleGraph::getIndirectSubordinates(const RoleName& role) {
     if (!roleExists(role))
-        return RoleNameIterator(NULL);
+        return RoleNameIterator(nullptr);
     return makeRoleNameIteratorForContainer(_roleToIndirectSubordinates[role]);
 }
 
 RoleNameIterator RoleGraph::getDirectMembers(const RoleName& role) {
     if (!roleExists(role))
-        return RoleNameIterator(NULL);
+        return RoleNameIterator(nullptr);
     return makeRoleNameIteratorForContainer(_roleToMembers[role]);
 }
 
diff --git a/src/mongo/db/auth/role_name.h b/src/mongo/db/auth/role_name.h
index 75aa6202920..ccabd86b4a2 100644
--- a/src/mongo/db/auth/role_name.h
+++ b/src/mongo/db/auth/role_name.h
@@ -134,7 +134,7 @@ public:
         Impl(){};
         virtual ~Impl(){};
         static Impl* clone(Impl* orig) {
-            return orig ? orig->doClone() : NULL;
+            return orig ? orig->doClone() : nullptr;
         }
         virtual bool more() const = 0;
         virtual const RoleName& get() const = 0;
diff --git a/src/mongo/db/catalog/collection_impl.h b/src/mongo/db/catalog/collection_impl.h
index 8657a48589f..25c85a660fb 100644
--- a/src/mongo/db/catalog/collection_impl.h
+++ b/src/mongo/db/catalog/collection_impl.h
@@ -330,7 +330,7 @@ public:
     }
 
     uint64_t getIndexSize(OperationContext* opCtx,
-                          BSONObjBuilder* details = NULL,
+                          BSONObjBuilder* details = nullptr,
                           int scale = 1) const final;
 
     /**
diff --git a/src/mongo/db/catalog/collection_info_cache_impl.cpp b/src/mongo/db/catalog/collection_info_cache_impl.cpp
index f08c5e3bbb1..bf4866b750a 100644
--- a/src/mongo/db/catalog/collection_info_cache_impl.cpp
+++ b/src/mongo/db/catalog/collection_info_cache_impl.cpp
@@ -167,7 +167,7 @@ void CollectionInfoCacheImpl::notifyOfQuery(OperationContext* opCtx,
     for (auto it = indexesUsed.begin(); it != indexesUsed.end(); ++it) {
         // This index should still exist, since the PlanExecutor would have been killed if the
         // index was dropped (and we would not get here).
-        dassert(NULL != _collection->getIndexCatalog()->findIndexByName(opCtx, *it));
+        dassert(nullptr != _collection->getIndexCatalog()->findIndexByName(opCtx, *it));
 
         _indexUsageTracker.recordIndexAccess(*it);
     }
@@ -175,7 +175,7 @@ void CollectionInfoCacheImpl::notifyOfQuery(OperationContext* opCtx,
 
 void CollectionInfoCacheImpl::clearQueryCache() {
     LOG(1) << _collection->ns() << ": clearing plan cache - collection info cache reset";
-    if (NULL != _planCache.get()) {
+    if (nullptr != _planCache.get()) {
         _planCache->clear();
     }
 }
diff --git a/src/mongo/db/catalog/database_holder_impl.cpp b/src/mongo/db/catalog/database_holder_impl.cpp
index 7d38bbc3c82..d499edbfc67 100644
--- a/src/mongo/db/catalog/database_holder_impl.cpp
+++ b/src/mongo/db/catalog/database_holder_impl.cpp
@@ -80,7 +80,7 @@ Database* DatabaseHolderImpl::getDb(OperationContext* opCtx, StringData ns) cons
         return it->second;
     }
 
-    return NULL;
+    return nullptr;
 }
 
 std::set<std::string> DatabaseHolderImpl::_getNamesWithConflictingCasing_inlock(StringData name) {
diff --git a/src/mongo/db/catalog/database_impl.cpp b/src/mongo/db/catalog/database_impl.cpp
index 8e7738e4e5f..ed556c88af4 100644
--- a/src/mongo/db/catalog/database_impl.cpp
+++ b/src/mongo/db/catalog/database_impl.cpp
@@ -583,7 +583,7 @@ void DatabaseImpl::_checkCanCreateCollection(OperationContext* opCtx,
                           << " bytes)",
             !nss.isNormal() || nss.size() <= NamespaceString::MaxNsCollectionLen);
 
-    uassert(17316, "cannot create a blank collection", nss.coll() > 0);
+    uassert(17316, "cannot create a blank collection", nss.coll() > nullptr);
     uassert(28838, "cannot create a non-capped oplog collection", options.capped || !nss.isOplog());
     uassert(ErrorCodes::DatabaseDropPending,
             str::stream() << "Cannot create collection " << nss
diff --git a/src/mongo/db/catalog/multi_index_block.cpp b/src/mongo/db/catalog/multi_index_block.cpp
index 2c03dce3e03..65c6ed1d142 100644
--- a/src/mongo/db/catalog/multi_index_block.cpp
+++ b/src/mongo/db/catalog/multi_index_block.cpp
@@ -575,7 +575,7 @@ Status MultiIndexBlock::dumpInsertsFromBulk(OperationContext* opCtx,
 
     invariant(opCtx->lockState()->isNoop() || !opCtx->lockState()->inAWriteUnitOfWork());
     for (size_t i = 0; i < _indexes.size(); i++) {
-        if (_indexes[i].bulk == NULL)
+        if (_indexes[i].bulk == nullptr)
             continue;
 
         // If 'dupRecords' is provided, it will be used to store all records that would result in
diff --git a/src/mongo/db/catalog/multi_index_block.h b/src/mongo/db/catalog/multi_index_block.h
index af53fa21e04..0d12e4630e6 100644
--- a/src/mongo/db/catalog/multi_index_block.h
+++ b/src/mongo/db/catalog/multi_index_block.h
@@ -297,7 +297,7 @@ private:
     struct IndexToBuild {
         std::unique_ptr<IndexCatalog::IndexBuildBlockInterface> block;
 
-        IndexAccessMethod* real = NULL;           // owned elsewhere
+        IndexAccessMethod* real = nullptr;        // owned elsewhere
         const MatchExpression* filterExpression;  // might be NULL, owned elsewhere
         std::unique_ptr<IndexAccessMethod::BulkBuilder> bulk;
 
diff --git a/src/mongo/db/client.cpp b/src/mongo/db/client.cpp
index b177bc24e07..8c1eb3c3bfb 100644
--- a/src/mongo/db/client.cpp
+++ b/src/mongo/db/client.cpp
@@ -117,13 +117,13 @@ ServiceContext::UniqueOperationContext Client::makeOperationContext() {
 
 void Client::setOperationContext(OperationContext* opCtx) {
     // We can only set the OperationContext once before resetting it.
-    invariant(opCtx != NULL && _opCtx == NULL);
+    invariant(opCtx != nullptr && _opCtx == nullptr);
     _opCtx = opCtx;
 }
 
 void Client::resetOperationContext() {
-    invariant(_opCtx != NULL);
-    _opCtx = NULL;
+    invariant(_opCtx != nullptr);
+    _opCtx = nullptr;
 }
 
 std::string Client::clientAddress(bool includePort) const {
diff --git a/src/mongo/db/cloner.cpp b/src/mongo/db/cloner.cpp
index 3e03837118f..730f3086e38 100644
--- a/src/mongo/db/cloner.cpp
+++ b/src/mongo/db/cloner.cpp
@@ -142,7 +142,7 @@ struct Cloner::Fun {
         auto db = databaseHolder->openDb(opCtx, _dbName);
 
         bool createdCollection = false;
-        Collection* collection = NULL;
+        Collection* collection = nullptr;
 
         collection = db->getCollection(opCtx, to_collection);
         if (!collection) {
@@ -177,7 +177,7 @@ struct Cloner::Fun {
 
         while (i.moreInCurrentBatch()) {
             if (numSeen % 128 == 127) {
-                time_t now = time(0);
+                time_t now = time(nullptr);
                 if (now - lastLog >= 60) {
                     // report progress
                     if (lastLog)
@@ -205,13 +205,13 @@ struct Cloner::Fun {
                 db = databaseHolder->getDb(opCtx, _dbName);
                 uassert(28593,
                         str::stream() << "Database " << _dbName << " dropped while cloning",
-                        db != NULL);
+                        db != nullptr);
 
                 collection = db->getCollection(opCtx, to_collection);
                 uassert(28594,
                         str::stream() << "Collection " << to_collection.ns()
                                       << " dropped while cloning",
-                        collection != NULL);
+                        collection != nullptr);
             }
 
             BSONObj tmp = i.nextSafe();
@@ -271,9 +271,9 @@ struct Cloner::Fun {
             });
 
             static Rarely sampler;
-            if (sampler.tick() && (time(0) - saveLast > 60)) {
+            if (sampler.tick() && (time(nullptr) - saveLast > 60)) {
                 log() << numSeen << " objects cloned so far from collection " << from_collection;
-                saveLast = time(0);
+                saveLast = time(nullptr);
             }
         }
     }
@@ -310,7 +310,7 @@ void Cloner::copy(OperationContext* opCtx,
     f.from_options = from_opts;
     f.from_id_index = from_id_index;
     f.to_collection = to_collection;
-    f.saveLast = time(0);
+    f.saveLast = time(nullptr);
     f._opts = opts;
 
     int options = QueryOption_NoCursorTimeout | (opts.slaveOk ? QueryOption_SlaveOk : 0) |
@@ -320,7 +320,7 @@ void Cloner::copy(OperationContext* opCtx,
         _conn->query(std::function<void(DBClientCursorBatchIterator&)>(f),
                      from_collection,
                      query,
-                     0,
+                     nullptr,
                      options);
     }
 
diff --git a/src/mongo/db/commands/dbcommands.cpp b/src/mongo/db/commands/dbcommands.cpp
index 2f960430e2a..71343fa05e4 100644
--- a/src/mongo/db/commands/dbcommands.cpp
+++ b/src/mongo/db/commands/dbcommands.cpp
@@ -484,7 +484,7 @@ public:
                                                                          keyPattern,
                                                                          true);  // requireSingleKey
 
-            if (idx == NULL) {
+            if (idx == nullptr) {
                 errmsg = "couldn't find valid index containing key pattern";
                 return false;
             }
diff --git a/src/mongo/db/commands/dbcommands_d.cpp b/src/mongo/db/commands/dbcommands_d.cpp
index 2681ed180b2..5b83d1e9877 100644
--- a/src/mongo/db/commands/dbcommands_d.cpp
+++ b/src/mongo/db/commands/dbcommands_d.cpp
@@ -265,7 +265,7 @@ public:
 
             BSONObj obj;
             PlanExecutor::ExecState state;
-            while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
+            while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
                 BSONElement ne = obj["n"];
                 verify(ne.isNumber());
                 int myn = ne.numberInt();
diff --git a/src/mongo/db/commands/dbhash.cpp b/src/mongo/db/commands/dbhash.cpp
index 7dc15854506..b24fcc3fd45 100644
--- a/src/mongo/db/commands/dbhash.cpp
+++ b/src/mongo/db/commands/dbhash.cpp
@@ -374,8 +374,8 @@ private:
         long long n = 0;
         PlanExecutor::ExecState state;
         BSONObj c;
-        verify(NULL != exec.get());
-        while (PlanExecutor::ADVANCED == (state = exec->getNext(&c, NULL))) {
+        verify(nullptr != exec.get());
+        while (PlanExecutor::ADVANCED == (state = exec->getNext(&c, nullptr))) {
             md5_append(&st, (const md5_byte_t*)c.objdata(), c.objsize());
             n++;
         }
diff --git a/src/mongo/db/commands/distinct.cpp b/src/mongo/db/commands/distinct.cpp
index e31a0843f2c..7d00315fd98 100644
--- a/src/mongo/db/commands/distinct.cpp
+++ b/src/mongo/db/commands/distinct.cpp
@@ -239,7 +239,7 @@ public:
 
         BSONObj obj;
         PlanExecutor::ExecState state;
-        while (PlanExecutor::ADVANCED == (state = executor.getValue()->getNext(&obj, NULL))) {
+        while (PlanExecutor::ADVANCED == (state = executor.getValue()->getNext(&obj, nullptr))) {
             // Distinct expands arrays.
             //
             // If our query is covered, each value of the key should be in the index key and
diff --git a/src/mongo/db/commands/getmore_cmd.cpp b/src/mongo/db/commands/getmore_cmd.cpp
index 83d2c3c5dcc..1549ca4f12b 100644
--- a/src/mongo/db/commands/getmore_cmd.cpp
+++ b/src/mongo/db/commands/getmore_cmd.cpp
@@ -277,7 +277,7 @@ public:
             BSONObj obj;
             try {
                 while (!FindCommon::enoughForGetMore(request.batchSize.value_or(0), *numResults) &&
-                       PlanExecutor::ADVANCED == (*state = exec->getNext(&obj, NULL))) {
+                       PlanExecutor::ADVANCED == (*state = exec->getNext(&obj, nullptr))) {
                     // If adding this object will cause us to exceed the message size limit, then we
                     // stash it for later.
                     if (!FindCommon::haveSpaceForNext(obj, *numResults, nextBatch->bytesUsed())) {
diff --git a/src/mongo/db/commands/index_filter_commands.cpp b/src/mongo/db/commands/index_filter_commands.cpp
index 6df4e890028..b5c65b1e2be 100644
--- a/src/mongo/db/commands/index_filter_commands.cpp
+++ b/src/mongo/db/commands/index_filter_commands.cpp
@@ -67,9 +67,9 @@ static Status getQuerySettingsAndPlanCache(OperationContext* opCtx,
                                            const string& ns,
                                            QuerySettings** querySettingsOut,
                                            PlanCache** planCacheOut) {
-    *querySettingsOut = NULL;
-    *planCacheOut = NULL;
-    if (NULL == collection) {
+    *querySettingsOut = nullptr;
+    *planCacheOut = nullptr;
+    if (nullptr == collection) {
         return Status(ErrorCodes::BadValue, "no such collection");
     }
 
diff --git a/src/mongo/db/commands/list_collections.cpp b/src/mongo/db/commands/list_collections.cpp
index 5c116d3a500..29cd4b02a29 100644
--- a/src/mongo/db/commands/list_collections.cpp
+++ b/src/mongo/db/commands/list_collections.cpp
@@ -366,7 +366,7 @@ public:
 
             for (long long objCount = 0; objCount < batchSize; objCount++) {
                 BSONObj next;
-                PlanExecutor::ExecState state = exec->getNext(&next, NULL);
+                PlanExecutor::ExecState state = exec->getNext(&next, nullptr);
                 if (state == PlanExecutor::IS_EOF) {
                     break;
                 }
diff --git a/src/mongo/db/commands/list_indexes.cpp b/src/mongo/db/commands/list_indexes.cpp
index bb0b394b273..59721e91ce4 100644
--- a/src/mongo/db/commands/list_indexes.cpp
+++ b/src/mongo/db/commands/list_indexes.cpp
@@ -199,7 +199,7 @@ public:
 
             for (long long objCount = 0; objCount < batchSize; objCount++) {
                 BSONObj next;
-                PlanExecutor::ExecState state = exec->getNext(&next, NULL);
+                PlanExecutor::ExecState state = exec->getNext(&next, nullptr);
                 if (state == PlanExecutor::IS_EOF) {
                     break;
                 }
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index f936129a526..d4a8b7da1b3 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -266,7 +266,7 @@ void JSMapper::map(const BSONObj& o) {
 BSONObj JSFinalizer::finalize(const BSONObj& o) {
     Scope* s = _func.scope();
 
-    s->invokeSafe(_func.func(), &o, 0);
+    s->invokeSafe(_func.func(), &o, nullptr);
 
     // We don't want to use o.objsize() to size b since there are many cases where the point of
     // finalize is converting many fields to 1
@@ -371,7 +371,7 @@ void JSReducer::_reduce(const BSONList& tuples, BSONObj& key, int& endSizeEstima
 
     Scope* s = _func.scope();
 
-    s->invokeSafe(_func.func(), &args, 0);
+    s->invokeSafe(_func.func(), &args, nullptr);
     ++numReduces;
 
     if (s->type("__returnValue") == Array) {
@@ -669,7 +669,7 @@ void State::appendResults(BSONObjBuilder& final) {
             "  result.push({_id: key, value: map[key]});"
             "}"
             "return result;");
-        _scope->invoke(getResult, 0, 0, 0, false);
+        _scope->invoke(getResult, nullptr, nullptr, 0, false);
         BSONObj obj = _scope->getObject("__returnValue");
         final.append("results", BSONArray(obj));
         return;
@@ -832,7 +832,7 @@ void State::insert(const NamespaceString& nss, const BSONObj& o) {
         WriteUnitOfWork wuow(_opCtx);
         BSONObjBuilder b;
         if (!o.hasField("_id")) {
-            b.appendOID("_id", NULL, true);
+            b.appendOID("_id", nullptr, true);
         }
         b.appendElements(o);
         BSONObj bo = b.obj();
@@ -934,7 +934,7 @@ State::~State() {
         try {
             ScriptingFunction cleanup =
                 _scope->createFunction("delete _emitCt; delete _keyCt; delete _mrMap;");
-            _scope->invoke(cleanup, 0, 0, 0, true);
+            _scope->invoke(cleanup, nullptr, nullptr, 0, true);
         } catch (const DBException&) {
             // not important because properties will be reset if scope is reused
             LOG(1) << "MapReduce terminated during state destruction";
@@ -962,7 +962,7 @@ void State::init() {
     _config.reducer->init(this);
     if (_config.finalizer)
         _config.finalizer->init(this);
-    _scope->setBoolean("_doFinal", _config.finalizer.get() != 0);
+    _scope->setBoolean("_doFinal", _config.finalizer.get() != nullptr);
 
     switchMode(_config.jsMode);  // set up js-mode based on Config
 
@@ -979,7 +979,7 @@ void State::init() {
         "if (typeof(_mrMap) === 'undefined') {"
         "  _mrMap = {};"
         "}");
-    _scope->invoke(init, 0, 0, 0, true);
+    _scope->invoke(init, nullptr, nullptr, 0, true);
 
     // js function to run reduce on all keys
     // redfunc = _scope->createFunction("for (var key in hashmap) {  print('Key is ' + key);
@@ -1085,7 +1085,7 @@ void State::bailFromJS() {
 
     // reduce and reemit into c++
     switchMode(false);
-    _scope->invoke(_reduceAndEmit, 0, 0, 0, true);
+    _scope->invoke(_reduceAndEmit, nullptr, nullptr, 0, true);
     // need to get the real number emitted so far
     _numEmits = _scope->getNumberInt("_emitCt");
     _config.reducer->numReduces = _scope->getNumberInt("_redCt");
@@ -1128,10 +1128,10 @@ void State::finalReduce(OperationContext* opCtx, CurOp* curOp) {
         // apply the reduce within JS
         if (_onDisk) {
             _scope->injectNative("_nativeToTemp", _nativeToTemp, this);
-            _scope->invoke(_reduceAndFinalizeAndInsert, 0, 0, 0, true);
+            _scope->invoke(_reduceAndFinalizeAndInsert, nullptr, nullptr, 0, true);
             return;
         } else {
-            _scope->invoke(_reduceAndFinalize, 0, 0, 0, true);
+            _scope->invoke(_reduceAndFinalize, nullptr, nullptr, 0, true);
             return;
         }
     }
@@ -1220,7 +1220,7 @@ void State::finalReduce(OperationContext* opCtx, CurOp* curOp) {
         // iterate over all sorted objects
         BSONObj o;
         PlanExecutor::ExecState state;
-        while (PlanExecutor::ADVANCED == (state = exec->getNext(&o, NULL))) {
+        while (PlanExecutor::ADVANCED == (state = exec->getNext(&o, nullptr))) {
             o = o.getOwned();  // we will be accessing outside of the lock
             pm.hit();
 
@@ -1357,7 +1357,7 @@ void State::reduceAndSpillInMemoryStateIfNeeded() {
         } else if (dupCt > (keyCt * _config.reduceTriggerRatio)) {
             // reduce now to lower mem usage
             Timer t;
-            _scope->invoke(_reduceAll, 0, 0, 0, true);
+            _scope->invoke(_reduceAll, nullptr, nullptr, 0, true);
             LOG(3) << "  MR - did reduceAll: keys=" << keyCt << " dups=" << dupCt
                    << " newKeys=" << _scope->getNumberInt("_keyCt") << " time=" << t.millis()
                    << "ms";
@@ -1549,7 +1549,7 @@ public:
 
                 BSONObj o;
                 PlanExecutor::ExecState execState;
-                while (PlanExecutor::ADVANCED == (execState = exec->getNext(&o, NULL))) {
+                while (PlanExecutor::ADVANCED == (execState = exec->getNext(&o, nullptr))) {
                     o = o.getOwned();  // The object will be accessed outside of collection lock
 
                     // Check to see if this is a new object we don't own yet because of a chunk
diff --git a/src/mongo/db/commands/plan_cache_commands.cpp b/src/mongo/db/commands/plan_cache_commands.cpp
index 6a89ca96bdf..c9a5566b11f 100644
--- a/src/mongo/db/commands/plan_cache_commands.cpp
+++ b/src/mongo/db/commands/plan_cache_commands.cpp
@@ -64,9 +64,9 @@ static Status getPlanCache(OperationContext* opCtx,
                            Collection* collection,
                            const string& ns,
                            PlanCache** planCacheOut) {
-    *planCacheOut = NULL;
+    *planCacheOut = nullptr;
 
-    if (NULL == collection) {
+    if (nullptr == collection) {
         return Status(ErrorCodes::BadValue, "no such collection");
     }
 
diff --git a/src/mongo/db/commands/server_status.cpp b/src/mongo/db/commands/server_status.cpp
index 75b5f7fe9e6..84b2eae0707 100644
--- a/src/mongo/db/commands/server_status.cpp
+++ b/src/mongo/db/commands/server_status.cpp
@@ -96,7 +96,7 @@ public:
         result.append("version", VersionInfoInterface::instance().version());
         result.append("process", serverGlobalParams.binaryName);
         result.append("pid", ProcessId::getCurrent().asLongLong());
-        result.append("uptime", (double)(time(0) - serverGlobalParams.started));
+        result.append("uptime", (double)(time(nullptr) - serverGlobalParams.started));
         auto uptime = clock->now() - _started;
         result.append("uptimeMillis", durationCount<Milliseconds>(uptime));
         result.append("uptimeEstimate", durationCount<Seconds>(uptime));
@@ -132,7 +132,7 @@ public:
         }
 
         // --- counters
-        bool includeMetricTree = MetricTree::theMetricTree != NULL;
+        bool includeMetricTree = MetricTree::theMetricTree != nullptr;
         if (cmdObj["metrics"].type() && !cmdObj["metrics"].trueValue())
             includeMetricTree = false;
 
@@ -144,7 +144,8 @@ public:
 
         {
             RamLog::LineIterator rl(RamLog::get("warnings"));
-            if (rl.lastWrite() >= time(0) - (10 * 60)) {  // only show warnings from last 10 minutes
+            if (rl.lastWrite() >=
+                time(nullptr) - (10 * 60)) {  // only show warnings from last 10 minutes
                 BSONArrayBuilder arr(result.subarrayStart("warnings"));
                 while (rl.more()) {
                     arr.append(rl.next());
diff --git a/src/mongo/db/commands/server_status_internal.cpp b/src/mongo/db/commands/server_status_internal.cpp
index 738b22e8945..7556eee5e01 100644
--- a/src/mongo/db/commands/server_status_internal.cpp
+++ b/src/mongo/db/commands/server_status_internal.cpp
@@ -41,7 +41,7 @@ using std::endl;
 using std::map;
 using std::string;
 
-MetricTree* MetricTree::theMetricTree = NULL;
+MetricTree* MetricTree::theMetricTree = nullptr;
 
 void MetricTree::add(ServerStatusMetric* metric) {
     string name = metric->getMetricName();
diff --git a/src/mongo/db/commands/server_status_metric.cpp b/src/mongo/db/commands/server_status_metric.cpp
index d56a2970ec6..8e8b749b729 100644
--- a/src/mongo/db/commands/server_status_metric.cpp
+++ b/src/mongo/db/commands/server_status_metric.cpp
@@ -37,7 +37,7 @@ using std::string;
 
 ServerStatusMetric::ServerStatusMetric(const string& nameIn)
     : _name(nameIn), _leafName(_parseLeafName(nameIn)) {
-    if (MetricTree::theMetricTree == 0)
+    if (MetricTree::theMetricTree == nullptr)
         MetricTree::theMetricTree = new MetricTree();
     MetricTree::theMetricTree->add(this);
 }
diff --git a/src/mongo/db/commands/user_management_commands.cpp b/src/mongo/db/commands/user_management_commands.cpp
index c47ca33f94c..645820be5ff 100644
--- a/src/mongo/db/commands/user_management_commands.cpp
+++ b/src/mongo/db/commands/user_management_commands.cpp
@@ -882,7 +882,7 @@ public:
         audit::logCreateUser(Client::getCurrent(),
                              args.userName,
                              args.hasPassword,
-                             args.hasCustomData ? &args.customData : NULL,
+                             args.hasCustomData ? &args.customData : nullptr,
                              args.roles,
                              args.authenticationRestrictions);
         status = insertPrivilegeDocument(opCtx, userObj);
@@ -1003,8 +1003,8 @@ public:
         audit::logUpdateUser(Client::getCurrent(),
                              args.userName,
                              args.hasPassword,
-                             args.hasCustomData ? &args.customData : NULL,
-                             args.hasRoles ? &args.roles : NULL,
+                             args.hasCustomData ? &args.customData : nullptr,
+                             args.hasRoles ? &args.roles : nullptr,
                              args.authenticationRestrictions);
 
         status = updatePrivilegeDocument(
@@ -2437,14 +2437,14 @@ public:
             audit::logCreateUser(Client::getCurrent(),
                                  userName,
                                  hasPwd,
-                                 userObj.hasField("customData") ? &customData : NULL,
+                                 userObj.hasField("customData") ? &customData : nullptr,
                                  roles,
                                  authenticationRestrictions);
         } else {
             audit::logUpdateUser(Client::getCurrent(),
                                  userName,
                                  hasPwd,
-                                 userObj.hasField("customData") ? &customData : NULL,
+                                 userObj.hasField("customData") ? &customData : nullptr,
                                  &roles,
                                  authenticationRestrictions);
         }
diff --git a/src/mongo/db/commands/validate.cpp b/src/mongo/db/commands/validate.cpp
index 586c87792d7..d30c820e747 100644
--- a/src/mongo/db/commands/validate.cpp
+++ b/src/mongo/db/commands/validate.cpp
@@ -125,7 +125,7 @@ public:
 
         AutoGetDb ctx(opCtx, nss.db(), MODE_IX);
         Lock::CollectionLock collLk(opCtx, nss, MODE_X);
-        Collection* collection = ctx.getDb() ? ctx.getDb()->getCollection(opCtx, nss) : NULL;
+        Collection* collection = ctx.getDb() ? ctx.getDb()->getCollection(opCtx, nss) : nullptr;
         if (!collection) {
             if (ctx.getDb() && ViewCatalog::get(ctx.getDb())->lookup(opCtx, nss.ns())) {
                 uasserted(ErrorCodes::CommandNotSupportedOnView, "Cannot validate a view");
diff --git a/src/mongo/db/concurrency/lock_request_list.h b/src/mongo/db/concurrency/lock_request_list.h
index c9009cdec4f..5423a11792f 100644
--- a/src/mongo/db/concurrency/lock_request_list.h
+++ b/src/mongo/db/concurrency/lock_request_list.h
@@ -48,10 +48,10 @@ class LockRequestList {
 public:
     void push_front(LockRequest* request) {
         // Sanity check that we do not reuse entries without cleaning them up
-        invariant(request->next == NULL);
-        invariant(request->prev == NULL);
+        invariant(request->next == nullptr);
+        invariant(request->prev == nullptr);
 
-        if (_front == NULL) {
+        if (_front == nullptr) {
             _front = _back = request;
         } else {
             request->next = _front;
@@ -63,10 +63,10 @@ public:
 
     void push_back(LockRequest* request) {
         // Sanity check that we do not reuse entries without cleaning them up
-        invariant(request->next == NULL);
-        invariant(request->prev == NULL);
+        invariant(request->next == nullptr);
+        invariant(request->prev == nullptr);
 
-        if (_front == NULL) {
+        if (_front == nullptr) {
             _front = _back = request;
         } else {
             request->prev = _back;
@@ -77,28 +77,28 @@ public:
     }
 
     void remove(LockRequest* request) {
-        if (request->prev != NULL) {
+        if (request->prev != nullptr) {
             request->prev->next = request->next;
         } else {
             _front = request->next;
         }
 
-        if (request->next != NULL) {
+        if (request->next != nullptr) {
             request->next->prev = request->prev;
         } else {
             _back = request->prev;
         }
 
-        request->prev = NULL;
-        request->next = NULL;
+        request->prev = nullptr;
+        request->next = nullptr;
     }
 
     void reset() {
-        _front = _back = NULL;
+        _front = _back = nullptr;
     }
 
     bool empty() const {
-        return _front == NULL;
+        return _front == nullptr;
     }
 
     // Pointers to the beginning and the end of the list
diff --git a/src/mongo/db/db.cpp b/src/mongo/db/db.cpp
index df1f2908406..1d5dd2b582c 100644
--- a/src/mongo/db/db.cpp
+++ b/src/mongo/db/db.cpp
@@ -212,7 +212,7 @@ void logStartup(OperationContext* opCtx) {
     toLog.append("_id", id.str());
     toLog.append("hostname", getHostNameCached());
 
-    toLog.appendTimeT("startTime", time(0));
+    toLog.appendTimeT("startTime", time(nullptr));
     toLog.append("startTimeLocal", dateToCtimeString(Date_t::now()));
 
     toLog.append("cmdLine", serverGlobalParams.parsedOpts);
diff --git a/src/mongo/db/dbdirectclient.h b/src/mongo/db/dbdirectclient.h
index ae348ab93bd..c700baf3d8f 100644
--- a/src/mongo/db/dbdirectclient.h
+++ b/src/mongo/db/dbdirectclient.h
@@ -62,7 +62,7 @@ public:
                                                   Query query,
                                                   int nToReturn = 0,
                                                   int nToSkip = 0,
-                                                  const BSONObj* fieldsToReturn = 0,
+                                                  const BSONObj* fieldsToReturn = nullptr,
                                                   int queryOptions = 0,
                                                   int batchSize = 0);
 
@@ -77,9 +77,9 @@ public:
     virtual bool call(Message& toSend,
                       Message& response,
                       bool assertOk = true,
-                      std::string* actualServer = 0);
+                      std::string* actualServer = nullptr);
 
-    virtual void say(Message& toSend, bool isRetry = false, std::string* actualServer = 0);
+    virtual void say(Message& toSend, bool isRetry = false, std::string* actualServer = nullptr);
 
     virtual unsigned long long count(const std::string& ns,
                                      const BSONObj& query = BSONObj(),
diff --git a/src/mongo/db/dbhelpers.cpp b/src/mongo/db/dbhelpers.cpp
index 1447ad18389..e9bfdf9dff1 100644
--- a/src/mongo/db/dbhelpers.cpp
+++ b/src/mongo/db/dbhelpers.cpp
@@ -176,7 +176,7 @@ bool Helpers::getSingleton(OperationContext* opCtx, const char* ns, BSONObj& res
     AutoGetCollectionForReadCommand ctx(opCtx, NamespaceString(ns));
     auto exec =
         InternalPlanner::collectionScan(opCtx, ns, ctx.getCollection(), PlanExecutor::NO_YIELD);
-    PlanExecutor::ExecState state = exec->getNext(&result, NULL);
+    PlanExecutor::ExecState state = exec->getNext(&result, nullptr);
 
     CurOp::get(opCtx)->done();
 
@@ -195,7 +195,7 @@ bool Helpers::getLast(OperationContext* opCtx, const char* ns, BSONObj& result)
     AutoGetCollectionForReadCommand autoColl(opCtx, NamespaceString(ns));
     auto exec = InternalPlanner::collectionScan(
         opCtx, ns, autoColl.getCollection(), PlanExecutor::NO_YIELD, InternalPlanner::BACKWARD);
-    PlanExecutor::ExecState state = exec->getNext(&result, NULL);
+    PlanExecutor::ExecState state = exec->getNext(&result, nullptr);
 
     // Non-yielding collection scans from InternalPlanner will never error.
     invariant(PlanExecutor::ADVANCED == state || PlanExecutor::IS_EOF == state);
diff --git a/src/mongo/db/dbhelpers.h b/src/mongo/db/dbhelpers.h
index 47af0b8ffc2..246130853ff 100644
--- a/src/mongo/db/dbhelpers.h
+++ b/src/mongo/db/dbhelpers.h
@@ -83,8 +83,8 @@ struct Helpers {
                          StringData ns,
                          BSONObj query,
                          BSONObj& result,
-                         bool* nsFound = 0,
-                         bool* indexFound = 0);
+                         bool* nsFound = nullptr,
+                         bool* indexFound = nullptr);
 
     /* TODO: should this move into Collection?
      * uasserts if no _id index.
diff --git a/src/mongo/db/dbmessage.cpp b/src/mongo/db/dbmessage.cpp
index f893b53eee9..75f2ecb8fbc 100644
--- a/src/mongo/db/dbmessage.cpp
+++ b/src/mongo/db/dbmessage.cpp
@@ -36,7 +36,7 @@
 
 namespace mongo {
 
-DbMessage::DbMessage(const Message& msg) : _msg(msg), _nsStart(NULL), _mark(NULL), _nsLen(0) {
+DbMessage::DbMessage(const Message& msg) : _msg(msg), _nsStart(nullptr), _mark(nullptr), _nsLen(0) {
     // for received messages, Message has only one buffer
     _theEnd = _msg.singleData().data() + _msg.singleData().dataLen();
     _nextjsobj = _msg.singleData().data();
@@ -89,7 +89,7 @@ const char* DbMessage::getArray(size_t count) const {
 BSONObj DbMessage::nextJsObj() {
     uassert(ErrorCodes::InvalidBSON,
             "Client Error: Remaining data too small for BSON object",
-            _nextjsobj != NULL && _theEnd - _nextjsobj >= 5);
+            _nextjsobj != nullptr && _theEnd - _nextjsobj >= 5);
 
     if (serverGlobalParams.objcheck) {
         Status status = validateBSON(
@@ -105,12 +105,12 @@ BSONObj DbMessage::nextJsObj() {
 
     _nextjsobj += js.objsize();
     if (_nextjsobj >= _theEnd)
-        _nextjsobj = NULL;
+        _nextjsobj = nullptr;
     return js;
 }
 
-void DbMessage::markReset(const char* toMark = NULL) {
-    if (toMark == NULL) {
+void DbMessage::markReset(const char* toMark = nullptr) {
+    if (toMark == nullptr) {
         toMark = _mark;
     }
 
diff --git a/src/mongo/db/dbmessage.h b/src/mongo/db/dbmessage.h
index 7828e2938f1..f6281c3614c 100644
--- a/src/mongo/db/dbmessage.h
+++ b/src/mongo/db/dbmessage.h
@@ -241,7 +241,7 @@ public:
 
     /* for insert and update msgs */
     bool moreJSObjs() const {
-        return _nextjsobj != 0 && _nextjsobj != _theEnd;
+        return _nextjsobj != nullptr && _nextjsobj != _theEnd;
     }
 
     BSONObj nextJsObj();
diff --git a/src/mongo/db/exec/collection_scan.cpp b/src/mongo/db/exec/collection_scan.cpp
index f416f8f3f9d..6a1e64dd30f 100644
--- a/src/mongo/db/exec/collection_scan.cpp
+++ b/src/mongo/db/exec/collection_scan.cpp
@@ -240,7 +240,7 @@ void CollectionScan::doReattachToOperationContext() {
 
 unique_ptr<PlanStageStats> CollectionScan::getStats() {
     // Add a BSON representation of the filter to the stats tree, if there is one.
-    if (NULL != _filter) {
+    if (nullptr != _filter) {
         BSONObjBuilder bob;
         _filter->serialize(&bob);
         _commonStats.filter = bob.obj();
diff --git a/src/mongo/db/exec/fetch.cpp b/src/mongo/db/exec/fetch.cpp
index c8abe5fa26b..2e30f53e302 100644
--- a/src/mongo/db/exec/fetch.cpp
+++ b/src/mongo/db/exec/fetch.cpp
@@ -186,7 +186,7 @@ unique_ptr<PlanStageStats> FetchStage::getStats() {
     _commonStats.isEOF = isEOF();
 
     // Add a BSON representation of the filter to the stats tree, if there is one.
-    if (NULL != _filter) {
+    if (nullptr != _filter) {
         BSONObjBuilder bob;
         _filter->serialize(&bob);
         _commonStats.filter = bob.obj();
diff --git a/src/mongo/db/exec/filter.h b/src/mongo/db/exec/filter.h
index dea812de1a8..dcc079c9136 100644
--- a/src/mongo/db/exec/filter.h
+++ b/src/mongo/db/exec/filter.h
@@ -151,21 +151,21 @@ public:
      * Returns false if 'wsm' does not satisfy the filter.
      */
     static bool passes(WorkingSetMember* wsm, const MatchExpression* filter) {
-        if (NULL == filter) {
+        if (nullptr == filter) {
             return true;
         }
         WorkingSetMatchableDocument doc(wsm);
-        return filter->matches(&doc, NULL);
+        return filter->matches(&doc, nullptr);
     }
 
     static bool passes(const BSONObj& keyData,
                        const BSONObj& keyPattern,
                        const MatchExpression* filter) {
-        if (NULL == filter) {
+        if (nullptr == filter) {
             return true;
         }
         IndexKeyMatchableDocument doc(keyData, keyPattern);
-        return filter->matches(&doc, NULL);
+        return filter->matches(&doc, nullptr);
     }
 };
 
diff --git a/src/mongo/db/exec/geo_near.cpp b/src/mongo/db/exec/geo_near.cpp
index 27b04a5be73..5fa04b917db 100644
--- a/src/mongo/db/exec/geo_near.cpp
+++ b/src/mongo/db/exec/geo_near.cpp
@@ -80,14 +80,14 @@ namespace {
 struct StoredGeometry {
     static StoredGeometry* parseFrom(const BSONElement& element) {
         if (!element.isABSONObj())
-            return NULL;
+            return nullptr;
 
         unique_ptr<StoredGeometry> stored(new StoredGeometry);
 
         // GeoNear stage can only be run with an existing index
         // Therefore, it is always safe to skip geometry validation
         if (!stored->geometry.parseFromStorage(element, true).isOK())
-            return NULL;
+            return nullptr;
         stored->element = element;
         return stored.release();
     }
@@ -343,7 +343,7 @@ void GeoNear2DStage::DensityEstimator::buildIndexScan(OperationContext* opCtx,
     IndexBoundsBuilder::intersectize(oil, &scanParams.bounds.fields[twoDFieldPosition]);
 
     invariant(!_indexScan);
-    _indexScan = new IndexScan(opCtx, scanParams, workingSet, NULL);
+    _indexScan = new IndexScan(opCtx, scanParams, workingSet, nullptr);
     _children->emplace_back(_indexScan);
 }
 
@@ -461,7 +461,7 @@ PlanStage::StageState GeoNear2DStage::initialize(OperationContext* opCtx,
         invariant(_boundsIncrement > 0.0);
 
         // Clean up
-        _densityEstimator.reset(NULL);
+        _densityEstimator.reset(nullptr);
     }
 
     return state;
@@ -530,7 +530,7 @@ public:
 
     unique_ptr<MatchExpression> shallowClone() const final {
         MONGO_UNREACHABLE;
-        return NULL;
+        return nullptr;
     }
 
 private:
@@ -897,7 +897,7 @@ void GeoNear2DSphereStage::DensityEstimator::buildIndexScan(OperationContext* op
 
     // Index scan
     invariant(!_indexScan);
-    _indexScan = new IndexScan(opCtx, scanParams, workingSet, NULL);
+    _indexScan = new IndexScan(opCtx, scanParams, workingSet, nullptr);
     _children->emplace_back(_indexScan);
 }
 
@@ -1003,7 +1003,7 @@ PlanStage::StageState GeoNear2DSphereStage::initialize(OperationContext* opCtx,
         invariant(_boundsIncrement > 0.0);
 
         // Clean up
-        _densityEstimator.reset(NULL);
+        _densityEstimator.reset(nullptr);
     }
 
     return state;
diff --git a/src/mongo/db/exec/geo_near.h b/src/mongo/db/exec/geo_near.h
index 2fd2700db86..33295de7b39 100644
--- a/src/mongo/db/exec/geo_near.h
+++ b/src/mongo/db/exec/geo_near.h
@@ -47,7 +47,8 @@ namespace mongo {
  * Generic parameters for a GeoNear search
  */
 struct GeoNearParams {
-    GeoNearParams() : filter(NULL), nearQuery(NULL), addPointMeta(false), addDistMeta(false) {}
+    GeoNearParams()
+        : filter(nullptr), nearQuery(nullptr), addPointMeta(false), addDistMeta(false) {}
 
     // MatchExpression to apply to the index keys and fetched documents
     // Not owned here, owned by solution nodes
diff --git a/src/mongo/db/exec/idhack.cpp b/src/mongo/db/exec/idhack.cpp
index b54a9d06a52..8cd352fa046 100644
--- a/src/mongo/db/exec/idhack.cpp
+++ b/src/mongo/db/exec/idhack.cpp
@@ -58,7 +58,7 @@ IDHackStage::IDHackStage(OperationContext* opCtx,
       _workingSet(ws),
       _key(query->getQueryObj()["_id"].wrap()) {
     _specificStats.indexName = descriptor->indexName();
-    if (NULL != query->getProj()) {
+    if (nullptr != query->getProj()) {
         _addKeyMetadata = query->getProj()->wantIndexKey();
     }
 }
diff --git a/src/mongo/db/exec/index_scan.cpp b/src/mongo/db/exec/index_scan.cpp
index 22c0cfe5898..f74743629bb 100644
--- a/src/mongo/db/exec/index_scan.cpp
+++ b/src/mongo/db/exec/index_scan.cpp
@@ -261,7 +261,7 @@ std::unique_ptr<PlanStageStats> IndexScan::getStats() {
     // catalog information here.
 
     // Add a BSON representation of the filter to the stats tree, if there is one.
-    if (NULL != _filter) {
+    if (nullptr != _filter) {
         BSONObjBuilder bob;
         _filter->serialize(&bob);
         _commonStats.filter = bob.obj();
diff --git a/src/mongo/db/exec/merge_sort.h b/src/mongo/db/exec/merge_sort.h
index 6992214064b..5a25a3243cd 100644
--- a/src/mongo/db/exec/merge_sort.h
+++ b/src/mongo/db/exec/merge_sort.h
@@ -76,7 +76,7 @@ public:
 
 private:
     struct StageWithValue {
-        StageWithValue() : id(WorkingSet::INVALID_ID), stage(NULL) {}
+        StageWithValue() : id(WorkingSet::INVALID_ID), stage(nullptr) {}
         WorkingSetID id;
         PlanStage* stage;
     };
@@ -135,7 +135,7 @@ private:
 // Parameters that must be provided to a MergeSortStage
 class MergeSortStageParams {
 public:
-    MergeSortStageParams() : collator(NULL), dedup(true) {}
+    MergeSortStageParams() : collator(nullptr), dedup(true) {}
 
     // How we're sorting.
     BSONObj pattern;
diff --git a/src/mongo/db/exec/multi_iterator.h b/src/mongo/db/exec/multi_iterator.h
index 93eea472d0c..88dd5586ff7 100644
--- a/src/mongo/db/exec/multi_iterator.h
+++ b/src/mongo/db/exec/multi_iterator.h
@@ -63,7 +63,7 @@ public:
 
     // Not used.
     SpecificStats* getSpecificStats() const final {
-        return NULL;
+        return nullptr;
     }
 
     // Not used.
diff --git a/src/mongo/db/exec/multi_plan.cpp b/src/mongo/db/exec/multi_plan.cpp
index af79d91af30..fa5a3ded422 100644
--- a/src/mongo/db/exec/multi_plan.cpp
+++ b/src/mongo/db/exec/multi_plan.cpp
@@ -166,7 +166,7 @@ size_t MultiPlanStage::getTrialPeriodWorks(OperationContext* opCtx, const Collec
     // Run each plan some number of times. This number is at least as great as
     // 'internalQueryPlanEvaluationWorks', but may be larger for big collections.
     size_t numWorks = internalQueryPlanEvaluationWorks.load();
-    if (NULL != collection) {
+    if (nullptr != collection) {
         // For large collections, the number of works is set to be this
         // fraction of the collection size.
         double fraction = internalQueryPlanEvaluationCollFraction;
@@ -307,7 +307,7 @@ Status MultiPlanStage::pickBestPlan(PlanYieldPolicy* yieldPolicy) {
         // XXX: One known example is 2D queries
         bool validSolutions = true;
         for (size_t ix = 0; ix < solutions.size(); ++ix) {
-            if (NULL == solutions[ix]->cacheData.get()) {
+            if (nullptr == solutions[ix]->cacheData.get()) {
                 LOG(5) << "Not caching query because this solution has no cache data: "
                        << redact(solutions[ix]->toString());
                 validSolutions = false;
@@ -413,7 +413,7 @@ int MultiPlanStage::bestPlanIdx() const {
 
 QuerySolution* MultiPlanStage::bestSolution() {
     if (_bestPlanIdx == kNoSuchPlan)
-        return NULL;
+        return nullptr;
 
     return _candidates[_bestPlanIdx].solution.get();
 }
diff --git a/src/mongo/db/exec/or.cpp b/src/mongo/db/exec/or.cpp
index 965c972669d..8269b599f43 100644
--- a/src/mongo/db/exec/or.cpp
+++ b/src/mongo/db/exec/or.cpp
@@ -125,7 +125,7 @@ unique_ptr<PlanStageStats> OrStage::getStats() {
     _commonStats.isEOF = isEOF();
 
     // Add a BSON representation of the filter to the stats tree, if there is one.
-    if (NULL != _filter) {
+    if (nullptr != _filter) {
         BSONObjBuilder bob;
         _filter->serialize(&bob);
         _commonStats.filter = bob.obj();
diff --git a/src/mongo/db/exec/projection_exec.cpp b/src/mongo/db/exec/projection_exec.cpp
index bc2a4a42d65..505027adc61 100644
--- a/src/mongo/db/exec/projection_exec.cpp
+++ b/src/mongo/db/exec/projection_exec.cpp
@@ -166,7 +166,7 @@ void ProjectionExec::add(const string& field, bool include) {
 
         ProjectionExec*& fm = _fields[subfield.c_str()];
 
-        if (NULL == fm) {
+        if (nullptr == fm) {
             fm = new ProjectionExec();
         }
 
@@ -187,7 +187,7 @@ void ProjectionExec::add(const string& field, int skip, int limit) {
 
         ProjectionExec*& fm = _fields[subfield.c_str()];
 
-        if (NULL == fm) {
+        if (nullptr == fm) {
             fm = new ProjectionExec();
         }
 
diff --git a/src/mongo/db/exec/projection_exec.h b/src/mongo/db/exec/projection_exec.h
index 805be89ef44..ab4dc5f48dc 100644
--- a/src/mongo/db/exec/projection_exec.h
+++ b/src/mongo/db/exec/projection_exec.h
@@ -211,7 +211,7 @@ private:
      */
     Status append(BSONObjBuilder* bob,
                   const BSONElement& elt,
-                  const MatchDetails* details = NULL,
+                  const MatchDetails* details = nullptr,
                   const ArrayOpType arrayOpType = ARRAY_OP_NORMAL) const;
 
     /**
diff --git a/src/mongo/db/exec/stagedebug_cmd.cpp b/src/mongo/db/exec/stagedebug_cmd.cpp
index a01bc911754..39ba8540c0f 100644
--- a/src/mongo/db/exec/stagedebug_cmd.cpp
+++ b/src/mongo/db/exec/stagedebug_cmd.cpp
@@ -184,7 +184,7 @@ public:
         unique_ptr<WorkingSet> ws(new WorkingSet());
 
         PlanStage* userRoot = parseQuery(opCtx, collection, planObj, ws.get(), &exprs);
-        uassert(16911, "Couldn't parse plan from " + cmdObj.toString(), NULL != userRoot);
+        uassert(16911, "Couldn't parse plan from " + cmdObj.toString(), nullptr != userRoot);
 
         // Add a fetch at the top for the user so we can get obj back for sure.
         // TODO: Do we want to do this for the user?  I think so.
@@ -200,7 +200,7 @@ public:
 
         BSONObj obj;
         PlanExecutor::ExecState state;
-        while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
+        while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
             resultBuilder.append(obj);
         }
 
@@ -224,11 +224,11 @@ public:
                           std::vector<std::unique_ptr<MatchExpression>>* exprs) {
         BSONElement firstElt = obj.firstElement();
         if (!firstElt.isABSONObj()) {
-            return NULL;
+            return nullptr;
         }
         BSONObj paramObj = firstElt.Obj();
 
-        MatchExpression* matcher = NULL;
+        MatchExpression* matcher = nullptr;
         BSONObj nodeArgs;
 
         // Every node has these two fields.
@@ -239,7 +239,7 @@ public:
         while (it.more()) {
             BSONElement e = it.next();
             if (!e.isABSONObj()) {
-                return NULL;
+                return nullptr;
             }
             BSONObj argObj = e.Obj();
             if (filterTag == e.fieldName()) {
@@ -252,12 +252,12 @@ public:
                                                  ExtensionsCallbackReal(opCtx, &collection->ns()),
                                                  MatchExpressionParser::kAllowAllSpecialFeatures);
                 if (!statusWithMatcher.isOK()) {
-                    return NULL;
+                    return nullptr;
                 }
                 std::unique_ptr<MatchExpression> me = std::move(statusWithMatcher.getValue());
                 // exprs is what will wind up deleting this.
                 matcher = me.get();
-                verify(NULL != matcher);
+                verify(nullptr != matcher);
                 exprs->push_back(std::move(me));
             } else if (argsTag == e.fieldName()) {
                 nodeArgs = argObj;
@@ -265,7 +265,7 @@ public:
                 uasserted(16910,
                           "Unknown fieldname " + string(e.fieldName()) + " in query node " +
                               obj.toString());
-                return NULL;
+                return nullptr;
             }
         }
 
@@ -323,8 +323,9 @@ public:
                 uassert(16922, "node of AND isn't an obj?: " + e.toString(), e.isABSONObj());
 
                 PlanStage* subNode = parseQuery(opCtx, collection, e.Obj(), workingSet, exprs);
-                uassert(
-                    16923, "Can't parse sub-node of AND: " + e.Obj().toString(), NULL != subNode);
+                uassert(16923,
+                        "Can't parse sub-node of AND: " + e.Obj().toString(),
+                        nullptr != subNode);
                 // takes ownership
                 andStage->addChild(subNode);
                 ++nodesAdded;
@@ -346,8 +347,9 @@ public:
                 uassert(16925, "node of AND isn't an obj?: " + e.toString(), e.isABSONObj());
 
                 PlanStage* subNode = parseQuery(opCtx, collection, e.Obj(), workingSet, exprs);
-                uassert(
-                    16926, "Can't parse sub-node of AND: " + e.Obj().toString(), NULL != subNode);
+                uassert(16926,
+                        "Can't parse sub-node of AND: " + e.Obj().toString(),
+                        nullptr != subNode);
                 // takes ownership
                 andStage->addChild(subNode);
                 ++nodesAdded;
@@ -366,11 +368,11 @@ public:
             while (it.more()) {
                 BSONElement e = it.next();
                 if (!e.isABSONObj()) {
-                    return NULL;
+                    return nullptr;
                 }
                 PlanStage* subNode = parseQuery(opCtx, collection, e.Obj(), workingSet, exprs);
                 uassert(
-                    16936, "Can't parse sub-node of OR: " + e.Obj().toString(), NULL != subNode);
+                    16936, "Can't parse sub-node of OR: " + e.Obj().toString(), nullptr != subNode);
                 // takes ownership
                 orStage->addChild(subNode);
             }
@@ -383,11 +385,12 @@ public:
                 parseQuery(opCtx, collection, nodeArgs["node"].Obj(), workingSet, exprs);
             uassert(28731,
                     "Can't parse sub-node of FETCH: " + nodeArgs["node"].Obj().toString(),
-                    NULL != subNode);
+                    nullptr != subNode);
             return new FetchStage(opCtx, workingSet, subNode, matcher, collection);
         } else if ("limit" == nodeName) {
-            uassert(
-                16937, "Limit stage doesn't have a filter (put it on the child)", NULL == matcher);
+            uassert(16937,
+                    "Limit stage doesn't have a filter (put it on the child)",
+                    nullptr == matcher);
             uassert(
                 16930, "Node argument must be provided to limit", nodeArgs["node"].isABSONObj());
             uassert(16931, "Num argument must be provided to limit", nodeArgs["num"].isNumber());
@@ -395,18 +398,19 @@ public:
                 parseQuery(opCtx, collection, nodeArgs["node"].Obj(), workingSet, exprs);
             uassert(28732,
                     "Can't parse sub-node of LIMIT: " + nodeArgs["node"].Obj().toString(),
-                    NULL != subNode);
+                    nullptr != subNode);
             return new LimitStage(opCtx, nodeArgs["num"].numberInt(), workingSet, subNode);
         } else if ("skip" == nodeName) {
-            uassert(
-                16938, "Skip stage doesn't have a filter (put it on the child)", NULL == matcher);
+            uassert(16938,
+                    "Skip stage doesn't have a filter (put it on the child)",
+                    nullptr == matcher);
             uassert(16932, "Node argument must be provided to skip", nodeArgs["node"].isABSONObj());
             uassert(16933, "Num argument must be provided to skip", nodeArgs["num"].isNumber());
             PlanStage* subNode =
                 parseQuery(opCtx, collection, nodeArgs["node"].Obj(), workingSet, exprs);
             uassert(28733,
                     "Can't parse sub-node of SKIP: " + nodeArgs["node"].Obj().toString(),
-                    NULL != subNode);
+                    nullptr != subNode);
             return new SkipStage(opCtx, nodeArgs["num"].numberInt(), workingSet, subNode);
         } else if ("cscan" == nodeName) {
             CollectionScanParams params;
@@ -443,7 +447,7 @@ public:
                 PlanStage* subNode = parseQuery(opCtx, collection, e.Obj(), workingSet, exprs);
                 uassert(16974,
                         "Can't parse sub-node of mergeSort: " + e.Obj().toString(),
-                        NULL != subNode);
+                        nullptr != subNode);
                 // takes ownership
                 mergeStage->addChild(subNode);
             }
@@ -466,7 +470,7 @@ public:
             // that can only be checked for equality.  We ignore this now.
             Status s = fam->getSpec().getIndexPrefix(BSONObj(), &params.indexPrefix);
             if (!s.isOK()) {
-                return NULL;
+                return nullptr;
             }
 
             params.spec = fam->getSpec();
@@ -476,13 +480,14 @@ public:
             params.query.setCaseSensitive(TextMatchExpressionBase::kCaseSensitiveDefault);
             params.query.setDiacriticSensitive(TextMatchExpressionBase::kDiacriticSensitiveDefault);
             if (!params.query.parse(fam->getSpec().getTextIndexVersion()).isOK()) {
-                return NULL;
+                return nullptr;
             }
 
             return new TextStage(opCtx, params, workingSet, matcher);
         } else if ("delete" == nodeName) {
-            uassert(
-                18636, "Delete stage doesn't have a filter (put it on the child)", NULL == matcher);
+            uassert(18636,
+                    "Delete stage doesn't have a filter (put it on the child)",
+                    nullptr == matcher);
             uassert(
                 18637, "node argument must be provided to delete", nodeArgs["node"].isABSONObj());
             uassert(18638,
@@ -492,12 +497,12 @@ public:
                 parseQuery(opCtx, collection, nodeArgs["node"].Obj(), workingSet, exprs);
             uassert(28734,
                     "Can't parse sub-node of DELETE: " + nodeArgs["node"].Obj().toString(),
-                    NULL != subNode);
+                    nullptr != subNode);
             auto params = std::make_unique<DeleteStageParams>();
             params->isMulti = nodeArgs["isMulti"].Bool();
             return new DeleteStage(opCtx, std::move(params), workingSet, collection, subNode);
         } else {
-            return NULL;
+            return nullptr;
         }
     }
 };
diff --git a/src/mongo/db/exec/subplan.cpp b/src/mongo/db/exec/subplan.cpp
index 2506db606b1..889ea82428f 100644
--- a/src/mongo/db/exec/subplan.cpp
+++ b/src/mongo/db/exec/subplan.cpp
@@ -190,7 +190,7 @@ Status tagOrChildAccordingToCache(PlanCacheIndexTree* compositeCacheData,
     invariant(compositeCacheData);
 
     // We want a well-formed *indexed* solution.
-    if (NULL == branchCacheData) {
+    if (nullptr == branchCacheData) {
         // For example, we don't cache things for 2d indices.
         str::stream ss;
         ss << "No cache data for subchild " << orChild->debugString();
@@ -298,7 +298,7 @@ Status SubplanStage::choosePlanForSubqueries(PlanYieldPolicy* yieldPolicy) {
 
             // Check that we have good cache data. For example, we don't cache things
             // for 2d indices.
-            if (NULL == bestSoln->cacheData.get()) {
+            if (nullptr == bestSoln->cacheData.get()) {
                 str::stream ss;
                 ss << "No cache data for subchild " << orChild->debugString();
                 return Status(ErrorCodes::BadValue, ss);
@@ -343,7 +343,7 @@ Status SubplanStage::choosePlanForSubqueries(PlanYieldPolicy* yieldPolicy) {
     _compositeSolution =
         QueryPlannerAnalysis::analyzeDataAccess(*_query, _plannerParams, std::move(solnRoot));
 
-    if (NULL == _compositeSolution.get()) {
+    if (nullptr == _compositeSolution.get()) {
         str::stream ss;
         ss << "Failed to analyze subplanned query";
         return Status(ErrorCodes::BadValue, ss);
@@ -487,11 +487,11 @@ unique_ptr<PlanStageStats> SubplanStage::getStats() {
 }
 
 bool SubplanStage::branchPlannedFromCache(size_t i) const {
-    return NULL != _branchResults[i]->cachedSolution.get();
+    return nullptr != _branchResults[i]->cachedSolution.get();
 }
 
 const SpecificStats* SubplanStage::getSpecificStats() const {
-    return NULL;
+    return nullptr;
 }
 
 }  // namespace mongo
diff --git a/src/mongo/db/exec/update_stage.cpp b/src/mongo/db/exec/update_stage.cpp
index 34953bb62ff..7f079f27d9f 100644
--- a/src/mongo/db/exec/update_stage.cpp
+++ b/src/mongo/db/exec/update_stage.cpp
@@ -168,7 +168,7 @@ UpdateStage::UpdateStage(OperationContext* opCtx,
       _ws(ws),
       _idRetrying(WorkingSet::INVALID_ID),
       _idReturning(WorkingSet::INVALID_ID),
-      _updatedRecordIds(params.request->isMulti() ? new RecordIdSet() : NULL),
+      _updatedRecordIds(params.request->isMulti() ? new RecordIdSet() : nullptr),
       _doc(params.driver->getDocument()) {
     _children.emplace_back(child);
 
@@ -282,7 +282,7 @@ BSONObj UpdateStage::transformAndUpdate(const Snapshotted<BSONObj>& oldObj, Reco
     }
 
     // See if the changes were applied in place
-    const char* source = NULL;
+    const char* source = nullptr;
     const bool inPlace = _doc.getInPlaceUpdates(&_damages, &source);
 
     if (inPlace && _damages.empty()) {
diff --git a/src/mongo/db/exec/update_stage.h b/src/mongo/db/exec/update_stage.h
index 93936166544..24beae7ffaa 100644
--- a/src/mongo/db/exec/update_stage.h
+++ b/src/mongo/db/exec/update_stage.h
@@ -47,7 +47,7 @@ struct PlanSummaryStats;
 
 struct UpdateStageParams {
     UpdateStageParams(const UpdateRequest* r, UpdateDriver* d, OpDebug* o)
-        : request(r), driver(d), opDebug(o), canonicalQuery(NULL) {}
+        : request(r), driver(d), opDebug(o), canonicalQuery(nullptr) {}
 
     // Contains update parameters like whether it's a multi update or an upsert. Not owned.
     // Must outlive the UpdateStage.
diff --git a/src/mongo/db/exec/working_set.cpp b/src/mongo/db/exec/working_set.cpp
index e9dd0ac7e9c..79a0fbbcaa6 100644
--- a/src/mongo/db/exec/working_set.cpp
+++ b/src/mongo/db/exec/working_set.cpp
@@ -39,7 +39,7 @@ using std::string;
 
 namespace dps = ::mongo::dotted_path_support;
 
-WorkingSet::MemberHolder::MemberHolder() : member(NULL) {}
+WorkingSet::MemberHolder::MemberHolder() : member(nullptr) {}
 WorkingSet::MemberHolder::~MemberHolder() {}
 
 WorkingSet::WorkingSet() : _freeList(INVALID_ID) {}
diff --git a/src/mongo/db/exec/working_set_test.cpp b/src/mongo/db/exec/working_set_test.cpp
index 9472c90fabe..eb8618552eb 100644
--- a/src/mongo/db/exec/working_set_test.cpp
+++ b/src/mongo/db/exec/working_set_test.cpp
@@ -52,12 +52,12 @@ protected:
         id = ws->allocate();
         ASSERT(id != WorkingSet::INVALID_ID);
         member = ws->get(id);
-        ASSERT(NULL != member);
+        ASSERT(nullptr != member);
     }
 
     void tearDown() {
         ws.reset();
-        member = NULL;
+        member = nullptr;
     }
 
     std::unique_ptr<WorkingSet> ws;
@@ -123,7 +123,7 @@ TEST_F(WorkingSetFixture, getFieldFromIndex) {
     string secondName = "y";
     int secondValue = 10;
 
-    member->keyData.push_back(IndexKeyDatum(BSON(firstName << 1), BSON("" << firstValue), NULL));
+    member->keyData.push_back(IndexKeyDatum(BSON(firstName << 1), BSON("" << firstValue), nullptr));
     // Also a minor lie as RecordId is bogus.
     ws->transitionToRecordIdAndIdx(id);
     BSONElement elt;
@@ -133,7 +133,8 @@ TEST_F(WorkingSetFixture, getFieldFromIndex) {
     ASSERT_FALSE(member->getFieldDotted("foo", &elt));
 
     // Add another index datum.
-    member->keyData.push_back(IndexKeyDatum(BSON(secondName << 1), BSON("" << secondValue), NULL));
+    member->keyData.push_back(
+        IndexKeyDatum(BSON(secondName << 1), BSON("" << secondValue), nullptr));
     ASSERT_TRUE(member->getFieldDotted(secondName, &elt));
     ASSERT_EQUALS(elt.numberInt(), secondValue);
     ASSERT_TRUE(member->getFieldDotted(firstName, &elt));
@@ -146,7 +147,7 @@ TEST_F(WorkingSetFixture, getDottedFieldFromIndex) {
     string firstName = "x.y";
     int firstValue = 5;
 
-    member->keyData.push_back(IndexKeyDatum(BSON(firstName << 1), BSON("" << firstValue), NULL));
+    member->keyData.push_back(IndexKeyDatum(BSON(firstName << 1), BSON("" << firstValue), nullptr));
     ws->transitionToRecordIdAndIdx(id);
     BSONElement elt;
     ASSERT_TRUE(member->getFieldDotted(firstName, &elt));
diff --git a/src/mongo/db/field_parser.h b/src/mongo/db/field_parser.h
index 748787affe9..45cbf50506b 100644
--- a/src/mongo/db/field_parser.h
+++ b/src/mongo/db/field_parser.h
@@ -85,102 +85,102 @@ public:
     static FieldState extract(BSONObj doc,
                               const BSONField<bool>& field,
                               bool* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<bool>& field,
                               bool* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<BSONArray>& field,
                               BSONArray* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<BSONArray>& field,
                               BSONArray* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<BSONObj>& field,
                               BSONObj* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<BSONObj>& field,
                               BSONObj* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<Date_t>& field,
                               Date_t* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<Date_t>& field,
                               Date_t* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<Timestamp>& field,
                               Timestamp* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<Timestamp>& field,
                               Timestamp* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<std::string>& field,
                               std::string* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<std::string>& field,
                               std::string* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<OID>& field,
                               OID* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<OID>& field,
                               OID* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<int>& field,
                               int* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<int>& field,
                               int* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<long long>& field,
                               long long* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<long long>& field,
                               long long* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONElement elem,
                               const BSONField<double>& field,
                               double* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     static FieldState extract(BSONObj doc,
                               const BSONField<double>& field,
                               double* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     /**
      * The following extractNumber methods do implicit conversion between any numeric type and
@@ -190,32 +190,32 @@ public:
     static FieldState extractNumber(BSONObj doc,
                                     const BSONField<int>& field,
                                     int* out,
-                                    std::string* errMsg = NULL);
+                                    std::string* errMsg = nullptr);
 
     static FieldState extractNumber(BSONElement elem,
                                     const BSONField<int>& field,
                                     int* out,
-                                    std::string* errMsg = NULL);
+                                    std::string* errMsg = nullptr);
 
     static FieldState extractNumber(BSONObj doc,
                                     const BSONField<long long>& field,
                                     long long* out,
-                                    std::string* errMsg = NULL);
+                                    std::string* errMsg = nullptr);
 
     static FieldState extractNumber(BSONElement elem,
                                     const BSONField<long long>& field,
                                     long long* out,
-                                    std::string* errMsg = NULL);
+                                    std::string* errMsg = nullptr);
 
     static FieldState extractNumber(BSONObj doc,
                                     const BSONField<double>& field,
                                     double* out,
-                                    std::string* errMsg = NULL);
+                                    std::string* errMsg = nullptr);
 
     static FieldState extractNumber(BSONElement elem,
                                     const BSONField<double>& field,
                                     double* out,
-                                    std::string* errMsg = NULL);
+                                    std::string* errMsg = nullptr);
 
     /**
      * Extracts a document id from a particular field name, which may be of any type but Array.
@@ -224,12 +224,12 @@ public:
     static FieldState extractID(BSONObj doc,
                                 const BSONField<BSONObj>& field,
                                 BSONObj* out,
-                                std::string* errMsg = NULL);
+                                std::string* errMsg = nullptr);
 
     static FieldState extractID(BSONElement elem,
                                 const BSONField<BSONObj>& field,
                                 BSONObj* out,
-                                std::string* errMsg = NULL);
+                                std::string* errMsg = nullptr);
 
     // TODO: BSONElement extraction of types below
 
@@ -242,7 +242,7 @@ public:
     static FieldState extract(BSONObj doc,
                               const BSONField<T>& field,
                               T* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     /**
      * Similar to the mandatory 'extract' but on a optional field. The '*out' value would only be
@@ -253,13 +253,13 @@ public:
     static FieldState extract(BSONObj doc,
                               const BSONField<T*>& field,
                               T** out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     template <typename T>
     static FieldState extract(BSONObj doc,
                               const BSONField<T>& field,
                               T** out,  // alloc variation
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     /**
      * Extracts a mandatory repetition of 'field', from the object 'doc'. Writes the extracted
@@ -272,7 +272,7 @@ public:
     static FieldState extract(BSONObj doc,
                               const BSONField<std::vector<T*>>& field,
                               std::vector<T*>* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     /**
      * Extracts a mandatory repetition of 'field', from the field 'elem'. Writes the extracted
@@ -285,7 +285,7 @@ public:
     static FieldState extract(BSONElement elem,
                               const BSONField<std::vector<T*>>& field,
                               std::vector<T*>* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     /**
      * Similar to the mandatory repetition' extract but on an optional field. The '*out' value would
@@ -298,7 +298,7 @@ public:
     static FieldState extract(BSONObj doc,
                               const BSONField<std::vector<T*>>& field,
                               std::vector<T*>** out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     //
     // ==================== Below DEPRECATED; use types instead ====================
@@ -317,25 +317,25 @@ public:
     static FieldState extract(BSONObj doc,
                               const BSONField<std::vector<T>>& field,
                               std::vector<T>* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     template <typename T>
     static FieldState extract(BSONElement elem,
                               const BSONField<std::vector<T>>& field,
                               std::vector<T>* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     template <typename K, typename T>
     static FieldState extract(BSONObj doc,
                               const BSONField<std::map<K, T>>& field,
                               std::map<K, T>* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 
     template <typename K, typename T>
     static FieldState extract(BSONElement elem,
                               const BSONField<std::map<K, T>>& field,
                               std::map<K, T>* out,
-                              std::string* errMsg = NULL);
+                              std::string* errMsg = nullptr);
 };
 
 template <typename T>
diff --git a/src/mongo/db/field_parser_test.cpp b/src/mongo/db/field_parser_test.cpp
index 9627b914c6b..a99ee1b45e8 100644
--- a/src/mongo/db/field_parser_test.cpp
+++ b/src/mongo/db/field_parser_test.cpp
@@ -180,31 +180,33 @@ TEST_F(ExtractionFixture, GetLong) {
 TEST_F(ExtractionFixture, IsFound) {
     bool bool_val;
     BSONField<bool> aBoolMissing("aBoolMissing");
-    ASSERT_EQUALS(FieldParser::extract(doc, aBool, &bool_val, NULL), FieldParser::FIELD_SET);
-    ASSERT_EQUALS(FieldParser::extract(doc, aBoolMissing, &bool_val, NULL),
+    ASSERT_EQUALS(FieldParser::extract(doc, aBool, &bool_val, nullptr), FieldParser::FIELD_SET);
+    ASSERT_EQUALS(FieldParser::extract(doc, aBoolMissing, &bool_val, nullptr),
                   FieldParser::FIELD_NONE);
 
     Date_t Date_t_val;
     BSONField<Date_t> aDateMissing("aDateMissing");
-    ASSERT_EQUALS(FieldParser::extract(doc, aDate, &Date_t_val, NULL), FieldParser::FIELD_SET);
-    ASSERT_EQUALS(FieldParser::extract(doc, aDateMissing, &Date_t_val, NULL),
+    ASSERT_EQUALS(FieldParser::extract(doc, aDate, &Date_t_val, nullptr), FieldParser::FIELD_SET);
+    ASSERT_EQUALS(FieldParser::extract(doc, aDateMissing, &Date_t_val, nullptr),
                   FieldParser::FIELD_NONE);
 
     string string_val;
     BSONField<string> aStringMissing("aStringMissing");
-    ASSERT_EQUALS(FieldParser::extract(doc, aString, &string_val, NULL), FieldParser::FIELD_SET);
-    ASSERT_EQUALS(FieldParser::extract(doc, aStringMissing, &string_val, NULL),
+    ASSERT_EQUALS(FieldParser::extract(doc, aString, &string_val, nullptr), FieldParser::FIELD_SET);
+    ASSERT_EQUALS(FieldParser::extract(doc, aStringMissing, &string_val, nullptr),
                   FieldParser::FIELD_NONE);
 
     OID OID_val;
     BSONField<OID> anOIDMissing("anOIDMissing");
-    ASSERT_EQUALS(FieldParser::extract(doc, anOID, &OID_val, NULL), FieldParser::FIELD_SET);
-    ASSERT_EQUALS(FieldParser::extract(doc, anOIDMissing, &OID_val, NULL), FieldParser::FIELD_NONE);
+    ASSERT_EQUALS(FieldParser::extract(doc, anOID, &OID_val, nullptr), FieldParser::FIELD_SET);
+    ASSERT_EQUALS(FieldParser::extract(doc, anOIDMissing, &OID_val, nullptr),
+                  FieldParser::FIELD_NONE);
 
     long long long_long_val;
     BSONField<long long> aLongMissing("aLongMissing");
-    ASSERT_EQUALS(FieldParser::extract(doc, aLong, &long_long_val, NULL), FieldParser::FIELD_SET);
-    ASSERT_EQUALS(FieldParser::extract(doc, aLongMissing, &long_long_val, NULL),
+    ASSERT_EQUALS(FieldParser::extract(doc, aLong, &long_long_val, nullptr),
+                  FieldParser::FIELD_SET);
+    ASSERT_EQUALS(FieldParser::extract(doc, aLongMissing, &long_long_val, nullptr),
                   FieldParser::FIELD_NONE);
 }
 
diff --git a/src/mongo/db/field_ref_set.cpp b/src/mongo/db/field_ref_set.cpp
index cbfcee236d3..2843f39d655 100644
--- a/src/mongo/db/field_ref_set.cpp
+++ b/src/mongo/db/field_ref_set.cpp
@@ -139,7 +139,7 @@ bool FieldRefSet::insert(const FieldRef* toInsert, const FieldRef** conflict) {
     }
 
     _fieldSet.insert(it, toInsert);
-    *conflict = NULL;
+    *conflict = nullptr;
     return true;
 }
 
diff --git a/src/mongo/db/field_ref_set_test.cpp b/src/mongo/db/field_ref_set_test.cpp
index 9b437f3b9ad..ae610a15cbf 100644
--- a/src/mongo/db/field_ref_set_test.cpp
+++ b/src/mongo/db/field_ref_set_test.cpp
@@ -44,17 +44,17 @@ TEST(EmptySet, Normal) {
     FieldRef bSimple("b");
     const FieldRef* conflict;
     ASSERT_TRUE(fieldSet.insert(&bSimple, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     // insert "a", OK
     FieldRef aSimple("a");
     ASSERT_TRUE(fieldSet.insert(&aSimple, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     // insert "c", OK
     FieldRef cSimple("c");
     ASSERT_TRUE(fieldSet.insert(&cSimple, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 }
 
 TEST(EmptySet, Conflict) {
@@ -63,7 +63,7 @@ TEST(EmptySet, Conflict) {
     FieldRef aDotB("a.b");
     const FieldRef* conflict;
     ASSERT_TRUE(fieldSet.insert(&aDotB, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     // insert "a", conflicts with "a.b"
     FieldRef prefix("a");
@@ -83,7 +83,7 @@ TEST(EmptySet, EmptyField) {
     FieldRef empty;
     const FieldRef* conflict;
     ASSERT_TRUE(fieldSet.insert(&empty, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     ASSERT_FALSE(fieldSet.insert(&empty, &conflict));
     ASSERT_EQUALS(empty, *conflict);
@@ -96,24 +96,24 @@ TEST(NotEmptySet, Normal) {
     FieldRef bDotE("b.e");
     const FieldRef* conflict;
     ASSERT_TRUE(fieldSet.insert(&bDotC, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
     ASSERT_TRUE(fieldSet.insert(&bDotE, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     // insert "a" before, OK
     FieldRef aSimple("a");
     ASSERT_TRUE(fieldSet.insert(&aSimple, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     // insert "b.d" in the middle, OK
     FieldRef bDotD("b.d");
     ASSERT_TRUE(fieldSet.insert(&bDotD, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     // insert "c" after, OK
     FieldRef cSimple("c");
     ASSERT_TRUE(fieldSet.insert(&cSimple, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 }
 
 TEST(NotEmpty, Conflict) {
@@ -123,9 +123,9 @@ TEST(NotEmpty, Conflict) {
     FieldRef bDotE("b.e");
     const FieldRef* conflict;
     ASSERT_TRUE(fieldSet.insert(&bDotC, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
     ASSERT_TRUE(fieldSet.insert(&bDotE, &conflict));
-    ASSERT_EQUALS(static_cast<const FieldRef*>(NULL), conflict);
+    ASSERT_EQUALS(static_cast<const FieldRef*>(nullptr), conflict);
 
     // insert "b" before, conflicts "b.c"
     FieldRef bSimple("b");
diff --git a/src/mongo/db/fts/fts_basic_phrase_matcher.cpp b/src/mongo/db/fts/fts_basic_phrase_matcher.cpp
index 320127c87dc..8b4c373e048 100644
--- a/src/mongo/db/fts/fts_basic_phrase_matcher.cpp
+++ b/src/mongo/db/fts/fts_basic_phrase_matcher.cpp
@@ -43,7 +43,7 @@ bool BasicFTSPhraseMatcher::phraseMatches(const string& phrase,
         return haystack.find(phrase) != string::npos;
     }
 
-    return strcasestr(haystack.c_str(), phrase.c_str()) != NULL;
+    return strcasestr(haystack.c_str(), phrase.c_str()) != nullptr;
 }
 
 }  // namespace fts
diff --git a/src/mongo/db/fts/fts_element_iterator.h b/src/mongo/db/fts/fts_element_iterator.h
index db0426de41a..611cf33c7fb 100644
--- a/src/mongo/db/fts/fts_element_iterator.h
+++ b/src/mongo/db/fts/fts_element_iterator.h
@@ -48,7 +48,7 @@ struct FTSIteratorValue {
     FTSIteratorValue(const char* text, const FTSLanguage* language, double weight)
         : _text(text), _language(language), _weight(weight), _valid(true) {}
 
-    FTSIteratorValue() : _text(NULL), _language(), _weight(0.0), _valid(false) {}
+    FTSIteratorValue() : _text(nullptr), _language(), _weight(0.0), _valid(false) {}
 
     bool valid() const {
         return _valid;
diff --git a/src/mongo/db/fts/stemmer.cpp b/src/mongo/db/fts/stemmer.cpp
index db5e97227da..5b9fcdadc3c 100644
--- a/src/mongo/db/fts/stemmer.cpp
+++ b/src/mongo/db/fts/stemmer.cpp
@@ -37,7 +37,7 @@ namespace mongo {
 namespace fts {
 
 Stemmer::Stemmer(const FTSLanguage* language) {
-    _stemmer = NULL;
+    _stemmer = nullptr;
     if (language->str() != "none")
         _stemmer = sb_stemmer_new(language->str().c_str(), "UTF_8");
 }
@@ -45,7 +45,7 @@ Stemmer::Stemmer(const FTSLanguage* language) {
 Stemmer::~Stemmer() {
     if (_stemmer) {
         sb_stemmer_delete(_stemmer);
-        _stemmer = NULL;
+        _stemmer = nullptr;
     }
 }
 
@@ -56,7 +56,7 @@ StringData Stemmer::stem(StringData word) const {
     const sb_symbol* sb_sym =
         sb_stemmer_stem(_stemmer, (const sb_symbol*)word.rawData(), word.size());
 
-    if (sb_sym == NULL) {
+    if (sb_sym == nullptr) {
         // out of memory
         MONGO_UNREACHABLE;
     }
diff --git a/src/mongo/db/geo/geometry_container.cpp b/src/mongo/db/geo/geometry_container.cpp
index 5b4ade3d062..5a4c066ee28 100644
--- a/src/mongo/db/geo/geometry_container.cpp
+++ b/src/mongo/db/geo/geometry_container.cpp
@@ -37,7 +37,7 @@
 namespace mongo {
 
 bool GeometryContainer::isSimpleContainer() const {
-    return NULL != _point || NULL != _line || NULL != _polygon;
+    return nullptr != _point || nullptr != _line || nullptr != _polygon;
 }
 
 bool GeometryContainer::isPoint() const {
@@ -45,37 +45,38 @@ bool GeometryContainer::isPoint() const {
 }
 
 bool GeometryContainer::supportsContains() const {
-    return NULL != _polygon || NULL != _box || NULL != _cap || NULL != _multiPolygon ||
-        (NULL != _geometryCollection && (_geometryCollection->polygons.vector().size() > 0 ||
-                                         _geometryCollection->multiPolygons.vector().size() > 0));
+    return nullptr != _polygon || nullptr != _box || nullptr != _cap || nullptr != _multiPolygon ||
+        (nullptr != _geometryCollection &&
+         (_geometryCollection->polygons.vector().size() > 0 ||
+          _geometryCollection->multiPolygons.vector().size() > 0));
 }
 
 bool GeometryContainer::hasS2Region() const {
-    return (NULL != _point && _point->crs == SPHERE) || NULL != _line ||
-        (NULL != _polygon && (_polygon->crs == SPHERE || _polygon->crs == STRICT_SPHERE)) ||
-        (NULL != _cap && _cap->crs == SPHERE) || NULL != _multiPoint || NULL != _multiLine ||
-        NULL != _multiPolygon || NULL != _geometryCollection;
+    return (nullptr != _point && _point->crs == SPHERE) || nullptr != _line ||
+        (nullptr != _polygon && (_polygon->crs == SPHERE || _polygon->crs == STRICT_SPHERE)) ||
+        (nullptr != _cap && _cap->crs == SPHERE) || nullptr != _multiPoint ||
+        nullptr != _multiLine || nullptr != _multiPolygon || nullptr != _geometryCollection;
 }
 
 const S2Region& GeometryContainer::getS2Region() const {
-    if (NULL != _point && SPHERE == _point->crs) {
+    if (nullptr != _point && SPHERE == _point->crs) {
         return _point->cell;
-    } else if (NULL != _line) {
+    } else if (nullptr != _line) {
         return _line->line;
-    } else if (NULL != _polygon && NULL != _polygon->s2Polygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->s2Polygon) {
         return *_polygon->s2Polygon;
-    } else if (NULL != _polygon && NULL != _polygon->bigPolygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->bigPolygon) {
         return *_polygon->bigPolygon;
-    } else if (NULL != _cap && SPHERE == _cap->crs) {
+    } else if (nullptr != _cap && SPHERE == _cap->crs) {
         return _cap->cap;
-    } else if (NULL != _multiPoint) {
+    } else if (nullptr != _multiPoint) {
         return *_s2Region;
-    } else if (NULL != _multiLine) {
+    } else if (nullptr != _multiLine) {
         return *_s2Region;
-    } else if (NULL != _multiPolygon) {
+    } else if (nullptr != _multiPolygon) {
         return *_s2Region;
     } else {
-        invariant(NULL != _geometryCollection);
+        invariant(nullptr != _geometryCollection);
         return *_s2Region;
     }
 }
@@ -233,23 +234,23 @@ bool GeometryContainer::contains(const GeometryContainer& otherContainer) const
         return false;
     }
 
-    if (NULL != _polygon && (FLAT == _polygon->crs)) {
-        if (NULL == otherContainer._point) {
+    if (nullptr != _polygon && (FLAT == _polygon->crs)) {
+        if (nullptr == otherContainer._point) {
             return false;
         }
         return _polygon->oldPolygon.contains(otherContainer._point->oldPoint);
     }
 
-    if (NULL != _box) {
+    if (nullptr != _box) {
         verify(FLAT == _box->crs);
-        if (NULL == otherContainer._point) {
+        if (nullptr == otherContainer._point) {
             return false;
         }
         return _box->box.inside(otherContainer._point->oldPoint);
     }
 
-    if (NULL != _cap && (FLAT == _cap->crs)) {
-        if (NULL == otherContainer._point) {
+    if (nullptr != _cap && (FLAT == _cap->crs)) {
+        if (nullptr == otherContainer._point) {
             return false;
         }
         // Let's be as consistent epsilon-wise as we can with the '2d' indextype.
@@ -260,20 +261,20 @@ bool GeometryContainer::contains(const GeometryContainer& otherContainer) const
     // Now we deal with all the SPHERE stuff.
 
     // Iterate over the other thing and see if we contain it all.
-    if (NULL != otherContainer._point) {
+    if (nullptr != otherContainer._point) {
         return contains(otherContainer._point->cell, otherContainer._point->point);
     }
 
-    if (NULL != otherContainer._line) {
+    if (nullptr != otherContainer._line) {
         return contains(otherContainer._line->line);
     }
 
-    if (NULL != otherContainer._polygon) {
-        invariant(NULL != otherContainer._polygon->s2Polygon);
+    if (nullptr != otherContainer._polygon) {
+        invariant(nullptr != otherContainer._polygon->s2Polygon);
         return contains(*otherContainer._polygon->s2Polygon);
     }
 
-    if (NULL != otherContainer._multiPoint) {
+    if (nullptr != otherContainer._multiPoint) {
         for (size_t i = 0; i < otherContainer._multiPoint->points.size(); ++i) {
             if (!contains(otherContainer._multiPoint->cells[i],
                           otherContainer._multiPoint->points[i])) {
@@ -283,7 +284,7 @@ bool GeometryContainer::contains(const GeometryContainer& otherContainer) const
         return true;
     }
 
-    if (NULL != otherContainer._multiLine) {
+    if (nullptr != otherContainer._multiLine) {
         const vector<S2Polyline*>& lines = otherContainer._multiLine->lines.vector();
         for (size_t i = 0; i < lines.size(); ++i) {
             if (!contains(*lines[i])) {
@@ -293,7 +294,7 @@ bool GeometryContainer::contains(const GeometryContainer& otherContainer) const
         return true;
     }
 
-    if (NULL != otherContainer._multiPolygon) {
+    if (nullptr != otherContainer._multiPolygon) {
         const vector<S2Polygon*>& polys = otherContainer._multiPolygon->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (!contains(*polys[i])) {
@@ -303,7 +304,7 @@ bool GeometryContainer::contains(const GeometryContainer& otherContainer) const
         return true;
     }
 
-    if (NULL != otherContainer._geometryCollection) {
+    if (nullptr != otherContainer._geometryCollection) {
         GeometryCollection& c = *otherContainer._geometryCollection;
 
         for (size_t i = 0; i < c.points.size(); ++i) {
@@ -372,21 +373,21 @@ bool containsPoint(const S2Polygon& poly, const S2Cell& otherCell, const S2Point
 }
 
 bool GeometryContainer::contains(const S2Cell& otherCell, const S2Point& otherPoint) const {
-    if (NULL != _polygon && (NULL != _polygon->s2Polygon)) {
+    if (nullptr != _polygon && (nullptr != _polygon->s2Polygon)) {
         return containsPoint(*_polygon->s2Polygon, otherCell, otherPoint);
     }
 
-    if (NULL != _polygon && (NULL != _polygon->bigPolygon)) {
+    if (nullptr != _polygon && (nullptr != _polygon->bigPolygon)) {
         if (_polygon->bigPolygon->Contains(otherPoint))
             return true;
         return _polygon->bigPolygon->MayIntersect(otherCell);
     }
 
-    if (NULL != _cap && (_cap->crs == SPHERE)) {
+    if (nullptr != _cap && (_cap->crs == SPHERE)) {
         return _cap->cap.MayIntersect(otherCell);
     }
 
-    if (NULL != _multiPolygon) {
+    if (nullptr != _multiPolygon) {
         const vector<S2Polygon*>& polys = _multiPolygon->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (containsPoint(*polys[i], otherCell, otherPoint)) {
@@ -395,7 +396,7 @@ bool GeometryContainer::contains(const S2Cell& otherCell, const S2Point& otherPo
         }
     }
 
-    if (NULL != _geometryCollection) {
+    if (nullptr != _geometryCollection) {
         const vector<PolygonWithCRS*>& polys = _geometryCollection->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (containsPoint(*polys[i]->s2Polygon, otherCell, otherPoint)) {
@@ -439,15 +440,15 @@ bool containsLine(const S2Polygon& poly, const S2Polyline& otherLine) {
 }
 
 bool GeometryContainer::contains(const S2Polyline& otherLine) const {
-    if (NULL != _polygon && NULL != _polygon->s2Polygon) {
+    if (nullptr != _polygon && nullptr != _polygon->s2Polygon) {
         return containsLine(*_polygon->s2Polygon, otherLine);
     }
 
-    if (NULL != _polygon && NULL != _polygon->bigPolygon) {
+    if (nullptr != _polygon && nullptr != _polygon->bigPolygon) {
         return _polygon->bigPolygon->Contains(otherLine);
     }
 
-    if (NULL != _cap && (_cap->crs == SPHERE)) {
+    if (nullptr != _cap && (_cap->crs == SPHERE)) {
         // If the radian distance of a line to the centroid of the complement spherical cap is less
         // than the arc radian of the complement cap, then the line is not within the spherical cap.
         S2Cap complementSphere = _cap->cap.Complement();
@@ -458,7 +459,7 @@ bool GeometryContainer::contains(const S2Polyline& otherLine) const {
         return true;
     }
 
-    if (NULL != _multiPolygon) {
+    if (nullptr != _multiPolygon) {
         const vector<S2Polygon*>& polys = _multiPolygon->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (containsLine(*polys[i], otherLine)) {
@@ -467,7 +468,7 @@ bool GeometryContainer::contains(const S2Polyline& otherLine) const {
         }
     }
 
-    if (NULL != _geometryCollection) {
+    if (nullptr != _geometryCollection) {
         const vector<PolygonWithCRS*>& polys = _geometryCollection->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (containsLine(*polys[i]->s2Polygon, otherLine)) {
@@ -495,15 +496,15 @@ bool containsPolygon(const S2Polygon& poly, const S2Polygon& otherPoly) {
 }
 
 bool GeometryContainer::contains(const S2Polygon& otherPolygon) const {
-    if (NULL != _polygon && NULL != _polygon->s2Polygon) {
+    if (nullptr != _polygon && nullptr != _polygon->s2Polygon) {
         return containsPolygon(*_polygon->s2Polygon, otherPolygon);
     }
 
-    if (NULL != _polygon && NULL != _polygon->bigPolygon) {
+    if (nullptr != _polygon && nullptr != _polygon->bigPolygon) {
         return _polygon->bigPolygon->Contains(otherPolygon);
     }
 
-    if (NULL != _cap && (_cap->crs == SPHERE)) {
+    if (nullptr != _cap && (_cap->crs == SPHERE)) {
         // If the radian distance of a polygon to the centroid of the complement spherical cap is
         // less than the arc radian of the complement cap, then the polygon is not within the
         // spherical cap.
@@ -515,7 +516,7 @@ bool GeometryContainer::contains(const S2Polygon& otherPolygon) const {
         return true;
     }
 
-    if (NULL != _multiPolygon) {
+    if (nullptr != _multiPolygon) {
         const vector<S2Polygon*>& polys = _multiPolygon->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (containsPolygon(*polys[i], otherPolygon)) {
@@ -524,7 +525,7 @@ bool GeometryContainer::contains(const S2Polygon& otherPolygon) const {
         }
     }
 
-    if (NULL != _geometryCollection) {
+    if (nullptr != _geometryCollection) {
         const vector<PolygonWithCRS*>& polys = _geometryCollection->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (containsPolygon(*polys[i]->s2Polygon, otherPolygon)) {
@@ -548,22 +549,22 @@ bool GeometryContainer::contains(const S2Polygon& otherPolygon) const {
 }
 
 bool GeometryContainer::intersects(const GeometryContainer& otherContainer) const {
-    if (NULL != otherContainer._point) {
+    if (nullptr != otherContainer._point) {
         return intersects(otherContainer._point->cell);
-    } else if (NULL != otherContainer._line) {
+    } else if (nullptr != otherContainer._line) {
         return intersects(otherContainer._line->line);
-    } else if (NULL != otherContainer._polygon) {
-        if (NULL == otherContainer._polygon->s2Polygon) {
+    } else if (nullptr != otherContainer._polygon) {
+        if (nullptr == otherContainer._polygon->s2Polygon) {
             return false;
         }
         return intersects(*otherContainer._polygon->s2Polygon);
-    } else if (NULL != otherContainer._multiPoint) {
+    } else if (nullptr != otherContainer._multiPoint) {
         return intersects(*otherContainer._multiPoint);
-    } else if (NULL != otherContainer._multiLine) {
+    } else if (nullptr != otherContainer._multiLine) {
         return intersects(*otherContainer._multiLine);
-    } else if (NULL != otherContainer._multiPolygon) {
+    } else if (nullptr != otherContainer._multiPolygon) {
         return intersects(*otherContainer._multiPolygon);
-    } else if (NULL != otherContainer._geometryCollection) {
+    } else if (nullptr != otherContainer._geometryCollection) {
         const GeometryCollection& c = *otherContainer._geometryCollection;
 
         for (size_t i = 0; i < c.points.size(); ++i) {
@@ -635,36 +636,36 @@ bool GeometryContainer::intersects(const MultiPolygonWithCRS& otherMultiPolygon)
 
 // Does this (GeometryContainer) intersect the provided data?
 bool GeometryContainer::intersects(const S2Cell& otherPoint) const {
-    if (NULL != _point) {
+    if (nullptr != _point) {
         return _point->cell.MayIntersect(otherPoint);
-    } else if (NULL != _line) {
+    } else if (nullptr != _line) {
         return _line->line.MayIntersect(otherPoint);
-    } else if (NULL != _polygon && NULL != _polygon->s2Polygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->s2Polygon) {
         return _polygon->s2Polygon->MayIntersect(otherPoint);
-    } else if (NULL != _polygon && NULL != _polygon->bigPolygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->bigPolygon) {
         return _polygon->bigPolygon->MayIntersect(otherPoint);
-    } else if (NULL != _multiPoint) {
+    } else if (nullptr != _multiPoint) {
         const vector<S2Cell>& cells = _multiPoint->cells;
         for (size_t i = 0; i < cells.size(); ++i) {
             if (cells[i].MayIntersect(otherPoint)) {
                 return true;
             }
         }
-    } else if (NULL != _multiLine) {
+    } else if (nullptr != _multiLine) {
         const vector<S2Polyline*>& lines = _multiLine->lines.vector();
         for (size_t i = 0; i < lines.size(); ++i) {
             if (lines[i]->MayIntersect(otherPoint)) {
                 return true;
             }
         }
-    } else if (NULL != _multiPolygon) {
+    } else if (nullptr != _multiPolygon) {
         const vector<S2Polygon*>& polys = _multiPolygon->polygons.vector();
         for (size_t i = 0; i < polys.size(); ++i) {
             if (polys[i]->MayIntersect(otherPoint)) {
                 return true;
             }
         }
-    } else if (NULL != _geometryCollection) {
+    } else if (nullptr != _geometryCollection) {
         const GeometryCollection& c = *_geometryCollection;
 
         for (size_t i = 0; i < c.points.size(); ++i) {
@@ -728,33 +729,33 @@ bool polygonLineIntersection(const S2Polyline& line, const S2Polygon& poly) {
 }
 
 bool GeometryContainer::intersects(const S2Polyline& otherLine) const {
-    if (NULL != _point) {
+    if (nullptr != _point) {
         return otherLine.MayIntersect(_point->cell);
-    } else if (NULL != _line) {
+    } else if (nullptr != _line) {
         return otherLine.Intersects(&_line->line);
-    } else if (NULL != _polygon && NULL != _polygon->s2Polygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->s2Polygon) {
         return polygonLineIntersection(otherLine, *_polygon->s2Polygon);
-    } else if (NULL != _polygon && NULL != _polygon->bigPolygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->bigPolygon) {
         return _polygon->bigPolygon->Intersects(otherLine);
-    } else if (NULL != _multiPoint) {
+    } else if (nullptr != _multiPoint) {
         for (size_t i = 0; i < _multiPoint->cells.size(); ++i) {
             if (otherLine.MayIntersect(_multiPoint->cells[i])) {
                 return true;
             }
         }
-    } else if (NULL != _multiLine) {
+    } else if (nullptr != _multiLine) {
         for (size_t i = 0; i < _multiLine->lines.vector().size(); ++i) {
             if (otherLine.Intersects(_multiLine->lines.vector()[i])) {
                 return true;
             }
         }
-    } else if (NULL != _multiPolygon) {
+    } else if (nullptr != _multiPolygon) {
         for (size_t i = 0; i < _multiPolygon->polygons.vector().size(); ++i) {
             if (polygonLineIntersection(otherLine, *_multiPolygon->polygons.vector()[i])) {
                 return true;
             }
         }
-    } else if (NULL != _geometryCollection) {
+    } else if (nullptr != _geometryCollection) {
         const GeometryCollection& c = *_geometryCollection;
 
         for (size_t i = 0; i < c.points.size(); ++i) {
@@ -808,33 +809,33 @@ bool GeometryContainer::intersects(const S2Polyline& otherLine) const {
 
 // Does 'this' intersect with the provided polygon?
 bool GeometryContainer::intersects(const S2Polygon& otherPolygon) const {
-    if (NULL != _point) {
+    if (nullptr != _point) {
         return otherPolygon.MayIntersect(_point->cell);
-    } else if (NULL != _line) {
+    } else if (nullptr != _line) {
         return polygonLineIntersection(_line->line, otherPolygon);
-    } else if (NULL != _polygon && NULL != _polygon->s2Polygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->s2Polygon) {
         return otherPolygon.Intersects(_polygon->s2Polygon.get());
-    } else if (NULL != _polygon && NULL != _polygon->bigPolygon) {
+    } else if (nullptr != _polygon && nullptr != _polygon->bigPolygon) {
         return _polygon->bigPolygon->Intersects(otherPolygon);
-    } else if (NULL != _multiPoint) {
+    } else if (nullptr != _multiPoint) {
         for (size_t i = 0; i < _multiPoint->cells.size(); ++i) {
             if (otherPolygon.MayIntersect(_multiPoint->cells[i])) {
                 return true;
             }
         }
-    } else if (NULL != _multiLine) {
+    } else if (nullptr != _multiLine) {
         for (size_t i = 0; i < _multiLine->lines.vector().size(); ++i) {
             if (polygonLineIntersection(*_multiLine->lines.vector()[i], otherPolygon)) {
                 return true;
             }
         }
-    } else if (NULL != _multiPolygon) {
+    } else if (nullptr != _multiPolygon) {
         for (size_t i = 0; i < _multiPolygon->polygons.vector().size(); ++i) {
             if (otherPolygon.Intersects(_multiPolygon->polygons.vector()[i])) {
                 return true;
             }
         }
-    } else if (NULL != _geometryCollection) {
+    } else if (nullptr != _geometryCollection) {
         const GeometryCollection& c = *_geometryCollection;
 
         for (size_t i = 0; i < c.points.size(); ++i) {
@@ -1069,23 +1070,23 @@ Status GeometryContainer::parseFromStorage(const BSONElement& elem, bool skipVal
 }
 
 string GeometryContainer::getDebugType() const {
-    if (NULL != _point) {
+    if (nullptr != _point) {
         return "pt";
-    } else if (NULL != _line) {
+    } else if (nullptr != _line) {
         return "ln";
-    } else if (NULL != _box) {
+    } else if (nullptr != _box) {
         return "bx";
-    } else if (NULL != _polygon) {
+    } else if (nullptr != _polygon) {
         return "pl";
-    } else if (NULL != _cap) {
+    } else if (nullptr != _cap) {
         return "cc";
-    } else if (NULL != _multiPoint) {
+    } else if (nullptr != _multiPoint) {
         return "mp";
-    } else if (NULL != _multiLine) {
+    } else if (nullptr != _multiLine) {
         return "ml";
-    } else if (NULL != _multiPolygon) {
+    } else if (nullptr != _multiPolygon) {
         return "my";
-    } else if (NULL != _geometryCollection) {
+    } else if (nullptr != _geometryCollection) {
         return "gc";
     } else {
         MONGO_UNREACHABLE;
@@ -1096,23 +1097,23 @@ string GeometryContainer::getDebugType() const {
 CRS GeometryContainer::getNativeCRS() const {
     // TODO: Fix geometry collection reporting when/if we support multiple CRSes
 
-    if (NULL != _point) {
+    if (nullptr != _point) {
         return _point->crs;
-    } else if (NULL != _line) {
+    } else if (nullptr != _line) {
         return _line->crs;
-    } else if (NULL != _box) {
+    } else if (nullptr != _box) {
         return _box->crs;
-    } else if (NULL != _polygon) {
+    } else if (nullptr != _polygon) {
         return _polygon->crs;
-    } else if (NULL != _cap) {
+    } else if (nullptr != _cap) {
         return _cap->crs;
-    } else if (NULL != _multiPoint) {
+    } else if (nullptr != _multiPoint) {
         return _multiPoint->crs;
-    } else if (NULL != _multiLine) {
+    } else if (nullptr != _multiLine) {
         return _multiLine->crs;
-    } else if (NULL != _multiPolygon) {
+    } else if (nullptr != _multiPolygon) {
         return _multiPolygon->crs;
-    } else if (NULL != _geometryCollection) {
+    } else if (nullptr != _geometryCollection) {
         return SPHERE;
     } else {
         MONGO_UNREACHABLE;
@@ -1123,24 +1124,24 @@ CRS GeometryContainer::getNativeCRS() const {
 bool GeometryContainer::supportsProject(CRS otherCRS) const {
     // TODO: Fix geometry collection reporting when/if we support more CRSes
 
-    if (NULL != _point) {
+    if (nullptr != _point) {
         return ShapeProjection::supportsProject(*_point, otherCRS);
-    } else if (NULL != _line) {
+    } else if (nullptr != _line) {
         return _line->crs == otherCRS;
-    } else if (NULL != _box) {
+    } else if (nullptr != _box) {
         return _box->crs == otherCRS;
-    } else if (NULL != _polygon) {
+    } else if (nullptr != _polygon) {
         return ShapeProjection::supportsProject(*_polygon, otherCRS);
-    } else if (NULL != _cap) {
+    } else if (nullptr != _cap) {
         return _cap->crs == otherCRS;
-    } else if (NULL != _multiPoint) {
+    } else if (nullptr != _multiPoint) {
         return _multiPoint->crs == otherCRS;
-    } else if (NULL != _multiLine) {
+    } else if (nullptr != _multiLine) {
         return _multiLine->crs == otherCRS;
-    } else if (NULL != _multiPolygon) {
+    } else if (nullptr != _multiPolygon) {
         return _multiPolygon->crs == otherCRS;
     } else {
-        invariant(NULL != _geometryCollection);
+        invariant(nullptr != _geometryCollection);
         return SPHERE == otherCRS;
     }
 }
@@ -1149,12 +1150,12 @@ void GeometryContainer::projectInto(CRS otherCRS) {
     if (getNativeCRS() == otherCRS)
         return;
 
-    if (NULL != _polygon) {
+    if (nullptr != _polygon) {
         ShapeProjection::projectInto(_polygon.get(), otherCRS);
         return;
     }
 
-    invariant(NULL != _point);
+    invariant(nullptr != _point);
     ShapeProjection::projectInto(_point.get(), otherCRS);
 }
 
@@ -1228,7 +1229,7 @@ static double s2MinDistanceRad(const S2Point& s2Point,
          ++it) {
         invariant(SPHERE == (*it)->crs);
         // We don't support distances for big polygons yet.
-        invariant(NULL != (*it)->s2Polygon);
+        invariant(nullptr != (*it)->s2Polygon);
         double nextDistance = S2Distance::minDistanceRad(s2Point, *((*it)->s2Polygon));
         if (minDistance < 0 || nextDistance < minDistance) {
             minDistance = nextDistance;
@@ -1272,7 +1273,7 @@ double GeometryContainer::minDistance(const PointWithCRS& otherPoint) const {
     const CRS crs = getNativeCRS();
 
     if (FLAT == crs) {
-        invariant(NULL != _point);
+        invariant(nullptr != _point);
 
         if (FLAT == otherPoint.crs) {
             return distance(_point->oldPoint, otherPoint.oldPoint);
@@ -1286,23 +1287,23 @@ double GeometryContainer::minDistance(const PointWithCRS& otherPoint) const {
 
         double minDistance = -1;
 
-        if (NULL != _point) {
+        if (nullptr != _point) {
             minDistance = S2Distance::distanceRad(otherPoint.point, _point->point);
-        } else if (NULL != _line) {
+        } else if (nullptr != _line) {
             minDistance = S2Distance::minDistanceRad(otherPoint.point, _line->line);
-        } else if (NULL != _polygon) {
+        } else if (nullptr != _polygon) {
             // We don't support distances for big polygons yet.
-            invariant(NULL != _polygon->s2Polygon);
+            invariant(nullptr != _polygon->s2Polygon);
             minDistance = S2Distance::minDistanceRad(otherPoint.point, *_polygon->s2Polygon);
-        } else if (NULL != _cap) {
+        } else if (nullptr != _cap) {
             minDistance = S2Distance::minDistanceRad(otherPoint.point, _cap->cap);
-        } else if (NULL != _multiPoint) {
+        } else if (nullptr != _multiPoint) {
             minDistance = s2MinDistanceRad(otherPoint.point, *_multiPoint);
-        } else if (NULL != _multiLine) {
+        } else if (nullptr != _multiLine) {
             minDistance = s2MinDistanceRad(otherPoint.point, *_multiLine);
-        } else if (NULL != _multiPolygon) {
+        } else if (nullptr != _multiPolygon) {
             minDistance = s2MinDistanceRad(otherPoint.point, *_multiPolygon);
-        } else if (NULL != _geometryCollection) {
+        } else if (nullptr != _geometryCollection) {
             minDistance = s2MinDistanceRad(otherPoint.point, *_geometryCollection);
         }
 
diff --git a/src/mongo/db/geo/hash.cpp b/src/mongo/db/geo/hash.cpp
index f74a403f77b..761f8c79213 100644
--- a/src/mongo/db/geo/hash.cpp
+++ b/src/mongo/db/geo/hash.cpp
@@ -738,7 +738,7 @@ GeoHash GeoHashConverter::hash(const Point& p) const {
 }
 
 GeoHash GeoHashConverter::hash(const BSONObj& o) const {
-    return hash(o, NULL);
+    return hash(o, nullptr);
 }
 
 // src is printed out as debugging information.  Maybe it is actually somehow the 'source' of o?
diff --git a/src/mongo/db/geo/r2_region_coverer.cpp b/src/mongo/db/geo/r2_region_coverer.cpp
index 4b170dbc1d3..67ebbf37924 100644
--- a/src/mongo/db/geo/r2_region_coverer.cpp
+++ b/src/mongo/db/geo/r2_region_coverer.cpp
@@ -61,7 +61,7 @@ R2RegionCoverer::R2RegionCoverer(GeoHashConverter* hashConverter)
       _minLevel(0u),
       _maxLevel(GeoHash::kMaxBits),
       _maxCells(kDefaultMaxCells),
-      _region(NULL),
+      _region(nullptr),
       _candidateQueue(new CandidateQueue),
       _results(new vector<GeoHash>) {}
 
@@ -126,7 +126,7 @@ void R2RegionCoverer::getCovering(const R2Region& region, vector<GeoHash>* cover
         LOG(3) << "Queue: " << _candidateQueue->size();
     }
 
-    _region = NULL;
+    _region = nullptr;
     cover->swap(*_results);
 }
 
@@ -136,7 +136,7 @@ R2RegionCoverer::Candidate* R2RegionCoverer::newCandidate(const GeoHash& cell) {
     Box box = _hashConverter->unhashToBoxCovering(cell);
 
     if (_region->fastDisjoint(box)) {
-        return NULL;
+        return nullptr;
     }
 
     Candidate* candidate = new Candidate();
@@ -152,7 +152,7 @@ R2RegionCoverer::Candidate* R2RegionCoverer::newCandidate(const GeoHash& cell) {
 
 // Takes ownership of "candidate"
 void R2RegionCoverer::addCandidate(Candidate* candidate) {
-    if (candidate == NULL)
+    if (candidate == nullptr)
         return;
 
     if (candidate->isTerminal) {
diff --git a/src/mongo/db/index/index_descriptor.cpp b/src/mongo/db/index/index_descriptor.cpp
index edae421b9f6..d90a8dddad3 100644
--- a/src/mongo/db/index/index_descriptor.cpp
+++ b/src/mongo/db/index/index_descriptor.cpp
@@ -112,7 +112,7 @@ IndexDescriptor::IndexDescriptor(Collection* collection,
       _sparse(infoObj[IndexDescriptor::kSparseFieldName].trueValue()),
       _unique(_isIdIndex || infoObj[kUniqueFieldName].trueValue()),
       _partial(!infoObj[kPartialFilterExprFieldName].eoo()),
-      _cachedEntry(NULL) {
+      _cachedEntry(nullptr) {
     _indexNamespace = NamespaceString(_parentNS).makeIndexNamespace(_indexName).ns();
 
     BSONElement e = _infoObj[IndexDescriptor::kIndexVersionFieldName];
diff --git a/src/mongo/db/initialize_server_global_state.cpp b/src/mongo/db/initialize_server_global_state.cpp
index 0565045ba9f..5fa77e32020 100644
--- a/src/mongo/db/initialize_server_global_state.cpp
+++ b/src/mongo/db/initialize_server_global_state.cpp
@@ -177,21 +177,21 @@ static bool forkServer() {
         // this is run in the final child process (the server)
 
         FILE* f = freopen("/dev/null", "w", stdout);
-        if (f == NULL) {
+        if (f == nullptr) {
             cout << "Cant reassign stdout while forking server process: " << strerror(errno)
                  << endl;
             return false;
         }
 
         f = freopen("/dev/null", "w", stderr);
-        if (f == NULL) {
+        if (f == nullptr) {
             cout << "Cant reassign stderr while forking server process: " << strerror(errno)
                  << endl;
             return false;
         }
 
         f = freopen("/dev/null", "r", stdin);
-        if (f == NULL) {
+        if (f == nullptr) {
             cout << "Cant reassign stdin while forking server process: " << strerror(errno) << endl;
             return false;
         }
diff --git a/src/mongo/db/matcher/expression_array.cpp b/src/mongo/db/matcher/expression_array.cpp
index af7205ef822..c00d5899eda 100644
--- a/src/mongo/db/matcher/expression_array.cpp
+++ b/src/mongo/db/matcher/expression_array.cpp
@@ -77,7 +77,7 @@ bool ElemMatchObjectMatchExpression::matchesArray(const BSONObj& anArray,
         BSONElement inner = i.next();
         if (!inner.isABSONObj())
             continue;
-        if (_sub->matchesBSON(inner.Obj(), NULL)) {
+        if (_sub->matchesBSON(inner.Obj(), nullptr)) {
             if (details && details->needRecord()) {
                 details->setElemMatchKey(inner.fieldName());
             }
@@ -92,7 +92,7 @@ void ElemMatchObjectMatchExpression::debugString(StringBuilder& debug, int inden
     debug << path() << " $elemMatch (obj)";
 
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
@@ -165,7 +165,7 @@ void ElemMatchValueMatchExpression::debugString(StringBuilder& debug, int indent
     debug << path() << " $elemMatch (value)";
 
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
@@ -218,7 +218,7 @@ void SizeMatchExpression::debugString(StringBuilder& debug, int indentationLevel
     debug << path() << " $size : " << _size << "\n";
 
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
diff --git a/src/mongo/db/matcher/expression_array_test.cpp b/src/mongo/db/matcher/expression_array_test.cpp
index 6c9ac139edd..40e94ef38ee 100644
--- a/src/mongo/db/matcher/expression_array_test.cpp
+++ b/src/mongo/db/matcher/expression_array_test.cpp
@@ -92,29 +92,30 @@ TEST(ElemMatchObjectMatchExpression, MatchesNonArray) {
     ElemMatchObjectMatchExpression op("a", eq.release());
     // Directly nested objects are not matched with $elemMatch.  An intervening array is
     // required.
-    ASSERT(!op.matchesBSON(BSON("a" << BSON("b" << 5)), NULL));
-    ASSERT(!op.matchesBSON(BSON("a" << BSON("0" << (BSON("b" << 5)))), NULL));
-    ASSERT(!op.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(!op.matchesBSON(BSON("a" << BSON("b" << 5)), nullptr));
+    ASSERT(!op.matchesBSON(BSON("a" << BSON("0" << (BSON("b" << 5)))), nullptr));
+    ASSERT(!op.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(ElemMatchObjectMatchExpression, MatchesArrayObject) {
     BSONObj baseOperand = BSON("b" << 5);
     unique_ptr<ComparisonMatchExpression> eq(new EqualityMatchExpression("b", baseOperand["b"]));
     ElemMatchObjectMatchExpression op("a", eq.release());
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 5))), NULL));
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(4 << BSON("b" << 5))), NULL));
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSONObj() << BSON("b" << 5))), NULL));
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 6) << BSON("b" << 5))), NULL));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 5))), nullptr));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(4 << BSON("b" << 5))), nullptr));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSONObj() << BSON("b" << 5))), nullptr));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 6) << BSON("b" << 5))), nullptr));
 }
 
 TEST(ElemMatchObjectMatchExpression, MatchesMultipleNamedValues) {
     BSONObj baseOperand = BSON("c" << 5);
     unique_ptr<ComparisonMatchExpression> eq(new EqualityMatchExpression("c", baseOperand["c"]));
     ElemMatchObjectMatchExpression op("a.b", eq.release());
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSON_ARRAY(BSON("c" << 5))))), NULL));
+    ASSERT(
+        op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSON_ARRAY(BSON("c" << 5))))), nullptr));
     ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSON_ARRAY(BSON("c" << 1)))
                                                  << BSON("b" << BSON_ARRAY(BSON("c" << 5))))),
-                          NULL));
+                          nullptr));
 }
 
 TEST(ElemMatchObjectMatchExpression, ElemMatchKey) {
@@ -202,27 +203,27 @@ TEST(ElemMatchValueMatchExpression, MatchesNonArray) {
     ElemMatchObjectMatchExpression op("a", gt.release());
     // Directly nested objects are not matched with $elemMatch.  An intervening array is
     // required.
-    ASSERT(!op.matchesBSON(BSON("a" << 6), NULL));
-    ASSERT(!op.matchesBSON(BSON("a" << BSON("0" << 6)), NULL));
+    ASSERT(!op.matchesBSON(BSON("a" << 6), nullptr));
+    ASSERT(!op.matchesBSON(BSON("a" << BSON("0" << 6)), nullptr));
 }
 
 TEST(ElemMatchValueMatchExpression, MatchesArrayScalar) {
     BSONObj baseOperand = BSON("$gt" << 5);
     unique_ptr<ComparisonMatchExpression> gt(new GTMatchExpression("", baseOperand["$gt"]));
     ElemMatchValueMatchExpression op("a", gt.release());
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(6)), NULL));
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), NULL));
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSONObj() << 7)), NULL));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(6)), nullptr));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), nullptr));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSONObj() << 7)), nullptr));
 }
 
 TEST(ElemMatchValueMatchExpression, MatchesMultipleNamedValues) {
     BSONObj baseOperand = BSON("$gt" << 5);
     unique_ptr<ComparisonMatchExpression> gt(new GTMatchExpression("", baseOperand["$gt"]));
     ElemMatchValueMatchExpression op("a.b", gt.release());
-    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSON_ARRAY(6)))), NULL));
+    ASSERT(op.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSON_ARRAY(6)))), nullptr));
     ASSERT(op.matchesBSON(
         BSON("a" << BSON_ARRAY(BSON("b" << BSON_ARRAY(4)) << BSON("b" << BSON_ARRAY(4 << 6)))),
-        NULL));
+        nullptr));
 }
 
 TEST(ElemMatchValueMatchExpression, ElemMatchKey) {
@@ -345,19 +346,19 @@ TEST(AndOfElemMatch, Matches) {
     andOfEM->add(elemMatch2.release());
 
     BSONObj nonArray = BSON("x" << 4);
-    ASSERT(!andOfEM->matchesBSON(nonArray, NULL));
+    ASSERT(!andOfEM->matchesBSON(nonArray, nullptr));
     BSONObj emptyArray = BSON("x" << BSONArray());
-    ASSERT(!andOfEM->matchesBSON(emptyArray, NULL));
+    ASSERT(!andOfEM->matchesBSON(emptyArray, nullptr));
     BSONObj nonNumberArray = BSON("x" << BSON_ARRAY("q"));
-    ASSERT(!andOfEM->matchesBSON(nonNumberArray, NULL));
+    ASSERT(!andOfEM->matchesBSON(nonNumberArray, nullptr));
     BSONObj singleMatch = BSON("x" << BSON_ARRAY(5));
-    ASSERT(!andOfEM->matchesBSON(singleMatch, NULL));
+    ASSERT(!andOfEM->matchesBSON(singleMatch, nullptr));
     BSONObj otherMatch = BSON("x" << BSON_ARRAY(105));
-    ASSERT(!andOfEM->matchesBSON(otherMatch, NULL));
+    ASSERT(!andOfEM->matchesBSON(otherMatch, nullptr));
     BSONObj bothMatch = BSON("x" << BSON_ARRAY(5 << 105));
-    ASSERT(andOfEM->matchesBSON(bothMatch, NULL));
+    ASSERT(andOfEM->matchesBSON(bothMatch, nullptr));
     BSONObj neitherMatch = BSON("x" << BSON_ARRAY(0 << 200));
-    ASSERT(!andOfEM->matchesBSON(neitherMatch, NULL));
+    ASSERT(!andOfEM->matchesBSON(neitherMatch, nullptr));
 }
 
 TEST(SizeMatchExpression, MatchesElement) {
@@ -382,15 +383,15 @@ TEST(SizeMatchExpression, MatchesNonArray) {
 
 TEST(SizeMatchExpression, MatchesArray) {
     SizeMatchExpression size("a", 2);
-    ASSERT(size.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5)), NULL));
+    ASSERT(size.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5)), nullptr));
     // Arrays are not unwound to look for matching subarrays.
-    ASSERT(!size.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5 << BSON_ARRAY(1 << 2))), NULL));
+    ASSERT(!size.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5 << BSON_ARRAY(1 << 2))), nullptr));
 }
 
 TEST(SizeMatchExpression, MatchesNestedArray) {
     SizeMatchExpression size("a.2", 2);
     // A numerically referenced nested array is matched.
-    ASSERT(size.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5 << BSON_ARRAY(1 << 2))), NULL));
+    ASSERT(size.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5 << BSON_ARRAY(1 << 2))), nullptr));
 }
 
 TEST(SizeMatchExpression, ElemMatchKey) {
diff --git a/src/mongo/db/matcher/expression_geo.cpp b/src/mongo/db/matcher/expression_geo.cpp
index 18e38b319f0..67ee37060d7 100644
--- a/src/mongo/db/matcher/expression_geo.cpp
+++ b/src/mongo/db/matcher/expression_geo.cpp
@@ -89,7 +89,7 @@ Status GeoExpression::parseQuery(const BSONObj& obj) {
         }
     }
 
-    if (geoContainer == NULL) {
+    if (geoContainer == nullptr) {
         return Status(ErrorCodes::BadValue, "geo query doesn't have any geometry");
     }
 
@@ -376,7 +376,7 @@ void GeoMatchExpression::debugString(StringBuilder& debug, int indentationLevel)
     debug << "GEO raw = " << builder.obj().toString();
 
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
@@ -434,7 +434,7 @@ void GeoNearMatchExpression::debugString(StringBuilder& debug, int indentationLe
     _debugAddSpace(debug, indentationLevel);
     debug << "GEONEAR " << _query->toString();
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
diff --git a/src/mongo/db/matcher/expression_leaf.cpp b/src/mongo/db/matcher/expression_leaf.cpp
index ee43237617e..3001eb59ba8 100644
--- a/src/mongo/db/matcher/expression_leaf.cpp
+++ b/src/mongo/db/matcher/expression_leaf.cpp
@@ -263,7 +263,7 @@ void RegexMatchExpression::debugString(StringBuilder& debug, int indentationLeve
     debug << path() << " regex /" << _regex << "/" << _flags;
 
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
@@ -306,7 +306,7 @@ void ModMatchExpression::debugString(StringBuilder& debug, int indentationLevel)
     _debugAddSpace(debug, indentationLevel);
     debug << path() << " mod " << _divisor << " % x == " << _remainder;
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
@@ -340,7 +340,7 @@ void ExistsMatchExpression::debugString(StringBuilder& debug, int indentationLev
     _debugAddSpace(debug, indentationLevel);
     debug << path() << " exists";
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
@@ -416,7 +416,7 @@ void InMatchExpression::debugString(StringBuilder& debug, int indentationLevel)
     }
     debug << "]";
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         debug << " ";
         td->debugString(&debug);
     }
diff --git a/src/mongo/db/matcher/expression_leaf_test.cpp b/src/mongo/db/matcher/expression_leaf_test.cpp
index bb06d26b7f7..859fbe3bc98 100644
--- a/src/mongo/db/matcher/expression_leaf_test.cpp
+++ b/src/mongo/db/matcher/expression_leaf_test.cpp
@@ -71,7 +71,7 @@ TEST(ComparisonMatchExpression, StringMatchingWithNullCollatorUsesBinaryComparis
     EqualityMatchExpression eq("a", operand["a"]);
     ASSERT(!eq.matchesBSON(BSON("a"
                                 << "string2"),
-                           NULL));
+                           nullptr));
 }
 
 TEST(ComparisonMatchExpression, StringMatchingRespectsCollation) {
@@ -82,7 +82,7 @@ TEST(ComparisonMatchExpression, StringMatchingRespectsCollation) {
     eq.setCollator(&collator);
     ASSERT(eq.matchesBSON(BSON("a"
                                << "string2"),
-                          NULL));
+                          nullptr));
 }
 
 TEST(EqOp, MatchesElement) {
@@ -105,40 +105,40 @@ DEATH_TEST(EqOp, InvalidEooOperand, "Invariant failure _rhs") {
 TEST(EqOp, MatchesScalar) {
     BSONObj operand = BSON("a" << 5);
     EqualityMatchExpression eq("a", operand["a"]);
-    ASSERT(eq.matchesBSON(BSON("a" << 5.0), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(eq.matchesBSON(BSON("a" << 5.0), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(EqOp, MatchesArrayValue) {
     BSONObj operand = BSON("a" << 5);
     EqualityMatchExpression eq("a", operand["a"]);
-    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(5.0 << 6)), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), NULL));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(5.0 << 6)), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), nullptr));
 }
 
 TEST(EqOp, MatchesReferencedObjectValue) {
     BSONObj operand = BSON("a.b" << 5);
     EqualityMatchExpression eq("a.b", operand["a.b"]);
-    ASSERT(eq.matchesBSON(BSON("a" << BSON("b" << 5)), NULL));
-    ASSERT(eq.matchesBSON(BSON("a" << BSON("b" << BSON_ARRAY(5))), NULL));
-    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 5))), NULL));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON("b" << 5)), nullptr));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON("b" << BSON_ARRAY(5))), nullptr));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 5))), nullptr));
 }
 
 TEST(EqOp, MatchesReferencedArrayValue) {
     BSONObj operand = BSON("a.0" << 5);
     EqualityMatchExpression eq("a.0", operand["a.0"]);
-    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(5)), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), NULL));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(5)), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), nullptr));
 }
 
 TEST(EqOp, MatchesNull) {
     BSONObj operand = BSON("a" << BSONNULL);
     EqualityMatchExpression eq("a", operand["a"]);
-    ASSERT(eq.matchesBSON(BSONObj(), NULL));
-    ASSERT(eq.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(eq.matchesBSON(BSONObj(), nullptr));
+    ASSERT(eq.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << 4), nullptr));
     // A non-existent field is treated same way as an empty bson object
-    ASSERT(eq.matchesBSON(BSON("b" << 4), NULL));
+    ASSERT(eq.matchesBSON(BSON("b" << 4), nullptr));
 }
 
 // This test documents how the matcher currently works,
@@ -147,19 +147,19 @@ TEST(EqOp, MatchesNestedNull) {
     BSONObj operand = BSON("a.b" << BSONNULL);
     EqualityMatchExpression eq("a.b", operand["a.b"]);
     // null matches any empty object that is on a subpath of a.b
-    ASSERT(eq.matchesBSON(BSONObj(), NULL));
-    ASSERT(eq.matchesBSON(BSON("a" << BSONObj()), NULL));
-    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(BSONObj())), NULL));
-    ASSERT(eq.matchesBSON(BSON("a" << BSON("b" << BSONNULL)), NULL));
+    ASSERT(eq.matchesBSON(BSONObj(), nullptr));
+    ASSERT(eq.matchesBSON(BSON("a" << BSONObj()), nullptr));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(BSONObj())), nullptr));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON("b" << BSONNULL)), nullptr));
     // b does not exist as an element in array under a.
-    ASSERT(!eq.matchesBSON(BSON("a" << BSONArray()), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(BSONNULL)), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), NULL));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSONArray()), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(BSONNULL)), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), nullptr));
     // a.b exists but is not null.
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON("b" << 4)), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON("b" << BSONObj())), NULL));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON("b" << 4)), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON("b" << BSONObj())), nullptr));
     // A non-existent field is treated same way as an empty bson object
-    ASSERT(eq.matchesBSON(BSON("b" << 4), NULL));
+    ASSERT(eq.matchesBSON(BSON("b" << 4), nullptr));
 }
 
 TEST(EqOp, MatchesMinKey) {
@@ -169,9 +169,9 @@ TEST(EqOp, MatchesMinKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(eq.matchesBSON(minKeyObj, NULL));
-    ASSERT(!eq.matchesBSON(maxKeyObj, NULL));
-    ASSERT(!eq.matchesBSON(numObj, NULL));
+    ASSERT(eq.matchesBSON(minKeyObj, nullptr));
+    ASSERT(!eq.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(!eq.matchesBSON(numObj, nullptr));
 
     ASSERT(eq.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(!eq.matchesSingleElement(maxKeyObj.firstElement()));
@@ -186,9 +186,9 @@ TEST(EqOp, MatchesMaxKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(!eq.matchesBSON(minKeyObj, NULL));
-    ASSERT(eq.matchesBSON(maxKeyObj, NULL));
-    ASSERT(!eq.matchesBSON(numObj, NULL));
+    ASSERT(!eq.matchesBSON(minKeyObj, nullptr));
+    ASSERT(eq.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(!eq.matchesBSON(numObj, nullptr));
 
     ASSERT(!eq.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(eq.matchesSingleElement(maxKeyObj.firstElement()));
@@ -198,17 +198,17 @@ TEST(EqOp, MatchesMaxKey) {
 TEST(EqOp, MatchesFullArray) {
     BSONObj operand = BSON("a" << BSON_ARRAY(1 << 2));
     EqualityMatchExpression eq("a", operand["a"]);
-    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2 << 3)), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(1)), NULL));
-    ASSERT(!eq.matchesBSON(BSON("a" << 1), NULL));
+    ASSERT(eq.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2 << 3)), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << BSON_ARRAY(1)), nullptr));
+    ASSERT(!eq.matchesBSON(BSON("a" << 1), nullptr));
 }
 
 TEST(EqOp, MatchesThroughNestedArray) {
     BSONObj operand = BSON("a.b.c.d" << 3);
     EqualityMatchExpression eq("a.b.c.d", operand["a.b.c.d"]);
     BSONObj obj = fromjson("{a:{b:[{c:[{d:1},{d:2}]},{c:[{d:3}]}]}}");
-    ASSERT(eq.matchesBSON(obj, NULL));
+    ASSERT(eq.matchesBSON(obj, nullptr));
 }
 
 TEST(EqOp, ElemMatchKey) {
@@ -273,57 +273,57 @@ DEATH_TEST(LtOp, InvalidEooOperand, "Invariant failure _rhs") {
 TEST(LtOp, MatchesScalar) {
     BSONObj operand = BSON("$lt" << 5);
     LTMatchExpression lt("a", operand["$lt"]);
-    ASSERT(lt.matchesBSON(BSON("a" << 4.5), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << 6), NULL));
+    ASSERT(lt.matchesBSON(BSON("a" << 4.5), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << 6), nullptr));
 }
 
 TEST(LtOp, MatchesScalarEmptyKey) {
     BSONObj operand = BSON("$lt" << 5);
     LTMatchExpression lt("", operand["$lt"]);
-    ASSERT(lt.matchesBSON(BSON("" << 4.5), NULL));
-    ASSERT(!lt.matchesBSON(BSON("" << 6), NULL));
+    ASSERT(lt.matchesBSON(BSON("" << 4.5), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("" << 6), nullptr));
 }
 
 TEST(LtOp, MatchesArrayValue) {
     BSONObj operand = BSON("$lt" << 5);
     LTMatchExpression lt("a", operand["$lt"]);
-    ASSERT(lt.matchesBSON(BSON("a" << BSON_ARRAY(6 << 4.5)), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), NULL));
+    ASSERT(lt.matchesBSON(BSON("a" << BSON_ARRAY(6 << 4.5)), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), nullptr));
 }
 
 TEST(LtOp, MatchesWholeArray) {
     BSONObj operand = BSON("$lt" << BSON_ARRAY(5));
     LTMatchExpression lt("a", operand["$lt"]);
-    ASSERT(lt.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(5)), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(6)), NULL));
+    ASSERT(lt.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(5)), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(6)), nullptr));
     // Nested array.
-    ASSERT(lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), NULL));
+    ASSERT(lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), nullptr));
 }
 
 TEST(LtOp, MatchesNull) {
     BSONObj operand = BSON("$lt" << BSONNULL);
     LTMatchExpression lt("a", operand["$lt"]);
-    ASSERT(!lt.matchesBSON(BSONObj(), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(!lt.matchesBSON(BSONObj(), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << 4), nullptr));
     // A non-existent field is treated same way as an empty bson object
-    ASSERT(!lt.matchesBSON(BSON("b" << 4), NULL));
+    ASSERT(!lt.matchesBSON(BSON("b" << 4), nullptr));
 }
 
 TEST(LtOp, MatchesDotNotationNull) {
     BSONObj operand = BSON("$lt" << BSONNULL);
     LTMatchExpression lt("a.b", operand["$lt"]);
-    ASSERT(!lt.matchesBSON(BSONObj(), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSONObj()), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), NULL));
+    ASSERT(!lt.matchesBSON(BSONObj(), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSONObj()), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(!lt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), nullptr));
 }
 
 TEST(LtOp, MatchesMinKey) {
@@ -333,9 +333,9 @@ TEST(LtOp, MatchesMinKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(!lt.matchesBSON(minKeyObj, NULL));
-    ASSERT(!lt.matchesBSON(maxKeyObj, NULL));
-    ASSERT(!lt.matchesBSON(numObj, NULL));
+    ASSERT(!lt.matchesBSON(minKeyObj, nullptr));
+    ASSERT(!lt.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(!lt.matchesBSON(numObj, nullptr));
 
     ASSERT(!lt.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(!lt.matchesSingleElement(maxKeyObj.firstElement()));
@@ -349,9 +349,9 @@ TEST(LtOp, MatchesMaxKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(lt.matchesBSON(minKeyObj, NULL));
-    ASSERT(!lt.matchesBSON(maxKeyObj, NULL));
-    ASSERT(lt.matchesBSON(numObj, NULL));
+    ASSERT(lt.matchesBSON(minKeyObj, nullptr));
+    ASSERT(!lt.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(lt.matchesBSON(numObj, nullptr));
 
     ASSERT(lt.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(!lt.matchesSingleElement(maxKeyObj.firstElement()));
@@ -394,50 +394,50 @@ DEATH_TEST(LteOp, InvalidEooOperand, "Invariant failure _rhs") {
 TEST(LteOp, MatchesScalar) {
     BSONObj operand = BSON("$lte" << 5);
     LTEMatchExpression lte("a", operand["$lte"]);
-    ASSERT(lte.matchesBSON(BSON("a" << 4.5), NULL));
-    ASSERT(!lte.matchesBSON(BSON("a" << 6), NULL));
+    ASSERT(lte.matchesBSON(BSON("a" << 4.5), nullptr));
+    ASSERT(!lte.matchesBSON(BSON("a" << 6), nullptr));
 }
 
 TEST(LteOp, MatchesArrayValue) {
     BSONObj operand = BSON("$lte" << 5);
     LTEMatchExpression lte("a", operand["$lte"]);
-    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(6 << 4.5)), NULL));
-    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), NULL));
+    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(6 << 4.5)), nullptr));
+    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), nullptr));
 }
 
 TEST(LteOp, MatchesWholeArray) {
     BSONObj operand = BSON("$lte" << BSON_ARRAY(5));
     LTEMatchExpression lte("a", operand["$lte"]);
-    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(5)), NULL));
-    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(6)), NULL));
+    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(5)), nullptr));
+    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(6)), nullptr));
     // Nested array.
-    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), NULL));
-    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), NULL));
+    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), nullptr));
+    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), nullptr));
 }
 
 TEST(LteOp, MatchesNull) {
     BSONObj operand = BSON("$lte" << BSONNULL);
     LTEMatchExpression lte("a", operand["$lte"]);
-    ASSERT(lte.matchesBSON(BSONObj(), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!lte.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(lte.matchesBSON(BSONObj(), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!lte.matchesBSON(BSON("a" << 4), nullptr));
     // A non-existent field is treated same way as an empty bson object
-    ASSERT(lte.matchesBSON(BSON("b" << 4), NULL));
+    ASSERT(lte.matchesBSON(BSON("b" << 4), nullptr));
 }
 
 TEST(LteOp, MatchesDotNotationNull) {
     BSONObj operand = BSON("$lte" << BSONNULL);
     LTEMatchExpression lte("a.b", operand["$lte"]);
-    ASSERT(lte.matchesBSON(BSONObj(), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << BSONObj()), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), NULL));
-    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), NULL));
-    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), NULL));
+    ASSERT(lte.matchesBSON(BSONObj(), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << BSONObj()), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), nullptr));
+    ASSERT(lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), nullptr));
+    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(!lte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), nullptr));
 }
 
 TEST(LteOp, MatchesMinKey) {
@@ -447,9 +447,9 @@ TEST(LteOp, MatchesMinKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(lte.matchesBSON(minKeyObj, NULL));
-    ASSERT(!lte.matchesBSON(maxKeyObj, NULL));
-    ASSERT(!lte.matchesBSON(numObj, NULL));
+    ASSERT(lte.matchesBSON(minKeyObj, nullptr));
+    ASSERT(!lte.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(!lte.matchesBSON(numObj, nullptr));
 
     ASSERT(lte.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(!lte.matchesSingleElement(maxKeyObj.firstElement()));
@@ -463,9 +463,9 @@ TEST(LteOp, MatchesMaxKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(lte.matchesBSON(minKeyObj, NULL));
-    ASSERT(lte.matchesBSON(maxKeyObj, NULL));
-    ASSERT(lte.matchesBSON(numObj, NULL));
+    ASSERT(lte.matchesBSON(minKeyObj, nullptr));
+    ASSERT(lte.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(lte.matchesBSON(numObj, nullptr));
 
     ASSERT(lte.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(lte.matchesSingleElement(maxKeyObj.firstElement()));
@@ -495,52 +495,52 @@ DEATH_TEST(GtOp, InvalidEooOperand, "Invariant failure _rhs") {
 TEST(GtOp, MatchesScalar) {
     BSONObj operand = BSON("$gt" << 5);
     GTMatchExpression gt("a", operand["$gt"]);
-    ASSERT(gt.matchesBSON(BSON("a" << 5.5), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(gt.matchesBSON(BSON("a" << 5.5), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(GtOp, MatchesArrayValue) {
     BSONObj operand = BSON("$gt" << 5);
     GTMatchExpression gt("a", operand["$gt"]);
-    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(3 << 5.5)), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(2 << 4)), NULL));
+    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(3 << 5.5)), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(2 << 4)), nullptr));
 }
 
 TEST(GtOp, MatchesWholeArray) {
     BSONObj operand = BSON("$gt" << BSON_ARRAY(5));
     GTMatchExpression gt("a", operand["$gt"]);
-    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(5)), NULL));
-    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(6)), NULL));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(5)), nullptr));
+    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(6)), nullptr));
     // Nested array.
     // XXX: The following assertion documents current behavior.
-    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), NULL));
+    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), nullptr));
     // XXX: The following assertion documents current behavior.
-    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), NULL));
-    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), NULL));
+    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), nullptr));
+    ASSERT(gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), nullptr));
 }
 
 TEST(GtOp, MatchesNull) {
     BSONObj operand = BSON("$gt" << BSONNULL);
     GTMatchExpression gt("a", operand["$gt"]);
-    ASSERT(!gt.matchesBSON(BSONObj(), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(!gt.matchesBSON(BSONObj(), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << 4), nullptr));
     // A non-existent field is treated same way as an empty bson object
-    ASSERT(!gt.matchesBSON(BSON("b" << 4), NULL));
+    ASSERT(!gt.matchesBSON(BSON("b" << 4), nullptr));
 }
 
 TEST(GtOp, MatchesDotNotationNull) {
     BSONObj operand = BSON("$gt" << BSONNULL);
     GTMatchExpression gt("a.b", operand["$gt"]);
-    ASSERT(!gt.matchesBSON(BSONObj(), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSONObj()), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), NULL));
+    ASSERT(!gt.matchesBSON(BSONObj(), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSONObj()), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(!gt.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), nullptr));
 }
 
 TEST(GtOp, MatchesMinKey) {
@@ -550,9 +550,9 @@ TEST(GtOp, MatchesMinKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(!gt.matchesBSON(minKeyObj, NULL));
-    ASSERT(gt.matchesBSON(maxKeyObj, NULL));
-    ASSERT(gt.matchesBSON(numObj, NULL));
+    ASSERT(!gt.matchesBSON(minKeyObj, nullptr));
+    ASSERT(gt.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(gt.matchesBSON(numObj, nullptr));
 
     ASSERT(!gt.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(gt.matchesSingleElement(maxKeyObj.firstElement()));
@@ -566,9 +566,9 @@ TEST(GtOp, MatchesMaxKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(!gt.matchesBSON(minKeyObj, NULL));
-    ASSERT(!gt.matchesBSON(maxKeyObj, NULL));
-    ASSERT(!gt.matchesBSON(numObj, NULL));
+    ASSERT(!gt.matchesBSON(minKeyObj, nullptr));
+    ASSERT(!gt.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(!gt.matchesBSON(numObj, nullptr));
 
     ASSERT(!gt.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(!gt.matchesSingleElement(maxKeyObj.firstElement()));
@@ -611,51 +611,51 @@ DEATH_TEST(GteOp, InvalidEooOperand, "Invariant failure _rhs") {
 TEST(GteOp, MatchesScalar) {
     BSONObj operand = BSON("$gte" << 5);
     GTEMatchExpression gte("a", operand["$gte"]);
-    ASSERT(gte.matchesBSON(BSON("a" << 5.5), NULL));
-    ASSERT(!gte.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(gte.matchesBSON(BSON("a" << 5.5), nullptr));
+    ASSERT(!gte.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(GteOp, MatchesArrayValue) {
     BSONObj operand = BSON("$gte" << 5);
     GTEMatchExpression gte("a", operand["$gte"]);
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5)), NULL));
-    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), NULL));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5)), nullptr));
+    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), nullptr));
 }
 
 TEST(GteOp, MatchesWholeArray) {
     BSONObj operand = BSON("$gte" << BSON_ARRAY(5));
     GTEMatchExpression gte("a", operand["$gte"]);
-    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(5)), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(6)), NULL));
+    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(5)), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(6)), nullptr));
     // Nested array.
     // XXX: The following assertion documents current behavior.
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), NULL));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(6))), nullptr));
 }
 
 TEST(GteOp, MatchesNull) {
     BSONObj operand = BSON("$gte" << BSONNULL);
     GTEMatchExpression gte("a", operand["$gte"]);
-    ASSERT(gte.matchesBSON(BSONObj(), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!gte.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(gte.matchesBSON(BSONObj(), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!gte.matchesBSON(BSON("a" << 4), nullptr));
     // A non-existent field is treated same way as an empty bson object
-    ASSERT(gte.matchesBSON(BSON("b" << 4), NULL));
+    ASSERT(gte.matchesBSON(BSON("b" << 4), nullptr));
 }
 
 TEST(GteOp, MatchesDotNotationNull) {
     BSONObj operand = BSON("$gte" << BSONNULL);
     GTEMatchExpression gte("a.b", operand["$gte"]);
-    ASSERT(gte.matchesBSON(BSONObj(), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSONObj()), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), NULL));
-    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), NULL));
-    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), NULL));
+    ASSERT(gte.matchesBSON(BSONObj(), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSONObj()), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << BSONNULL))), nullptr));
+    ASSERT(gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("a" << 4) << BSON("b" << 4))), nullptr));
+    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(!gte.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 4))), nullptr));
 }
 
 TEST(GteOp, MatchesMinKey) {
@@ -665,9 +665,9 @@ TEST(GteOp, MatchesMinKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(gte.matchesBSON(minKeyObj, NULL));
-    ASSERT(gte.matchesBSON(maxKeyObj, NULL));
-    ASSERT(gte.matchesBSON(numObj, NULL));
+    ASSERT(gte.matchesBSON(minKeyObj, nullptr));
+    ASSERT(gte.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(gte.matchesBSON(numObj, nullptr));
 
     ASSERT(gte.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(gte.matchesSingleElement(maxKeyObj.firstElement()));
@@ -681,9 +681,9 @@ TEST(GteOp, MatchesMaxKey) {
     BSONObj maxKeyObj = BSON("a" << MaxKey);
     BSONObj numObj = BSON("a" << 4);
 
-    ASSERT(!gte.matchesBSON(minKeyObj, NULL));
-    ASSERT(gte.matchesBSON(maxKeyObj, NULL));
-    ASSERT(!gte.matchesBSON(numObj, NULL));
+    ASSERT(!gte.matchesBSON(minKeyObj, nullptr));
+    ASSERT(gte.matchesBSON(maxKeyObj, nullptr));
+    ASSERT(!gte.matchesBSON(numObj, nullptr));
 
     ASSERT(!gte.matchesSingleElement(minKeyObj.firstElement()));
     ASSERT(gte.matchesSingleElement(maxKeyObj.firstElement()));
@@ -862,26 +862,26 @@ TEST(RegexMatchExpression, MatchesScalar) {
     RegexMatchExpression regex("a", "b", "");
     ASSERT(regex.matchesBSON(BSON("a"
                                   << "b"),
-                             NULL));
+                             nullptr));
     ASSERT(!regex.matchesBSON(BSON("a"
                                    << "c"),
-                              NULL));
+                              nullptr));
 }
 
 TEST(RegexMatchExpression, MatchesArrayValue) {
     RegexMatchExpression regex("a", "b", "");
     ASSERT(regex.matchesBSON(BSON("a" << BSON_ARRAY("c"
                                                     << "b")),
-                             NULL));
+                             nullptr));
     ASSERT(!regex.matchesBSON(BSON("a" << BSON_ARRAY("d"
                                                      << "c")),
-                              NULL));
+                              nullptr));
 }
 
 TEST(RegexMatchExpression, MatchesNull) {
     RegexMatchExpression regex("a", "b", "");
-    ASSERT(!regex.matchesBSON(BSONObj(), NULL));
-    ASSERT(!regex.matchesBSON(BSON("a" << BSONNULL), NULL));
+    ASSERT(!regex.matchesBSON(BSONObj(), nullptr));
+    ASSERT(!regex.matchesBSON(BSON("a" << BSONNULL), nullptr));
 }
 
 TEST(RegexMatchExpression, ElemMatchKey) {
@@ -1034,20 +1034,20 @@ TEST(ModMatchExpression, ZeroDivisor) {
 
 TEST(ModMatchExpression, MatchesScalar) {
     ModMatchExpression mod("a", 5, 2);
-    ASSERT(mod.matchesBSON(BSON("a" << 7.0), NULL));
-    ASSERT(!mod.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(mod.matchesBSON(BSON("a" << 7.0), nullptr));
+    ASSERT(!mod.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(ModMatchExpression, MatchesArrayValue) {
     ModMatchExpression mod("a", 5, 2);
-    ASSERT(mod.matchesBSON(BSON("a" << BSON_ARRAY(5 << 12LL)), NULL));
-    ASSERT(!mod.matchesBSON(BSON("a" << BSON_ARRAY(6 << 8)), NULL));
+    ASSERT(mod.matchesBSON(BSON("a" << BSON_ARRAY(5 << 12LL)), nullptr));
+    ASSERT(!mod.matchesBSON(BSON("a" << BSON_ARRAY(6 << 8)), nullptr));
 }
 
 TEST(ModMatchExpression, MatchesNull) {
     ModMatchExpression mod("a", 5, 2);
-    ASSERT(!mod.matchesBSON(BSONObj(), NULL));
-    ASSERT(!mod.matchesBSON(BSON("a" << BSONNULL), NULL));
+    ASSERT(!mod.matchesBSON(BSONObj(), nullptr));
+    ASSERT(!mod.matchesBSON(BSON("a" << BSONNULL), nullptr));
 }
 
 TEST(ModMatchExpression, ElemMatchKey) {
@@ -1095,14 +1095,14 @@ TEST(ExistsMatchExpression, MatchesElementExistsTrueValue) {
 
 TEST(ExistsMatchExpression, MatchesScalar) {
     ExistsMatchExpression exists("a");
-    ASSERT(exists.matchesBSON(BSON("a" << 1), NULL));
-    ASSERT(exists.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!exists.matchesBSON(BSON("b" << 1), NULL));
+    ASSERT(exists.matchesBSON(BSON("a" << 1), nullptr));
+    ASSERT(exists.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!exists.matchesBSON(BSON("b" << 1), nullptr));
 }
 
 TEST(ExistsMatchExpression, MatchesArray) {
     ExistsMatchExpression exists("a");
-    ASSERT(exists.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5)), NULL));
+    ASSERT(exists.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5.5)), nullptr));
 }
 
 TEST(ExistsMatchExpression, ElemMatchKey) {
@@ -1142,8 +1142,8 @@ TEST(InMatchExpression, MatchesEmpty) {
 
     BSONObj notMatch = BSON("a" << 2);
     ASSERT(!in.matchesSingleElement(notMatch["a"]));
-    ASSERT(!in.matchesBSON(BSON("a" << 1), NULL));
-    ASSERT(!in.matchesBSON(BSONObj(), NULL));
+    ASSERT(!in.matchesBSON(BSON("a" << 1), nullptr));
+    ASSERT(!in.matchesBSON(BSONObj(), nullptr));
 }
 
 TEST(InMatchExpression, MatchesElementMultiple) {
@@ -1170,8 +1170,8 @@ TEST(InMatchExpression, MatchesScalar) {
     std::vector<BSONElement> equalities{operand.firstElement()};
     ASSERT_OK(in.setEqualities(std::move(equalities)));
 
-    ASSERT(in.matchesBSON(BSON("a" << 5.0), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(in.matchesBSON(BSON("a" << 5.0), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(InMatchExpression, MatchesArrayValue) {
@@ -1180,9 +1180,9 @@ TEST(InMatchExpression, MatchesArrayValue) {
     std::vector<BSONElement> equalities{operand.firstElement()};
     ASSERT_OK(in.setEqualities(std::move(equalities)));
 
-    ASSERT(in.matchesBSON(BSON("a" << BSON_ARRAY(5.0 << 6)), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), NULL));
+    ASSERT(in.matchesBSON(BSON("a" << BSON_ARRAY(5.0 << 6)), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(6 << 7)), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(5))), nullptr));
 }
 
 TEST(InMatchExpression, MatchesNull) {
@@ -1192,11 +1192,11 @@ TEST(InMatchExpression, MatchesNull) {
     std::vector<BSONElement> equalities{operand.firstElement()};
     ASSERT_OK(in.setEqualities(std::move(equalities)));
 
-    ASSERT(in.matchesBSON(BSONObj(), NULL));
-    ASSERT(in.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(in.matchesBSON(BSONObj(), nullptr));
+    ASSERT(in.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << 4), nullptr));
     // A non-existent field is treated same way as an empty bson object
-    ASSERT(in.matchesBSON(BSON("b" << 4), NULL));
+    ASSERT(in.matchesBSON(BSON("b" << 4), nullptr));
 }
 
 TEST(InMatchExpression, MatchesUndefined) {
@@ -1213,9 +1213,9 @@ TEST(InMatchExpression, MatchesMinKey) {
     std::vector<BSONElement> equalities{operand.firstElement()};
     ASSERT_OK(in.setEqualities(std::move(equalities)));
 
-    ASSERT(in.matchesBSON(BSON("a" << MinKey), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << MaxKey), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(in.matchesBSON(BSON("a" << MinKey), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << MaxKey), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(InMatchExpression, MatchesMaxKey) {
@@ -1224,9 +1224,9 @@ TEST(InMatchExpression, MatchesMaxKey) {
     std::vector<BSONElement> equalities{operand.firstElement()};
     ASSERT_OK(in.setEqualities(std::move(equalities)));
 
-    ASSERT(in.matchesBSON(BSON("a" << MaxKey), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << MinKey), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(in.matchesBSON(BSON("a" << MaxKey), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << MinKey), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(InMatchExpression, MatchesFullArray) {
@@ -1235,10 +1235,10 @@ TEST(InMatchExpression, MatchesFullArray) {
     std::vector<BSONElement> equalities{operand[0], operand[1], operand[2]};
     ASSERT_OK(in.setEqualities(std::move(equalities)));
 
-    ASSERT(in.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2 << 3)), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(1)), NULL));
-    ASSERT(!in.matchesBSON(BSON("a" << 1), NULL));
+    ASSERT(in.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2)), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(1 << 2 << 3)), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << BSON_ARRAY(1)), nullptr));
+    ASSERT(!in.matchesBSON(BSON("a" << 1), nullptr));
 }
 
 TEST(InMatchExpression, ElemMatchKey) {
diff --git a/src/mongo/db/matcher/expression_serialization_test.cpp b/src/mongo/db/matcher/expression_serialization_test.cpp
index 7384c53e410..862b955423c 100644
--- a/src/mongo/db/matcher/expression_serialization_test.cpp
+++ b/src/mongo/db/matcher/expression_serialization_test.cpp
@@ -1695,7 +1695,7 @@ TEST(SerializeInternalBinDataSubType, ExpressionBinDataSubTypeSerializesCorrectl
                       fromjson("{x: {$_internalSchemaBinDataSubType: 1}}"));
     ASSERT_BSONOBJ_EQ(*reserialized.getQuery(), serialize(reserialized.getMatchExpression()));
 
-    BSONObj obj = BSON("x" << BSONBinData(NULL, 0, BinDataType::bdtCustom));
+    BSONObj obj = BSON("x" << BSONBinData(nullptr, 0, BinDataType::bdtCustom));
     ASSERT_EQ(original.matches(obj), reserialized.matches(obj));
 
     uint8_t bytes[] = {0, 1, 2, 10, 11, 12};
diff --git a/src/mongo/db/matcher/expression_text_base.cpp b/src/mongo/db/matcher/expression_text_base.cpp
index ea3fa147de2..e9d18bb2e2e 100644
--- a/src/mongo/db/matcher/expression_text_base.cpp
+++ b/src/mongo/db/matcher/expression_text_base.cpp
@@ -48,7 +48,7 @@ void TextMatchExpressionBase::debugString(StringBuilder& debug, int indentationL
           << ", caseSensitive=" << ftsQuery.getCaseSensitive()
           << ", diacriticSensitive=" << ftsQuery.getDiacriticSensitive() << ", tag=";
     MatchExpression::TagData* td = getTag();
-    if (NULL != td) {
+    if (nullptr != td) {
         td->debugString(&debug);
     } else {
         debug << "NULL";
diff --git a/src/mongo/db/matcher/expression_tree.cpp b/src/mongo/db/matcher/expression_tree.cpp
index b56e96f4924..1fb9cbc4af5 100644
--- a/src/mongo/db/matcher/expression_tree.cpp
+++ b/src/mongo/db/matcher/expression_tree.cpp
@@ -241,7 +241,7 @@ bool AndMatchExpression::isTriviallyTrue() const {
 
 bool OrMatchExpression::matches(const MatchableDocument* doc, MatchDetails* details) const {
     for (size_t i = 0; i < numChildren(); i++) {
-        if (getChild(i)->matches(doc, NULL)) {
+        if (getChild(i)->matches(doc, nullptr)) {
             return true;
         }
     }
@@ -284,7 +284,7 @@ bool OrMatchExpression::isTriviallyFalse() const {
 
 bool NorMatchExpression::matches(const MatchableDocument* doc, MatchDetails* details) const {
     for (size_t i = 0; i < numChildren(); i++) {
-        if (getChild(i)->matches(doc, NULL)) {
+        if (getChild(i)->matches(doc, nullptr)) {
             return false;
         }
     }
diff --git a/src/mongo/db/matcher/expression_tree.h b/src/mongo/db/matcher/expression_tree.h
index afecd935d79..b08ce6b03fb 100644
--- a/src/mongo/db/matcher/expression_tree.h
+++ b/src/mongo/db/matcher/expression_tree.h
@@ -110,7 +110,7 @@ public:
     AndMatchExpression() : ListOfMatchExpression(AND) {}
     virtual ~AndMatchExpression() {}
 
-    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = 0) const;
+    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = nullptr) const;
 
     bool matchesSingleElement(const BSONElement&, MatchDetails* details = nullptr) const final;
 
@@ -139,7 +139,7 @@ public:
     OrMatchExpression() : ListOfMatchExpression(OR) {}
     virtual ~OrMatchExpression() {}
 
-    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = 0) const;
+    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = nullptr) const;
 
     bool matchesSingleElement(const BSONElement&, MatchDetails* details = nullptr) const final;
 
@@ -168,7 +168,7 @@ public:
     NorMatchExpression() : ListOfMatchExpression(NOR) {}
     virtual ~NorMatchExpression() {}
 
-    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = 0) const;
+    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = nullptr) const;
 
     bool matchesSingleElement(const BSONElement&, MatchDetails* details = nullptr) const final;
 
@@ -201,8 +201,8 @@ public:
         return std::move(self);
     }
 
-    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = 0) const {
-        return !_exp->matches(doc, NULL);
+    virtual bool matches(const MatchableDocument* doc, MatchDetails* details = nullptr) const {
+        return !_exp->matches(doc, nullptr);
     }
 
     bool matchesSingleElement(const BSONElement& elt, MatchDetails* details = nullptr) const final {
diff --git a/src/mongo/db/matcher/expression_tree_test.cpp b/src/mongo/db/matcher/expression_tree_test.cpp
index a0770c2a4df..33bf9352e33 100644
--- a/src/mongo/db/matcher/expression_tree_test.cpp
+++ b/src/mongo/db/matcher/expression_tree_test.cpp
@@ -46,18 +46,18 @@ TEST(NotMatchExpression, MatchesScalar) {
     BSONObj baseOperand = BSON("$lt" << 5);
     unique_ptr<ComparisonMatchExpression> lt(new LTMatchExpression("a", baseOperand["$lt"]));
     NotMatchExpression notOp(lt.release());
-    ASSERT(notOp.matchesBSON(BSON("a" << 6), NULL));
-    ASSERT(!notOp.matchesBSON(BSON("a" << 4), NULL));
+    ASSERT(notOp.matchesBSON(BSON("a" << 6), nullptr));
+    ASSERT(!notOp.matchesBSON(BSON("a" << 4), nullptr));
 }
 
 TEST(NotMatchExpression, MatchesArray) {
     BSONObj baseOperand = BSON("$lt" << 5);
     unique_ptr<ComparisonMatchExpression> lt(new LTMatchExpression("a", baseOperand["$lt"]));
     NotMatchExpression notOp(lt.release());
-    ASSERT(notOp.matchesBSON(BSON("a" << BSON_ARRAY(6)), NULL));
-    ASSERT(!notOp.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
+    ASSERT(notOp.matchesBSON(BSON("a" << BSON_ARRAY(6)), nullptr));
+    ASSERT(!notOp.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
     // All array elements must match.
-    ASSERT(!notOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5 << 6)), NULL));
+    ASSERT(!notOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5 << 6)), nullptr));
 }
 
 TEST(NotMatchExpression, ElemMatchKey) {
@@ -89,7 +89,7 @@ TEST(NotMatchExpression, SetCollatorPropagatesToChild) {
 
 TEST(AndOp, NoClauses) {
     AndMatchExpression andMatchExpression;
-    ASSERT(andMatchExpression.matchesBSON(BSONObj(), NULL));
+    ASSERT(andMatchExpression.matchesBSON(BSONObj(), nullptr));
 }
 
 TEST(AndOp, MatchesElementThreeClauses) {
@@ -129,10 +129,10 @@ TEST(AndOp, MatchesSingleClause) {
     AndMatchExpression andOp;
     andOp.add(ne.release());
 
-    ASSERT(andOp.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(andOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), NULL));
-    ASSERT(!andOp.matchesBSON(BSON("a" << 5), NULL));
-    ASSERT(!andOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5)), NULL));
+    ASSERT(andOp.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(andOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), nullptr));
+    ASSERT(!andOp.matchesBSON(BSON("a" << 5), nullptr));
+    ASSERT(!andOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5)), nullptr));
 }
 
 TEST(AndOp, MatchesThreeClauses) {
@@ -149,11 +149,11 @@ TEST(AndOp, MatchesThreeClauses) {
     andOp.add(sub2.release());
     andOp.add(sub3.release());
 
-    ASSERT(andOp.matchesBSON(BSON("a" << 5 << "b" << 6), NULL));
-    ASSERT(!andOp.matchesBSON(BSON("a" << 5), NULL));
-    ASSERT(!andOp.matchesBSON(BSON("b" << 6), NULL));
-    ASSERT(!andOp.matchesBSON(BSON("a" << 1 << "b" << 6), NULL));
-    ASSERT(!andOp.matchesBSON(BSON("a" << 10 << "b" << 6), NULL));
+    ASSERT(andOp.matchesBSON(BSON("a" << 5 << "b" << 6), nullptr));
+    ASSERT(!andOp.matchesBSON(BSON("a" << 5), nullptr));
+    ASSERT(!andOp.matchesBSON(BSON("b" << 6), nullptr));
+    ASSERT(!andOp.matchesBSON(BSON("a" << 1 << "b" << 6), nullptr));
+    ASSERT(!andOp.matchesBSON(BSON("a" << 10 << "b" << 6), nullptr));
 }
 
 TEST(AndOp, ElemMatchKey) {
@@ -181,7 +181,7 @@ TEST(AndOp, ElemMatchKey) {
 
 TEST(OrOp, NoClauses) {
     OrMatchExpression orOp;
-    ASSERT(!orOp.matchesBSON(BSONObj(), NULL));
+    ASSERT(!orOp.matchesBSON(BSONObj(), nullptr));
 }
 
 TEST(OrOp, MatchesSingleClause) {
@@ -192,10 +192,10 @@ TEST(OrOp, MatchesSingleClause) {
     OrMatchExpression orOp;
     orOp.add(ne.release());
 
-    ASSERT(orOp.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(orOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), NULL));
-    ASSERT(!orOp.matchesBSON(BSON("a" << 5), NULL));
-    ASSERT(!orOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5)), NULL));
+    ASSERT(orOp.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(orOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), nullptr));
+    ASSERT(!orOp.matchesBSON(BSON("a" << 5), nullptr));
+    ASSERT(!orOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5)), nullptr));
 }
 
 TEST(OrOp, MatchesThreeClauses) {
@@ -211,13 +211,13 @@ TEST(OrOp, MatchesThreeClauses) {
     orOp.add(sub2.release());
     orOp.add(sub3.release());
 
-    ASSERT(orOp.matchesBSON(BSON("a" << -1), NULL));
-    ASSERT(orOp.matchesBSON(BSON("a" << 11), NULL));
-    ASSERT(!orOp.matchesBSON(BSON("a" << 5), NULL));
-    ASSERT(orOp.matchesBSON(BSON("b" << 100), NULL));
-    ASSERT(!orOp.matchesBSON(BSON("b" << 101), NULL));
-    ASSERT(!orOp.matchesBSON(BSONObj(), NULL));
-    ASSERT(orOp.matchesBSON(BSON("a" << 11 << "b" << 100), NULL));
+    ASSERT(orOp.matchesBSON(BSON("a" << -1), nullptr));
+    ASSERT(orOp.matchesBSON(BSON("a" << 11), nullptr));
+    ASSERT(!orOp.matchesBSON(BSON("a" << 5), nullptr));
+    ASSERT(orOp.matchesBSON(BSON("b" << 100), nullptr));
+    ASSERT(!orOp.matchesBSON(BSON("b" << 101), nullptr));
+    ASSERT(!orOp.matchesBSON(BSONObj(), nullptr));
+    ASSERT(orOp.matchesBSON(BSON("a" << 11 << "b" << 100), nullptr));
 }
 
 TEST(OrOp, ElemMatchKey) {
@@ -243,7 +243,7 @@ TEST(OrOp, ElemMatchKey) {
 
 TEST(NorOp, NoClauses) {
     NorMatchExpression norOp;
-    ASSERT(norOp.matchesBSON(BSONObj(), NULL));
+    ASSERT(norOp.matchesBSON(BSONObj(), nullptr));
 }
 
 TEST(NorOp, MatchesSingleClause) {
@@ -254,10 +254,10 @@ TEST(NorOp, MatchesSingleClause) {
     NorMatchExpression norOp;
     norOp.add(ne.release());
 
-    ASSERT(!norOp.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(!norOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), NULL));
-    ASSERT(norOp.matchesBSON(BSON("a" << 5), NULL));
-    ASSERT(norOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5)), NULL));
+    ASSERT(!norOp.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(!norOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 6)), nullptr));
+    ASSERT(norOp.matchesBSON(BSON("a" << 5), nullptr));
+    ASSERT(norOp.matchesBSON(BSON("a" << BSON_ARRAY(4 << 5)), nullptr));
 }
 
 TEST(NorOp, MatchesThreeClauses) {
@@ -274,13 +274,13 @@ TEST(NorOp, MatchesThreeClauses) {
     norOp.add(sub2.release());
     norOp.add(sub3.release());
 
-    ASSERT(!norOp.matchesBSON(BSON("a" << -1), NULL));
-    ASSERT(!norOp.matchesBSON(BSON("a" << 11), NULL));
-    ASSERT(norOp.matchesBSON(BSON("a" << 5), NULL));
-    ASSERT(!norOp.matchesBSON(BSON("b" << 100), NULL));
-    ASSERT(norOp.matchesBSON(BSON("b" << 101), NULL));
-    ASSERT(norOp.matchesBSON(BSONObj(), NULL));
-    ASSERT(!norOp.matchesBSON(BSON("a" << 11 << "b" << 100), NULL));
+    ASSERT(!norOp.matchesBSON(BSON("a" << -1), nullptr));
+    ASSERT(!norOp.matchesBSON(BSON("a" << 11), nullptr));
+    ASSERT(norOp.matchesBSON(BSON("a" << 5), nullptr));
+    ASSERT(!norOp.matchesBSON(BSON("b" << 100), nullptr));
+    ASSERT(norOp.matchesBSON(BSON("b" << 101), nullptr));
+    ASSERT(norOp.matchesBSON(BSONObj(), nullptr));
+    ASSERT(!norOp.matchesBSON(BSON("a" << 11 << "b" << 100), nullptr));
 }
 
 TEST(NorOp, ElemMatchKey) {
diff --git a/src/mongo/db/matcher/expression_type_test.cpp b/src/mongo/db/matcher/expression_type_test.cpp
index 403a60ee9f4..b4e9ed4b405 100644
--- a/src/mongo/db/matcher/expression_type_test.cpp
+++ b/src/mongo/db/matcher/expression_type_test.cpp
@@ -75,17 +75,17 @@ TEST(ExpressionTypeTest, MatchesElementNumber) {
 
 TEST(ExpressionTypeTest, MatchesScalar) {
     TypeMatchExpression type("a", Bool);
-    ASSERT(type.matchesBSON(BSON("a" << true), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << 1), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << true), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << 1), nullptr));
 }
 
 TEST(ExpressionTypeTest, MatchesArray) {
     TypeMatchExpression type("a", NumberInt);
-    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(4)), NULL));
-    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(4 << "a")), NULL));
-    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY("a" << 4)), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY("a")), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(4)), nullptr));
+    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(4 << "a")), nullptr));
+    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY("a" << 4)), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY("a")), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(4))), nullptr));
 }
 
 TEST(ExpressionTypeTest, TypeArrayMatchesOuterAndInnerArray) {
@@ -100,39 +100,39 @@ TEST(ExpressionTypeTest, TypeArrayMatchesOuterAndInnerArray) {
 
 TEST(ExpressionTypeTest, MatchesObject) {
     TypeMatchExpression type("a", Object);
-    ASSERT(type.matchesBSON(BSON("a" << BSON("b" << 1)), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << 1), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << BSON("b" << 1)), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << 1), nullptr));
 }
 
 TEST(ExpressionTypeTest, MatchesDotNotationFieldObject) {
     TypeMatchExpression type("a.b", Object);
-    ASSERT(type.matchesBSON(BSON("a" << BSON("b" << BSON("c" << 1))), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << BSON("b" << 1)), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << BSON("b" << BSON("c" << 1))), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << BSON("b" << 1)), nullptr));
 }
 
 TEST(ExpressionTypeTest, MatchesDotNotationArrayElementArray) {
     TypeMatchExpression type("a.0", Array);
-    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(1))), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY("b")), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(BSON_ARRAY(1))), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY("b")), nullptr));
 }
 
 TEST(ExpressionTypeTest, MatchesDotNotationArrayElementScalar) {
     TypeMatchExpression type("a.0", String);
-    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY("b")), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY(1)), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY("b")), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY(1)), nullptr));
 }
 
 TEST(ExpressionTypeTest, MatchesDotNotationArrayElementObject) {
     TypeMatchExpression type("a.0", Object);
-    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 1))), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY(1)), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << BSON_ARRAY(BSON("b" << 1))), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << BSON_ARRAY(1)), nullptr));
 }
 
 TEST(ExpressionTypeTest, MatchesNull) {
     TypeMatchExpression type("a", jstNULL);
-    ASSERT(type.matchesBSON(BSON("a" << BSONNULL), NULL));
-    ASSERT(!type.matchesBSON(BSON("a" << 4), NULL));
-    ASSERT(!type.matchesBSON(BSONObj(), NULL));
+    ASSERT(type.matchesBSON(BSON("a" << BSONNULL), nullptr));
+    ASSERT(!type.matchesBSON(BSON("a" << 4), nullptr));
+    ASSERT(!type.matchesBSON(BSONObj(), nullptr));
 }
 
 TEST(ExpressionTypeTest, ElemMatchKey) {
@@ -218,48 +218,48 @@ TEST(ExpressionTypeTest, InternalSchemaTypeExprWithMultipleTypesMatchesAllSuchTy
 }
 
 TEST(ExpressionBinDataSubTypeTest, MatchesBinDataGeneral) {
-    BSONObj match = BSON("a" << BSONBinData(NULL, 0, BinDataType::BinDataGeneral));
-    BSONObj notMatch = BSON("a" << BSONBinData(NULL, 0, BinDataType::bdtCustom));
+    BSONObj match = BSON("a" << BSONBinData(nullptr, 0, BinDataType::BinDataGeneral));
+    BSONObj notMatch = BSON("a" << BSONBinData(nullptr, 0, BinDataType::bdtCustom));
     InternalSchemaBinDataSubTypeExpression type("", BinDataType::BinDataGeneral);
     ASSERT_TRUE(type.matchesSingleElement(match["a"]));
     ASSERT_FALSE(type.matchesSingleElement(notMatch["a"]));
 }
 
 TEST(ExpressionBinDataSubTypeTest, MatchesBinDataFunction) {
-    BSONObj match = BSON("a" << BSONBinData(NULL, 0, BinDataType::Function));
-    BSONObj notMatch = BSON("a" << BSONBinData(NULL, 0, BinDataType::MD5Type));
+    BSONObj match = BSON("a" << BSONBinData(nullptr, 0, BinDataType::Function));
+    BSONObj notMatch = BSON("a" << BSONBinData(nullptr, 0, BinDataType::MD5Type));
     InternalSchemaBinDataSubTypeExpression type("", BinDataType::Function);
     ASSERT_TRUE(type.matchesSingleElement(match["a"]));
     ASSERT_FALSE(type.matchesSingleElement(notMatch["a"]));
 }
 
 TEST(ExpressionBinDataSubTypeTest, MatchesBinDataNewUUID) {
-    BSONObj match = BSON("a" << BSONBinData(NULL, 0, BinDataType::newUUID));
-    BSONObj notMatch = BSON("a" << BSONBinData(NULL, 0, BinDataType::BinDataGeneral));
+    BSONObj match = BSON("a" << BSONBinData(nullptr, 0, BinDataType::newUUID));
+    BSONObj notMatch = BSON("a" << BSONBinData(nullptr, 0, BinDataType::BinDataGeneral));
     InternalSchemaBinDataSubTypeExpression type("", BinDataType::newUUID);
     ASSERT_TRUE(type.matchesSingleElement(match["a"]));
     ASSERT_FALSE(type.matchesSingleElement(notMatch["a"]));
 }
 
 TEST(ExpressionBinDataSubTypeTest, MatchesBinDataMD5Type) {
-    BSONObj match = BSON("a" << BSONBinData(NULL, 0, BinDataType::MD5Type));
-    BSONObj notMatch = BSON("a" << BSONBinData(NULL, 0, BinDataType::newUUID));
+    BSONObj match = BSON("a" << BSONBinData(nullptr, 0, BinDataType::MD5Type));
+    BSONObj notMatch = BSON("a" << BSONBinData(nullptr, 0, BinDataType::newUUID));
     InternalSchemaBinDataSubTypeExpression type("", BinDataType::MD5Type);
     ASSERT_TRUE(type.matchesSingleElement(match["a"]));
     ASSERT_FALSE(type.matchesSingleElement(notMatch["a"]));
 }
 
 TEST(ExpressionBinDataSubTypeTest, MatchesBinDataEncryptType) {
-    BSONObj match = BSON("a" << BSONBinData(NULL, 0, BinDataType::Encrypt));
-    BSONObj notMatch = BSON("a" << BSONBinData(NULL, 0, BinDataType::newUUID));
+    BSONObj match = BSON("a" << BSONBinData(nullptr, 0, BinDataType::Encrypt));
+    BSONObj notMatch = BSON("a" << BSONBinData(nullptr, 0, BinDataType::newUUID));
     InternalSchemaBinDataSubTypeExpression type("", BinDataType::Encrypt);
     ASSERT_TRUE(type.matchesSingleElement(match["a"]));
     ASSERT_FALSE(type.matchesSingleElement(notMatch["a"]));
 }
 
 TEST(ExpressionBinDataSubTypeTest, MatchesBinDataBdtCustom) {
-    BSONObj match = BSON("a" << BSONBinData(NULL, 0, BinDataType::bdtCustom));
-    BSONObj notMatch = BSON("a" << BSONBinData(NULL, 0, BinDataType::Function));
+    BSONObj match = BSON("a" << BSONBinData(nullptr, 0, BinDataType::bdtCustom));
+    BSONObj notMatch = BSON("a" << BSONBinData(nullptr, 0, BinDataType::Function));
     InternalSchemaBinDataSubTypeExpression type("", BinDataType::bdtCustom);
     ASSERT_TRUE(type.matchesSingleElement(match["a"]));
     ASSERT_FALSE(type.matchesSingleElement(notMatch["a"]));
@@ -268,11 +268,11 @@ TEST(ExpressionBinDataSubTypeTest, MatchesBinDataBdtCustom) {
 TEST(ExpressionBinDataSubTypeTest, DoesNotMatchArrays) {
     InternalSchemaBinDataSubTypeExpression type("a", BinDataType::BinDataGeneral);
     ASSERT_FALSE(type.matchesBSON(
-        BSON("a" << BSON_ARRAY(BSONBinData(NULL, 0, BinDataType::BinDataGeneral)
-                               << BSONBinData(NULL, 0, BinDataType::BinDataGeneral)))));
-    ASSERT_FALSE(
-        type.matchesBSON(BSON("a" << BSON_ARRAY(BSONBinData(NULL, 0, BinDataType::BinDataGeneral)
-                                                << BSONBinData(NULL, 0, BinDataType::Function)))));
+        BSON("a" << BSON_ARRAY(BSONBinData(nullptr, 0, BinDataType::BinDataGeneral)
+                               << BSONBinData(nullptr, 0, BinDataType::BinDataGeneral)))));
+    ASSERT_FALSE(type.matchesBSON(
+        BSON("a" << BSON_ARRAY(BSONBinData(nullptr, 0, BinDataType::BinDataGeneral)
+                               << BSONBinData(nullptr, 0, BinDataType::Function)))));
 }
 
 TEST(ExpressionBinDataSubTypeTest, DoesNotMatchString) {
diff --git a/src/mongo/db/matcher/expression_where.cpp b/src/mongo/db/matcher/expression_where.cpp
index ff2069fe9ed..a171c10c140 100644
--- a/src/mongo/db/matcher/expression_where.cpp
+++ b/src/mongo/db/matcher/expression_where.cpp
@@ -54,7 +54,7 @@ WhereMatchExpression::WhereMatchExpression(OperationContext* opCtx,
                                            WhereParams params,
                                            StringData dbName)
     : WhereMatchExpressionBase(std::move(params)), _dbName(dbName.toString()), _opCtx(opCtx) {
-    invariant(_opCtx != NULL);
+    invariant(_opCtx != nullptr);
 
     uassert(
         ErrorCodes::BadValue, "no globalScriptEngine in $where parsing", getGlobalScriptEngine());
@@ -87,7 +87,7 @@ bool WhereMatchExpression::matches(const MatchableDocument* doc, MatchDetails* d
     _scope->setObject("obj", const_cast<BSONObj&>(obj));
     _scope->setBoolean("fullObject", true);  // this is a hack b/c fullObject used to be relevant
 
-    int err = _scope->invoke(_func, 0, &obj, 1000 * 60, false);
+    int err = _scope->invoke(_func, nullptr, &obj, 1000 * 60, false);
     if (err == -3) {  // INVOKE_ERROR
         stringstream ss;
         ss << "error on invocation of $where function:\n" << _scope->getError();
diff --git a/src/mongo/db/matcher/matcher.h b/src/mongo/db/matcher/matcher.h
index ae39f597bf3..ff7aeaa60dc 100644
--- a/src/mongo/db/matcher/matcher.h
+++ b/src/mongo/db/matcher/matcher.h
@@ -59,7 +59,7 @@ public:
             MatchExpressionParser::AllowedFeatureSet allowedFeatures =
                 MatchExpressionParser::kDefaultSpecialFeatures);
 
-    bool matches(const BSONObj& doc, MatchDetails* details = NULL) const;
+    bool matches(const BSONObj& doc, MatchDetails* details = nullptr) const;
 
     const BSONObj* getQuery() const {
         return &_pattern;
diff --git a/src/mongo/db/matcher/path.cpp b/src/mongo/db/matcher/path.cpp
index efd2c69aa06..e06412814df 100644
--- a/src/mongo/db/matcher/path.cpp
+++ b/src/mongo/db/matcher/path.cpp
@@ -78,7 +78,7 @@ ElementIterator::Context SimpleArrayElementIterator::next() {
 
 // ------
 BSONElementIterator::BSONElementIterator() {
-    _path = NULL;
+    _path = nullptr;
 }
 
 BSONElementIterator::BSONElementIterator(const ElementPath* path,
diff --git a/src/mongo/db/ops/insert.cpp b/src/mongo/db/ops/insert.cpp
index d891c998a7c..1939cbe1e3b 100644
--- a/src/mongo/db/ops/insert.cpp
+++ b/src/mongo/db/ops/insert.cpp
@@ -155,7 +155,7 @@ StatusWith<BSONObj> fixDocumentForInsert(ServiceContext* service, const BSONObj&
         if (e.type()) {
             b.append(e);
         } else {
-            b.appendOID("_id", NULL, true);
+            b.appendOID("_id", nullptr, true);
         }
     }
 
diff --git a/src/mongo/db/ops/parsed_delete.cpp b/src/mongo/db/ops/parsed_delete.cpp
index 63262fac82d..9e3a4f5250b 100644
--- a/src/mongo/db/ops/parsed_delete.cpp
+++ b/src/mongo/db/ops/parsed_delete.cpp
@@ -119,11 +119,11 @@ PlanExecutor::YieldPolicy ParsedDelete::yieldPolicy() const {
 }
 
 bool ParsedDelete::hasParsedQuery() const {
-    return _canonicalQuery.get() != NULL;
+    return _canonicalQuery.get() != nullptr;
 }
 
 std::unique_ptr<CanonicalQuery> ParsedDelete::releaseParsedQuery() {
-    invariant(_canonicalQuery.get() != NULL);
+    invariant(_canonicalQuery.get() != nullptr);
     return std::move(_canonicalQuery);
 }
 
diff --git a/src/mongo/db/ops/parsed_update.cpp b/src/mongo/db/ops/parsed_update.cpp
index c2e355e945a..039bd51f238 100644
--- a/src/mongo/db/ops/parsed_update.cpp
+++ b/src/mongo/db/ops/parsed_update.cpp
@@ -203,11 +203,11 @@ PlanExecutor::YieldPolicy ParsedUpdate::yieldPolicy() const {
 }
 
 bool ParsedUpdate::hasParsedQuery() const {
-    return _canonicalQuery.get() != NULL;
+    return _canonicalQuery.get() != nullptr;
 }
 
 std::unique_ptr<CanonicalQuery> ParsedUpdate::releaseParsedQuery() {
-    invariant(_canonicalQuery.get() != NULL);
+    invariant(_canonicalQuery.get() != nullptr);
     return std::move(_canonicalQuery);
 }
 
diff --git a/src/mongo/db/pipeline/document.cpp b/src/mongo/db/pipeline/document.cpp
index 1b8d8ecb5cb..2ae7e9fcb09 100644
--- a/src/mongo/db/pipeline/document.cpp
+++ b/src/mongo/db/pipeline/document.cpp
@@ -379,7 +379,7 @@ Document Document::fromBsonWithMetaData(const BSONObj& bson) {
 }
 
 MutableDocument::MutableDocument(size_t expectedFields)
-    : _storageHolder(NULL), _storage(_storageHolder) {
+    : _storageHolder(nullptr), _storage(_storageHolder) {
     if (expectedFields) {
         storage().reserveFields(expectedFields);
     }
diff --git a/src/mongo/db/pipeline/document.h b/src/mongo/db/pipeline/document.h
index f465ecce0e2..c4a9cf3e38b 100644
--- a/src/mongo/db/pipeline/document.h
+++ b/src/mongo/db/pipeline/document.h
@@ -409,7 +409,7 @@ private:
 
     /// Used by MutableDocument(MutableValue)
     const RefCountable*& getDocPtr() {
-        if (_val.getType() != Object || _val._storage.genericRCPtr == NULL) {
+        if (_val.getType() != Object || _val._storage.genericRCPtr == nullptr) {
             // If the current value isn't an object we replace it with a Object-typed Value.
             // Note that we can't just use Document() here because that is a NULL pointer and
             // Value doesn't refcount NULL pointers. This led to a memory leak (SERVER-10554)
@@ -451,11 +451,11 @@ public:
      *
      *  TODO: find some way to convey field-name sizes to make even more efficient
      */
-    MutableDocument() : _storageHolder(NULL), _storage(_storageHolder) {}
+    MutableDocument() : _storageHolder(nullptr), _storage(_storageHolder) {}
     explicit MutableDocument(size_t expectedFields);
 
     /// No copy of data yet. Copy-on-write. See storage()
-    explicit MutableDocument(Document d) : _storageHolder(NULL), _storage(_storageHolder) {
+    explicit MutableDocument(Document d) : _storageHolder(nullptr), _storage(_storageHolder) {
         reset(std::move(d));
     }
 
@@ -589,7 +589,7 @@ public:
         Document ret;
         boost::intrusive_ptr<const DocumentStorage> temp(storagePtr(), /*inc_ref_count=*/false);
         temp.swap(ret._storage);
-        _storage = NULL;
+        _storage = nullptr;
         return ret;
     }
 
@@ -614,7 +614,7 @@ public:
 
 private:
     friend class MutableValue;  // for access to next constructor
-    explicit MutableDocument(MutableValue mv) : _storageHolder(NULL), _storage(mv.getDocPtr()) {}
+    explicit MutableDocument(MutableValue mv) : _storageHolder(nullptr), _storage(mv.getDocPtr()) {}
 
     void reset(boost::intrusive_ptr<const DocumentStorage> ds) {
         if (_storage)
diff --git a/src/mongo/db/pipeline/document_internal.h b/src/mongo/db/pipeline/document_internal.h
index 1d2b1b58951..29b541a52a3 100644
--- a/src/mongo/db/pipeline/document_internal.h
+++ b/src/mongo/db/pipeline/document_internal.h
@@ -184,8 +184,8 @@ private:
 class DocumentStorage : public RefCountable {
 public:
     DocumentStorage()
-        : _buffer(NULL),
-          _bufferEnd(NULL),
+        : _buffer(nullptr),
+          _bufferEnd(nullptr),
           _usedBytes(0),
           _numFields(0),
           _hashTabMask(0),
diff --git a/src/mongo/db/pipeline/document_source.cpp b/src/mongo/db/pipeline/document_source.cpp
index 158e97b33fa..fdd49626589 100644
--- a/src/mongo/db/pipeline/document_source.cpp
+++ b/src/mongo/db/pipeline/document_source.cpp
@@ -50,7 +50,7 @@ using std::string;
 using std::vector;
 
 DocumentSource::DocumentSource(const intrusive_ptr<ExpressionContext>& pCtx)
-    : pSource(NULL), pExpCtx(pCtx) {}
+    : pSource(nullptr), pExpCtx(pCtx) {}
 
 namespace {
 // Used to keep track of which DocumentSources are registered under which name.
diff --git a/src/mongo/db/pipeline/document_source_match_test.cpp b/src/mongo/db/pipeline/document_source_match_test.cpp
index 9449f9b55c2..83283bbefeb 100644
--- a/src/mongo/db/pipeline/document_source_match_test.cpp
+++ b/src/mongo/db/pipeline/document_source_match_test.cpp
@@ -184,7 +184,7 @@ TEST_F(DocumentSourceMatchTest, RedactSafePortion) {
     assertExpectedRedactSafePortion("{a: {$in: [1, 0, null]}}", "{}");
 
     {
-        const char* comparisonOps[] = {"$gt", "$lt", "$gte", "$lte", NULL};
+        const char* comparisonOps[] = {"$gt", "$lt", "$gte", "$lte", nullptr};
         for (int i = 0; comparisonOps[i]; i++) {
             const char* op = comparisonOps[i];
             assertExpectedRedactSafePortion(string("{a: {") + op + ": 1}}",
@@ -610,7 +610,7 @@ TEST_F(DocumentSourceMatchTest, ShouldCorrectlyEvaluateJSONSchemaPredicate) {
         fromjson("{$jsonSchema: {properties: {a: {type: 'number'}}}}"), getExpCtx());
 
     const auto mock = DocumentSourceMock::createForTest(
-        {Document{{"a", 1}}, Document{{"a", "str"_sd}}, Document{{"a", {Document{{0, 1}}}}}});
+        {Document{{"a", 1}}, Document{{"a", "str"_sd}}, Document{{"a", {Document{{nullptr, 1}}}}}});
 
     match->setSource(mock.get());
 
diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index c1bf5957066..004fb15b16f 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -5871,7 +5871,7 @@ int ExpressionRegex::execute(RegexExecutionState* regexState) const {
     invariant(regexState->pcrePtr);
 
     int execResult = pcre_exec(regexState->pcrePtr.get(),
-                               0,
+                               nullptr,
                                regexState->input->c_str(),
                                regexState->input->size(),
                                regexState->startBytePos,
@@ -5981,8 +5981,10 @@ void ExpressionRegex::_compile(RegexExecutionState* executionState) const {
             executionState->pcrePtr);
 
     // Calculate the number of capture groups present in 'pattern' and store in 'numCaptures'.
-    const int pcre_retval = pcre_fullinfo(
-        executionState->pcrePtr.get(), NULL, PCRE_INFO_CAPTURECOUNT, &executionState->numCaptures);
+    const int pcre_retval = pcre_fullinfo(executionState->pcrePtr.get(),
+                                          nullptr,
+                                          PCRE_INFO_CAPTURECOUNT,
+                                          &executionState->numCaptures);
     invariant(pcre_retval == 0);
 
     // The first two-thirds of the vector is used to pass back captured substrings' start and
diff --git a/src/mongo/db/query/canonical_query.cpp b/src/mongo/db/query/canonical_query.cpp
index cba8c2e2736..03424a838d6 100644
--- a/src/mongo/db/query/canonical_query.cpp
+++ b/src/mongo/db/query/canonical_query.cpp
@@ -299,7 +299,7 @@ void CanonicalQuery::sortTree(MatchExpression* tree) {
         sortTree(tree->getChild(i));
     }
     std::vector<MatchExpression*>* children = tree->getChildVector();
-    if (NULL != children) {
+    if (nullptr != children) {
         std::sort(children->begin(), children->end(), matchExpressionLessThan);
     }
 }
diff --git a/src/mongo/db/query/explain.cpp b/src/mongo/db/query/explain.cpp
index 977b7fdb1a1..4f6093959b4 100644
--- a/src/mongo/db/query/explain.cpp
+++ b/src/mongo/db/query/explain.cpp
@@ -669,7 +669,7 @@ void Explain::generatePlannerInfo(PlanExecutor* exec,
     // In general we should have a canonical query, but sometimes we may avoid
     // creating a canonical query as an optimization (specifically, the update system
     // does not canonicalize for idhack updates). In these cases, 'query' is NULL.
-    if (NULL != query) {
+    if (nullptr != query) {
         BSONObjBuilder parsedQueryBob(plannerBob.subobjStart("parsedQuery"));
         query->root()->serialize(&parsedQueryBob);
         parsedQueryBob.doneFast();
@@ -938,7 +938,7 @@ std::string Explain::getPlanSummary(const PlanStage* root) {
 
 // static
 void Explain::getSummaryStats(const PlanExecutor& exec, PlanSummaryStats* statsOut) {
-    invariant(NULL != statsOut);
+    invariant(nullptr != statsOut);
 
     PlanStage* root = exec.getRootStage();
 
diff --git a/src/mongo/db/query/find.cpp b/src/mongo/db/query/find.cpp
index ff1e443abc9..0a47bc2ce0a 100644
--- a/src/mongo/db/query/find.cpp
+++ b/src/mongo/db/query/find.cpp
@@ -182,7 +182,7 @@ void generateBatch(int ntoreturn,
 
     BSONObj obj;
     while (!FindCommon::enoughForGetMore(ntoreturn, *numResults) &&
-           PlanExecutor::ADVANCED == (*state = exec->getNext(&obj, NULL))) {
+           PlanExecutor::ADVANCED == (*state = exec->getNext(&obj, nullptr))) {
         // If we can't fit this result inside the current batch, then we stash it for later.
         if (!FindCommon::haveSpaceForNext(obj, *numResults, bb->len())) {
             exec->enqueue(obj);
@@ -680,7 +680,7 @@ std::string runQuery(OperationContext* opCtx,
         curOp.setPlanSummary_inlock(Explain::getPlanSummary(exec.get()));
     }
 
-    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
+    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
         // If we can't fit this result inside the current batch, then we stash it for later.
         if (!FindCommon::haveSpaceForNext(obj, numResults, bb.len())) {
             exec->enqueue(obj);
diff --git a/src/mongo/db/query/get_executor.cpp b/src/mongo/db/query/get_executor.cpp
index 5d82c6bc539..da9207b93f6 100644
--- a/src/mongo/db/query/get_executor.cpp
+++ b/src/mongo/db/query/get_executor.cpp
@@ -370,7 +370,7 @@ StatusWith<PrepareExecutionResult> prepareExecution(OperationContext* opCtx,
     unique_ptr<PlanStage> root;
 
     // This can happen as we're called by internal clients as well.
-    if (NULL == collection) {
+    if (nullptr == collection) {
         const string& ns = canonicalQuery->ns();
         LOG(2) << "Collection " << ns << " does not exist."
                << " Using EOF plan: " << redact(canonicalQuery->toStringShort());
@@ -745,7 +745,7 @@ StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> _getExecutorFind(
     unique_ptr<CanonicalQuery> canonicalQuery,
     PlanExecutor::YieldPolicy yieldPolicy,
     size_t plannerOptions) {
-    if (NULL != collection && canonicalQuery->getQueryRequest().isOplogReplay()) {
+    if (nullptr != collection && canonicalQuery->getQueryRequest().isOplogReplay()) {
         return getOplogStartHack(
             opCtx, collection, std::move(canonicalQuery), plannerOptions, yieldPolicy);
     }
@@ -1131,7 +1131,7 @@ bool turnIxscanIntoCount(QuerySolution* soln) {
         return false;
     }
 
-    if (STAGE_FETCH == root->getType() && NULL != root->filter.get()) {
+    if (STAGE_FETCH == root->getType() && nullptr != root->filter.get()) {
         return false;
     }
 
@@ -1148,7 +1148,7 @@ bool turnIxscanIntoCount(QuerySolution* soln) {
     // isSimpleRange here?  because we could well use it.  I just don't think we ever do see
     // it.
 
-    if (NULL != isn->filter.get() || isn->bounds.isSimpleRange) {
+    if (nullptr != isn->filter.get() || isn->bounds.isSimpleRange) {
         return false;
     }
 
diff --git a/src/mongo/db/query/index_tag.cpp b/src/mongo/db/query/index_tag.cpp
index 0381e2ac9ba..61e0204d3da 100644
--- a/src/mongo/db/query/index_tag.cpp
+++ b/src/mongo/db/query/index_tag.cpp
@@ -45,12 +45,12 @@ namespace {
 
 bool TagComparison(const MatchExpression* lhs, const MatchExpression* rhs) {
     IndexTag* lhsTag = static_cast<IndexTag*>(lhs->getTag());
-    size_t lhsValue = (NULL == lhsTag) ? IndexTag::kNoIndex : lhsTag->index;
-    size_t lhsPos = (NULL == lhsTag) ? IndexTag::kNoIndex : lhsTag->pos;
+    size_t lhsValue = (nullptr == lhsTag) ? IndexTag::kNoIndex : lhsTag->index;
+    size_t lhsPos = (nullptr == lhsTag) ? IndexTag::kNoIndex : lhsTag->pos;
 
     IndexTag* rhsTag = static_cast<IndexTag*>(rhs->getTag());
-    size_t rhsValue = (NULL == rhsTag) ? IndexTag::kNoIndex : rhsTag->index;
-    size_t rhsPos = (NULL == rhsTag) ? IndexTag::kNoIndex : rhsTag->pos;
+    size_t rhsValue = (nullptr == rhsTag) ? IndexTag::kNoIndex : rhsTag->index;
+    size_t rhsPos = (nullptr == rhsTag) ? IndexTag::kNoIndex : rhsTag->pos;
 
     // First, order on indices.
     if (lhsValue != rhsValue) {
@@ -94,7 +94,7 @@ void sortUsingTags(MatchExpression* tree) {
         sortUsingTags(tree->getChild(i));
     }
     std::vector<MatchExpression*>* children = tree->getChildVector();
-    if (NULL != children) {
+    if (nullptr != children) {
         std::sort(children->begin(), children->end(), TagComparison);
     }
 }
diff --git a/src/mongo/db/query/index_tag.h b/src/mongo/db/query/index_tag.h
index be4423d3179..ac69dc16870 100644
--- a/src/mongo/db/query/index_tag.h
+++ b/src/mongo/db/query/index_tag.h
@@ -88,7 +88,7 @@ public:
 // used internally
 class RelevantTag : public MatchExpression::TagData {
 public:
-    RelevantTag() : elemMatchExpr(NULL), pathPrefix("") {}
+    RelevantTag() : elemMatchExpr(nullptr), pathPrefix("") {}
 
     std::vector<size_t> first;
     std::vector<size_t> notFirst;
diff --git a/src/mongo/db/query/internal_plans.cpp b/src/mongo/db/query/internal_plans.cpp
index bfd88fb27df..2fa5359bd48 100644
--- a/src/mongo/db/query/internal_plans.cpp
+++ b/src/mongo/db/query/internal_plans.cpp
@@ -55,7 +55,7 @@ std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> InternalPlanner::collection
     const RecordId startLoc) {
     std::unique_ptr<WorkingSet> ws = std::make_unique<WorkingSet>();
 
-    if (NULL == collection) {
+    if (nullptr == collection) {
         auto eof = std::make_unique<EOFStage>(opCtx);
         // Takes ownership of 'ws' and 'eof'.
         auto statusWithPlanExecutor = PlanExecutor::make(
diff --git a/src/mongo/db/query/lru_key_value_test.cpp b/src/mongo/db/query/lru_key_value_test.cpp
index 6b9ee7b90d6..9f15aad6c9a 100644
--- a/src/mongo/db/query/lru_key_value_test.cpp
+++ b/src/mongo/db/query/lru_key_value_test.cpp
@@ -41,7 +41,7 @@ namespace {
 //
 
 void assertInKVStore(LRUKeyValue<int, int>& cache, int key, int value) {
-    int* cachedValue = NULL;
+    int* cachedValue = nullptr;
     ASSERT_TRUE(cache.hasKey(key));
     Status s = cache.get(key, &cachedValue);
     ASSERT_OK(s);
@@ -49,7 +49,7 @@ void assertInKVStore(LRUKeyValue<int, int>& cache, int key, int value) {
 }
 
 void assertNotInKVStore(LRUKeyValue<int, int>& cache, int key) {
-    int* cachedValue = NULL;
+    int* cachedValue = nullptr;
     ASSERT_FALSE(cache.hasKey(key));
     Status s = cache.get(key, &cachedValue);
     ASSERT_NOT_OK(s);
@@ -99,7 +99,7 @@ TEST(LRUKeyValueTest, EvictionTest) {
     LRUKeyValue<int, int> cache(maxSize);
     for (int i = 0; i < maxSize; ++i) {
         std::unique_ptr<int> evicted = cache.add(i, new int(i));
-        ASSERT(NULL == evicted.get());
+        ASSERT(nullptr == evicted.get());
     }
     ASSERT_EQUALS(cache.size(), (size_t)maxSize);
 
@@ -115,7 +115,7 @@ TEST(LRUKeyValueTest, EvictionTest) {
     // Adding another entry causes an eviction.
     std::unique_ptr<int> evicted = cache.add(maxSize + 1, new int(maxSize + 1));
     ASSERT_EQUALS(cache.size(), (size_t)maxSize);
-    ASSERT(NULL != evicted.get());
+    ASSERT(nullptr != evicted.get());
     ASSERT_EQUALS(*evicted, evictKey);
 
     // Check that the least recently accessed has been evicted.
@@ -139,7 +139,7 @@ TEST(LRUKeyValueTest, PromotionTest) {
     LRUKeyValue<int, int> cache(maxSize);
     for (int i = 0; i < maxSize; ++i) {
         std::unique_ptr<int> evicted = cache.add(i, new int(i));
-        ASSERT(NULL == evicted.get());
+        ASSERT(nullptr == evicted.get());
     }
     ASSERT_EQUALS(cache.size(), (size_t)maxSize);
 
@@ -150,7 +150,7 @@ TEST(LRUKeyValueTest, PromotionTest) {
     // Evict all but one of the original entries.
     for (int i = maxSize; i < (maxSize + maxSize - 1); ++i) {
         std::unique_ptr<int> evicted = cache.add(i, new int(i));
-        ASSERT(NULL != evicted.get());
+        ASSERT(nullptr != evicted.get());
     }
     ASSERT_EQUALS(cache.size(), (size_t)maxSize);
 
diff --git a/src/mongo/db/query/parsed_projection_test.cpp b/src/mongo/db/query/parsed_projection_test.cpp
index 84669166c8d..075858687fd 100644
--- a/src/mongo/db/query/parsed_projection_test.cpp
+++ b/src/mongo/db/query/parsed_projection_test.cpp
@@ -58,7 +58,7 @@ unique_ptr<ParsedProjection> createParsedProjection(const BSONObj& query, const
         MatchExpressionParser::parse(query, std::move(expCtx));
     ASSERT(statusWithMatcher.isOK());
     std::unique_ptr<MatchExpression> queryMatchExpr = std::move(statusWithMatcher.getValue());
-    ParsedProjection* out = NULL;
+    ParsedProjection* out = nullptr;
     Status status = ParsedProjection::make(opCtx.get(), projObj, queryMatchExpr.get(), &out);
     if (!status.isOK()) {
         FAIL(str::stream() << "failed to parse projection " << projObj << " (query: " << query
@@ -91,7 +91,7 @@ void assertInvalidProjection(const char* queryStr, const char* projStr) {
         MatchExpressionParser::parse(query, std::move(expCtx));
     ASSERT(statusWithMatcher.isOK());
     std::unique_ptr<MatchExpression> queryMatchExpr = std::move(statusWithMatcher.getValue());
-    ParsedProjection* out = NULL;
+    ParsedProjection* out = nullptr;
     Status status = ParsedProjection::make(opCtx.get(), projObj, queryMatchExpr.get(), &out);
     std::unique_ptr<ParsedProjection> destroy(out);
     ASSERT(!status.isOK());
@@ -213,9 +213,9 @@ TEST(ParsedProjectionTest, InvalidPositionalProjectionDefaultPathMatchExpression
     QueryTestServiceContext serviceCtx;
     auto opCtx = serviceCtx.makeOperationContext();
     unique_ptr<MatchExpression> queryMatchExpr(new AlwaysFalseMatchExpression());
-    ASSERT(NULL == queryMatchExpr->path().rawData());
+    ASSERT(nullptr == queryMatchExpr->path().rawData());
 
-    ParsedProjection* out = NULL;
+    ParsedProjection* out = nullptr;
     BSONObj projObj = fromjson("{'a.$': 1}");
     Status status = ParsedProjection::make(opCtx.get(), projObj, queryMatchExpr.get(), &out);
     ASSERT(!status.isOK());
diff --git a/src/mongo/db/query/plan_cache.cpp b/src/mongo/db/query/plan_cache.cpp
index ba32ff91e7f..3464c22a86f 100644
--- a/src/mongo/db/query/plan_cache.cpp
+++ b/src/mongo/db/query/plan_cache.cpp
@@ -269,7 +269,7 @@ void PlanCacheIndexTree::setIndexEntry(const IndexEntry& ie) {
 
 PlanCacheIndexTree* PlanCacheIndexTree::clone() const {
     PlanCacheIndexTree* root = new PlanCacheIndexTree();
-    if (NULL != entry.get()) {
+    if (nullptr != entry.get()) {
         root->index_pos = index_pos;
         root->setIndexEntry(*entry.get());
         root->canCombineBounds = canCombineBounds;
@@ -298,7 +298,7 @@ std::string PlanCacheIndexTree::toString(int indents) const {
         return result.str();
     } else {
         result << std::string(3 * indents, '-') << "Leaf ";
-        if (NULL != entry.get()) {
+        if (nullptr != entry.get()) {
             result << entry->identifier << ", pos: " << index_pos << ", can combine? "
                    << canCombineBounds;
         }
@@ -326,7 +326,7 @@ std::string PlanCacheIndexTree::toString(int indents) const {
 
 SolutionCacheData* SolutionCacheData::clone() const {
     SolutionCacheData* other = new SolutionCacheData();
-    if (NULL != this->tree.get()) {
+    if (nullptr != this->tree.get()) {
         // 'tree' could be NULL if the cached solution
         // is a collection scan.
         other->tree.reset(this->tree->clone());
@@ -542,7 +542,7 @@ Status PlanCache::set(const CanonicalQuery& query,
 
     std::unique_ptr<PlanCacheEntry> evictedEntry = _cache.add(key, newEntry.release());
 
-    if (NULL != evictedEntry.get()) {
+    if (nullptr != evictedEntry.get()) {
         LOG(1) << _ns << ": plan cache maximum size exceeded - "
                << "removed least recently used entry " << redact(evictedEntry->toString());
     }
diff --git a/src/mongo/db/query/plan_cache_test.cpp b/src/mongo/db/query/plan_cache_test.cpp
index c6543f5da59..a2ab4e1f475 100644
--- a/src/mongo/db/query/plan_cache_test.cpp
+++ b/src/mongo/db/query/plan_cache_test.cpp
@@ -1161,7 +1161,7 @@ protected:
         dumpSolutions(ss);
         FAIL(ss);
 
-        return NULL;
+        return nullptr;
     }
 
     /**
@@ -1216,8 +1216,8 @@ protected:
      */
     void assertNotCached(const string& solnJson) {
         QuerySolution* bestSoln = firstMatchingSolution(solnJson);
-        ASSERT(NULL != bestSoln);
-        ASSERT(NULL == bestSoln->cacheData.get());
+        ASSERT(nullptr != bestSoln);
+        ASSERT(nullptr == bestSoln->cacheData.get());
     }
 
     static const PlanCacheKey ck;
diff --git a/src/mongo/db/query/plan_enumerator.cpp b/src/mongo/db/query/plan_enumerator.cpp
index 19f2188f303..7163d69e474 100644
--- a/src/mongo/db/query/plan_enumerator.cpp
+++ b/src/mongo/db/query/plan_enumerator.cpp
@@ -290,7 +290,7 @@ std::string PlanEnumerator::dumpMemo() {
 }
 
 string PlanEnumerator::NodeAssignment::toString() const {
-    if (NULL != andAssignment) {
+    if (nullptr != andAssignment) {
         str::stream ss;
         ss << "AND enumstate counter " << andAssignment->counter;
         for (size_t i = 0; i < andAssignment->choices.size(); ++i) {
@@ -316,7 +316,7 @@ string PlanEnumerator::NodeAssignment::toString() const {
             }
         }
         return ss;
-    } else if (NULL != arrayAssignment) {
+    } else if (nullptr != arrayAssignment) {
         str::stream ss;
         ss << "ARRAY SUBNODES enumstate " << arrayAssignment->counter << "/ ONE OF: [ ";
         for (size_t i = 0; i < arrayAssignment->subnodes.size(); ++i) {
@@ -325,7 +325,7 @@ string PlanEnumerator::NodeAssignment::toString() const {
         ss << "]";
         return ss;
     } else {
-        verify(NULL != orAssignment);
+        verify(nullptr != orAssignment);
         str::stream ss;
         ss << "ALL OF: [ ";
         for (size_t i = 0; i < orAssignment->subnodes.size(); ++i) {
@@ -506,7 +506,7 @@ bool PlanEnumerator::prepMemo(MatchExpression* node, PrepMemoContext context) {
 
         // There can only be one mandatory predicate (at most one $text, at most one
         // $geoNear, can't combine $text/$geoNear).
-        MatchExpression* mandatoryPred = NULL;
+        MatchExpression* mandatoryPred = nullptr;
 
         // There could be multiple indices which we could use to satisfy the mandatory
         // predicate. Keep the set of such indices. Currently only one text index is
@@ -528,7 +528,7 @@ bool PlanEnumerator::prepMemo(MatchExpression* node, PrepMemoContext context) {
                 // This should include only TEXT and GEO_NEAR preds.
 
                 // We expect either 0 or 1 mandatory predicates.
-                invariant(NULL == mandatoryPred);
+                invariant(nullptr == mandatoryPred);
 
                 // Mandatory predicates are TEXT or GEO_NEAR.
                 invariant(MatchExpression::TEXT == child->matchType() ||
@@ -577,7 +577,7 @@ bool PlanEnumerator::prepMemo(MatchExpression* node, PrepMemoContext context) {
             return true;
         }
 
-        if (NULL != mandatoryPred) {
+        if (nullptr != mandatoryPred) {
             // We must have at least one index which can be used to answer 'mandatoryPred'.
             invariant(!mandatoryIndices.empty());
             return enumerateMandatoryIndex(
@@ -1325,7 +1325,7 @@ void PlanEnumerator::getMultikeyCompoundablePreds(const vector<MatchExpression*>
     // initializing the top-level scope with the prefix of the full path.
     for (size_t i = 0; i < assigned.size(); i++) {
         const MatchExpression* assignedPred = assigned[i];
-        invariant(NULL != assignedPred->getTag());
+        invariant(nullptr != assignedPred->getTag());
         RelevantTag* usedRt = static_cast<RelevantTag*>(assignedPred->getTag());
         set<string> usedPrefixes;
         usedPrefixes.insert(getPathPrefix(usedRt->path));
@@ -1336,7 +1336,7 @@ void PlanEnumerator::getMultikeyCompoundablePreds(const vector<MatchExpression*>
         // the $elemMatch context. For example, if 'assigned' is {a: {$elemMatch: {b: 1}}},
         // then we will have already added "a" to the set for NULL. We now
         // also need to add "b" to the set for the $elemMatch.
-        if (NULL != usedRt->elemMatchExpr) {
+        if (nullptr != usedRt->elemMatchExpr) {
             set<string> elemMatchUsed;
             // Whereas getPathPrefix(usedRt->path) is the prefix of the full path,
             // usedRt->pathPrefix contains the prefix of the portion of the
@@ -1570,17 +1570,17 @@ void PlanEnumerator::compound(const vector<MatchExpression*>& tryCompound,
 void PlanEnumerator::tagMemo(size_t id) {
     LOG(5) << "Tagging memoID " << id;
     NodeAssignment* assign = _memo[id];
-    verify(NULL != assign);
+    verify(nullptr != assign);
 
-    if (NULL != assign->orAssignment) {
+    if (nullptr != assign->orAssignment) {
         OrAssignment* oa = assign->orAssignment.get();
         for (size_t i = 0; i < oa->subnodes.size(); ++i) {
             tagMemo(oa->subnodes[i]);
         }
-    } else if (NULL != assign->arrayAssignment) {
+    } else if (nullptr != assign->arrayAssignment) {
         ArrayAssignment* aa = assign->arrayAssignment.get();
         tagMemo(aa->subnodes[aa->counter]);
-    } else if (NULL != assign->andAssignment) {
+    } else if (nullptr != assign->andAssignment) {
         AndAssignment* aa = assign->andAssignment.get();
         verify(aa->counter < aa->choices.size());
 
@@ -1622,9 +1622,9 @@ void PlanEnumerator::tagMemo(size_t id) {
 
 bool PlanEnumerator::nextMemo(size_t id) {
     NodeAssignment* assign = _memo[id];
-    verify(NULL != assign);
+    verify(nullptr != assign);
 
-    if (NULL != assign->orAssignment) {
+    if (nullptr != assign->orAssignment) {
         OrAssignment* oa = assign->orAssignment.get();
 
         // Limit the number of OR enumerations
@@ -1644,7 +1644,7 @@ bool PlanEnumerator::nextMemo(size_t id) {
         }
         // If we're here, the last subnode had a carry, therefore the OR has a carry.
         return true;
-    } else if (NULL != assign->arrayAssignment) {
+    } else if (nullptr != assign->arrayAssignment) {
         ArrayAssignment* aa = assign->arrayAssignment.get();
         // moving to next on current subnode is OK
         if (!nextMemo(aa->subnodes[aa->counter])) {
@@ -1657,7 +1657,7 @@ bool PlanEnumerator::nextMemo(size_t id) {
         }
         aa->counter = 0;
         return true;
-    } else if (NULL != assign->andAssignment) {
+    } else if (nullptr != assign->andAssignment) {
         AndAssignment* aa = assign->andAssignment.get();
 
         // One of our subnodes might have to move on to its next enumeration state.
diff --git a/src/mongo/db/query/plan_enumerator.h b/src/mongo/db/query/plan_enumerator.h
index 0ae89741132..33c7923119e 100644
--- a/src/mongo/db/query/plan_enumerator.h
+++ b/src/mongo/db/query/plan_enumerator.h
@@ -158,7 +158,7 @@ private:
     };
 
     struct PrepMemoContext {
-        PrepMemoContext() : elemMatchExpr(NULL) {}
+        PrepMemoContext() : elemMatchExpr(nullptr) {}
         MatchExpression* elemMatchExpr;
 
         // Maps from indexable predicates that can be pushed into the current node to the route
diff --git a/src/mongo/db/query/plan_executor_impl.cpp b/src/mongo/db/query/plan_executor_impl.cpp
index 849993364c5..0ff05e2bd27 100644
--- a/src/mongo/db/query/plan_executor_impl.cpp
+++ b/src/mongo/db/query/plan_executor_impl.cpp
@@ -122,7 +122,7 @@ PlanStage* getStageByType(PlanStage* root, StageType type) {
         }
     }
 
-    return NULL;
+    return nullptr;
 }
 }  // namespace
 
@@ -379,7 +379,7 @@ void PlanExecutorImpl::reattachToOperationContext(OperationContext* opCtx) {
 
 PlanExecutor::ExecState PlanExecutorImpl::getNext(BSONObj* objOut, RecordId* dlOut) {
     Snapshotted<BSONObj> snapshotted;
-    ExecState state = _getNextImpl(objOut ? &snapshotted : NULL, dlOut);
+    ExecState state = _getNextImpl(objOut ? &snapshotted : nullptr, dlOut);
 
     if (objOut) {
         *objOut = snapshotted.value();
@@ -483,7 +483,7 @@ PlanExecutor::ExecState PlanExecutorImpl::_getNextImpl(Snapshotted<BSONObj>* obj
 
     invariant(_currentState == kUsable);
     if (isMarkedAsKilled()) {
-        if (NULL != objOut) {
+        if (nullptr != objOut) {
             *objOut = Snapshotted<BSONObj>(SnapshotId(),
                                            WorkingSetCommon::buildMemberStatusObject(_killStatus));
         }
@@ -535,7 +535,7 @@ PlanExecutor::ExecState PlanExecutorImpl::_getNextImpl(Snapshotted<BSONObj>* obj
             WorkingSetMember* member = _workingSet->get(id);
             bool hasRequestedData = true;
 
-            if (NULL != objOut) {
+            if (nullptr != objOut) {
                 if (WorkingSetMember::RID_AND_IDX == member->getState()) {
                     if (1 != member->keyData.size()) {
                         _workingSet->free(id);
@@ -553,7 +553,7 @@ PlanExecutor::ExecState PlanExecutorImpl::_getNextImpl(Snapshotted<BSONObj>* obj
                 }
             }
 
-            if (NULL != dlOut) {
+            if (nullptr != dlOut) {
                 if (member->hasRecordId()) {
                     *dlOut = member->recordId;
                 } else {
@@ -602,7 +602,7 @@ PlanExecutor::ExecState PlanExecutorImpl::_getNextImpl(Snapshotted<BSONObj>* obj
         } else {
             invariant(PlanStage::FAILURE == code);
 
-            if (NULL != objOut) {
+            if (nullptr != objOut) {
                 BSONObj statusObj;
                 invariant(WorkingSet::INVALID_ID != id);
                 WorkingSetCommon::getStatusMemberObject(*_workingSet, id, &statusObj);
@@ -641,7 +641,7 @@ Status PlanExecutorImpl::executePlan() {
     BSONObj obj;
     PlanExecutor::ExecState state = PlanExecutor::ADVANCED;
     while (PlanExecutor::ADVANCED == state) {
-        state = this->getNext(&obj, NULL);
+        state = this->getNext(&obj, nullptr);
     }
 
     if (PlanExecutor::FAILURE == state) {
diff --git a/src/mongo/db/query/planner_access.cpp b/src/mongo/db/query/planner_access.cpp
index 9ac03670c3a..ef4ef25bcac 100644
--- a/src/mongo/db/query/planner_access.cpp
+++ b/src/mongo/db/query/planner_access.cpp
@@ -205,7 +205,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::makeLeafNode(
             auto ret = std::make_unique<GeoNear2DNode>(index);
             ret->nq = &nearExpr->getData();
             ret->baseBounds.fields.resize(index.keyPattern.nFields());
-            if (NULL != query.getProj()) {
+            if (nullptr != query.getProj()) {
                 ret->addPointMeta = query.getProj()->wantGeoNearPoint();
                 ret->addDistMeta = query.getProj()->wantGeoNearDistance();
             }
@@ -215,7 +215,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::makeLeafNode(
             auto ret = std::make_unique<GeoNear2DSphereNode>(index);
             ret->nq = &nearExpr->getData();
             ret->baseBounds.fields.resize(index.keyPattern.nFields());
-            if (NULL != query.getProj()) {
+            if (nullptr != query.getProj()) {
                 ret->addPointMeta = query.getProj()->wantGeoNearPoint();
                 ret->addDistMeta = query.getProj()->wantGeoNearDistance();
             }
@@ -266,11 +266,11 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::makeLeafNode(
 bool QueryPlannerAccess::shouldMergeWithLeaf(const MatchExpression* expr,
                                              const ScanBuildingState& scanState) {
     const QuerySolutionNode* node = scanState.currentScan.get();
-    if (NULL == node || NULL == expr) {
+    if (nullptr == node || nullptr == expr) {
         return false;
     }
 
-    if (NULL == scanState.ixtag) {
+    if (nullptr == scanState.ixtag) {
         return false;
     }
 
@@ -340,7 +340,7 @@ bool QueryPlannerAccess::shouldMergeWithLeaf(const MatchExpression* expr,
 
 void QueryPlannerAccess::mergeWithLeafNode(MatchExpression* expr, ScanBuildingState* scanState) {
     QuerySolutionNode* node = scanState->currentScan.get();
-    invariant(NULL != node);
+    invariant(nullptr != node);
 
     const MatchExpression::MatchType mergeType = scanState->root->matchType();
     size_t pos = scanState->ixtag->pos;
@@ -369,7 +369,7 @@ void QueryPlannerAccess::mergeWithLeafNode(MatchExpression* expr, ScanBuildingSt
         return;
     }
 
-    IndexBounds* boundsToFillOut = NULL;
+    IndexBounds* boundsToFillOut = nullptr;
 
     if (STAGE_GEO_NEAR_2D == type) {
         invariant(INDEX_2D == index.type);
@@ -459,7 +459,7 @@ void QueryPlannerAccess::finishTextNode(QuerySolutionNode* node, const IndexEntr
     // We can't create a text stage if there aren't EQ predicates on its prefix terms.  So
     // if we've made it this far, we should have collected the prefix predicates in the
     // filter.
-    invariant(NULL != tn->filter.get());
+    invariant(nullptr != tn->filter.get());
     MatchExpression* textFilterMe = tn->filter.get();
 
     BSONObjBuilder prefixBob;
@@ -489,10 +489,10 @@ void QueryPlannerAccess::finishTextNode(QuerySolutionNode* node, const IndexEntr
         while (curChild < amExpr->numChildren()) {
             MatchExpression* child = amExpr->getChild(curChild);
             IndexTag* ixtag = static_cast<IndexTag*>(child->getTag());
-            invariant(NULL != ixtag);
+            invariant(nullptr != ixtag);
             // Skip this child if it's not part of a prefix, or if we've already assigned a
             // predicate to this prefix position.
-            if (ixtag->pos >= tn->numPrefixFields || prefixExprs[ixtag->pos] != NULL) {
+            if (ixtag->pos >= tn->numPrefixFields || prefixExprs[ixtag->pos] != nullptr) {
                 ++curChild;
                 continue;
             }
@@ -505,7 +505,7 @@ void QueryPlannerAccess::finishTextNode(QuerySolutionNode* node, const IndexEntr
         // Go through the prefix equalities in order and create an index prefix out of them.
         for (size_t i = 0; i < prefixExprs.size(); ++i) {
             MatchExpression* prefixMe = prefixExprs[i];
-            invariant(NULL != prefixMe);
+            invariant(nullptr != prefixMe);
             invariant(MatchExpression::EQ == prefixMe->matchType());
             EqualityMatchExpression* eqExpr = static_cast<EqualityMatchExpression*>(prefixMe);
             prefixBob.append(eqExpr->getData());
@@ -651,12 +651,12 @@ void QueryPlannerAccess::findElemMatchChildren(const MatchExpression* node,
                                                vector<MatchExpression*>* subnodesOut) {
     for (size_t i = 0; i < node->numChildren(); ++i) {
         MatchExpression* child = node->getChild(i);
-        if (Indexability::isBoundsGenerating(child) && NULL != child->getTag()) {
+        if (Indexability::isBoundsGenerating(child) && nullptr != child->getTag()) {
             out->push_back(child);
         } else if (MatchExpression::AND == child->matchType() ||
                    Indexability::arrayUsesIndexOnChildren(child)) {
             findElemMatchChildren(child, out, subnodesOut);
-        } else if (NULL != child->getTag()) {
+        } else if (nullptr != child->getTag()) {
             subnodesOut->push_back(child);
         }
     }
@@ -728,7 +728,7 @@ bool QueryPlannerAccess::processIndexScans(const CanonicalQuery& query,
 
         // If there is no tag, it's not using an index.  We've sorted our children such that the
         // children with tags are first, so we stop now.
-        if (NULL == child->getTag()) {
+        if (nullptr == child->getTag()) {
             break;
         }
 
@@ -789,7 +789,7 @@ bool QueryPlannerAccess::processIndexScans(const CanonicalQuery& query,
             mergeWithLeafNode(child, &scanState);
             handleFilter(&scanState);
         } else {
-            if (NULL != scanState.currentScan.get()) {
+            if (nullptr != scanState.currentScan.get()) {
                 // Output the current scan before starting to construct a new out.
                 finishAndOutputLeaf(&scanState, out);
             } else {
@@ -810,7 +810,7 @@ bool QueryPlannerAccess::processIndexScans(const CanonicalQuery& query,
     }
 
     // Output the scan we're done with, if it exists.
-    if (NULL != scanState.currentScan.get()) {
+    if (nullptr != scanState.currentScan.get()) {
         finishAndOutputLeaf(&scanState, out);
     }
 
@@ -876,13 +876,13 @@ bool QueryPlannerAccess::processIndexScansElemMatch(
     // the complete $elemMatch expression will be affixed as a filter later on.
     for (size_t i = 0; i < emChildren.size(); ++i) {
         MatchExpression* emChild = emChildren[i];
-        invariant(NULL != emChild->getTag());
+        invariant(nullptr != emChild->getTag());
         scanState->ixtag = static_cast<IndexTag*>(emChild->getTag());
 
         // If 'emChild' is a NOT, then the tag we're interested in is on the NOT's
         // child node.
         if (MatchExpression::NOT == emChild->matchType()) {
-            invariant(NULL != emChild->getChild(0)->getTag());
+            invariant(nullptr != emChild->getChild(0)->getTag());
             scanState->ixtag = static_cast<IndexTag*>(emChild->getChild(0)->getTag());
             invariant(IndexTag::kNoIndex != scanState->ixtag->index);
         }
@@ -895,7 +895,7 @@ bool QueryPlannerAccess::processIndexScansElemMatch(
             scanState->tightness = IndexBoundsBuilder::INEXACT_FETCH;
             mergeWithLeafNode(emChild, scanState);
         } else {
-            if (NULL != scanState->currentScan.get()) {
+            if (nullptr != scanState->currentScan.get()) {
                 finishAndOutputLeaf(scanState, out);
             } else {
                 verify(IndexTag::kNoIndex == scanState->currentIndexNumber);
@@ -972,7 +972,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::buildIndexedAnd(
     std::vector<std::unique_ptr<QuerySolutionNode>> ixscanNodes;
     const bool inArrayOperator = !ownedRoot;
     if (!processIndexScans(query, root, inArrayOperator, indices, params, &ixscanNodes)) {
-        return NULL;
+        return nullptr;
     }
 
     //
@@ -1095,7 +1095,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::buildIndexedOr(
     const bool inArrayOperator = !ownedRoot;
     std::vector<std::unique_ptr<QuerySolutionNode>> ixscanNodes;
     if (!processIndexScans(query, root, inArrayOperator, indices, params, &ixscanNodes)) {
-        return NULL;
+        return nullptr;
     }
 
     // Unlike an AND, an OR cannot have filters hanging off of it.  We stop processing
@@ -1106,7 +1106,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::buildIndexedOr(
         // We won't enumerate an OR without indices for each child, so this isn't an issue, even
         // if we have an AND with an OR child -- we won't get here unless the OR is fully
         // indexed.
-        return NULL;
+        return nullptr;
     }
 
     // If all index scans are identical, then we collapse them into a single scan. This prevents
@@ -1196,7 +1196,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::_buildIndexedDataAccess(
 
             IndexBoundsBuilder::BoundsTightness tightness = IndexBoundsBuilder::EXACT;
             auto soln = makeLeafNode(query, indices[tag->index], tag->pos, root, &tightness);
-            verify(NULL != soln);
+            verify(nullptr != soln);
             finishLeafNode(soln.get(), indices[tag->index]);
 
             if (!ownedRoot) {
@@ -1216,7 +1216,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::_buildIndexedDataAccess(
                 return soln;
             } else if (tightness == IndexBoundsBuilder::INEXACT_COVERED &&
                        !indices[tag->index].multikey) {
-                verify(NULL == soln->filter.get());
+                verify(nullptr == soln->filter.get());
                 soln->filter = std::move(ownedRoot);
                 return soln;
             } else {
@@ -1293,7 +1293,7 @@ std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::scanWholeIndex(
 void QueryPlannerAccess::addFilterToSolutionNode(QuerySolutionNode* node,
                                                  MatchExpression* match,
                                                  MatchExpression::MatchType type) {
-    if (NULL == node->filter) {
+    if (nullptr == node->filter) {
         node->filter.reset(match);
     } else if (type == node->filter->matchType()) {
         // The 'node' already has either an AND or OR filter that matches 'type'. Add 'match' as
diff --git a/src/mongo/db/query/planner_access.h b/src/mongo/db/query/planner_access.h
index e0744d55311..3c9b03ff4d0 100644
--- a/src/mongo/db/query/planner_access.h
+++ b/src/mongo/db/query/planner_access.h
@@ -146,7 +146,7 @@ private:
               currentScan(nullptr),
               curChild(0),
               currentIndexNumber(IndexTag::kNoIndex),
-              ixtag(NULL),
+              ixtag(nullptr),
               tightness(IndexBoundsBuilder::INEXACT_FETCH),
               curOr(nullptr),
               loosestBounds(IndexBoundsBuilder::EXACT) {}
@@ -157,7 +157,7 @@ private:
          * This always should be called prior to allocating a new 'currentScan'.
          */
         void resetForNextScan(IndexTag* newTag) {
-            currentScan.reset(NULL);
+            currentScan.reset(nullptr);
             currentIndexNumber = newTag->index;
             tightness = IndexBoundsBuilder::INEXACT_FETCH;
             loosestBounds = IndexBoundsBuilder::EXACT;
diff --git a/src/mongo/db/query/planner_analysis.cpp b/src/mongo/db/query/planner_analysis.cpp
index 1e8e84da6a7..2be65fbf8d2 100644
--- a/src/mongo/db/query/planner_analysis.cpp
+++ b/src/mongo/db/query/planner_analysis.cpp
@@ -628,7 +628,7 @@ QuerySolutionNode* QueryPlannerAnalysis::analyzeSort(const CanonicalQuery& query
     // If we're not allowed to put a blocking sort in, bail out.
     if (params.options & QueryPlannerParams::NO_BLOCKING_SORT) {
         delete solnRoot;
-        return NULL;
+        return nullptr;
     }
 
     if (!solnRoot->fetched()) {
diff --git a/src/mongo/db/query/planner_ixselect.cpp b/src/mongo/db/query/planner_ixselect.cpp
index 77f662a4701..f15b87b470c 100644
--- a/src/mongo/db/query/planner_ixselect.cpp
+++ b/src/mongo/db/query/planner_ixselect.cpp
@@ -557,7 +557,7 @@ bool QueryPlannerIXSelect::_compatible(const BSONElement& keyPatternElt,
             const CapWithCRS* cap = gc.getCapGeometryHack();
 
             // 2d indices can answer centerSphere queries.
-            if (NULL == cap) {
+            if (nullptr == cap) {
                 return false;
             }
 
@@ -666,7 +666,7 @@ void QueryPlannerIXSelect::_rateIndices(MatchExpression* node,
             fullPath = prefix + node->path().toString();
         }
 
-        verify(NULL == node->getTag());
+        verify(nullptr == node->getTag());
         node->setTag(new RelevantTag());
         auto rt = static_cast<RelevantTag*>(node->getTag());
         rt->path = fullPath;
@@ -995,7 +995,7 @@ static void stripInvalidAssignmentsToTextIndex(MatchExpression* node,
         MatchExpression* child = node->getChild(i);
         RelevantTag* tag = static_cast<RelevantTag*>(child->getTag());
 
-        if (NULL == tag) {
+        if (nullptr == tag) {
             // 'child' could be a logical operator.  Maybe there are some assignments hiding
             // inside.
             stripInvalidAssignmentsToTextIndex(child, idx, prefixPaths);
diff --git a/src/mongo/db/query/query_planner.cpp b/src/mongo/db/query/query_planner.cpp
index ad97acfc6c1..9735dbade0e 100644
--- a/src/mongo/db/query/query_planner.cpp
+++ b/src/mongo/db/query/query_planner.cpp
@@ -373,16 +373,16 @@ StatusWith<std::unique_ptr<PlanCacheIndexTree>> QueryPlanner::cacheDataFromTagge
 Status QueryPlanner::tagAccordingToCache(MatchExpression* filter,
                                          const PlanCacheIndexTree* const indexTree,
                                          const map<IndexEntry::Identifier, size_t>& indexMap) {
-    if (NULL == filter) {
+    if (nullptr == filter) {
         return Status(ErrorCodes::BadValue, "Cannot tag tree: filter is NULL.");
     }
-    if (NULL == indexTree) {
+    if (nullptr == indexTree) {
         return Status(ErrorCodes::BadValue, "Cannot tag tree: indexTree is NULL.");
     }
 
     // We're tagging the tree here, so it shouldn't have
     // any tags hanging off yet.
-    verify(NULL == filter->getTag());
+    verify(nullptr == filter->getTag());
 
     if (filter->numChildren() != indexTree->children.size()) {
         str::stream ss;
@@ -721,7 +721,7 @@ StatusWith<std::vector<std::unique_ptr<QuerySolution>>> QueryPlanner::plan(
     LOG(5) << "Rated tree:" << endl << redact(query.root()->debugString());
 
     // If there is a GEO_NEAR it must have an index it can use directly.
-    const MatchExpression* gnNode = NULL;
+    const MatchExpression* gnNode = nullptr;
     if (QueryPlannerCommon::hasNode(query.root(), MatchExpression::GEO_NEAR, &gnNode)) {
         // No index for GEO_NEAR?  No query.
         RelevantTag* tag = static_cast<RelevantTag*>(gnNode->getTag());
@@ -736,7 +736,7 @@ StatusWith<std::vector<std::unique_ptr<QuerySolution>>> QueryPlanner::plan(
     }
 
     // Likewise, if there is a TEXT it must have an index it can use directly.
-    const MatchExpression* textNode = NULL;
+    const MatchExpression* textNode = nullptr;
     if (QueryPlannerCommon::hasNode(query.root(), MatchExpression::TEXT, &textNode)) {
         RelevantTag* tag = static_cast<RelevantTag*>(textNode->getTag());
 
@@ -832,7 +832,8 @@ StatusWith<std::vector<std::unique_ptr<QuerySolution>>> QueryPlanner::plan(
 
     // Produce legible error message for failed OR planning with a TEXT child.
     // TODO: support collection scan for non-TEXT children of OR.
-    if (out.size() == 0 && textNode != NULL && MatchExpression::OR == query.root()->matchType()) {
+    if (out.size() == 0 && textNode != nullptr &&
+        MatchExpression::OR == query.root()->matchType()) {
         MatchExpression* root = query.root();
         for (size_t i = 0; i < root->numChildren(); ++i) {
             if (textNode == root->getChild(i)) {
diff --git a/src/mongo/db/query/query_planner_common.h b/src/mongo/db/query/query_planner_common.h
index 4cbfc1147dc..c232291e0e3 100644
--- a/src/mongo/db/query/query_planner_common.h
+++ b/src/mongo/db/query/query_planner_common.h
@@ -47,9 +47,9 @@ public:
      */
     static bool hasNode(const MatchExpression* root,
                         MatchExpression::MatchType type,
-                        const MatchExpression** out = NULL) {
+                        const MatchExpression** out = nullptr) {
         if (type == root->matchType()) {
-            if (NULL != out) {
+            if (nullptr != out) {
                 *out = root;
             }
             return true;
diff --git a/src/mongo/db/query/query_planner_test.cpp b/src/mongo/db/query/query_planner_test.cpp
index 757625df59d..6a91e1ec742 100644
--- a/src/mongo/db/query/query_planner_test.cpp
+++ b/src/mongo/db/query/query_planner_test.cpp
@@ -4605,7 +4605,7 @@ TEST_F(QueryPlannerTest, KeyPatternOverflowsInt) {
 TEST_F(QueryPlannerTest, CacheDataFromTaggedTreeFailsOnBadInput) {
     // Null match expression.
     std::vector<IndexEntry> relevantIndices;
-    ASSERT_NOT_OK(QueryPlanner::cacheDataFromTaggedTree(NULL, relevantIndices).getStatus());
+    ASSERT_NOT_OK(QueryPlanner::cacheDataFromTaggedTree(nullptr, relevantIndices).getStatus());
 
     // No relevant index matching the index tag.
     relevantIndices.push_back(buildSimpleIndexEntry(BSON("a" << 1), "a_1"));
@@ -4636,11 +4636,11 @@ TEST_F(QueryPlannerTest, TagAccordingToCacheFailsOnBadInput) {
     std::map<IndexEntry::Identifier, size_t> indexMap;
 
     // Null filter.
-    Status s = QueryPlanner::tagAccordingToCache(NULL, indexTree.get(), indexMap);
+    Status s = QueryPlanner::tagAccordingToCache(nullptr, indexTree.get(), indexMap);
     ASSERT_NOT_OK(s);
 
     // Null indexTree.
-    s = QueryPlanner::tagAccordingToCache(scopedCq->root(), NULL, indexMap);
+    s = QueryPlanner::tagAccordingToCache(scopedCq->root(), nullptr, indexMap);
     ASSERT_NOT_OK(s);
 
     // Index not found.
diff --git a/src/mongo/db/query/query_planner_test_lib.cpp b/src/mongo/db/query/query_planner_test_lib.cpp
index 2cfcc54985b..f0861044b3a 100644
--- a/src/mongo/db/query/query_planner_test_lib.cpp
+++ b/src/mongo/db/query/query_planner_test_lib.cpp
@@ -58,7 +58,7 @@ using std::string;
 bool filterMatches(const BSONObj& testFilter,
                    const BSONObj& testCollation,
                    const QuerySolutionNode* trueFilterNode) {
-    if (NULL == trueFilterNode->filter) {
+    if (nullptr == trueFilterNode->filter) {
         return false;
     }
 
@@ -267,7 +267,7 @@ bool QueryPlannerTestLib::solutionMatches(const BSONObj& testSoln,
         if (filter.eoo()) {
             return true;
         } else if (filter.isNull()) {
-            return NULL == csn->filter;
+            return nullptr == csn->filter;
         } else if (!filter.isABSONObj()) {
             return false;
         }
@@ -336,7 +336,7 @@ bool QueryPlannerTestLib::solutionMatches(const BSONObj& testSoln,
         if (filter.eoo()) {
             return true;
         } else if (filter.isNull()) {
-            return NULL == ixn->filter;
+            return nullptr == ixn->filter;
         } else if (!filter.isABSONObj()) {
             return false;
         }
@@ -453,7 +453,7 @@ bool QueryPlannerTestLib::solutionMatches(const BSONObj& testSoln,
         BSONElement filter = textObj["filter"];
         if (!filter.eoo()) {
             if (filter.isNull()) {
-                if (NULL != node->filter) {
+                if (nullptr != node->filter) {
                     return false;
                 }
             } else if (!filter.isABSONObj()) {
@@ -490,7 +490,7 @@ bool QueryPlannerTestLib::solutionMatches(const BSONObj& testSoln,
         BSONElement filter = fetchObj["filter"];
         if (!filter.eoo()) {
             if (filter.isNull()) {
-                if (NULL != fn->filter) {
+                if (nullptr != fn->filter) {
                     return false;
                 }
             } else if (!filter.isABSONObj()) {
@@ -533,7 +533,7 @@ bool QueryPlannerTestLib::solutionMatches(const BSONObj& testSoln,
         BSONElement filter = andHashObj["filter"];
         if (!filter.eoo()) {
             if (filter.isNull()) {
-                if (NULL != ahn->filter) {
+                if (nullptr != ahn->filter) {
                     return false;
                 }
             } else if (!filter.isABSONObj()) {
@@ -564,7 +564,7 @@ bool QueryPlannerTestLib::solutionMatches(const BSONObj& testSoln,
         BSONElement filter = andSortedObj["filter"];
         if (!filter.eoo()) {
             if (filter.isNull()) {
-                if (NULL != asn->filter) {
+                if (nullptr != asn->filter) {
                     return false;
                 }
             } else if (!filter.isABSONObj()) {
diff --git a/src/mongo/db/query/query_solution.cpp b/src/mongo/db/query/query_solution.cpp
index 23c83c6fb8a..9f1951c14a9 100644
--- a/src/mongo/db/query/query_solution.cpp
+++ b/src/mongo/db/query/query_solution.cpp
@@ -203,7 +203,7 @@ void TextNode::appendToString(str::stream* ss, int indent) const {
     *ss << "diacriticSensitive= " << ftsQuery->getDiacriticSensitive() << '\n';
     addIndent(ss, indent + 1);
     *ss << "indexPrefix = " << indexPrefix.toString() << '\n';
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << " filter = " << filter->debugString();
     }
@@ -233,7 +233,7 @@ void CollectionScanNode::appendToString(str::stream* ss, int indent) const {
     *ss << "COLLSCAN\n";
     addIndent(ss, indent + 1);
     *ss << "ns = " << name << '\n';
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << "filter = " << filter->debugString();
     }
@@ -265,7 +265,7 @@ AndHashNode::~AndHashNode() {}
 void AndHashNode::appendToString(str::stream* ss, int indent) const {
     addIndent(ss, indent);
     *ss << "AND_HASH\n";
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << " filter = " << filter->debugString() << '\n';
     }
@@ -369,7 +369,7 @@ OrNode::~OrNode() {}
 void OrNode::appendToString(str::stream* ss, int indent) const {
     addIndent(ss, indent);
     *ss << "OR\n";
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << " filter = " << filter->debugString() << '\n';
     }
@@ -430,7 +430,7 @@ MergeSortNode::~MergeSortNode() {}
 void MergeSortNode::appendToString(str::stream* ss, int indent) const {
     addIndent(ss, indent);
     *ss << "MERGE_SORT\n";
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << " filter = " << filter->debugString() << '\n';
     }
@@ -489,7 +489,7 @@ FetchNode::FetchNode() : _sorts(SimpleBSONObjComparator::kInstance.makeBSONObjSe
 void FetchNode::appendToString(str::stream* ss, int indent) const {
     addIndent(ss, indent);
     *ss << "FETCH\n";
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         StringBuilder sb;
         *ss << "filter:\n";
@@ -529,7 +529,7 @@ void IndexScanNode::appendToString(str::stream* ss, int indent) const {
     addIndent(ss, indent + 1);
     *ss << "indexName = " << index.identifier.catalogName << '\n';
     *ss << "keyPattern = " << index.keyPattern << '\n';
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << "filter = " << filter->debugString();
     }
@@ -1041,7 +1041,7 @@ void GeoNear2DNode::appendToString(str::stream* ss, int indent) const {
     *ss << "keyPattern = " << index.keyPattern.toString() << '\n';
     addCommon(ss, indent);
     *ss << "nearQuery = " << nq->toString() << '\n';
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << " filter = " << filter->debugString();
     }
@@ -1075,7 +1075,7 @@ void GeoNear2DSphereNode::appendToString(str::stream* ss, int indent) const {
     *ss << "baseBounds = " << baseBounds.toString() << '\n';
     addIndent(ss, indent + 1);
     *ss << "nearQuery = " << nq->toString() << '\n';
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         *ss << " filter = " << filter->debugString();
     }
@@ -1101,7 +1101,7 @@ QuerySolutionNode* GeoNear2DSphereNode::clone() const {
 void ShardingFilterNode::appendToString(str::stream* ss, int indent) const {
     addIndent(ss, indent);
     *ss << "SHARDING_FILTER\n";
-    if (NULL != filter) {
+    if (nullptr != filter) {
         addIndent(ss, indent + 1);
         StringBuilder sb;
         *ss << "filter:\n";
diff --git a/src/mongo/db/query/query_solution.h b/src/mongo/db/query/query_solution.h
index 44c63d4bfb6..a665b823529 100644
--- a/src/mongo/db/query/query_solution.h
+++ b/src/mongo/db/query/query_solution.h
@@ -147,7 +147,7 @@ struct QuerySolutionNode {
         for (size_t i = 0; i < this->children.size(); i++) {
             other->children.push_back(this->children[i]->clone());
         }
-        if (NULL != this->filter) {
+        if (nullptr != this->filter) {
             other->filter = this->filter->shallowClone();
         }
     }
@@ -229,7 +229,7 @@ struct QuerySolution {
      * Output a human-readable std::string representing the plan.
      */
     std::string toString() {
-        if (NULL == root) {
+        if (nullptr == root) {
             return "empty query solution";
         }
 
diff --git a/src/mongo/db/repl/idempotency_test_fixture.cpp b/src/mongo/db/repl/idempotency_test_fixture.cpp
index 63c769e58be..6a5fe64ba4a 100644
--- a/src/mongo/db/repl/idempotency_test_fixture.cpp
+++ b/src/mongo/db/repl/idempotency_test_fixture.cpp
@@ -550,13 +550,13 @@ std::string IdempotencyTest::computeDataHash(Collection* collection) {
                                            PlanExecutor::NO_YIELD,
                                            InternalPlanner::FORWARD,
                                            InternalPlanner::IXSCAN_FETCH);
-    ASSERT(NULL != exec.get());
+    ASSERT(nullptr != exec.get());
     md5_state_t st;
     md5_init(&st);
 
     PlanExecutor::ExecState state;
     BSONObj obj;
-    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
+    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
         obj = this->canonicalizeDocumentForDataHash(obj);
         md5_append(&st, (const md5_byte_t*)obj.objdata(), obj.objsize());
     }
diff --git a/src/mongo/db/repl/isself.cpp b/src/mongo/db/repl/isself.cpp
index a78298933fd..f864cbb13de 100644
--- a/src/mongo/db/repl/isself.cpp
+++ b/src/mongo/db/repl/isself.cpp
@@ -107,7 +107,7 @@ std::string stringifyError(int code) {
 std::vector<std::string> getAddrsForHost(const std::string& iporhost,
                                          const int port,
                                          const bool ipv6enabled) {
-    addrinfo* addrs = NULL;
+    addrinfo* addrs = nullptr;
     addrinfo hints = {0};
     hints.ai_socktype = SOCK_STREAM;
     hints.ai_family = (ipv6enabled ? AF_UNSPEC : AF_INET);
@@ -126,13 +126,13 @@ std::vector<std::string> getAddrsForHost(const std::string& iporhost,
 
     ON_BLOCK_EXIT([&] { freeaddrinfo(addrs); });
 
-    for (addrinfo* addr = addrs; addr != NULL; addr = addr->ai_next) {
+    for (addrinfo* addr = addrs; addr != nullptr; addr = addr->ai_next) {
         int family = addr->ai_family;
         char host[NI_MAXHOST];
 
         if (family == AF_INET || family == AF_INET6) {
             err = getnameinfo(
-                addr->ai_addr, addr->ai_addrlen, host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);
+                addr->ai_addr, addr->ai_addrlen, host, NI_MAXHOST, nullptr, 0, NI_NUMERICHOST);
             if (err) {
                 warning() << "getnameinfo() failed: " << stringifyError(err) << std::endl;
                 continue;
@@ -235,8 +235,8 @@ std::vector<std::string> getBoundAddrs(const bool ipv6enabled) {
     ON_BLOCK_EXIT([&] { freeifaddrs(addrs); });
 
     // based on example code from linux getifaddrs manpage
-    for (ifaddrs* addr = addrs; addr != NULL; addr = addr->ifa_next) {
-        if (addr->ifa_addr == NULL)
+    for (ifaddrs* addr = addrs; addr != nullptr; addr = addr->ifa_next) {
+        if (addr->ifa_addr == nullptr)
             continue;
         int family = addr->ifa_addr->sa_family;
         char host[NI_MAXHOST];
@@ -247,7 +247,7 @@ std::vector<std::string> getBoundAddrs(const bool ipv6enabled) {
                 (family == AF_INET ? sizeof(struct sockaddr_in) : sizeof(struct sockaddr_in6)),
                 host,
                 NI_MAXHOST,
-                NULL,
+                nullptr,
                 0,
                 NI_NUMERICHOST);
             if (err) {
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index e628976f83c..0f1d20a7ef7 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -608,7 +608,7 @@ std::vector<OpTime> logInsertOps(OperationContext* opCtx,
                                           nss,
                                           uuid,
                                           begin[i].doc,
-                                          NULL,
+                                          nullptr,
                                           fromMigrate,
                                           insertStatementOplogSlot,
                                           wallClockTime,
@@ -1683,7 +1683,7 @@ Status applyOperation_inlock(OperationContext* opCtx,
                     // such as an updateCriteria of the form
                     // { _id:..., { x : {$size:...} }
                     // thus this is not ideal.
-                    if (collection == NULL ||
+                    if (collection == nullptr ||
                         (indexCatalog->haveIdIndex(opCtx) &&
                          Helpers::findById(opCtx, collection, updateCriteria).isNull()) ||
                         // capped collections won't have an _id index
@@ -1980,7 +1980,7 @@ void initTimestampFromOplog(OperationContext* opCtx, const NamespaceString& oplo
     DBDirectClient c(opCtx);
     static const BSONObj reverseNaturalObj = BSON("$natural" << -1);
     BSONObj lastOp =
-        c.findOne(oplogNss.ns(), Query().sort(reverseNaturalObj), NULL, QueryOption_SlaveOk);
+        c.findOne(oplogNss.ns(), Query().sort(reverseNaturalObj), nullptr, QueryOption_SlaveOk);
 
     if (!lastOp.isEmpty()) {
         LOG(1) << "replSet setting last Timestamp";
diff --git a/src/mongo/db/repl/oplogreader.cpp b/src/mongo/db/repl/oplogreader.cpp
index 5be1c01ecfc..17811adcf9a 100644
--- a/src/mongo/db/repl/oplogreader.cpp
+++ b/src/mongo/db/repl/oplogreader.cpp
@@ -75,7 +75,7 @@ OplogReader::OplogReader() {
 }
 
 bool OplogReader::connect(const HostAndPort& host) {
-    if (conn() == NULL || _host != host) {
+    if (conn() == nullptr || _host != host) {
         resetConnection();
         _conn = std::shared_ptr<DBClientConnection>(
             new DBClientConnection(false, durationCount<Seconds>(kSocketTimeout)));
diff --git a/src/mongo/db/repl/oplogreader.h b/src/mongo/db/repl/oplogreader.h
index 10abc580087..dca256bf871 100644
--- a/src/mongo/db/repl/oplogreader.h
+++ b/src/mongo/db/repl/oplogreader.h
@@ -73,7 +73,7 @@ public:
         return _conn.get();
     }
     BSONObj findOne(const char* ns, const Query& q) {
-        return conn()->findOne(ns, q, 0, QueryOption_SlaveOk);
+        return conn()->findOne(ns, q, nullptr, QueryOption_SlaveOk);
     }
     BSONObj findOneByUUID(const std::string& db, UUID uuid, const BSONObj& filter) {
         // Note that the findOneByUUID() function of DBClient passes SlaveOK to the client.
@@ -91,7 +91,7 @@ public:
     void tailCheck();
 
     bool haveCursor() {
-        return cursor.get() != 0;
+        return cursor.get() != nullptr;
     }
 
     void tailingQuery(const char* ns, const BSONObj& query);
diff --git a/src/mongo/db/repl/repl_set_commands.cpp b/src/mongo/db/repl/repl_set_commands.cpp
index a38d510fd5a..c7b3c3ec3d2 100644
--- a/src/mongo/db/repl/repl_set_commands.cpp
+++ b/src/mongo/db/repl/repl_set_commands.cpp
@@ -248,14 +248,14 @@ void parseReplSetSeedList(ReplicationCoordinatorExternalState* externalState,
         *setname = p;
     }
 
-    if (slash == 0) {
+    if (slash == nullptr) {
         return;
     }
 
     p = slash + 1;
     while (1) {
         const char* comma = strchr(p, ',');
-        if (comma == 0) {
+        if (comma == nullptr) {
             comma = strchr(p, 0);
         }
         if (p == comma) {
diff --git a/src/mongo/db/repl/repl_set_config.cpp b/src/mongo/db/repl/repl_set_config.cpp
index a3f27decf09..371ec2b7e87 100644
--- a/src/mongo/db/repl/repl_set_config.cpp
+++ b/src/mongo/db/repl/repl_set_config.cpp
@@ -742,7 +742,7 @@ const MemberConfig* ReplSetConfig::findMemberByID(int id) const {
             return &(*it);
         }
     }
-    return NULL;
+    return nullptr;
 }
 
 int ReplSetConfig::findMemberIndexByHostAndPort(const HostAndPort& hap) const {
@@ -770,7 +770,7 @@ int ReplSetConfig::findMemberIndexByConfigId(long long configId) const {
 
 const MemberConfig* ReplSetConfig::findMemberByHostAndPort(const HostAndPort& hap) const {
     int idx = findMemberIndexByHostAndPort(hap);
-    return idx != -1 ? &getMemberAt(idx) : NULL;
+    return idx != -1 ? &getMemberAt(idx) : nullptr;
 }
 
 Milliseconds ReplSetConfig::getHeartbeatInterval() const {
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index b963d5c9849..f97ebb90f04 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -2359,7 +2359,7 @@ Status ReplicationCoordinatorImpl::processReplSetGetStatus(
     _topCoord->prepareStatusResponse(
         TopologyCoordinator::ReplSetStatusArgs{
             _replExecutor->now(),
-            static_cast<unsigned>(time(0) - serverGlobalParams.started),
+            static_cast<unsigned>(time(nullptr) - serverGlobalParams.started),
             _getCurrentCommittedSnapshotOpTimeAndWallTime_inlock(),
             initialSyncProgress,
             _storage->getLastStableCheckpointTimestampDeprecated(_service),
diff --git a/src/mongo/db/repl/replication_coordinator_impl_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
index 448504218b4..ee096286774 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
@@ -3364,7 +3364,7 @@ TEST_F(ReplCoordTest, DoNotProcessSelfWhenUpdatePositionContainsInfoAboutSelf) {
                                 << UpdatePositionArgs::kAppliedWallTimeFieldName
                                 << Date_t() + Seconds(time2.getSecs()))))));
 
-    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args, 0));
+    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args, nullptr));
     ASSERT_EQUALS(ErrorCodes::WriteConcernFailed,
                   getReplCoord()->awaitReplication(opCtx.get(), time2, writeConcern).status);
 }
@@ -3488,7 +3488,8 @@ TEST_F(ReplCoordTest, DoNotProcessUpdatePositionOfMembersWhoseIdsAreNotInTheConf
     auto opCtx = makeOperationContext();
 
 
-    ASSERT_EQUALS(ErrorCodes::NodeNotFound, getReplCoord()->processReplSetUpdatePosition(args, 0));
+    ASSERT_EQUALS(ErrorCodes::NodeNotFound,
+                  getReplCoord()->processReplSetUpdatePosition(args, nullptr));
     ASSERT_EQUALS(ErrorCodes::WriteConcernFailed,
                   getReplCoord()->awaitReplication(opCtx.get(), time2, writeConcern).status);
 }
@@ -3565,7 +3566,7 @@ TEST_F(ReplCoordTest,
     auto opCtx = makeOperationContext();
 
 
-    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args, 0));
+    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args, nullptr));
     ASSERT_OK(getReplCoord()->awaitReplication(opCtx.get(), time2, writeConcern).status);
 
     writeConcern.wNumNodes = 3;
@@ -6122,7 +6123,7 @@ TEST_F(ReplCoordTest, StepDownWhenHandleLivenessTimeoutMarksAMajorityOfVotingNod
                                    << UpdatePositionArgs::kDurableWallTimeFieldName
                                    << Date_t() + Seconds(startingOpTime.getSecs()))))));
 
-    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args, 0));
+    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args, nullptr));
     // Become PRIMARY.
     simulateSuccessfulV1Election();
 
@@ -6161,7 +6162,7 @@ TEST_F(ReplCoordTest, StepDownWhenHandleLivenessTimeoutMarksAMajorityOfVotingNod
     const Date_t startDate = getNet()->now();
     getNet()->enterNetwork();
     getNet()->runUntil(startDate + Milliseconds(100));
-    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args1, 0));
+    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args1, nullptr));
 
     // Confirm that the node remains PRIMARY after the other two nodes are marked DOWN.
     getNet()->runUntil(startDate + Milliseconds(2080));
@@ -6212,7 +6213,7 @@ TEST_F(ReplCoordTest, StepDownWhenHandleLivenessTimeoutMarksAMajorityOfVotingNod
                                 << startingOpTime.toBSON()
                                 << UpdatePositionArgs::kAppliedWallTimeFieldName
                                 << Date_t() + Seconds(startingOpTime.getSecs()))))));
-    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args2, 0));
+    ASSERT_OK(getReplCoord()->processReplSetUpdatePosition(args2, nullptr));
 
     hbArgs.setSetName("mySet");
     hbArgs.setConfigVersion(2);
diff --git a/src/mongo/db/repl/replication_info.cpp b/src/mongo/db/repl/replication_info.cpp
index e3f26e73513..701b6411d6a 100644
--- a/src/mongo/db/repl/replication_info.cpp
+++ b/src/mongo/db/repl/replication_info.cpp
@@ -101,7 +101,7 @@ void appendReplicationInfo(OperationContext* opCtx, BSONObjBuilder& result, int
                 opCtx, localSources.ns(), ctx.getCollection(), PlanExecutor::NO_YIELD);
             BSONObj obj;
             PlanExecutor::ExecState state;
-            while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
+            while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
                 src.push_back(obj.getOwned());
             }
 
diff --git a/src/mongo/db/repl/rollback_source_impl.cpp b/src/mongo/db/repl/rollback_source_impl.cpp
index 26a9240bbc8..aecd404f865 100644
--- a/src/mongo/db/repl/rollback_source_impl.cpp
+++ b/src/mongo/db/repl/rollback_source_impl.cpp
@@ -67,11 +67,13 @@ int RollbackSourceImpl::getRollbackId() const {
 
 BSONObj RollbackSourceImpl::getLastOperation() const {
     const Query query = Query().sort(BSON("$natural" << -1));
-    return _getConnection()->findOne(_collectionName, query, 0, QueryOption_SlaveOk);
+    return _getConnection()->findOne(_collectionName, query, nullptr, QueryOption_SlaveOk);
 }
 
 BSONObj RollbackSourceImpl::findOne(const NamespaceString& nss, const BSONObj& filter) const {
-    return _getConnection()->findOne(nss.toString(), filter, NULL, QueryOption_SlaveOk).getOwned();
+    return _getConnection()
+        ->findOne(nss.toString(), filter, nullptr, QueryOption_SlaveOk)
+        .getOwned();
 }
 
 std::pair<BSONObj, NamespaceString> RollbackSourceImpl::findOneByUUID(const std::string& db,
diff --git a/src/mongo/db/repl/rs_rollback.cpp b/src/mongo/db/repl/rs_rollback.cpp
index e2fc2bcdb23..26491c2728d 100644
--- a/src/mongo/db/repl/rs_rollback.cpp
+++ b/src/mongo/db/repl/rs_rollback.cpp
@@ -793,7 +793,7 @@ void dropCollection(OperationContext* opCtx,
             opCtx, nss.toString(), collection, PlanExecutor::YIELD_AUTO);
         BSONObj curObj;
         PlanExecutor::ExecState execState;
-        while (PlanExecutor::ADVANCED == (execState = exec->getNext(&curObj, NULL))) {
+        while (PlanExecutor::ADVANCED == (execState = exec->getNext(&curObj, nullptr))) {
             auto status = removeSaver.goingToDelete(curObj);
             if (!status.isOK()) {
                 severe() << "Rolling back createCollection on " << nss
@@ -1319,7 +1319,7 @@ void rollback_internal::syncFixUp(OperationContext* opCtx,
     log() << "Deleting and updating documents to roll back insert, update and remove "
              "operations";
     unsigned deletes = 0, updates = 0;
-    time_t lastProgressUpdate = time(0);
+    time_t lastProgressUpdate = time(nullptr);
     time_t progressUpdateGap = 10;
 
     for (const auto& nsAndGoodVersionsByDocID : goodVersions) {
@@ -1345,7 +1345,7 @@ void rollback_internal::syncFixUp(OperationContext* opCtx,
 
         const auto& goodVersionsByDocID = nsAndGoodVersionsByDocID.second;
         for (const auto& idAndDoc : goodVersionsByDocID) {
-            time_t now = time(0);
+            time_t now = time(nullptr);
             if (now - lastProgressUpdate > progressUpdateGap) {
                 log() << deletes << " delete and " << updates
                       << " update operations processed out of " << goodVersions.size()
diff --git a/src/mongo/db/repl/topology_coordinator.cpp b/src/mongo/db/repl/topology_coordinator.cpp
index 7300fdc17cb..ffcf36c57be 100644
--- a/src/mongo/db/repl/topology_coordinator.cpp
+++ b/src/mongo/db/repl/topology_coordinator.cpp
@@ -1409,7 +1409,7 @@ void TopologyCoordinator::setCurrentPrimary_forTest(int primaryIndex,
 
 const MemberConfig* TopologyCoordinator::_currentPrimaryMember() const {
     if (_currentPrimaryIndex == -1)
-        return NULL;
+        return nullptr;
 
     return &(_rsConfig.getMemberAt(_currentPrimaryIndex));
 }
diff --git a/src/mongo/db/repl/vote_requester_test.cpp b/src/mongo/db/repl/vote_requester_test.cpp
index 97e5736cd76..4fc8382bf4a 100644
--- a/src/mongo/db/repl/vote_requester_test.cpp
+++ b/src/mongo/db/repl/vote_requester_test.cpp
@@ -98,7 +98,7 @@ public:
     }
 
     virtual void tearDown() {
-        _requester.reset(NULL);
+        _requester.reset(nullptr);
     }
 
 protected:
diff --git a/src/mongo/db/s/check_sharding_index_command.cpp b/src/mongo/db/s/check_sharding_index_command.cpp
index 7bc56741ae8..88cd5d4b0eb 100644
--- a/src/mongo/db/s/check_sharding_index_command.cpp
+++ b/src/mongo/db/s/check_sharding_index_command.cpp
@@ -121,7 +121,7 @@ public:
             collection->getIndexCatalog()->findShardKeyPrefixedIndex(opCtx,
                                                                      keyPattern,
                                                                      true);  // requireSingleKey
-        if (idx == NULL) {
+        if (idx == nullptr) {
             errmsg = "couldn't find valid index for shard key";
             return false;
         }
diff --git a/src/mongo/db/s/split_chunk.cpp b/src/mongo/db/s/split_chunk.cpp
index c76edbf8c6d..be2560efcee 100644
--- a/src/mongo/db/s/split_chunk.cpp
+++ b/src/mongo/db/s/split_chunk.cpp
@@ -76,8 +76,8 @@ bool checkIfSingleDoc(OperationContext* opCtx,
     // check if exactly one document found
     PlanExecutor::ExecState state;
     BSONObj obj;
-    if (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
-        if (PlanExecutor::IS_EOF == (state = exec->getNext(&obj, NULL))) {
+    if (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
+        if (PlanExecutor::IS_EOF == (state = exec->getNext(&obj, nullptr))) {
             return true;
         }
     }
diff --git a/src/mongo/db/s/split_vector.cpp b/src/mongo/db/s/split_vector.cpp
index 816d0b8dd92..62bc2dcd021 100644
--- a/src/mongo/db/s/split_vector.cpp
+++ b/src/mongo/db/s/split_vector.cpp
@@ -86,7 +86,7 @@ StatusWith<std::vector<BSONObj>> splitVector(OperationContext* opCtx,
         // any multi-key index prefixed by shard key cannot be multikey over the shard key fields.
         const IndexDescriptor* idx =
             collection->getIndexCatalog()->findShardKeyPrefixedIndex(opCtx, keyPattern, false);
-        if (idx == NULL) {
+        if (idx == nullptr) {
             return {ErrorCodes::IndexNotFound,
                     "couldn't find index over splitting key " +
                         keyPattern.clientReadable().toString()};
@@ -171,7 +171,7 @@ StatusWith<std::vector<BSONObj>> splitVector(OperationContext* opCtx,
                                                InternalPlanner::FORWARD);
 
         BSONObj currKey;
-        PlanExecutor::ExecState state = exec->getNext(&currKey, NULL);
+        PlanExecutor::ExecState state = exec->getNext(&currKey, nullptr);
         if (PlanExecutor::ADVANCED != state) {
             return {ErrorCodes::OperationFailed,
                     "can't open a cursor to scan the range (desired range is possibly empty)"};
@@ -189,7 +189,7 @@ StatusWith<std::vector<BSONObj>> splitVector(OperationContext* opCtx,
                                                    PlanExecutor::YIELD_AUTO,
                                                    InternalPlanner::BACKWARD);
 
-            PlanExecutor::ExecState state = exec->getNext(&maxKeyInChunk, NULL);
+            PlanExecutor::ExecState state = exec->getNext(&maxKeyInChunk, nullptr);
             if (PlanExecutor::ADVANCED != state) {
                 return {ErrorCodes::OperationFailed,
                         "can't open a cursor to find final key in range (desired range is possibly "
@@ -241,7 +241,7 @@ StatusWith<std::vector<BSONObj>> splitVector(OperationContext* opCtx,
                     break;
                 }
 
-                state = exec->getNext(&currKey, NULL);
+                state = exec->getNext(&currKey, nullptr);
             }
 
             if (PlanExecutor::FAILURE == state) {
@@ -271,7 +271,7 @@ StatusWith<std::vector<BSONObj>> splitVector(OperationContext* opCtx,
                                               PlanExecutor::YIELD_AUTO,
                                               InternalPlanner::FORWARD);
 
-            state = exec->getNext(&currKey, NULL);
+            state = exec->getNext(&currKey, nullptr);
         }
 
         //
diff --git a/src/mongo/db/server_options.h b/src/mongo/db/server_options.h
index 14237da05e2..08a944fec1d 100644
--- a/src/mongo/db/server_options.h
+++ b/src/mongo/db/server_options.h
@@ -115,7 +115,7 @@ struct ServerGlobalParams {
         bool storageDetailsCmdEnabled;  // -- enableExperimentalStorageDetailsCmd
     } experimental;
 
-    time_t started = ::time(0);
+    time_t started = ::time(nullptr);
 
     BSONArray argvArray;
     BSONObj parsedOpts;
diff --git a/src/mongo/db/server_options_helpers.cpp b/src/mongo/db/server_options_helpers.cpp
index 4a9e1a3acef..01c0f1c0c8c 100644
--- a/src/mongo/db/server_options_helpers.cpp
+++ b/src/mongo/db/server_options_helpers.cpp
@@ -340,7 +340,8 @@ Status storeBaseOptions(const moe::Environment& params) {
         bool set = false;
         // match facility string to facility value
         size_t facilitynamesLength = sizeof(facilitynames) / sizeof(facilitynames[0]);
-        for (unsigned long i = 0; i < facilitynamesLength && facilitynames[i].c_name != NULL; i++) {
+        for (unsigned long i = 0; i < facilitynamesLength && facilitynames[i].c_name != nullptr;
+             i++) {
             if (!facility.compare(facilitynames[i].c_name)) {
                 serverGlobalParams.syslogFacility = facilitynames[i].c_val;
                 set = true;
@@ -399,8 +400,8 @@ Status storeBaseOptions(const moe::Environment& params) {
             ServerParameter* parameter =
                 mapFindWithDefault(ServerParameterSet::getGlobal()->getMap(),
                                    parametersIt->first,
-                                   static_cast<ServerParameter*>(NULL));
-            if (NULL == parameter) {
+                                   static_cast<ServerParameter*>(nullptr));
+            if (nullptr == parameter) {
                 StringBuilder sb;
                 sb << "Illegal --setParameter parameter: \"" << parametersIt->first << "\"";
                 return Status(ErrorCodes::BadValue, sb.str());
diff --git a/src/mongo/db/service_entry_point_common.cpp b/src/mongo/db/service_entry_point_common.cpp
index 5c48ade9178..89076c67f13 100644
--- a/src/mongo/db/service_entry_point_common.cpp
+++ b/src/mongo/db/service_entry_point_common.cpp
@@ -1240,7 +1240,7 @@ DbResponse ServiceEntryPointCommon::handleRequest(OperationContext* opCtx,
         invariant(!opCtx->lockState()->isLocked());
     }
 
-    const char* ns = dbmsg.messageShouldHaveNs() ? dbmsg.getns() : NULL;
+    const char* ns = dbmsg.messageShouldHaveNs() ? dbmsg.getns() : nullptr;
     const NamespaceString nsString = ns ? NamespaceString(ns) : NamespaceString();
 
     if (op == dbQuery) {
diff --git a/src/mongo/db/sorter/sorter_test.cpp b/src/mongo/db/sorter/sorter_test.cpp
index 18fcf91f0b1..513954cb684 100644
--- a/src/mongo/db/sorter/sorter_test.cpp
+++ b/src/mongo/db/sorter/sorter_test.cpp
@@ -516,7 +516,7 @@ class Dupes : public Basic {
 template <bool Random = true>
 class LotsOfDataLittleMemory : public Basic {
 public:
-    LotsOfDataLittleMemory() : _array(new int[NUM_ITEMS]), _random(int64_t(time(0))) {
+    LotsOfDataLittleMemory() : _array(new int[NUM_ITEMS]), _random(int64_t(time(nullptr))) {
         for (int i = 0; i < NUM_ITEMS; i++)
             _array[i] = i;
 
diff --git a/src/mongo/db/storage/biggie/biggie_record_store.h b/src/mongo/db/storage/biggie/biggie_record_store.h
index 5f62b5ab5e8..813c575ecf7 100644
--- a/src/mongo/db/storage/biggie/biggie_record_store.h
+++ b/src/mongo/db/storage/biggie/biggie_record_store.h
@@ -64,7 +64,7 @@ public:
     virtual bool isCapped() const;
     virtual void setCappedCallback(CappedCallback*);
     virtual int64_t storageSize(OperationContext* opCtx,
-                                BSONObjBuilder* extraInfo = NULL,
+                                BSONObjBuilder* extraInfo = nullptr,
                                 int infoLevel = 0) const;
 
     virtual bool findRecord(OperationContext* opCtx, const RecordId& loc, RecordData* rd) const;
diff --git a/src/mongo/db/storage/devnull/devnull_kv_engine.cpp b/src/mongo/db/storage/devnull/devnull_kv_engine.cpp
index 6500879bde3..59a45b990ea 100644
--- a/src/mongo/db/storage/devnull/devnull_kv_engine.cpp
+++ b/src/mongo/db/storage/devnull/devnull_kv_engine.cpp
@@ -87,7 +87,7 @@ public:
     }
 
     virtual int64_t storageSize(OperationContext* opCtx,
-                                BSONObjBuilder* extraInfo = NULL,
+                                BSONObjBuilder* extraInfo = nullptr,
                                 int infoLevel = 0) const {
         return 0;
     }
diff --git a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store.h b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store.h
index 37b526f4c1a..439cbe1cdf6 100644
--- a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store.h
+++ b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store.h
@@ -104,7 +104,7 @@ public:
     virtual Status touch(OperationContext* opCtx, BSONObjBuilder* output) const;
 
     virtual int64_t storageSize(OperationContext* opCtx,
-                                BSONObjBuilder* extraInfo = NULL,
+                                BSONObjBuilder* extraInfo = nullptr,
                                 int infoLevel = 0) const;
 
     virtual long long dataSize(OperationContext* opCtx) const {
diff --git a/src/mongo/db/storage/key_string.cpp b/src/mongo/db/storage/key_string.cpp
index a7fab7792c3..d30ac2d93b0 100644
--- a/src/mongo/db/storage/key_string.cpp
+++ b/src/mongo/db/storage/key_string.cpp
@@ -346,7 +346,7 @@ void KeyString::_appendAllElementsForIndexing(const BSONObj& obj,
         const int elemIdx = elemCount++;
         const bool invert = (ord.get(elemIdx) == -1);
 
-        _appendBsonValue(elem, invert, NULL);
+        _appendBsonValue(elem, invert, nullptr);
 
         dassert(elem.fieldNameSize() < 3);  // fieldNameSize includes the NUL
 
@@ -517,7 +517,7 @@ void KeyString::_appendArray(const BSONArray& val, bool invert) {
     _append(CType::kArray, invert);
     BSONForEach(elem, val) {
         // No generic ctype byte needed here since no name is encoded.
-        _appendBsonValue(elem, invert, NULL);
+        _appendBsonValue(elem, invert, nullptr);
     }
     _append(int8_t(0), invert);
 }
diff --git a/src/mongo/db/storage/kv/kv_catalog.cpp b/src/mongo/db/storage/kv/kv_catalog.cpp
index b9922cea3f9..46a821a805c 100644
--- a/src/mongo/db/storage/kv/kv_catalog.cpp
+++ b/src/mongo/db/storage/kv/kv_catalog.cpp
@@ -330,7 +330,7 @@ KVCatalog::KVCatalog(RecordStore* rs,
       _engine(engine) {}
 
 KVCatalog::~KVCatalog() {
-    _rs = NULL;
+    _rs = nullptr;
 }
 
 std::string KVCatalog::_newRand() {
diff --git a/src/mongo/db/storage/mobile/mobile_record_store.h b/src/mongo/db/storage/mobile/mobile_record_store.h
index ac2d7e4e229..9379a7760f7 100644
--- a/src/mongo/db/storage/mobile/mobile_record_store.h
+++ b/src/mongo/db/storage/mobile/mobile_record_store.h
@@ -113,7 +113,7 @@ public:
     Status touch(OperationContext* opCtx, BSONObjBuilder* output) const override;
 
     int64_t storageSize(OperationContext* opCtx,
-                        BSONObjBuilder* extraInfo = NULL,
+                        BSONObjBuilder* extraInfo = nullptr,
                         int infoLevel = 0) const override;
 
     long long dataSize(OperationContext* opCtx) const override;
diff --git a/src/mongo/db/storage/mobile/mobile_recovery_unit.cpp b/src/mongo/db/storage/mobile/mobile_recovery_unit.cpp
index d8ff95a9e50..60181ac0b02 100644
--- a/src/mongo/db/storage/mobile/mobile_recovery_unit.cpp
+++ b/src/mongo/db/storage/mobile/mobile_recovery_unit.cpp
@@ -146,7 +146,7 @@ bool MobileRecoveryUnit::waitUntilDurable() {
             Lock::GlobalLock lk(opCtx, MODE_X);
             // Use FULL mode to guarantee durability
             ret = sqlite3_wal_checkpoint_v2(_session.get()->getSession(),
-                                            NULL,
+                                            nullptr,
                                             SQLITE_CHECKPOINT_FULL,
                                             &framesInWAL,
                                             &checkpointedFrames);
diff --git a/src/mongo/db/storage/mobile/mobile_sqlite_statement.cpp b/src/mongo/db/storage/mobile/mobile_sqlite_statement.cpp
index 151ad0d68d7..7760dff5788 100644
--- a/src/mongo/db/storage/mobile/mobile_sqlite_statement.cpp
+++ b/src/mongo/db/storage/mobile/mobile_sqlite_statement.cpp
@@ -59,14 +59,14 @@ void SqliteStatement::finalize() {
 
     int status = sqlite3_finalize(_stmt);
     fassert(37053, status == _exceptionStatus);
-    _stmt = NULL;
+    _stmt = nullptr;
 }
 
 void SqliteStatement::prepare(const MobileSession& session) {
     SQLITE_STMT_TRACE() << "Preparing: " << _sqlQuery.data();
 
-    int status =
-        sqlite3_prepare_v2(session.getSession(), _sqlQuery.data(), _sqlQuery.size(), &_stmt, NULL);
+    int status = sqlite3_prepare_v2(
+        session.getSession(), _sqlQuery.data(), _sqlQuery.size(), &_stmt, nullptr);
     if (status == SQLITE_BUSY) {
         SQLITE_STMT_TRACE() << "Throwing writeConflictException, "
                             << "SQLITE_BUSY while preparing: " << _sqlQuery.data();
@@ -150,8 +150,8 @@ const char* SqliteStatement::getColText(int colIndex) {
 void SqliteStatement::_execQuery(sqlite3* session, const char* query) {
     LOG(MOBILE_TRACE_LEVEL) << "MobileSE: SQLite sqlite3_exec: " << query;
 
-    char* errMsg = NULL;
-    int status = sqlite3_exec(session, query, NULL, NULL, &errMsg);
+    char* errMsg = nullptr;
+    int status = sqlite3_exec(session, query, nullptr, nullptr, &errMsg);
 
     if (status == SQLITE_BUSY || status == SQLITE_LOCKED) {
         LOG(MOBILE_TRACE_LEVEL) << "MobileSE: " << (status == SQLITE_BUSY ? "Busy" : "Locked")
diff --git a/src/mongo/db/storage/mobile/mobile_util.cpp b/src/mongo/db/storage/mobile/mobile_util.cpp
index 141cff1a070..3159dd169f8 100644
--- a/src/mongo/db/storage/mobile/mobile_util.cpp
+++ b/src/mongo/db/storage/mobile/mobile_util.cpp
@@ -91,7 +91,7 @@ Status sqliteRCToStatus(int retCode, const char* prefix) {
 }
 
 const char* sqliteStatusToStr(int retStatus) {
-    const char* msg = NULL;
+    const char* msg = nullptr;
 
     switch (retStatus) {
         case SQLITE_OK:
diff --git a/src/mongo/db/storage/mobile/mobile_util.h b/src/mongo/db/storage/mobile/mobile_util.h
index 93ca3fdd51d..9cdb8bf0e15 100644
--- a/src/mongo/db/storage/mobile/mobile_util.h
+++ b/src/mongo/db/storage/mobile/mobile_util.h
@@ -44,7 +44,7 @@ namespace embedded {
 /**
  * Converts SQLite return codes to MongoDB statuses.
  */
-Status sqliteRCToStatus(int retCode, const char* prefix = NULL);
+Status sqliteRCToStatus(int retCode, const char* prefix = nullptr);
 
 /**
  * Converts SQLite return codes to string equivalents.
@@ -54,7 +54,10 @@ const char* sqliteStatusToStr(int retStatus);
 /**
  * Checks if retStatus == desiredStatus; else calls fassert.
  */
-void checkStatus(int retStatus, int desiredStatus, const char* fnName, const char* errMsg = NULL);
+void checkStatus(int retStatus,
+                 int desiredStatus,
+                 const char* fnName,
+                 const char* errMsg = nullptr);
 
 /**
  * Validate helper function to log an error and append the error to the results.
diff --git a/src/mongo/db/storage/record_data.h b/src/mongo/db/storage/record_data.h
index 5cc99b7f50d..67a3feb8413 100644
--- a/src/mongo/db/storage/record_data.h
+++ b/src/mongo/db/storage/record_data.h
@@ -43,7 +43,7 @@ namespace mongo {
  */
 class RecordData {
 public:
-    RecordData() : _data(NULL), _size(0) {}
+    RecordData() : _data(nullptr), _size(0) {}
     RecordData(const char* data, int size) : _data(data), _size(size) {}
 
     RecordData(SharedBuffer ownedData, int size)
diff --git a/src/mongo/db/storage/record_store.h b/src/mongo/db/storage/record_store.h
index 7880616da03..d5152e51d23 100644
--- a/src/mongo/db/storage/record_store.h
+++ b/src/mongo/db/storage/record_store.h
@@ -286,7 +286,7 @@ public:
      * @return total estimate size (in bytes) on stable storage
      */
     virtual int64_t storageSize(OperationContext* opCtx,
-                                BSONObjBuilder* extraInfo = NULL,
+                                BSONObjBuilder* extraInfo = nullptr,
                                 int infoLevel = 0) const = 0;
 
     // CRUD related
diff --git a/src/mongo/db/storage/record_store_test_harness.cpp b/src/mongo/db/storage/record_store_test_harness.cpp
index 6a72d25e954..b93e8029d34 100644
--- a/src/mongo/db/storage/record_store_test_harness.cpp
+++ b/src/mongo/db/storage/record_store_test_harness.cpp
@@ -75,7 +75,7 @@ TEST(RecordStoreTestHarness, Simple1) {
 
         RecordData rd;
         ASSERT(!rs->findRecord(opCtx.get(), RecordId(111, 17), &rd));
-        ASSERT(rd.data() == NULL);
+        ASSERT(rd.data() == nullptr);
 
         ASSERT(rs->findRecord(opCtx.get(), loc1, &rd));
         ASSERT_EQUALS(s, rd.data());
diff --git a/src/mongo/db/storage/record_store_test_recordstore.cpp b/src/mongo/db/storage/record_store_test_recordstore.cpp
index c5a95f250c2..38649fa89da 100644
--- a/src/mongo/db/storage/record_store_test_recordstore.cpp
+++ b/src/mongo/db/storage/record_store_test_recordstore.cpp
@@ -48,7 +48,7 @@ TEST(RecordStoreTestHarness, RecordStoreName) {
 
     {
         const char* name = rs->name();
-        ASSERT(name != NULL && name[0] != '\0');
+        ASSERT(name != nullptr && name[0] != '\0');
     }
 }
 
diff --git a/src/mongo/db/storage/record_store_test_storagesize.cpp b/src/mongo/db/storage/record_store_test_storagesize.cpp
index 743559a1079..cba9e555c16 100644
--- a/src/mongo/db/storage/record_store_test_storagesize.cpp
+++ b/src/mongo/db/storage/record_store_test_storagesize.cpp
@@ -75,7 +75,7 @@ TEST(RecordStoreTestHarness, StorageSizeNonEmpty) {
 
     {
         ServiceContext::UniqueOperationContext opCtx(harnessHelper->newOperationContext());
-        ASSERT(rs->storageSize(opCtx.get(), NULL) >= 0);
+        ASSERT(rs->storageSize(opCtx.get(), nullptr) >= 0);
     }
 }
 
diff --git a/src/mongo/db/storage/record_store_test_touch.cpp b/src/mongo/db/storage/record_store_test_touch.cpp
index 43b52b39ba2..edafde0683e 100644
--- a/src/mongo/db/storage/record_store_test_touch.cpp
+++ b/src/mongo/db/storage/record_store_test_touch.cpp
@@ -122,7 +122,7 @@ TEST(RecordStoreTestHarness, TouchEmptyWithNullStats) {
     {
         ServiceContext::UniqueOperationContext opCtx(
             harnessHelper->newOperationContext(harnessHelper->client()));
-        Status status = rs->touch(opCtx.get(), NULL /* stats output */);
+        Status status = rs->touch(opCtx.get(), nullptr /* stats output */);
         ASSERT(status.isOK() || status.code() == ErrorCodes::CommandNotSupported);
     }
 }
@@ -164,7 +164,7 @@ TEST(RecordStoreTestHarness, TouchNonEmptyWithNullStats) {
             harnessHelper->newOperationContext(harnessHelper->client()));
         // XXX does not verify the collection was loaded into cache
         // (even if supported by storage engine)
-        Status status = rs->touch(opCtx.get(), NULL /* stats output */);
+        Status status = rs->touch(opCtx.get(), nullptr /* stats output */);
         ASSERT(status.isOK() || status.code() == ErrorCodes::CommandNotSupported);
     }
 }
diff --git a/src/mongo/db/storage/remove_saver.cpp b/src/mongo/db/storage/remove_saver.cpp
index d49e1cc5dd5..16ad9b482e9 100644
--- a/src/mongo/db/storage/remove_saver.cpp
+++ b/src/mongo/db/storage/remove_saver.cpp
@@ -135,7 +135,7 @@ Status RemoveSaver::goingToDelete(const BSONObj& o) {
                                        << " for remove saving: " << redact(errnoWithDescription());
             error() << msg;
             _out.reset();
-            _out = 0;
+            _out = nullptr;
             return Status(ErrorCodes::FileNotOpen, msg);
         }
     }
diff --git a/src/mongo/db/storage/sorted_data_interface.h b/src/mongo/db/storage/sorted_data_interface.h
index ee745bf7cfe..8bda0d3d660 100644
--- a/src/mongo/db/storage/sorted_data_interface.h
+++ b/src/mongo/db/storage/sorted_data_interface.h
@@ -180,7 +180,7 @@ public:
      */
     virtual long long numEntries(OperationContext* opCtx) const {
         long long x = -1;
-        fullValidate(opCtx, &x, NULL);
+        fullValidate(opCtx, &x, nullptr);
         return x;
     }
 
diff --git a/src/mongo/db/storage/sorted_data_interface_test_fullvalidate.cpp b/src/mongo/db/storage/sorted_data_interface_test_fullvalidate.cpp
index db5d4493df5..e396052e9fa 100644
--- a/src/mongo/db/storage/sorted_data_interface_test_fullvalidate.cpp
+++ b/src/mongo/db/storage/sorted_data_interface_test_fullvalidate.cpp
@@ -69,7 +69,7 @@ TEST(SortedDataInterface, FullValidate) {
     {
         long long numKeysOut;
         const ServiceContext::UniqueOperationContext opCtx(harnessHelper->newOperationContext());
-        sorted->fullValidate(opCtx.get(), &numKeysOut, NULL);
+        sorted->fullValidate(opCtx.get(), &numKeysOut, nullptr);
         // fullValidate() can set numKeysOut as the number of existing keys or -1.
         ASSERT(numKeysOut == nToInsert || numKeysOut == -1);
     }
diff --git a/src/mongo/db/storage/sorted_data_interface_test_harness.cpp b/src/mongo/db/storage/sorted_data_interface_test_harness.cpp
index f92ba9c83bb..43bb6df5c4a 100644
--- a/src/mongo/db/storage/sorted_data_interface_test_harness.cpp
+++ b/src/mongo/db/storage/sorted_data_interface_test_harness.cpp
@@ -97,7 +97,7 @@ TEST(SortedDataInterface, InsertWithDups1) {
         ASSERT_EQUALS(2, sorted->numEntries(opCtx.get()));
 
         long long x = 0;
-        sorted->fullValidate(opCtx.get(), &x, NULL);
+        sorted->fullValidate(opCtx.get(), &x, nullptr);
         ASSERT_EQUALS(2, x);
     }
 }
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp
index 95fe1bf3b50..966cfe4c8c4 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_index.cpp
@@ -79,7 +79,7 @@ MONGO_FAIL_POINT_DEFINE(WTEmulateOutOfOrderNextIndexKey);
 using std::string;
 using std::vector;
 
-static const WiredTigerItem emptyItem(NULL, 0);
+static const WiredTigerItem emptyItem(nullptr, 0);
 
 
 bool hasFieldNames(const BSONObj& obj) {
@@ -572,14 +572,14 @@ protected:
         // an unexpected pause in building an index.
         WT_SESSION* session = _session->getSession();
         int err = session->open_cursor(
-            session, idx->uri().c_str(), NULL, "bulk,checkpoint_wait=false", &cursor);
+            session, idx->uri().c_str(), nullptr, "bulk,checkpoint_wait=false", &cursor);
         if (!err)
             return cursor;
 
         warning() << "failed to create WiredTiger bulk cursor: " << wiredtiger_strerror(err);
         warning() << "falling back to non-bulk cursor for index " << idx->uri();
 
-        invariantWTOK(session->open_cursor(session, idx->uri().c_str(), NULL, NULL, &cursor));
+        invariantWTOK(session->open_cursor(session, idx->uri().c_str(), nullptr, nullptr, &cursor));
         return cursor;
     }
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
index 9971b1e387d..38dc2f6913a 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
@@ -631,7 +631,7 @@ WiredTigerKVEngine::WiredTigerKVEngine(const std::string& canonicalName,
                 Status s(wtRCToStatus(ret));
                 msgasserted(28718, s.reason());
             }
-            invariantWTOK(_conn->close(_conn, NULL));
+            invariantWTOK(_conn->close(_conn, nullptr));
             // After successful recovery, remove the journal directory.
             try {
                 boost::filesystem::remove_all(journalPath);
@@ -706,7 +706,7 @@ WiredTigerKVEngine::~WiredTigerKVEngine() {
         cleanShutdown();
     }
 
-    _sessionCache.reset(NULL);
+    _sessionCache.reset(nullptr);
 }
 
 void WiredTigerKVEngine::appendGlobalStats(BSONObjBuilder& b) {
@@ -887,7 +887,7 @@ Status WiredTigerKVEngine::_salvageIfNeeded(const char* uri) {
     WiredTigerSession sessionWrapper(_conn);
     WT_SESSION* session = sessionWrapper.getSession();
 
-    int rc = (session->verify)(session, uri, NULL);
+    int rc = (session->verify)(session, uri, nullptr);
     if (rc == 0) {
         log() << "Verify succeeded on uri " << uri << ". Not salvaging.";
         return Status::OK();
@@ -912,7 +912,7 @@ Status WiredTigerKVEngine::_salvageIfNeeded(const char* uri) {
     }
 
     log() << "Verify failed on uri " << uri << ". Running a salvage operation.";
-    auto status = wtRCToStatus(session->salvage(session, uri, NULL), "Salvage failed:");
+    auto status = wtRCToStatus(session->salvage(session, uri, nullptr), "Salvage failed:");
     if (status.isOK()) {
         return {ErrorCodes::DataModifiedByRepair, str::stream() << "Salvaged data for " << uri};
     }
@@ -952,7 +952,7 @@ Status WiredTigerKVEngine::_rebuildIdent(WT_SESSION* session, const char* uri) {
         return swMetadata.getStatus();
     }
 
-    int rc = session->drop(session, uri, NULL);
+    int rc = session->drop(session, uri, nullptr);
     if (rc != 0) {
         error() << "Failed to drop " << uri;
         return wtRCToStatus(rc);
@@ -995,9 +995,9 @@ Status WiredTigerKVEngine::beginBackup(OperationContext* opCtx) {
 
     // This cursor will be freed by the backupSession being closed as the session is uncached
     auto session = std::make_unique<WiredTigerSession>(_conn);
-    WT_CURSOR* c = NULL;
+    WT_CURSOR* c = nullptr;
     WT_SESSION* s = session->getSession();
-    int ret = WT_OP_CHECK(s->open_cursor(s, "backup:", NULL, NULL, &c));
+    int ret = WT_OP_CHECK(s->open_cursor(s, "backup:", nullptr, nullptr, &c));
     if (ret != 0) {
         return wtRCToStatus(ret);
     }
@@ -1025,9 +1025,9 @@ StatusWith<std::vector<std::string>> WiredTigerKVEngine::beginNonBlockingBackup(
 
     // This cursor will be freed by the backupSession being closed as the session is uncached
     auto sessionRaii = std::make_unique<WiredTigerSession>(_conn);
-    WT_CURSOR* cursor = NULL;
+    WT_CURSOR* cursor = nullptr;
     WT_SESSION* session = sessionRaii->getSession();
-    int wtRet = session->open_cursor(session, "backup:", NULL, NULL, &cursor);
+    int wtRet = session->open_cursor(session, "backup:", nullptr, nullptr, &cursor);
     if (wtRet != 0) {
         return wtRCToStatus(wtRet);
     }
@@ -1059,9 +1059,9 @@ StatusWith<std::vector<std::string>> WiredTigerKVEngine::extendBackupCursor(
     uassert(51033, "Cannot extend backup cursor with in-memory mode.", !isEphemeral());
     invariant(_backupCursor);
 
-    WT_CURSOR* cursor = NULL;
+    WT_CURSOR* cursor = nullptr;
     WT_SESSION* session = _backupSession->getSession();
-    int wtRet = session->open_cursor(session, NULL, _backupCursor, "target=(\"log:\")", &cursor);
+    int wtRet = session->open_cursor(session, nullptr, _backupCursor, "target=(\"log:\")", &cursor);
     if (wtRet != 0) {
         return wtRCToStatus(wtRet);
     }
@@ -1475,8 +1475,8 @@ bool WiredTigerKVEngine::hasIdent(OperationContext* opCtx, StringData ident) con
 
 bool WiredTigerKVEngine::_hasUri(WT_SESSION* session, const std::string& uri) const {
     // can't use WiredTigerCursor since this is called from constructor.
-    WT_CURSOR* c = NULL;
-    int ret = session->open_cursor(session, "metadata:create", NULL, NULL, &c);
+    WT_CURSOR* c = nullptr;
+    int ret = session->open_cursor(session, "metadata:create", nullptr, nullptr, &c);
     if (ret == ENOENT)
         return false;
     invariantWTOK(ret);
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp
index 3ded0dc99b6..df39f655421 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_index_test.cpp
@@ -56,9 +56,9 @@ using std::string;
 
 class MyHarnessHelper final : public SortedDataInterfaceHarnessHelper {
 public:
-    MyHarnessHelper() : _dbpath("wt_test"), _conn(NULL) {
+    MyHarnessHelper() : _dbpath("wt_test"), _conn(nullptr) {
         const char* config = "create,cache_size=1G,";
-        int ret = wiredtiger_open(_dbpath.path().c_str(), NULL, config, &_conn);
+        int ret = wiredtiger_open(_dbpath.path().c_str(), nullptr, config, &_conn);
         invariantWTOK(ret);
 
         _fastClockSource = std::make_unique<SystemClockSource>();
@@ -67,7 +67,7 @@ public:
 
     ~MyHarnessHelper() final {
         delete _sessionCache;
-        _conn->close(_conn, NULL);
+        _conn->close(_conn, nullptr);
     }
 
     std::unique_ptr<SortedDataInterface> newSortedDataInterface(bool unique, bool partial) final {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
index 84d2f3ece7b..0b16064f6e8 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
@@ -1502,7 +1502,7 @@ Status WiredTigerRecordStore::truncate(OperationContext* opCtx) {
     invariantWTOK(ret);
 
     WT_SESSION* session = WiredTigerRecoveryUnit::get(opCtx)->getSession()->getSession();
-    invariantWTOK(WT_OP_CHECK(session->truncate(session, NULL, start, NULL, NULL)));
+    invariantWTOK(WT_OP_CHECK(session->truncate(session, nullptr, start, nullptr, nullptr)));
     _changeNumRecords(opCtx, -numRecords(opCtx));
     _increaseDataSize(opCtx, -dataSize(opCtx));
 
@@ -1714,7 +1714,7 @@ public:
     DataSizeChange(WiredTigerRecordStore* rs, int64_t amount) : _rs(rs), _amount(amount) {}
     virtual void commit(boost::optional<Timestamp>) {}
     virtual void rollback() {
-        _rs->_increaseDataSize(NULL, -_amount);
+        _rs->_increaseDataSize(nullptr, -_amount);
     }
 
 private:
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h
index f47db72d8a7..3e2121cdd5d 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h
@@ -130,7 +130,7 @@ public:
     virtual bool isCapped() const;
 
     virtual int64_t storageSize(OperationContext* opCtx,
-                                BSONObjBuilder* extraInfo = NULL,
+                                BSONObjBuilder* extraInfo = nullptr,
                                 int infoLevel = 0) const;
 
     // CRUD related
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp
index f6040a92621..2b59fc2c762 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp
@@ -144,8 +144,8 @@ TEST(WiredTigerRecordStoreTest, Isolation1) {
             rs->updateRecord(t2.get(), id1, "c", 2).transitional_ignore();
             ASSERT(0);
         } catch (WriteConflictException&) {
-            w2.reset(NULL);
-            t2.reset(NULL);
+            w2.reset(nullptr);
+            t2.reset(nullptr);
         }
 
         w1->commit();  // this should succeed
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp
index 5769add2cb1..0363230e58b 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp
@@ -146,7 +146,7 @@ public:
     void getCursor(WiredTigerRecoveryUnit* ru, WT_CURSOR** cursor) {
         WT_SESSION* wt_session = ru->getSession()->getSession();
         invariantWTOK(wt_session->create(wt_session, wt_uri, wt_config));
-        invariantWTOK(wt_session->open_cursor(wt_session, wt_uri, NULL, NULL, cursor));
+        invariantWTOK(wt_session->open_cursor(wt_session, wt_uri, nullptr, nullptr, cursor));
     }
 
     void setUp() override {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
index 5344e0163fc..91a40336e9f 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
@@ -56,11 +56,11 @@ const std::string kWTRepairMsg =
 WiredTigerSession::WiredTigerSession(WT_CONNECTION* conn, uint64_t epoch, uint64_t cursorEpoch)
     : _epoch(epoch),
       _cursorEpoch(cursorEpoch),
-      _session(NULL),
+      _session(nullptr),
       _cursorGen(0),
       _cursorsOut(0),
       _idleExpireTime(Date_t::min()) {
-    invariantWTOK(conn->open_session(conn, NULL, "isolation=snapshot", &_session));
+    invariantWTOK(conn->open_session(conn, nullptr, "isolation=snapshot", &_session));
 }
 
 WiredTigerSession::WiredTigerSession(WT_CONNECTION* conn,
@@ -70,16 +70,16 @@ WiredTigerSession::WiredTigerSession(WT_CONNECTION* conn,
     : _epoch(epoch),
       _cursorEpoch(cursorEpoch),
       _cache(cache),
-      _session(NULL),
+      _session(nullptr),
       _cursorGen(0),
       _cursorsOut(0),
       _idleExpireTime(Date_t::min()) {
-    invariantWTOK(conn->open_session(conn, NULL, "isolation=snapshot", &_session));
+    invariantWTOK(conn->open_session(conn, nullptr, "isolation=snapshot", &_session));
 }
 
 WiredTigerSession::~WiredTigerSession() {
     if (_session) {
-        invariantWTOK(_session->close(_session, NULL));
+        invariantWTOK(_session->close(_session, nullptr));
     }
 }
 
@@ -88,7 +88,7 @@ void _openCursor(WT_SESSION* session,
                  const std::string& uri,
                  const char* config,
                  WT_CURSOR** cursorOut) {
-    int ret = session->open_cursor(session, uri.c_str(), NULL, config, cursorOut);
+    int ret = session->open_cursor(session, uri.c_str(), nullptr, config, cursorOut);
     if (ret == EBUSY) {
         // This can only happen when trying to open a cursor on the oplog and it is currently locked
         // by a verify or salvage, because we don't employ database locks to protect the oplog.
@@ -116,7 +116,7 @@ WT_CURSOR* WiredTigerSession::getCursor(const std::string& uri, uint64_t id, boo
         }
     }
 
-    WT_CURSOR* cursor = NULL;
+    WT_CURSOR* cursor = nullptr;
     _openCursor(_session, uri, allowOverwrite ? "" : "overwrite=false", &cursor);
     _cursorsOut++;
     return cursor;
@@ -125,7 +125,7 @@ WT_CURSOR* WiredTigerSession::getCursor(const std::string& uri, uint64_t id, boo
 WT_CURSOR* WiredTigerSession::getReadOnceCursor(const std::string& uri, bool allowOverwrite) {
     const char* config = allowOverwrite ? "read_once=true" : "read_once=true,overwrite=false";
 
-    WT_CURSOR* cursor = NULL;
+    WT_CURSOR* cursor = nullptr;
     _openCursor(_session, uri, config, &cursor);
     _cursorsOut++;
     return cursor;
@@ -288,7 +288,7 @@ void WiredTigerSessionCache::waitUntilDurable(bool forceCheckpoint, bool stableC
     // Initialize on first use.
     if (!_waitUntilDurableSession) {
         invariantWTOK(
-            _conn->open_session(_conn, NULL, "isolation=snapshot", &_waitUntilDurableSession));
+            _conn->open_session(_conn, nullptr, "isolation=snapshot", &_waitUntilDurableSession));
     }
 
     // Use the journal when available, or a checkpoint otherwise.
@@ -296,7 +296,7 @@ void WiredTigerSessionCache::waitUntilDurable(bool forceCheckpoint, bool stableC
         invariantWTOK(_waitUntilDurableSession->log_flush(_waitUntilDurableSession, "sync=on"));
         LOG(4) << "flushed journal";
     } else {
-        invariantWTOK(_waitUntilDurableSession->checkpoint(_waitUntilDurableSession, NULL));
+        invariantWTOK(_waitUntilDurableSession->checkpoint(_waitUntilDurableSession, nullptr));
         LOG(4) << "created checkpoint";
     }
     _journalListener->onDurable(token);
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache_test.cpp
index 37ac7eddc4e..7d3326f57db 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache_test.cpp
@@ -46,18 +46,18 @@ using std::stringstream;
 
 class WiredTigerConnection {
 public:
-    WiredTigerConnection(StringData dbpath, StringData extraStrings) : _conn(NULL) {
+    WiredTigerConnection(StringData dbpath, StringData extraStrings) : _conn(nullptr) {
         std::stringstream ss;
         ss << "create,";
         ss << extraStrings;
         string config = ss.str();
         _fastClockSource = std::make_unique<SystemClockSource>();
-        int ret = wiredtiger_open(dbpath.toString().c_str(), NULL, config.c_str(), &_conn);
+        int ret = wiredtiger_open(dbpath.toString().c_str(), nullptr, config.c_str(), &_conn);
         ASSERT_OK(wtRCToStatus(ret));
         ASSERT(_conn);
     }
     ~WiredTigerConnection() {
-        _conn->close(_conn, NULL);
+        _conn->close(_conn, nullptr);
     }
     WT_CONNECTION* getConnection() const {
         return _conn;
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp
index 6fe47de5eca..0185b30fadd 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_index_test.cpp
@@ -56,9 +56,9 @@ using std::string;
 
 class MyHarnessHelper final : public SortedDataInterfaceHarnessHelper {
 public:
-    MyHarnessHelper() : _dbpath("wt_test"), _conn(NULL) {
+    MyHarnessHelper() : _dbpath("wt_test"), _conn(nullptr) {
         const char* config = "create,cache_size=1G,";
-        int ret = wiredtiger_open(_dbpath.path().c_str(), NULL, config, &_conn);
+        int ret = wiredtiger_open(_dbpath.path().c_str(), nullptr, config, &_conn);
         invariantWTOK(ret);
 
         _fastClockSource = std::make_unique<SystemClockSource>();
@@ -67,7 +67,7 @@ public:
 
     ~MyHarnessHelper() final {
         delete _sessionCache;
-        _conn->close(_conn, NULL);
+        _conn->close(_conn, nullptr);
     }
 
     std::unique_ptr<SortedDataInterface> newSortedDataInterface(bool unique, bool partial) final {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp
index 1c4a436831d..1f790206918 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp
@@ -242,7 +242,7 @@ TEST(WiredTigerRecordStoreTest, SizeStorer1) {
         ASSERT_EQUALS(N, rs->numRecords(opCtx.get()));
     }
 
-    rs.reset(NULL);
+    rs.reset(nullptr);
 
     {
         auto& info = *ss.load(uri);
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
index e426394574f..fb424183586 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
@@ -119,7 +119,7 @@ StatusWith<std::string> WiredTigerUtil::getMetadataRaw(WT_SESSION* session, Stri
     } else if (ret != 0) {
         return StatusWith<std::string>(wtRCToStatus(ret));
     }
-    const char* metadata = NULL;
+    const char* metadata = nullptr;
     ret = cursor->get_value(cursor, &metadata);
     if (ret != 0) {
         return StatusWith<std::string>(wtRCToStatus(ret));
@@ -147,7 +147,7 @@ StatusWith<std::string> WiredTigerUtil::getMetadata(OperationContext* opCtx, Str
     } else if (ret != 0) {
         return StatusWith<std::string>(wtRCToStatus(ret));
     }
-    const char* metadata = NULL;
+    const char* metadata = nullptr;
     ret = cursor->get_value(cursor, &metadata);
     if (ret != 0) {
         return StatusWith<std::string>(wtRCToStatus(ret));
@@ -314,9 +314,9 @@ StatusWith<int64_t> WiredTigerUtil::getStatisticsValue(WT_SESSION* session,
                                                        const std::string& config,
                                                        int statisticsKey) {
     invariant(session);
-    WT_CURSOR* cursor = NULL;
-    const char* cursorConfig = config.empty() ? NULL : config.c_str();
-    int ret = session->open_cursor(session, uri.c_str(), NULL, cursorConfig, &cursor);
+    WT_CURSOR* cursor = nullptr;
+    const char* cursorConfig = config.empty() ? nullptr : config.c_str();
+    int ret = session->open_cursor(session, uri.c_str(), nullptr, cursorConfig, &cursor);
     if (ret != 0) {
         return StatusWith<int64_t>(ErrorCodes::CursorNotFound,
                                    str::stream() << "unable to open cursor at URI " << uri
@@ -516,11 +516,11 @@ int WiredTigerUtil::verifyTable(OperationContext* opCtx,
     // Open a new session with custom error handlers.
     WT_CONNECTION* conn = WiredTigerRecoveryUnit::get(opCtx)->getSessionCache()->conn();
     WT_SESSION* session;
-    invariantWTOK(conn->open_session(conn, &eventHandler, NULL, &session));
+    invariantWTOK(conn->open_session(conn, &eventHandler, nullptr, &session));
     ON_BLOCK_EXIT([&] { session->close(session, ""); });
 
     // Do the verify. Weird parens prevent treating "verify" as a macro.
-    return (session->verify)(session, uri.c_str(), NULL);
+    return (session->verify)(session, uri.c_str(), nullptr);
 }
 
 bool WiredTigerUtil::useTableLogging(NamespaceString ns, bool replEnabled) {
@@ -612,9 +612,9 @@ Status WiredTigerUtil::exportTableToBSON(WT_SESSION* session,
                                          const std::vector<std::string>& filter) {
     invariant(session);
     invariant(bob);
-    WT_CURSOR* c = NULL;
-    const char* cursorConfig = config.empty() ? NULL : config.c_str();
-    int ret = session->open_cursor(session, uri.c_str(), NULL, cursorConfig, &c);
+    WT_CURSOR* c = nullptr;
+    const char* cursorConfig = config.empty() ? nullptr : config.c_str();
+    int ret = session->open_cursor(session, uri.c_str(), nullptr, cursorConfig, &c);
     if (ret != 0) {
         return Status(ErrorCodes::CursorNotFound,
                       str::stream() << "unable to open cursor at URI " << uri << ". reason: "
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_util.h b/src/mongo/db/storage/wiredtiger/wiredtiger_util.h
index 6c03efc774d..42729da118e 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util.h
@@ -55,7 +55,7 @@ Status wtRCToStatus_slow(int retCode, const char* prefix);
 /**
  * converts wiredtiger return codes to mongodb statuses.
  */
-inline Status wtRCToStatus(int retCode, const char* prefix = NULL) {
+inline Status wtRCToStatus(int retCode, const char* prefix = nullptr) {
     if (MONGO_likely(retCode == 0))
         return Status::OK();
 
@@ -247,7 +247,7 @@ public:
      */
     static int verifyTable(OperationContext* opCtx,
                            const std::string& uri,
-                           std::vector<std::string>* errors = NULL);
+                           std::vector<std::string>* errors = nullptr);
 
     static bool useTableLogging(NamespaceString ns, bool replEnabled);
 
@@ -278,12 +278,12 @@ class WiredTigerConfigParser {
 public:
     WiredTigerConfigParser(StringData config) {
         invariantWTOK(
-            wiredtiger_config_parser_open(NULL, config.rawData(), config.size(), &_parser));
+            wiredtiger_config_parser_open(nullptr, config.rawData(), config.size(), &_parser));
     }
 
     WiredTigerConfigParser(const WT_CONFIG_ITEM& nested) {
         invariant(nested.type == WT_CONFIG_ITEM::WT_CONFIG_ITEM_STRUCT);
-        invariantWTOK(wiredtiger_config_parser_open(NULL, nested.str, nested.len, &_parser));
+        invariantWTOK(wiredtiger_config_parser_open(nullptr, nested.str, nested.len, &_parser));
     }
 
     ~WiredTigerConfigParser() {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_util_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_util_test.cpp
index 0199cd8a1ed..0a3442459d9 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util_test.cpp
@@ -50,18 +50,18 @@ using std::stringstream;
 
 class WiredTigerConnection {
 public:
-    WiredTigerConnection(StringData dbpath, StringData extraStrings) : _conn(NULL) {
+    WiredTigerConnection(StringData dbpath, StringData extraStrings) : _conn(nullptr) {
         std::stringstream ss;
         ss << "create,";
         ss << extraStrings;
         string config = ss.str();
         _fastClockSource = std::make_unique<SystemClockSource>();
-        int ret = wiredtiger_open(dbpath.toString().c_str(), NULL, config.c_str(), &_conn);
+        int ret = wiredtiger_open(dbpath.toString().c_str(), nullptr, config.c_str(), &_conn);
         ASSERT_OK(wtRCToStatus(ret));
         ASSERT(_conn);
     }
     ~WiredTigerConnection() {
-        _conn->close(_conn, NULL);
+        _conn->close(_conn, nullptr);
     }
     WT_CONNECTION* getConnection() const {
         return _conn;
@@ -111,8 +111,8 @@ public:
     }
 
     virtual void tearDown() {
-        _opCtx.reset(NULL);
-        _harnessHelper.reset(NULL);
+        _opCtx.reset(nullptr);
+        _harnessHelper.reset(nullptr);
     }
 
 protected:
@@ -143,7 +143,7 @@ TEST_F(WiredTigerUtilMetadataTest, GetConfigurationStringInvalidURI) {
 }
 
 TEST_F(WiredTigerUtilMetadataTest, GetConfigurationStringNull) {
-    const char* config = NULL;
+    const char* config = nullptr;
     createSession(config);
     StatusWith<std::string> result = WiredTigerUtil::getMetadata(getOperationContext(), getURI());
     ASSERT_OK(result.getStatus());
@@ -166,7 +166,7 @@ TEST_F(WiredTigerUtilMetadataTest, GetApplicationMetadataInvalidURI) {
 }
 
 TEST_F(WiredTigerUtilMetadataTest, GetApplicationMetadataNull) {
-    const char* config = NULL;
+    const char* config = nullptr;
     createSession(config);
     StatusWith<BSONObj> result =
         WiredTigerUtil::getApplicationMetadata(getOperationContext(), getURI());
@@ -282,7 +282,7 @@ TEST(WiredTigerUtilTest, GetStatisticsValueStatisticsDisabled) {
                                         harnessHelper.getOplogManager());
     WiredTigerSession* session = recoveryUnit.getSession();
     WT_SESSION* wtSession = session->getSession();
-    ASSERT_OK(wtRCToStatus(wtSession->create(wtSession, "table:mytable", NULL)));
+    ASSERT_OK(wtRCToStatus(wtSession->create(wtSession, "table:mytable", nullptr)));
     auto result = WiredTigerUtil::getStatisticsValue(session->getSession(),
                                                      "statistics:table:mytable",
                                                      "statistics=(fast)",
@@ -297,7 +297,7 @@ TEST(WiredTigerUtilTest, GetStatisticsValueInvalidKey) {
                                         harnessHelper.getOplogManager());
     WiredTigerSession* session = recoveryUnit.getSession();
     WT_SESSION* wtSession = session->getSession();
-    ASSERT_OK(wtRCToStatus(wtSession->create(wtSession, "table:mytable", NULL)));
+    ASSERT_OK(wtRCToStatus(wtSession->create(wtSession, "table:mytable", nullptr)));
     // Use connection statistics key which does not apply to a table.
     auto result = WiredTigerUtil::getStatisticsValue(session->getSession(),
                                                      "statistics:table:mytable",
@@ -313,7 +313,7 @@ TEST(WiredTigerUtilTest, GetStatisticsValueValidKey) {
                                         harnessHelper.getOplogManager());
     WiredTigerSession* session = recoveryUnit.getSession();
     WT_SESSION* wtSession = session->getSession();
-    ASSERT_OK(wtRCToStatus(wtSession->create(wtSession, "table:mytable", NULL)));
+    ASSERT_OK(wtRCToStatus(wtSession->create(wtSession, "table:mytable", nullptr)));
     // Use connection statistics key which does not apply to a table.
     auto result = WiredTigerUtil::getStatisticsValue(session->getSession(),
                                                      "statistics:table:mytable",
diff --git a/src/mongo/db/update/field_checker.cpp b/src/mongo/db/update/field_checker.cpp
index a915da0a6ab..a6aba4eb559 100644
--- a/src/mongo/db/update/field_checker.cpp
+++ b/src/mongo/db/update/field_checker.cpp
@@ -66,7 +66,7 @@ bool isPositionalElement(const StringData& field) {
 bool isPositional(const FieldRef& fieldRef, size_t* pos, size_t* count) {
     // 'count' is optional.
     size_t dummy;
-    if (count == NULL) {
+    if (count == nullptr) {
         count = &dummy;
     }
 
diff --git a/src/mongo/db/update/field_checker.h b/src/mongo/db/update/field_checker.h
index 117a30995a9..1bc75b51709 100644
--- a/src/mongo/db/update/field_checker.h
+++ b/src/mongo/db/update/field_checker.h
@@ -58,7 +58,7 @@ bool isPositionalElement(const StringData& field);
  *   isPositional assumes that the field is updatable. Call isUpdatable() above to
  *   verify.
  */
-bool isPositional(const FieldRef& fieldRef, size_t* pos, size_t* count = NULL);
+bool isPositional(const FieldRef& fieldRef, size_t* pos, size_t* count = nullptr);
 
 /**
  * Returns true iff 'field' is an array filter (matching the regular expression /\$\[.*\]/).
diff --git a/src/mongo/db/update/path_support.cpp b/src/mongo/db/update/path_support.cpp
index 6b9fc80a284..55f369164a8 100644
--- a/src/mongo/db/update/path_support.cpp
+++ b/src/mongo/db/update/path_support.cpp
@@ -420,7 +420,7 @@ Status extractFullEqualityMatches(const MatchExpression& root,
 }
 
 Status extractEqualityMatches(const MatchExpression& root, EqualityMatches* equalities) {
-    return _extractFullEqualityMatches(root, NULL, equalities);
+    return _extractFullEqualityMatches(root, nullptr, equalities);
 }
 
 Status addEqualitiesToDoc(const EqualityMatches& equalities, mutablebson::Document* doc) {
diff --git a/src/mongo/db/update/path_support_test.cpp b/src/mongo/db/update/path_support_test.cpp
index b9c3c0685a8..ecd2fa9bab5 100644
--- a/src/mongo/db/update/path_support_test.cpp
+++ b/src/mongo/db/update/path_support_test.cpp
@@ -724,7 +724,7 @@ public:
 
     void addPath(const string& path) {
         _ownedPaths.push_back(std::make_unique<FieldRef>(path));
-        FieldRef const* conflictPath = NULL;
+        FieldRef const* conflictPath = nullptr;
         ASSERT(_immutablePathSet.insert(_ownedPaths.back().get(), &conflictPath));
     }
 
diff --git a/src/mongo/db/update/update_driver.cpp b/src/mongo/db/update/update_driver.cpp
index 4cd79d7b1cf..7dab889aa35 100644
--- a/src/mongo/db/update/update_driver.cpp
+++ b/src/mongo/db/update/update_driver.cpp
@@ -261,7 +261,7 @@ Status UpdateDriver::update(StringData matchedField,
 
     _affectIndices =
         ((_updateType == UpdateType::kReplacement || _updateType == UpdateType::kPipeline) &&
-         (_indexedFields != NULL));
+         (_indexedFields != nullptr));
 
     _logDoc.reset();
     LogBuilder logBuilder(_logDoc.root());
diff --git a/src/mongo/dbtests/framework.cpp b/src/mongo/dbtests/framework.cpp
index f3d0b6f2ebb..c4947ebba57 100644
--- a/src/mongo/dbtests/framework.cpp
+++ b/src/mongo/dbtests/framework.cpp
@@ -66,7 +66,7 @@ namespace dbtests {
 
 int runDbTests(int argc, char** argv) {
     frameworkGlobalParams.perfHist = 1;
-    frameworkGlobalParams.seed = time(0);
+    frameworkGlobalParams.seed = time(nullptr);
     frameworkGlobalParams.runsPerTest = 1;
 
     registerShutdownTask([] {
diff --git a/src/mongo/dbtests/jsobjtests.cpp b/src/mongo/dbtests/jsobjtests.cpp
index 65b4b142ac1..e7398a5116d 100644
--- a/src/mongo/dbtests/jsobjtests.cpp
+++ b/src/mongo/dbtests/jsobjtests.cpp
@@ -1072,9 +1072,9 @@ class append {
 public:
     void run() {
         BSONObjBuilder b;
-        b.appendOID("a", 0);
-        b.appendOID("b", 0, false);
-        b.appendOID("c", 0, true);
+        b.appendOID("a", nullptr);
+        b.appendOID("b", nullptr, false);
+        b.appendOID("c", nullptr, true);
         BSONObj o = b.obj();
         ASSERT(o["a"].__oid().toString() == "000000000000000000000000");
         ASSERT(o["b"].__oid().toString() == "000000000000000000000000");
@@ -1086,7 +1086,7 @@ class increasing {
 public:
     BSONObj g() {
         BSONObjBuilder b;
-        b.appendOID("_id", 0, true);
+        b.appendOID("_id", nullptr, true);
         return b.obj();
     }
     void run() {
@@ -1869,7 +1869,7 @@ public:
                 state = 1;
             } catch (std::exception& e) {
                 state = 2;
-                ASSERT(strstr(e.what(), "_id: 5") != NULL);
+                ASSERT(strstr(e.what(), "_id: 5") != nullptr);
             }
             free(crap);
             ASSERT_EQUALS(2, state);
diff --git a/src/mongo/dbtests/jstests.cpp b/src/mongo/dbtests/jstests.cpp
index 7f06eea59f1..051bc478dbc 100644
--- a/src/mongo/dbtests/jstests.cpp
+++ b/src/mongo/dbtests/jstests.cpp
@@ -141,25 +141,25 @@ public:
     void run() {
         unique_ptr<Scope> s((getGlobalScriptEngine()->*scopeFactory)());
 
-        s->invoke("x=5;", 0, 0);
+        s->invoke("x=5;", nullptr, nullptr);
         ASSERT(5 == s->getNumber("x"));
 
-        s->invoke("return 17;", 0, 0);
+        s->invoke("return 17;", nullptr, nullptr);
         ASSERT(17 == s->getNumber("__returnValue"));
 
-        s->invoke("function(){ return 18; }", 0, 0);
+        s->invoke("function(){ return 18; }", nullptr, nullptr);
         ASSERT(18 == s->getNumber("__returnValue"));
 
         s->setNumber("x", 1.76);
-        s->invoke("return x == 1.76; ", 0, 0);
+        s->invoke("return x == 1.76; ", nullptr, nullptr);
         ASSERT(s->getBoolean("__returnValue"));
 
         s->setNumber("x", 1.76);
-        s->invoke("return x == 1.79; ", 0, 0);
+        s->invoke("return x == 1.79; ", nullptr, nullptr);
         ASSERT(!s->getBoolean("__returnValue"));
 
         BSONObj obj = BSON("" << 11.0);
-        s->invoke("function( z ){ return 5 + z; }", &obj, 0);
+        s->invoke("function( z ){ return 5 + z; }", &obj, nullptr);
         ASSERT_EQUALS(16, s->getNumber("__returnValue"));
     }
 };
@@ -240,12 +240,12 @@ public:
         unique_ptr<Scope> scope((getGlobalScriptEngine()->*scopeFactory)());
 
         // No error is logged for a valid statement.
-        ASSERT_EQUALS(0, scope->invoke("validStatement = true", 0, 0));
+        ASSERT_EQUALS(0, scope->invoke("validStatement = true", nullptr, nullptr));
         ASSERT(!_logger.logged());
 
         // An error is logged for an invalid statement.
         try {
-            scope->invoke("notAFunction()", 0, 0);
+            scope->invoke("notAFunction()", nullptr, nullptr);
         } catch (const DBException&) {
             // ignore the exception; just test that we logged something
         }
@@ -276,48 +276,48 @@ public:
                              << "sara");
         s->setObject("blah", o);
 
-        s->invoke("return blah.x;", 0, 0);
+        s->invoke("return blah.x;", nullptr, nullptr);
         ASSERT_EQUALS(17, s->getNumber("__returnValue"));
-        s->invoke("return blah.y;", 0, 0);
+        s->invoke("return blah.y;", nullptr, nullptr);
         ASSERT_EQUALS("eliot", s->getString("__returnValue"));
 
-        s->invoke("return this.z;", 0, &o);
+        s->invoke("return this.z;", nullptr, &o);
         ASSERT_EQUALS("sara", s->getString("__returnValue"));
 
-        s->invoke("return this.z == 'sara';", 0, &o);
+        s->invoke("return this.z == 'sara';", nullptr, &o);
         ASSERT_EQUALS(true, s->getBoolean("__returnValue"));
 
-        s->invoke("this.z == 'sara';", 0, &o);
+        s->invoke("this.z == 'sara';", nullptr, &o);
         ASSERT_EQUALS(true, s->getBoolean("__returnValue"));
 
-        s->invoke("this.z == 'asara';", 0, &o);
+        s->invoke("this.z == 'asara';", nullptr, &o);
         ASSERT_EQUALS(false, s->getBoolean("__returnValue"));
 
-        s->invoke("return this.x == 17;", 0, &o);
+        s->invoke("return this.x == 17;", nullptr, &o);
         ASSERT_EQUALS(true, s->getBoolean("__returnValue"));
 
-        s->invoke("return this.x == 18;", 0, &o);
+        s->invoke("return this.x == 18;", nullptr, &o);
         ASSERT_EQUALS(false, s->getBoolean("__returnValue"));
 
-        s->invoke("function(){ return this.x == 17; }", 0, &o);
+        s->invoke("function(){ return this.x == 17; }", nullptr, &o);
         ASSERT_EQUALS(true, s->getBoolean("__returnValue"));
 
-        s->invoke("function(){ return this.x == 18; }", 0, &o);
+        s->invoke("function(){ return this.x == 18; }", nullptr, &o);
         ASSERT_EQUALS(false, s->getBoolean("__returnValue"));
 
-        s->invoke("function (){ return this.x == 17; }", 0, &o);
+        s->invoke("function (){ return this.x == 17; }", nullptr, &o);
         ASSERT_EQUALS(true, s->getBoolean("__returnValue"));
 
-        s->invoke("function z(){ return this.x == 18; }", 0, &o);
+        s->invoke("function z(){ return this.x == 18; }", nullptr, &o);
         ASSERT_EQUALS(false, s->getBoolean("__returnValue"));
 
-        s->invoke("function (){ this.x == 17; }", 0, &o);
+        s->invoke("function (){ this.x == 17; }", nullptr, &o);
         ASSERT_EQUALS(false, s->getBoolean("__returnValue"));
 
-        s->invoke("function z(){ this.x == 18; }", 0, &o);
+        s->invoke("function z(){ this.x == 18; }", nullptr, &o);
         ASSERT_EQUALS(false, s->getBoolean("__returnValue"));
 
-        s->invoke("x = 5; for( ; x <10; x++){ a = 1; }", 0, &o);
+        s->invoke("x = 5; for( ; x <10; x++){ a = 1; }", nullptr, &o);
         ASSERT_EQUALS(10, s->getNumber("x"));
     }
 };
@@ -328,12 +328,12 @@ public:
     void run() {
         unique_ptr<Scope> s((getGlobalScriptEngine()->*scopeFactory)());
 
-        s->invoke("z = { num : 1 };", 0, 0);
+        s->invoke("z = { num : 1 };", nullptr, nullptr);
         BSONObj out = s->getObject("z");
         ASSERT_EQUALS(1, out["num"].number());
         ASSERT_EQUALS(1, out.nFields());
 
-        s->invoke("z = { x : 'eliot' };", 0, 0);
+        s->invoke("z = { x : 'eliot' };", nullptr, nullptr);
         out = s->getObject("z");
         ASSERT_EQUALS((string) "eliot", out["x"].valuestr());
         ASSERT_EQUALS(1, out.nFields());
@@ -417,14 +417,15 @@ public:
 
         BSONObj out;
 
-        ASSERT_THROWS(s->invoke("blah.y = 'e'", 0, 0), mongo::AssertionException);
-        ASSERT_THROWS(s->invoke("blah.a = 19;", 0, 0), mongo::AssertionException);
-        ASSERT_THROWS(s->invoke("blah.zz.a = 19;", 0, 0), mongo::AssertionException);
-        ASSERT_THROWS(s->invoke("blah.zz = { a : 19 };", 0, 0), mongo::AssertionException);
-        ASSERT_THROWS(s->invoke("delete blah['x']", 0, 0), mongo::AssertionException);
+        ASSERT_THROWS(s->invoke("blah.y = 'e'", nullptr, nullptr), mongo::AssertionException);
+        ASSERT_THROWS(s->invoke("blah.a = 19;", nullptr, nullptr), mongo::AssertionException);
+        ASSERT_THROWS(s->invoke("blah.zz.a = 19;", nullptr, nullptr), mongo::AssertionException);
+        ASSERT_THROWS(s->invoke("blah.zz = { a : 19 };", nullptr, nullptr),
+                      mongo::AssertionException);
+        ASSERT_THROWS(s->invoke("delete blah['x']", nullptr, nullptr), mongo::AssertionException);
 
         // read-only object itself can be overwritten
-        s->invoke("blah = {}", 0, 0);
+        s->invoke("blah = {}", nullptr, nullptr);
         out = s->getObject("blah");
         ASSERT(out.isEmpty());
 
@@ -456,13 +457,13 @@ public:
             }
             s->setObject("x", o);
 
-            s->invoke("return x.d.getTime() != 12;", 0, 0);
+            s->invoke("return x.d.getTime() != 12;", nullptr, nullptr);
             ASSERT_EQUALS(true, s->getBoolean("__returnValue"));
 
-            s->invoke("z = x.d.getTime();", 0, 0);
+            s->invoke("z = x.d.getTime();", nullptr, nullptr);
             ASSERT_EQUALS(123456789, s->getNumber("z"));
 
-            s->invoke("z = { z : x.d }", 0, 0);
+            s->invoke("z = { z : x.d }", nullptr, nullptr);
             BSONObj out = s->getObject("z");
             ASSERT(out["z"].type() == Date);
         }
@@ -477,16 +478,16 @@ public:
             }
             s->setObject("x", o);
 
-            s->invoke("z = x.r.test( 'b' );", 0, 0);
+            s->invoke("z = x.r.test( 'b' );", nullptr, nullptr);
             ASSERT_EQUALS(false, s->getBoolean("z"));
 
-            s->invoke("z = x.r.test( 'a' );", 0, 0);
+            s->invoke("z = x.r.test( 'a' );", nullptr, nullptr);
             ASSERT_EQUALS(true, s->getBoolean("z"));
 
-            s->invoke("z = x.r.test( 'ba' );", 0, 0);
+            s->invoke("z = x.r.test( 'ba' );", nullptr, nullptr);
             ASSERT_EQUALS(false, s->getBoolean("z"));
 
-            s->invoke("z = { a : x.r };", 0, 0);
+            s->invoke("z = { a : x.r };", nullptr, nullptr);
 
             BSONObj out = s->getObject("z");
             ASSERT_EQUALS((string) "^a", out["a"].regex());
@@ -505,7 +506,7 @@ public:
                 "    }"
                 "    assert(threw);"
                 "}";
-            ASSERT_EQUALS(s->invoke(code, &invalidRegex, NULL), 0);
+            ASSERT_EQUALS(s->invoke(code, &invalidRegex, nullptr), 0);
         }
 
         // array
@@ -559,7 +560,7 @@ public:
 
         s->setObject("z", b.obj());
 
-        ASSERT(s->invoke("y = { a : z.a , b : z.b , c : z.c , d: z.d }", 0, 0) == 0);
+        ASSERT(s->invoke("y = { a : z.a , b : z.b , c : z.c , d: z.d }", nullptr, nullptr) == 0);
 
         BSONObj out = s->getObject("y");
         ASSERT_EQUALS(bsonTimestamp, out["a"].type());
@@ -592,7 +593,7 @@ public:
         ASSERT_EQUALS(NumberDouble, o["b"].type());
 
         s->setObject("z", o);
-        s->invoke("return z", 0, 0);
+        s->invoke("return z", nullptr, nullptr);
         BSONObj out = s->getObject("__returnValue");
         ASSERT_EQUALS(5, out["a"].number());
         ASSERT_EQUALS(5.6, out["b"].number());
@@ -610,7 +611,7 @@ public:
         }
 
         s->setObject("z", o, false);
-        s->invoke("return z", 0, 0);
+        s->invoke("return z", nullptr, nullptr);
         out = s->getObject("__returnValue");
         ASSERT_EQUALS(5, out["a"].number());
         ASSERT_EQUALS(5.6, out["b"].number());
@@ -643,7 +644,7 @@ public:
         ASSERT_EQUALS(NumberDouble, out["a"].embeddedObjectUserCheck()["0"].type());
         ASSERT_EQUALS(NumberInt, out["a"].embeddedObjectUserCheck()["1"].type());
 
-        s->invokeSafe("z.z = 5;", 0, 0);
+        s->invokeSafe("z.z = 5;", nullptr, nullptr);
         out = s->getObject("z");
         ASSERT_EQUALS(5, out["z"].number());
         ASSERT_EQUALS(NumberDouble, out["a"].embeddedObjectUserCheck()["0"].type());
@@ -913,10 +914,10 @@ public:
 
         for (int i = 5; i < 100; i += 10) {
             s->setObject("a", build(i), false);
-            s->invokeSafe("tojson( a )", 0, 0);
+            s->invokeSafe("tojson( a )", nullptr, nullptr);
 
             s->setObject("a", build(5), true);
-            s->invokeSafe("tojson( a )", 0, 0);
+            s->invokeSafe("tojson( a )", nullptr, nullptr);
         }
     }
 };
@@ -970,8 +971,8 @@ public:
                 "function() {         "
                 "    while (true) { } "
                 "}                    ",
-                0,
-                0,
+                nullptr,
+                nullptr,
                 1);
         } catch (const DBException&) {
             caught = true;
@@ -1040,8 +1041,8 @@ public:
             "function() { "
             "  for (var i=0; i<1; i++) { ; } "
             "} ",
-            0,
-            0,
+            nullptr,
+            nullptr,
             5 * 60 * 1000);
     }
 };
@@ -1111,8 +1112,8 @@ public:
             s->setObject("x", in);
         }
 
-        s->invokeSafe("myb = x.b; print( myb ); printjson( myb );", 0, 0);
-        s->invokeSafe("y = { c : myb };", 0, 0);
+        s->invokeSafe("myb = x.b; print( myb ); printjson( myb );", nullptr, nullptr);
+        s->invokeSafe("y = { c : myb };", nullptr, nullptr);
 
         BSONObj out = s->getObject("y");
         ASSERT_EQUALS(BinData, out["c"].type());
@@ -1121,7 +1122,7 @@ public:
         ASSERT_EQUALS(0, in["b"].woCompare(out["c"], false));
 
         // check that BinData js class is utilized
-        s->invokeSafe("q = x.b.toString();", 0, 0);
+        s->invokeSafe("q = x.b.toString();", nullptr, nullptr);
         stringstream expected;
         expected << "BinData(" << BinDataGeneral << ",\"" << base64 << "\")";
         ASSERT_EQUALS(expected.str(), s->getString("q"));
@@ -1130,12 +1131,12 @@ public:
         scriptBuilder << "z = { c : new BinData( " << BinDataGeneral << ", \"" << base64
                       << "\" ) };";
         string script = scriptBuilder.str();
-        s->invokeSafe(script.c_str(), 0, 0);
+        s->invokeSafe(script.c_str(), nullptr, nullptr);
         out = s->getObject("z");
         //            pp( "out" , out["c"] );
         ASSERT_EQUALS(0, in["b"].woCompare(out["c"], false));
 
-        s->invokeSafe("a = { f: new BinData( 128, \"\" ) };", 0, 0);
+        s->invokeSafe("a = { f: new BinData( 128, \"\" ) };", nullptr, nullptr);
         out = s->getObject("a");
         int len = -1;
         out["f"].binData(len);
@@ -1187,14 +1188,14 @@ public:
         unique_ptr<Scope> s;
         s.reset((getGlobalScriptEngine()->*scopeFactory)());
 
-        s->invokeSafe("x = 5;", 0, 0);
+        s->invokeSafe("x = 5;", nullptr, nullptr);
         {
             BSONObjBuilder b;
             s->append(b, "z", "x");
             ASSERT_BSONOBJ_EQ(BSON("z" << 5), b.obj());
         }
 
-        s->invokeSafe("x = function(){ return 17; }", 0, 0);
+        s->invokeSafe("x = function(){ return 17; }", nullptr, nullptr);
         BSONObj temp;
         {
             BSONObjBuilder b;
@@ -1202,7 +1203,7 @@ public:
             temp = b.obj();
         }
 
-        s->invokeSafe("foo = this.z();", 0, &temp);
+        s->invokeSafe("foo = this.z();", nullptr, &temp);
         ASSERT_EQUALS(17, s->getNumber("foo"));
     }
 };
@@ -1244,7 +1245,7 @@ public:
 
         s->setObject("val", BSONObj(reinterpret_cast<char*>(bits)).getOwned());
 
-        s->invoke("val[\"a\"];", 0, 0);
+        s->invoke("val[\"a\"];", nullptr, nullptr);
         ASSERT_TRUE(std::isnan(s->getNumber("__returnValue")));
     }
 };
@@ -1255,43 +1256,43 @@ public:
     void run() {
         unique_ptr<Scope> s((getGlobalScriptEngine()->*scopeFactory)());
 
-        s->invoke("x=5;", 0, 0);
+        s->invoke("x=5;", nullptr, nullptr);
         ASSERT_EQUALS(5, s->getNumber("__returnValue"));
 
-        s->invoke("x='test'", 0, 0);
+        s->invoke("x='test'", nullptr, nullptr);
         ASSERT_EQUALS("test", s->getString("__returnValue"));
 
-        s->invoke("x='return'", 0, 0);
+        s->invoke("x='return'", nullptr, nullptr);
         ASSERT_EQUALS("return", s->getString("__returnValue"));
 
-        s->invoke("return 'return'", 0, 0);
+        s->invoke("return 'return'", nullptr, nullptr);
         ASSERT_EQUALS("return", s->getString("__returnValue"));
 
-        s->invoke("x = ' return '", 0, 0);
+        s->invoke("x = ' return '", nullptr, nullptr);
         ASSERT_EQUALS(" return ", s->getString("__returnValue"));
 
-        s->invoke("x = \" return \"", 0, 0);
+        s->invoke("x = \" return \"", nullptr, nullptr);
         ASSERT_EQUALS(" return ", s->getString("__returnValue"));
 
-        s->invoke("x = \"' return '\"", 0, 0);
+        s->invoke("x = \"' return '\"", nullptr, nullptr);
         ASSERT_EQUALS("' return '", s->getString("__returnValue"));
 
-        s->invoke("x = '\" return \"'", 0, 0);
+        s->invoke("x = '\" return \"'", nullptr, nullptr);
         ASSERT_EQUALS("\" return \"", s->getString("__returnValue"));
 
-        s->invoke(";return 5", 0, 0);
+        s->invoke(";return 5", nullptr, nullptr);
         ASSERT_EQUALS(5, s->getNumber("__returnValue"));
 
-        s->invoke("String('return')", 0, 0);
+        s->invoke("String('return')", nullptr, nullptr);
         ASSERT_EQUALS("return", s->getString("__returnValue"));
 
-        s->invoke("String(' return ')", 0, 0);
+        s->invoke("String(' return ')", nullptr, nullptr);
         ASSERT_EQUALS(" return ", s->getString("__returnValue"));
 
-        s->invoke("String(\"'return\")", 0, 0);
+        s->invoke("String(\"'return\")", nullptr, nullptr);
         ASSERT_EQUALS("'return", s->getString("__returnValue"));
 
-        s->invoke("String('\"return')", 0, 0);
+        s->invoke("String('\"return')", nullptr, nullptr);
         ASSERT_EQUALS("\"return", s->getString("__returnValue"));
     }
 };
@@ -1302,7 +1303,7 @@ public:
     static BSONObj callback(const BSONObj& args, void* data) {
         auto scope = static_cast<Scope*>(data);
 
-        scope->invoke("x = 10;", 0, 0);
+        scope->invoke("x = 10;", nullptr, nullptr);
 
         return BSONObj();
     }
@@ -1311,7 +1312,7 @@ public:
         unique_ptr<Scope> s((getGlobalScriptEngine()->*scopeFactory)());
 
         s->injectNative("foo", callback, s.get());
-        s->invoke("var x = 1; foo();", 0, 0);
+        s->invoke("var x = 1; foo();", nullptr, nullptr);
         ASSERT_EQUALS(s->getNumberInt("x"), 10);
     }
 };
@@ -1325,7 +1326,7 @@ public:
         {
             bool threwException = false;
             try {
-                s->invoke("\"use strict\"; x = 10;", 0, 0);
+                s->invoke("\"use strict\"; x = 10;", nullptr, nullptr);
             } catch (...) {
                 threwException = true;
 
@@ -1340,7 +1341,7 @@ public:
         {
             bool threwException = false;
             try {
-                s->invoke("UUID(1,2,3,4,5);", 0, 0);
+                s->invoke("UUID(1,2,3,4,5);", nullptr, nullptr);
             } catch (...) {
                 threwException = true;
 
@@ -1368,7 +1369,9 @@ public:
         s->injectNative("foo", sidecarThrowingFunc);
 
         ASSERT_THROWS_WITH_CHECK(
-            s->invoke("try { foo(); } catch (e) { throw e; } throw new Error(\"bar\");", 0, 0),
+            s->invoke("try { foo(); } catch (e) { throw e; } throw new Error(\"bar\");",
+                      nullptr,
+                      nullptr),
             ExceptionFor<ErrorCodes::ForTestingErrorExtraInfo>,
             [](const auto& ex) { ASSERT_EQ(ex->data, 123); });
     }
@@ -1423,7 +1426,7 @@ class ConvertShardKeyToHashed {
 public:
     void check(shared_ptr<Scope> s, const mongo::BSONObj& o) {
         s->setObject("o", o, true);
-        s->invoke("return convertShardKeyToHashed(o);", 0, 0);
+        s->invoke("return convertShardKeyToHashed(o);", nullptr, nullptr);
         const auto scopeShardKey = s->getNumber("__returnValue");
 
         // Wrapping to form a proper element
@@ -1438,7 +1441,7 @@ public:
     void checkWithSeed(shared_ptr<Scope> s, const mongo::BSONObj& o, int seed) {
         s->setObject("o", o, true);
         s->setNumber("seed", seed);
-        s->invoke("return convertShardKeyToHashed(o, seed);", 0, 0);
+        s->invoke("return convertShardKeyToHashed(o, seed);", nullptr, nullptr);
         const auto scopeShardKey = s->getNumber("__returnValue");
 
         // Wrapping to form a proper element
@@ -1450,19 +1453,19 @@ public:
     }
 
     void checkNoArgs(shared_ptr<Scope> s) {
-        s->invoke("return convertShardKeyToHashed();", 0, 0);
+        s->invoke("return convertShardKeyToHashed();", nullptr, nullptr);
     }
 
     void checkWithExtraArg(shared_ptr<Scope> s, const mongo::BSONObj& o, int seed) {
         s->setObject("o", o, true);
         s->setNumber("seed", seed);
-        s->invoke("return convertShardKeyToHashed(o, seed, 1);", 0, 0);
+        s->invoke("return convertShardKeyToHashed(o, seed, 1);", nullptr, nullptr);
     }
 
     void checkWithBadSeed(shared_ptr<Scope> s, const mongo::BSONObj& o) {
         s->setObject("o", o, true);
         s->setString("seed", "sunflower");
-        s->invoke("return convertShardKeyToHashed(o, seed);", 0, 0);
+        s->invoke("return convertShardKeyToHashed(o, seed);", nullptr, nullptr);
     }
 
     void run() {
@@ -1520,12 +1523,12 @@ public:
             "let f = async function() {  return 28; };"
             "f().then(function(y){ x = y; });"
             "return x;",
-            0,
-            0);
+            nullptr,
+            nullptr);
         ASSERT(0 == scope->getNumber("__returnValue"));
         /* When we return x the second time the value has been updated
          * by the async function */
-        scope->invoke("return x;", 0, 0);
+        scope->invoke("return x;", nullptr, nullptr);
         ASSERT(28 == scope->getNumber("__returnValue"));
     }
 };
diff --git a/src/mongo/dbtests/mock/mock_dbclient_connection.h b/src/mongo/dbtests/mock/mock_dbclient_connection.h
index 8995e92ab19..aaa4968d58e 100644
--- a/src/mongo/dbtests/mock/mock_dbclient_connection.h
+++ b/src/mongo/dbtests/mock/mock_dbclient_connection.h
@@ -78,7 +78,7 @@ public:
                                                  mongo::Query query = mongo::Query(),
                                                  int nToReturn = 0,
                                                  int nToSkip = 0,
-                                                 const mongo::BSONObj* fieldsToReturn = 0,
+                                                 const mongo::BSONObj* fieldsToReturn = nullptr,
                                                  int queryOptions = 0,
                                                  int batchSize = 0) override;
 
@@ -107,7 +107,7 @@ public:
     unsigned long long query(std::function<void(mongo::DBClientCursorBatchIterator&)> f,
                              const NamespaceStringOrUUID& nsOrUuid,
                              mongo::Query query,
-                             const mongo::BSONObj* fieldsToReturn = 0,
+                             const mongo::BSONObj* fieldsToReturn = nullptr,
                              int queryOptions = 0,
                              int batchSize = 0) override;
 
@@ -120,7 +120,9 @@ public:
               mongo::Message& response,
               bool assertOk,
               std::string* actualServer) override;
-    void say(mongo::Message& toSend, bool isRetry = false, std::string* actualServer = 0) override;
+    void say(mongo::Message& toSend,
+             bool isRetry = false,
+             std::string* actualServer = nullptr) override;
     bool lazySupported() const override;
 
 private:
diff --git a/src/mongo/dbtests/mock/mock_remote_db_server.h b/src/mongo/dbtests/mock/mock_remote_db_server.h
index 1ccddf63942..6c0ccc8170d 100644
--- a/src/mongo/dbtests/mock/mock_remote_db_server.h
+++ b/src/mongo/dbtests/mock/mock_remote_db_server.h
@@ -166,7 +166,7 @@ public:
                            mongo::Query query = mongo::Query(),
                            int nToReturn = 0,
                            int nToSkip = 0,
-                           const mongo::BSONObj* fieldsToReturn = 0,
+                           const mongo::BSONObj* fieldsToReturn = nullptr,
                            int queryOptions = 0,
                            int batchSize = 0);
 
diff --git a/src/mongo/dbtests/mock/mock_replica_set.cpp b/src/mongo/dbtests/mock/mock_replica_set.cpp
index f6158af9abb..fb17ad1a960 100644
--- a/src/mongo/dbtests/mock/mock_replica_set.cpp
+++ b/src/mongo/dbtests/mock/mock_replica_set.cpp
@@ -166,7 +166,7 @@ vector<string> MockReplicaSet::getSecondaries() const {
 }
 
 MockRemoteDBServer* MockReplicaSet::getNode(const string& hostAndPort) {
-    return mapFindWithDefault(_nodeMap, hostAndPort, static_cast<MockRemoteDBServer*>(NULL));
+    return mapFindWithDefault(_nodeMap, hostAndPort, static_cast<MockRemoteDBServer*>(nullptr));
 }
 
 repl::ReplSetConfig MockReplicaSet::getReplConfig() const {
@@ -342,7 +342,7 @@ void MockReplicaSet::mockReplSetGetStatusCmd() {
         // TODO: syncingTo
 
         fullStatBuilder.append("set", _setName);
-        fullStatBuilder.appendTimeT("date", time(0));
+        fullStatBuilder.appendTimeT("date", time(nullptr));
         fullStatBuilder.append("myState", getState(node->getServerAddress()));
         fullStatBuilder.append("members", hostsField);
         fullStatBuilder.append("ok", true);
diff --git a/src/mongo/dbtests/mock_replica_set_test.cpp b/src/mongo/dbtests/mock_replica_set_test.cpp
index 44a6c09e8aa..2a44c20ec31 100644
--- a/src/mongo/dbtests/mock_replica_set_test.cpp
+++ b/src/mongo/dbtests/mock_replica_set_test.cpp
@@ -68,7 +68,7 @@ TEST(MockReplicaSetTest, GetNode) {
     ASSERT_EQUALS("$n0:27017", replSet.getNode("$n0:27017")->getServerAddress());
     ASSERT_EQUALS("$n1:27017", replSet.getNode("$n1:27017")->getServerAddress());
     ASSERT_EQUALS("$n2:27017", replSet.getNode("$n2:27017")->getServerAddress());
-    ASSERT(replSet.getNode("$n3:27017") == NULL);
+    ASSERT(replSet.getNode("$n3:27017") == nullptr);
 }
 
 TEST(MockReplicaSetTest, IsMasterNode0) {
diff --git a/src/mongo/dbtests/plan_executor_invalidation_test.cpp b/src/mongo/dbtests/plan_executor_invalidation_test.cpp
index 2cc4eccd7fa..48e9a7adfb1 100644
--- a/src/mongo/dbtests/plan_executor_invalidation_test.cpp
+++ b/src/mongo/dbtests/plan_executor_invalidation_test.cpp
@@ -76,7 +76,7 @@ public:
         params.direction = CollectionScanParams::FORWARD;
         params.tailable = false;
         unique_ptr<CollectionScan> scan(
-            new CollectionScan(&_opCtx, collection(), params, ws.get(), NULL));
+            new CollectionScan(&_opCtx, collection(), params, ws.get(), nullptr));
 
         // Create a plan executor to hold it
         auto qr = std::make_unique<QueryRequest>(nss);
@@ -138,7 +138,7 @@ TEST_F(PlanExecutorInvalidationTest, ExecutorToleratesDeletedDocumentsDuringYiel
 
     // Read some of it.
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -153,11 +153,11 @@ TEST_F(PlanExecutorInvalidationTest, ExecutorToleratesDeletedDocumentsDuringYiel
     // Make sure that the PlanExecutor moved forward over the deleted data.  We don't see foo==10 or
     // foo==11.
     for (int i = 12; i < N(); ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
-    ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&obj, NULL));
+    ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&obj, nullptr));
 }
 
 TEST_F(PlanExecutorInvalidationTest, PlanExecutorThrowsOnRestoreWhenCollectionIsDropped) {
@@ -166,7 +166,7 @@ TEST_F(PlanExecutorInvalidationTest, PlanExecutorThrowsOnRestoreWhenCollectionIs
 
     // Read some of it.
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -177,7 +177,7 @@ TEST_F(PlanExecutorInvalidationTest, PlanExecutorThrowsOnRestoreWhenCollectionIs
 
     exec->restoreState();
 
-    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
     ASSERT_EQUALS(10, obj["foo"].numberInt());
 
     exec->saveState();
@@ -195,7 +195,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanExecutorDoesNotDieWhenAllIndicesDro
 
     // Read some of it.
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -205,7 +205,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanExecutorDoesNotDieWhenAllIndicesDro
 
     // Read the rest of the collection.
     for (int i = 10; i < N(); ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 }
@@ -218,7 +218,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanExecutorDoesNotDieWhenOneIndexDropp
 
     // Read some of it.
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -228,7 +228,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanExecutorDoesNotDieWhenOneIndexDropp
 
     // Read the rest of the collection.
     for (int i = 10; i < N(); ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 }
@@ -245,7 +245,7 @@ TEST_F(PlanExecutorInvalidationTest, IxscanExecutorDiesWhenAllIndexesDropped) {
     // Start scanning the index.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj.firstElement().numberInt());
     }
 
@@ -266,7 +266,7 @@ TEST_F(PlanExecutorInvalidationTest, IxscanExecutorDiesWhenIndexBeingScannedIsDr
     // Start scanning the index.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj.firstElement().numberInt());
     }
 
@@ -289,7 +289,7 @@ TEST_F(PlanExecutorInvalidationTest, IxscanExecutorSurvivesWhenUnrelatedIndexIsD
     // Start scanning the index.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj.firstElement().numberInt());
     }
 
@@ -301,7 +301,7 @@ TEST_F(PlanExecutorInvalidationTest, IxscanExecutorSurvivesWhenUnrelatedIndexIsD
 
     // Scan the rest of the index.
     for (int i = 10; i < N(); ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj.firstElement().numberInt());
     }
 }
@@ -312,7 +312,7 @@ TEST_F(PlanExecutorInvalidationTest, ExecutorThrowsOnRestoreWhenDatabaseIsDroppe
 
     // Read some of it.
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -325,7 +325,7 @@ TEST_F(PlanExecutorInvalidationTest, ExecutorThrowsOnRestoreWhenDatabaseIsDroppe
     _ctx.reset(new dbtests::WriteContextForTests(&_opCtx, nss.ns()));
     exec->restoreState();
 
-    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
     ASSERT_EQUALS(10, obj["foo"].numberInt());
 
     exec->saveState();
@@ -344,7 +344,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanDiesOnCollectionRenameWithinDatabas
     // Partially scan the collection.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -371,7 +371,7 @@ TEST_F(PlanExecutorInvalidationTest, IxscanDiesOnCollectionRenameWithinDatabase)
     // Partially scan the index.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj.firstElement().numberInt());
     }
 
@@ -400,7 +400,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanDiesOnRestartCatalog) {
     // Partially scan the collection.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -421,7 +421,7 @@ TEST_F(PlanExecutorInvalidationTest, IxscanDiesWhenTruncateCollectionDropsAllInd
     // Partially scan the index.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj.firstElement().numberInt());
     }
 
@@ -438,7 +438,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanExecutorSurvivesCollectionTruncate)
     // Partially scan the collection.
     BSONObj obj;
     for (int i = 0; i < 10; ++i) {
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
         ASSERT_EQUALS(i, obj["foo"].numberInt());
     }
 
@@ -449,7 +449,7 @@ TEST_F(PlanExecutorInvalidationTest, CollScanExecutorSurvivesCollectionTruncate)
     exec->restoreState();
 
     // Since all documents in the collection have been deleted, the PlanExecutor should issue EOF.
-    ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&obj, NULL));
+    ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&obj, nullptr));
 }
 
 }  // namespace mongo
diff --git a/src/mongo/dbtests/plan_ranking.cpp b/src/mongo/dbtests/plan_ranking.cpp
index 9e965b270c3..4709a63c8bc 100644
--- a/src/mongo/dbtests/plan_ranking.cpp
+++ b/src/mongo/dbtests/plan_ranking.cpp
@@ -147,7 +147,7 @@ public:
      * Was a backup plan picked during the ranking process?
      */
     bool hasBackupPlan() const {
-        ASSERT(NULL != _mps.get());
+        ASSERT(nullptr != _mps.get());
         return _mps->hasBackupPlan();
     }
 
@@ -256,7 +256,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         verify(statusWithCQ.isOK());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         // Turn on the "force intersect" option.
         // This will be reverted by PlanRankingTestBase's destructor when the test completes.
@@ -297,7 +297,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         ASSERT_OK(statusWithCQ.getStatus());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         QuerySolution* soln = pickBestPlan(cq.get());
 
@@ -331,7 +331,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         ASSERT_OK(statusWithCQ.getStatus());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         QuerySolution* soln = pickBestPlan(cq.get());
 
@@ -370,7 +370,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         ASSERT_OK(statusWithCQ.getStatus());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         QuerySolution* soln = pickBestPlan(cq.get());
         // Prefer the fully covered plan.
@@ -403,7 +403,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         verify(statusWithCQ.isOK());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         // {a: 100} is super selective so choose that.
         QuerySolution* soln = pickBestPlan(cq.get());
@@ -439,7 +439,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         verify(statusWithCQ.isOK());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         // {a: 100} is super selective so choose that.
         QuerySolution* soln = pickBestPlan(cq.get());
@@ -498,7 +498,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         verify(statusWithCQ.isOK());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         QuerySolution* soln = pickBestPlan(cq.get());
 
@@ -532,7 +532,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         ASSERT_OK(statusWithCQ.getStatus());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         // No results will be returned during the trial period,
         // so we expect to choose {d: 1, e: 1}, as it allows us
@@ -569,7 +569,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         ASSERT_OK(statusWithCQ.getStatus());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         // Use index on 'b'.
         QuerySolution* soln = pickBestPlan(cq.get());
@@ -601,7 +601,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
         ASSERT_OK(statusWithCQ.getStatus());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        ASSERT(NULL != cq.get());
+        ASSERT(nullptr != cq.get());
 
         // Expect to use index {a: 1, b: 1}.
         QuerySolution* soln = pickBestPlan(cq.get());
diff --git a/src/mongo/dbtests/query_plan_executor.cpp b/src/mongo/dbtests/query_plan_executor.cpp
index d790c24dca0..4d645862ffc 100644
--- a/src/mongo/dbtests/query_plan_executor.cpp
+++ b/src/mongo/dbtests/query_plan_executor.cpp
@@ -112,7 +112,7 @@ public:
         auto statusWithCQ = CanonicalQuery::canonicalize(&_opCtx, std::move(qr));
         ASSERT_OK(statusWithCQ.getStatus());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        verify(NULL != cq.get());
+        verify(nullptr != cq.get());
 
         // Make the stage.
         unique_ptr<PlanStage> root(
@@ -151,14 +151,14 @@ public:
         const Collection* coll = db->getCollection(&_opCtx, nss);
 
         unique_ptr<WorkingSet> ws(new WorkingSet());
-        IndexScan* ix = new IndexScan(&_opCtx, ixparams, ws.get(), NULL);
-        unique_ptr<PlanStage> root(new FetchStage(&_opCtx, ws.get(), ix, NULL, coll));
+        IndexScan* ix = new IndexScan(&_opCtx, ixparams, ws.get(), nullptr);
+        unique_ptr<PlanStage> root(new FetchStage(&_opCtx, ws.get(), ix, nullptr, coll));
 
         auto qr = std::make_unique<QueryRequest>(nss);
         auto statusWithCQ = CanonicalQuery::canonicalize(&_opCtx, std::move(qr));
         verify(statusWithCQ.isOK());
         unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-        verify(NULL != cq.get());
+        verify(nullptr != cq.get());
 
         // Hand the plan off to the executor.
         auto statusWithPlanExecutor = PlanExecutor::make(&_opCtx,
@@ -334,7 +334,7 @@ protected:
         BSONObj objOut;
         int idcount = 0;
         PlanExecutor::ExecState state;
-        while (PlanExecutor::ADVANCED == (state = exec->getNext(&objOut, NULL))) {
+        while (PlanExecutor::ADVANCED == (state = exec->getNext(&objOut, nullptr))) {
             ASSERT_EQUALS(expectedIds[idcount], objOut["_id"].numberInt());
             ++idcount;
         }
@@ -358,7 +358,7 @@ TEST_F(PlanExecutorSnapshotTest, SnapshotControl) {
     auto exec = makeCollScanExec(coll, filterObj);
 
     BSONObj objOut;
-    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&objOut, NULL));
+    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&objOut, nullptr));
     ASSERT_EQUALS(2, objOut["a"].numberInt());
 
     forceDocumentMove();
@@ -382,7 +382,7 @@ TEST_F(PlanExecutorSnapshotTest, SnapshotTest) {
     auto exec = makeIndexScanExec(ctx.db(), indexSpec, 2, 5);
 
     BSONObj objOut;
-    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&objOut, NULL));
+    ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&objOut, nullptr));
     ASSERT_EQUALS(2, objOut["a"].numberInt());
 
     forceDocumentMove();
diff --git a/src/mongo/dbtests/query_stage_and.cpp b/src/mongo/dbtests/query_stage_and.cpp
index aab96cdff95..1bad15c7280 100644
--- a/src/mongo/dbtests/query_stage_and.cpp
+++ b/src/mongo/dbtests/query_stage_and.cpp
@@ -205,12 +205,12 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar >= 10.
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 10);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // 'ah' reads the first child into its hash table: foo=20, foo=19, ..., foo=0
         // in that order. Read half of them.
@@ -292,13 +292,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar <= 19 (descending).
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 19);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // First call to work reads the first result from the children. The first result for the
         // first scan over foo is {foo: 20, bar: 20, baz: 20}. The first result for the second scan
@@ -372,13 +372,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar >= 10
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 10);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // foo == bar == baz, and foo<=20, bar>=10, so our values are:
         // foo == 10, 11, 12, 13, 14, 15. 16, 17, 18, 19, 20
@@ -421,13 +421,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1 << "big" << 1), coll));
         params.bounds.startKey = BSON("" << 20 << "" << big);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar >= 10
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 10);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Stage execution should fail.
         ASSERT_EQUALS(-1, countResults(ah.get()));
@@ -468,13 +468,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar >= 10
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1 << "big" << 1), coll));
         params.bounds.startKey = BSON("" << 10 << "" << big);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // foo == bar == baz, and foo<=20, bar>=10, so our values are:
         // foo == 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.
@@ -510,18 +510,18 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar >= 10
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 10);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // 5 <= baz <= 15
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("baz" << 1), coll));
         params.bounds.startKey = BSON("" << 5);
         params.bounds.endKey = BSON("" << 15);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // foo == bar == baz, and foo<=20, bar>=10, 5<=baz<=15, so our values are:
         // foo == 10, 11, 12, 13, 14, 15.
@@ -568,18 +568,18 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar >= 10
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1 << "big" << 1), coll));
         params.bounds.startKey = BSON("" << 10 << "" << big);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // 5 <= baz <= 15
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("baz" << 1), coll));
         params.bounds.startKey = BSON("" << 5);
         params.bounds.endKey = BSON("" << 15);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Stage execution should fail.
         ASSERT_EQUALS(-1, countResults(ah.get()));
@@ -613,13 +613,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar == 5.  Index scan should be eof.
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 5);
         params.bounds.endKey = BSON("" << 5);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         int count = 0;
         int works = 0;
@@ -669,7 +669,7 @@ public:
         // Foo >= 100
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 100);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar <= 100
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
@@ -681,7 +681,7 @@ public:
                                     << "");
         params.bounds.boundInclusion = BoundInclusion::kIncludeStartKeyOnly;
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         ASSERT_EQUALS(0, countResults(ah.get()));
     }
@@ -717,17 +717,17 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        IndexScan* firstScan = new IndexScan(&_opCtx, params, &ws, NULL);
+        IndexScan* firstScan = new IndexScan(&_opCtx, params, &ws, nullptr);
 
         // First child of the AND_HASH stage is a Fetch. The NULL in the
         // constructor means there is no filter.
-        FetchStage* fetch = new FetchStage(&_opCtx, &ws, firstScan, NULL, coll);
+        FetchStage* fetch = new FetchStage(&_opCtx, &ws, firstScan, nullptr, coll);
         ah->addChild(fetch);
 
         // Bar >= 10
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 10);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Check that the AndHash stage returns docs {foo: 10, bar: 10}
         // through {foo: 20, bar: 20}.
@@ -769,16 +769,16 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.direction = -1;
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar >= 10
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 10);
-        IndexScan* secondScan = new IndexScan(&_opCtx, params, &ws, NULL);
+        IndexScan* secondScan = new IndexScan(&_opCtx, params, &ws, nullptr);
 
         // Second child of the AND_HASH stage is a Fetch. The NULL in the
         // constructor means there is no filter.
-        FetchStage* fetch = new FetchStage(&_opCtx, &ws, secondScan, NULL, coll);
+        FetchStage* fetch = new FetchStage(&_opCtx, &ws, secondScan, nullptr, coll);
         ah->addChild(fetch);
 
         // Check that the AndHash stage returns docs {foo: 10, bar: 10}
@@ -955,13 +955,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Scan over bar == 1.
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Get the set of RecordIds in our collection to use later.
         set<RecordId> data;
@@ -1072,19 +1072,19 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // bar == 1
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // baz == 1
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("baz" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         ASSERT_EQUALS(50, countResults(ah.get()));
     }
@@ -1117,13 +1117,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 7);
         params.bounds.endKey = BSON("" << 7);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Bar == 20, not EOF.
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.bounds.endKey = BSON("" << 20);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         ASSERT_EQUALS(0, countResults(ah.get()));
     }
@@ -1160,13 +1160,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 7);
         params.bounds.endKey = BSON("" << 7);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // bar == 20.
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 20);
         params.bounds.endKey = BSON("" << 20);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         ASSERT_EQUALS(0, countResults(ah.get()));
     }
@@ -1199,13 +1199,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // Intersect with 7 <= bar < 10000
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 7);
         params.bounds.endKey = BSON("" << 10000);
-        ah->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        ah->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         WorkingSetID lastId = WorkingSet::INVALID_ID;
 
@@ -1261,18 +1261,18 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        IndexScan* firstScan = new IndexScan(&_opCtx, params, &ws, NULL);
+        IndexScan* firstScan = new IndexScan(&_opCtx, params, &ws, nullptr);
 
         // First child of the AND_SORTED stage is a Fetch. The NULL in the
         // constructor means there is no filter.
-        FetchStage* fetch = new FetchStage(&_opCtx, &ws, firstScan, NULL, coll);
+        FetchStage* fetch = new FetchStage(&_opCtx, &ws, firstScan, nullptr, coll);
         as->addChild(fetch);
 
         // bar == 1
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        as->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        as->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         for (int i = 0; i < 50; i++) {
             BSONObj obj = getNext(as.get(), &ws);
@@ -1313,17 +1313,17 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(BSON("foo" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        as->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+        as->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
 
         // bar == 1
         params = makeIndexScanParams(&_opCtx, getIndex(BSON("bar" << 1), coll));
         params.bounds.startKey = BSON("" << 1);
         params.bounds.endKey = BSON("" << 1);
-        IndexScan* secondScan = new IndexScan(&_opCtx, params, &ws, NULL);
+        IndexScan* secondScan = new IndexScan(&_opCtx, params, &ws, nullptr);
 
         // Second child of the AND_SORTED stage is a Fetch. The NULL in the
         // constructor means there is no filter.
-        FetchStage* fetch = new FetchStage(&_opCtx, &ws, secondScan, NULL, coll);
+        FetchStage* fetch = new FetchStage(&_opCtx, &ws, secondScan, nullptr, coll);
         as->addChild(fetch);
 
         for (int i = 0; i < 50; i++) {
diff --git a/src/mongo/dbtests/query_stage_collscan.cpp b/src/mongo/dbtests/query_stage_collscan.cpp
index 615f30f6869..2a5e808e6b0 100644
--- a/src/mongo/dbtests/query_stage_collscan.cpp
+++ b/src/mongo/dbtests/query_stage_collscan.cpp
@@ -114,7 +114,7 @@ public:
         // Use the runner to count the number of objects scanned.
         int count = 0;
         PlanExecutor::ExecState state;
-        for (BSONObj obj; PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL));) {
+        for (BSONObj obj; PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr));) {
             ++count;
         }
         ASSERT_EQUALS(PlanExecutor::IS_EOF, state);
@@ -130,7 +130,8 @@ public:
         params.direction = direction;
         params.tailable = false;
 
-        unique_ptr<CollectionScan> scan(new CollectionScan(&_opCtx, collection, params, &ws, NULL));
+        unique_ptr<CollectionScan> scan(
+            new CollectionScan(&_opCtx, collection, params, &ws, nullptr));
         while (!scan->isEOF()) {
             WorkingSetID id = WorkingSet::INVALID_ID;
             PlanStage::StageState state = scan->work(&id);
@@ -227,7 +228,7 @@ public:
 
         int count = 0;
         PlanExecutor::ExecState state;
-        for (BSONObj obj; PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL));) {
+        for (BSONObj obj; PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr));) {
             // Make sure we get the objects in the order we want
             ASSERT_EQUALS(count, obj["foo"].numberInt());
             ++count;
@@ -262,7 +263,7 @@ public:
 
         int count = 0;
         PlanExecutor::ExecState state;
-        for (BSONObj obj; PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL));) {
+        for (BSONObj obj; PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr));) {
             ++count;
             ASSERT_EQUALS(numObj() - count, obj["foo"].numberInt());
         }
@@ -293,7 +294,7 @@ public:
         params.tailable = false;
 
         WorkingSet ws;
-        unique_ptr<PlanStage> scan(new CollectionScan(&_opCtx, coll, params, &ws, NULL));
+        unique_ptr<PlanStage> scan(new CollectionScan(&_opCtx, coll, params, &ws, nullptr));
 
         int count = 0;
         while (count < 10) {
@@ -352,7 +353,7 @@ public:
         params.tailable = false;
 
         WorkingSet ws;
-        unique_ptr<PlanStage> scan(new CollectionScan(&_opCtx, coll, params, &ws, NULL));
+        unique_ptr<PlanStage> scan(new CollectionScan(&_opCtx, coll, params, &ws, nullptr));
 
         int count = 0;
         while (count < 10) {
diff --git a/src/mongo/dbtests/query_stage_count.cpp b/src/mongo/dbtests/query_stage_count.cpp
index 80770a69e70..003beb748d9 100644
--- a/src/mongo/dbtests/query_stage_count.cpp
+++ b/src/mongo/dbtests/query_stage_count.cpp
@@ -57,7 +57,9 @@ const int kInterjections = kDocuments;
 class CountStageTest {
 public:
     CountStageTest()
-        : _dbLock(&_opCtx, nsToDatabaseSubstring(ns()), MODE_X), _ctx(&_opCtx, ns()), _coll(NULL) {}
+        : _dbLock(&_opCtx, nsToDatabaseSubstring(ns()), MODE_X),
+          _ctx(&_opCtx, ns()),
+          _coll(nullptr) {}
 
     virtual ~CountStageTest() {}
 
@@ -94,7 +96,7 @@ public:
         params.direction = CollectionScanParams::FORWARD;
         params.tailable = false;
 
-        unique_ptr<CollectionScan> scan(new CollectionScan(&_opCtx, _coll, params, &ws, NULL));
+        unique_ptr<CollectionScan> scan(new CollectionScan(&_opCtx, _coll, params, &ws, nullptr));
         while (!scan->isEOF()) {
             WorkingSetID id = WorkingSet::INVALID_ID;
             PlanStage::StageState state = scan->work(&id);
@@ -129,7 +131,7 @@ public:
                               Snapshotted<BSONObj>(_opCtx.recoveryUnit()->getSnapshotId(), oldDoc),
                               newDoc,
                               true,
-                              NULL,
+                              nullptr,
                               &args);
         wunit.commit();
     }
diff --git a/src/mongo/dbtests/query_stage_delete.cpp b/src/mongo/dbtests/query_stage_delete.cpp
index f10b7390243..708d68e068a 100644
--- a/src/mongo/dbtests/query_stage_delete.cpp
+++ b/src/mongo/dbtests/query_stage_delete.cpp
@@ -90,7 +90,8 @@ public:
         params.direction = direction;
         params.tailable = false;
 
-        unique_ptr<CollectionScan> scan(new CollectionScan(&_opCtx, collection, params, &ws, NULL));
+        unique_ptr<CollectionScan> scan(
+            new CollectionScan(&_opCtx, collection, params, &ws, nullptr));
         while (!scan->isEOF()) {
             WorkingSetID id = WorkingSet::INVALID_ID;
             PlanStage::StageState state = scan->work(&id);
@@ -150,7 +151,7 @@ public:
                                 std::move(deleteStageParams),
                                 &ws,
                                 coll,
-                                new CollectionScan(&_opCtx, coll, collScanParams, &ws, NULL));
+                                new CollectionScan(&_opCtx, coll, collScanParams, &ws, nullptr));
 
         const DeleteStats* stats = static_cast<const DeleteStats*>(deleteStage.getSpecificStats());
 
diff --git a/src/mongo/dbtests/query_stage_fetch.cpp b/src/mongo/dbtests/query_stage_fetch.cpp
index 2eb09c39057..f8bf178e5c3 100644
--- a/src/mongo/dbtests/query_stage_fetch.cpp
+++ b/src/mongo/dbtests/query_stage_fetch.cpp
@@ -138,7 +138,7 @@ public:
         }
 
         unique_ptr<FetchStage> fetchStage(
-            new FetchStage(&_opCtx, &ws, mockStage.release(), NULL, coll));
+            new FetchStage(&_opCtx, &ws, mockStage.release(), nullptr, coll));
 
         WorkingSetID id = WorkingSet::INVALID_ID;
         PlanStage::StageState state;
diff --git a/src/mongo/dbtests/query_stage_ixscan.cpp b/src/mongo/dbtests/query_stage_ixscan.cpp
index d5112419175..d38c26eb009 100644
--- a/src/mongo/dbtests/query_stage_ixscan.cpp
+++ b/src/mongo/dbtests/query_stage_ixscan.cpp
@@ -47,7 +47,9 @@ const auto kIndexVersion = IndexDescriptor::IndexVersion::kV2;
 class IndexScanTest {
 public:
     IndexScanTest()
-        : _dbLock(&_opCtx, nsToDatabaseSubstring(ns()), MODE_X), _ctx(&_opCtx, ns()), _coll(NULL) {}
+        : _dbLock(&_opCtx, nsToDatabaseSubstring(ns()), MODE_X),
+          _ctx(&_opCtx, ns()),
+          _coll(nullptr) {}
 
     virtual ~IndexScanTest() {}
 
@@ -109,7 +111,7 @@ public:
         params.direction = 1;
 
         // This child stage gets owned and freed by the caller.
-        MatchExpression* filter = NULL;
+        MatchExpression* filter = nullptr;
         return new IndexScan(&_opCtx, params, &_ws, filter);
     }
 
@@ -133,7 +135,7 @@ public:
         oil.intervals.push_back(Interval(bob.obj(), startInclusive, endInclusive));
         params.bounds.fields.push_back(oil);
 
-        MatchExpression* filter = NULL;
+        MatchExpression* filter = nullptr;
         return new IndexScan(&_opCtx, params, &_ws, filter);
     }
 
diff --git a/src/mongo/dbtests/query_stage_merge_sort.cpp b/src/mongo/dbtests/query_stage_merge_sort.cpp
index aa6cb5e174a..5656174f7b3 100644
--- a/src/mongo/dbtests/query_stage_merge_sort.cpp
+++ b/src/mongo/dbtests/query_stage_merge_sort.cpp
@@ -173,11 +173,11 @@ public:
 
         // a:1
         auto params = makeIndexScanParams(&_opCtx, getIndex(firstIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         // b:1
         params = makeIndexScanParams(&_opCtx, getIndex(secondIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
@@ -189,9 +189,9 @@ public:
 
         for (int i = 0; i < N; ++i) {
             BSONObj first, second;
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, nullptr));
             first = first.getOwned();
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, nullptr));
             ASSERT_EQUALS(first["c"].numberInt(), second["c"].numberInt());
             ASSERT_EQUALS(i, first["c"].numberInt());
             ASSERT((first.hasField("a") && second.hasField("b")) ||
@@ -200,7 +200,7 @@ public:
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_NOT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&foo, NULL));
+        ASSERT_NOT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&foo, nullptr));
     }
 };
 
@@ -238,11 +238,11 @@ public:
 
         // a:1
         auto params = makeIndexScanParams(&_opCtx, getIndex(firstIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         // b:1
         params = makeIndexScanParams(&_opCtx, getIndex(secondIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
 
@@ -253,9 +253,9 @@ public:
 
         for (int i = 0; i < N; ++i) {
             BSONObj first, second;
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, nullptr));
             first = first.getOwned();
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, nullptr));
             ASSERT_EQUALS(first["c"].numberInt(), second["c"].numberInt());
             ASSERT_EQUALS(i, first["c"].numberInt());
             ASSERT((first.hasField("a") && second.hasField("b")) ||
@@ -264,7 +264,7 @@ public:
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, NULL));
+        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, nullptr));
     }
 };
 
@@ -302,11 +302,11 @@ public:
 
         // a:1
         auto params = makeIndexScanParams(&_opCtx, getIndex(firstIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         // b:1
         params = makeIndexScanParams(&_opCtx, getIndex(secondIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
 
@@ -318,9 +318,9 @@ public:
         for (int i = 0; i < N; ++i) {
             BSONObj first, second;
             // We inserted N objects but we get 2 * N from the runner because of dups.
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, nullptr));
             first = first.getOwned();
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, nullptr));
             ASSERT_EQUALS(first["c"].numberInt(), second["c"].numberInt());
             ASSERT_EQUALS(i, first["c"].numberInt());
             ASSERT((first.hasField("a") && second.hasField("b")) ||
@@ -329,7 +329,7 @@ public:
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, NULL));
+        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, nullptr));
     }
 };
 
@@ -370,13 +370,13 @@ public:
         auto params = makeIndexScanParams(&_opCtx, getIndex(firstIndex, coll));
         params.bounds.startKey = objWithMaxKey(1);
         params.bounds.endKey = objWithMinKey(1);
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         // b:1
         params = makeIndexScanParams(&_opCtx, getIndex(secondIndex, coll));
         params.bounds.startKey = objWithMaxKey(1);
         params.bounds.endKey = objWithMinKey(1);
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
 
@@ -387,9 +387,9 @@ public:
 
         for (int i = 0; i < N; ++i) {
             BSONObj first, second;
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, nullptr));
             first = first.getOwned();
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, nullptr));
             ASSERT_EQUALS(first["c"].numberInt(), second["c"].numberInt());
             ASSERT_EQUALS(N - i - 1, first["c"].numberInt());
             ASSERT((first.hasField("a") && second.hasField("b")) ||
@@ -398,7 +398,7 @@ public:
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, NULL));
+        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, nullptr));
     }
 };
 
@@ -436,13 +436,13 @@ public:
 
         // a:1
         auto params = makeIndexScanParams(&_opCtx, getIndex(firstIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         // b:51 (EOF)
         params = makeIndexScanParams(&_opCtx, getIndex(secondIndex, coll));
         params.bounds.startKey = BSON("" << 51 << "" << MinKey);
         params.bounds.endKey = BSON("" << 51 << "" << MaxKey);
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
 
@@ -454,14 +454,14 @@ public:
         // Only getting results from the a:1 index scan.
         for (int i = 0; i < N; ++i) {
             BSONObj obj;
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
             ASSERT_EQUALS(i, obj["c"].numberInt());
             ASSERT_EQUALS(1, obj["a"].numberInt());
         }
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, NULL));
+        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, nullptr));
     }
 };
 
@@ -493,7 +493,7 @@ public:
             BSONObj indexSpec = BSON(index << 1 << "foo" << 1);
             addIndex(indexSpec);
             auto params = makeIndexScanParams(&_opCtx, getIndex(indexSpec, coll));
-            ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+            ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
         }
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
@@ -505,7 +505,7 @@ public:
 
         for (int i = 0; i < numIndices; ++i) {
             BSONObj obj;
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&obj, nullptr));
             ASSERT_EQUALS(i, obj["foo"].numberInt());
             string index(1, 'a' + i);
             ASSERT_EQUALS(1, obj[index].numberInt());
@@ -513,7 +513,7 @@ public:
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, NULL));
+        ASSERT_EQUALS(PlanExecutor::IS_EOF, exec->getNext(&foo, nullptr));
     }
 };
 
@@ -547,7 +547,7 @@ public:
             BSONObj indexSpec = BSON(index << 1 << "foo" << 1);
             addIndex(indexSpec);
             auto params = makeIndexScanParams(&_opCtx, getIndex(indexSpec, coll));
-            ms->addChild(new IndexScan(&_opCtx, params, &ws, NULL));
+            ms->addChild(new IndexScan(&_opCtx, params, &ws, nullptr));
         }
 
         set<RecordId> recordIds;
@@ -765,11 +765,11 @@ public:
 
         // a:1
         auto params = makeIndexScanParams(&_opCtx, getIndex(firstIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         // b:1
         params = makeIndexScanParams(&_opCtx, getIndex(secondIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
@@ -781,9 +781,9 @@ public:
 
         for (int i = 0; i < N; ++i) {
             BSONObj first, second;
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, nullptr));
             first = first.getOwned();
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, nullptr));
             ASSERT_EQUALS(first["c"].numberInt(), second["c"].numberInt());
             ASSERT_EQUALS(i, first["c"].numberInt());
             // {a: 1, c: i, d: "abc"} should precede {b: 1, c: i, d: "bca"}.
@@ -792,7 +792,7 @@ public:
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_NOT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&foo, NULL));
+        ASSERT_NOT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&foo, nullptr));
     }
 };
 
@@ -833,11 +833,11 @@ public:
 
         // a:1
         auto params = makeIndexScanParams(&_opCtx, getIndex(firstIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         // b:1
         params = makeIndexScanParams(&_opCtx, getIndex(secondIndex, coll));
-        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), NULL));
+        ms->addChild(new IndexScan(&_opCtx, params, ws.get(), nullptr));
 
         unique_ptr<FetchStage> fetchStage =
             make_unique<FetchStage>(&_opCtx, ws.get(), ms, nullptr, coll);
@@ -849,9 +849,9 @@ public:
 
         for (int i = 0; i < N; ++i) {
             BSONObj first, second;
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&first, nullptr));
             first = first.getOwned();
-            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, NULL));
+            ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&second, nullptr));
             ASSERT_EQUALS(first["c"].numberInt(), second["c"].numberInt());
             ASSERT_EQUALS(i, first["c"].numberInt());
             // {b: 1, c: i, d: "cba"} should precede {a: 1, c: i, d: "abc"}.
@@ -860,7 +860,7 @@ public:
 
         // Should be done now.
         BSONObj foo;
-        ASSERT_NOT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&foo, NULL));
+        ASSERT_NOT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&foo, nullptr));
     }
 };
 
diff --git a/src/mongo/dbtests/query_stage_multiplan.cpp b/src/mongo/dbtests/query_stage_multiplan.cpp
index 622d284045b..97c50d74952 100644
--- a/src/mongo/dbtests/query_stage_multiplan.cpp
+++ b/src/mongo/dbtests/query_stage_multiplan.cpp
@@ -267,7 +267,7 @@ TEST_F(QueryStageMultiPlanTest, MPSCollectionScanVsHighlySelectiveIXScan) {
     int results = 0;
     BSONObj obj;
     PlanExecutor::ExecState state;
-    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
+    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
         ASSERT_EQUALS(obj["foo"].numberInt(), 7);
         ++results;
     }
@@ -378,7 +378,7 @@ TEST_F(QueryStageMultiPlanTest, MPSBackupPlan) {
     auto statusWithCQ = CanonicalQuery::canonicalize(opCtx(), std::move(qr));
     verify(statusWithCQ.isOK());
     unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
-    ASSERT(NULL != cq.get());
+    ASSERT(nullptr != cq.get());
 
     // Force index intersection.
     bool forceIxisectOldValue = internalQueryForceIntersectionPlans.load();
diff --git a/src/mongo/dbtests/query_stage_sort.cpp b/src/mongo/dbtests/query_stage_sort.cpp
index a50de5f0d3f..1982273bc79 100644
--- a/src/mongo/dbtests/query_stage_sort.cpp
+++ b/src/mongo/dbtests/query_stage_sort.cpp
@@ -175,7 +175,7 @@ public:
         // Look at pairs of objects to make sure that the sort order is pairwise (and therefore
         // totally) correct.
         BSONObj last;
-        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&last, NULL));
+        ASSERT_EQUALS(PlanExecutor::ADVANCED, exec->getNext(&last, nullptr));
         last = last.getOwned();
 
         // Count 'last'.
@@ -183,7 +183,7 @@ public:
 
         BSONObj current;
         PlanExecutor::ExecState state;
-        while (PlanExecutor::ADVANCED == (state = exec->getNext(&current, NULL))) {
+        while (PlanExecutor::ADVANCED == (state = exec->getNext(&current, nullptr))) {
             int cmp = sgn(dps::compareObjectsAccordingToSort(current, last, params.pattern));
             // The next object should be equal to the previous or oriented according to the sort
             // pattern.
@@ -364,7 +364,7 @@ public:
         CollectionUpdateArgs args;
         {
             WriteUnitOfWork wuow(&_opCtx);
-            coll->updateDocument(&_opCtx, *it, oldDoc, newDoc(oldDoc), false, NULL, &args);
+            coll->updateDocument(&_opCtx, *it, oldDoc, newDoc(oldDoc), false, nullptr, &args);
             wuow.commit();
         }
         exec->restoreState();
@@ -382,7 +382,7 @@ public:
             oldDoc = coll->docFor(&_opCtx, *it);
             {
                 WriteUnitOfWork wuow(&_opCtx);
-                coll->updateDocument(&_opCtx, *it++, oldDoc, newDoc(oldDoc), false, NULL, &args);
+                coll->updateDocument(&_opCtx, *it++, oldDoc, newDoc(oldDoc), false, nullptr, &args);
                 wuow.commit();
             }
         }
@@ -571,7 +571,7 @@ public:
             &_opCtx, std::move(ws), std::move(fetchStage), coll, PlanExecutor::NO_YIELD);
         auto exec = std::move(statusWithPlanExecutor.getValue());
 
-        PlanExecutor::ExecState runnerState = exec->getNext(NULL, NULL);
+        PlanExecutor::ExecState runnerState = exec->getNext(nullptr, nullptr);
         ASSERT_EQUALS(PlanExecutor::FAILURE, runnerState);
     }
 };
diff --git a/src/mongo/dbtests/query_stage_tests.cpp b/src/mongo/dbtests/query_stage_tests.cpp
index ec2a54934e3..ffa55f0040b 100644
--- a/src/mongo/dbtests/query_stage_tests.cpp
+++ b/src/mongo/dbtests/query_stage_tests.cpp
@@ -102,7 +102,7 @@ public:
 
         int count = 0;
         PlanExecutor::ExecState state;
-        for (RecordId dl; PlanExecutor::ADVANCED == (state = exec->getNext(NULL, &dl));) {
+        for (RecordId dl; PlanExecutor::ADVANCED == (state = exec->getNext(nullptr, &dl));) {
             ++count;
         }
         ASSERT_EQUALS(PlanExecutor::IS_EOF, state);
diff --git a/src/mongo/dbtests/query_stage_update.cpp b/src/mongo/dbtests/query_stage_update.cpp
index 99829659d0c..adafcaadccd 100644
--- a/src/mongo/dbtests/query_stage_update.cpp
+++ b/src/mongo/dbtests/query_stage_update.cpp
@@ -131,7 +131,8 @@ public:
         params.direction = CollectionScanParams::FORWARD;
         params.tailable = false;
 
-        unique_ptr<CollectionScan> scan(new CollectionScan(&_opCtx, collection, params, &ws, NULL));
+        unique_ptr<CollectionScan> scan(
+            new CollectionScan(&_opCtx, collection, params, &ws, nullptr));
         while (!scan->isEOF()) {
             WorkingSetID id = WorkingSet::INVALID_ID;
             PlanStage::StageState state = scan->work(&id);
@@ -152,7 +153,8 @@ public:
         params.direction = direction;
         params.tailable = false;
 
-        unique_ptr<CollectionScan> scan(new CollectionScan(&_opCtx, collection, params, &ws, NULL));
+        unique_ptr<CollectionScan> scan(
+            new CollectionScan(&_opCtx, collection, params, &ws, nullptr));
         while (!scan->isEOF()) {
             WorkingSetID id = WorkingSet::INVALID_ID;
             PlanStage::StageState state = scan->work(&id);
diff --git a/src/mongo/dbtests/querytests.cpp b/src/mongo/dbtests/querytests.cpp
index c981c80a888..a41e2d9054b 100644
--- a/src/mongo/dbtests/querytests.cpp
+++ b/src/mongo/dbtests/querytests.cpp
@@ -220,7 +220,7 @@ public:
             WriteUnitOfWork wunit(&_opCtx);
             Database* db = ctx.db();
             if (db->getCollection(&_opCtx, nss())) {
-                _collection = NULL;
+                _collection = nullptr;
                 db->dropCollection(&_opCtx, nss()).transitional_ignore();
             }
             _collection = db->createCollection(&_opCtx, nss(), CollectionOptions(), false);
@@ -338,7 +338,8 @@ public:
         }
 
         // Create a cursor on the collection, with a batch size of 200.
-        unique_ptr<DBClientCursor> cursor = _client.query(NamespaceString(ns), "", 0, 0, 0, 0, 200);
+        unique_ptr<DBClientCursor> cursor =
+            _client.query(NamespaceString(ns), "", 0, 0, nullptr, 0, 200);
 
         // Count 500 results, spanning a few batches of documents.
         for (int i = 0; i < 500; ++i) {
@@ -383,7 +384,8 @@ public:
         }
 
         // Create a cursor on the collection, with a batch size of 200.
-        unique_ptr<DBClientCursor> cursor = _client.query(NamespaceString(ns), "", 0, 0, 0, 0, 200);
+        unique_ptr<DBClientCursor> cursor =
+            _client.query(NamespaceString(ns), "", 0, 0, nullptr, 0, 200);
         CursorId cursorId = cursor->getCursorId();
 
         // Count 500 results, spanning a few batches of documents.
@@ -461,7 +463,7 @@ public:
                                                      Query().hint(BSON("$natural" << 1)),
                                                      2,
                                                      0,
-                                                     0,
+                                                     nullptr,
                                                      QueryOption_CursorTailable);
         ASSERT(0 != c->getCursorId());
         while (c->more())
@@ -493,7 +495,7 @@ public:
                                                      Query().hint(BSON("$natural" << 1)),
                                                      2,
                                                      0,
-                                                     0,
+                                                     nullptr,
                                                      QueryOption_CursorTailable);
         ASSERT_EQUALS(0, c->getCursorId());
         ASSERT(c->isDead());
@@ -502,7 +504,7 @@ public:
                           QUERY("a" << 1).hint(BSON("$natural" << 1)),
                           2,
                           0,
-                          0,
+                          nullptr,
                           QueryOption_CursorTailable);
         ASSERT(0 != c->getCursorId());
         ASSERT(!c->isDead());
@@ -528,7 +530,7 @@ public:
                                                      Query().hint(BSON("$natural" << 1)),
                                                      2,
                                                      0,
-                                                     0,
+                                                     nullptr,
                                                      QueryOption_CursorTailable);
         c->next();
         c->next();
@@ -560,7 +562,7 @@ public:
                                                      Query().hint(BSON("$natural" << 1)),
                                                      2,
                                                      0,
-                                                     0,
+                                                     nullptr,
                                                      QueryOption_CursorTailable);
         c->next();
         c->next();
@@ -594,7 +596,7 @@ public:
                                                      Query().hint(BSON("$natural" << 1)),
                                                      2,
                                                      0,
-                                                     0,
+                                                     nullptr,
                                                      QueryOption_CursorTailable);
         c->next();
         c->next();
@@ -616,7 +618,8 @@ public:
         const char* ns = "unittests.querytests.TailCappedOnly";
         _client.insert(ns, BSONObj());
         ASSERT_THROWS(
-            _client.query(NamespaceString(ns), BSONObj(), 0, 0, 0, QueryOption_CursorTailable),
+            _client.query(
+                NamespaceString(ns), BSONObj(), 0, 0, nullptr, QueryOption_CursorTailable),
             AssertionException);
     }
 };
@@ -629,8 +632,8 @@ public:
 
     void insertA(const char* ns, int a) {
         BSONObjBuilder b;
-        b.appendOID("_id", 0, true);
-        b.appendOID("value", 0, true);
+        b.appendOID("_id", nullptr, true);
+        b.appendOID("value", nullptr, true);
         b.append("a", a);
         insert(ns, b.obj());
     }
@@ -656,11 +659,15 @@ public:
         insertA(ns, 0);
         insertA(ns, 1);
         unique_ptr<DBClientCursor> c1 = _client.query(
-            NamespaceString(ns), QUERY("a" << GT << -1), 0, 0, 0, QueryOption_CursorTailable);
+            NamespaceString(ns), QUERY("a" << GT << -1), 0, 0, nullptr, QueryOption_CursorTailable);
         OID id;
         id.init("000000000000000000000000");
-        unique_ptr<DBClientCursor> c2 = _client.query(
-            NamespaceString(ns), QUERY("value" << GT << id), 0, 0, 0, QueryOption_CursorTailable);
+        unique_ptr<DBClientCursor> c2 = _client.query(NamespaceString(ns),
+                                                      QUERY("value" << GT << id),
+                                                      0,
+                                                      0,
+                                                      nullptr,
+                                                      QueryOption_CursorTailable);
         c1->next();
         c1->next();
         ASSERT(!c1->more());
@@ -703,7 +710,7 @@ public:
                           QUERY("ts" << GT << Timestamp(1000, 1)).hint(BSON("$natural" << 1)),
                           0,
                           0,
-                          0,
+                          nullptr,
                           QueryOption_OplogReplay);
         ASSERT(c->more());
         ASSERT_EQUALS(2u, c->next()["ts"].timestamp().getInc());
@@ -714,7 +721,7 @@ public:
                           QUERY("ts" << GT << Timestamp(1000, 1)).hint(BSON("$natural" << 1)),
                           0,
                           0,
-                          0,
+                          nullptr,
                           QueryOption_OplogReplay);
         ASSERT(c->more());
         ASSERT_EQUALS(2u, c->next()["ts"].timestamp().getInc());
@@ -747,7 +754,7 @@ public:
             QUERY("ts" << GT << Timestamp(1000, 1)).hint(BSON("$natural" << 1)).explain(),
             0,
             0,
-            0,
+            nullptr,
             QueryOption_OplogReplay);
         ASSERT(c->more());
 
@@ -1370,7 +1377,7 @@ public:
                           QUERY("i" << GT << 0).hint(BSON("$natural" << 1)),
                           0,
                           0,
-                          0,
+                          nullptr,
                           QueryOption_CursorTailable);
         int n = 0;
         while (c->more()) {
@@ -1397,7 +1404,7 @@ public:
 
     void insertNext() {
         BSONObjBuilder b;
-        b.appendOID("_id", 0, true);
+        b.appendOID("_id", nullptr, true);
         b.append("i", _n++);
         insert(ns(), b.obj());
     }
@@ -1539,7 +1546,7 @@ public:
                                   QUERY("ts" << GTE << Timestamp(1000, j)),
                                   0,
                                   0,
-                                  0,
+                                  nullptr,
                                   QueryOption_OplogReplay);
                 ASSERT(c->more());
                 BSONObj next = c->next();
@@ -1596,7 +1603,7 @@ public:
                                   QUERY("ts" << GTE << Timestamp(1000, j)),
                                   0,
                                   0,
-                                  0,
+                                  nullptr,
                                   QueryOption_OplogReplay);
                 ASSERT(c->more());
                 BSONObj next = c->next();
@@ -1634,7 +1641,7 @@ public:
                                                       QUERY("ts" << GTE << Timestamp(1000, 50)),
                                                       0,
                                                       0,
-                                                      0,
+                                                      nullptr,
                                                       QueryOption_OplogReplay);
         ASSERT(!c0->more());
 
@@ -1656,7 +1663,7 @@ public:
                                                      QUERY("ts" << GTE << Timestamp(1000, 50)),
                                                      0,
                                                      0,
-                                                     0,
+                                                     nullptr,
                                                      QueryOption_OplogReplay);
         ASSERT(!c->more());
 
@@ -1667,7 +1674,7 @@ public:
                           QUERY("ts" << GTE << Timestamp(1000, 50)),
                           0,
                           0,
-                          0,
+                          nullptr,
                           QueryOption_OplogReplay);
         ASSERT(c->more());
         ASSERT_EQUALS(100u, c->next()["ts"].timestamp().getInc());
@@ -1752,7 +1759,7 @@ public:
                              BSON("ts" << GTE << Timestamp(1000, 0)),
                              0,
                              0,
-                             0,
+                             nullptr,
                              QueryOption_OplogReplay | QueryOption_CursorTailable |
                                  QueryOption_Exhaust,
                              message);
diff --git a/src/mongo/dbtests/rollbacktests.cpp b/src/mongo/dbtests/rollbacktests.cpp
index 71824e31bb1..d7d1607c1c2 100644
--- a/src/mongo/dbtests/rollbacktests.cpp
+++ b/src/mongo/dbtests/rollbacktests.cpp
@@ -117,12 +117,12 @@ void assertEmpty(OperationContext* opCtx, const NamespaceString& nss) {
 bool indexExists(OperationContext* opCtx, const NamespaceString& nss, const string& idxName) {
     auto databaseHolder = DatabaseHolder::get(opCtx);
     auto coll = databaseHolder->getDb(opCtx, nss.db())->getCollection(opCtx, nss);
-    return coll->getIndexCatalog()->findIndexByName(opCtx, idxName, true) != NULL;
+    return coll->getIndexCatalog()->findIndexByName(opCtx, idxName, true) != nullptr;
 }
 bool indexReady(OperationContext* opCtx, const NamespaceString& nss, const string& idxName) {
     auto databaseHolder = DatabaseHolder::get(opCtx);
     auto coll = databaseHolder->getDb(opCtx, nss.db())->getCollection(opCtx, nss);
-    return coll->getIndexCatalog()->findIndexByName(opCtx, idxName, false) != NULL;
+    return coll->getIndexCatalog()->findIndexByName(opCtx, idxName, false) != nullptr;
 }
 size_t getNumIndexEntries(OperationContext* opCtx,
                           const NamespaceString& nss,
diff --git a/src/mongo/executor/task_executor.h b/src/mongo/executor/task_executor.h
index 2cceb303a56..a392f72b974 100644
--- a/src/mongo/executor/task_executor.h
+++ b/src/mongo/executor/task_executor.h
@@ -448,7 +448,7 @@ struct TaskExecutor::CallbackArgs {
     CallbackArgs(TaskExecutor* theExecutor,
                  CallbackHandle theHandle,
                  Status theStatus,
-                 OperationContext* opCtx = NULL);
+                 OperationContext* opCtx = nullptr);
 
     TaskExecutor* executor;
     CallbackHandle myHandle;
diff --git a/src/mongo/logger/ramlog.cpp b/src/mongo/logger/ramlog.cpp
index a1f32e26726..a2bf4bffd15 100644
--- a/src/mongo/logger/ramlog.cpp
+++ b/src/mongo/logger/ramlog.cpp
@@ -43,8 +43,8 @@ using std::string;
 
 namespace {
 typedef std::map<string, RamLog*> RM;
-stdx::mutex* _namedLock = NULL;
-RM* _named = NULL;
+stdx::mutex* _namedLock = nullptr;
+RM* _named = nullptr;
 
 }  // namespace
 
@@ -58,7 +58,7 @@ RamLog::~RamLog() {}
 
 void RamLog::write(const std::string& str) {
     stdx::lock_guard<stdx::mutex> lk(_mutex);
-    _lastWrite = time(0);
+    _lastWrite = time(nullptr);
     _totalLinesWritten++;
 
     char* p = lines[(h + n) % N];
@@ -136,7 +136,7 @@ string RamLog::clean(const std::vector<const char*>& v, int i, string line) {
 string RamLog::linkify(const char* s) {
     const char* p = s;
     const char* h = strstr(p, "http://");
-    if (h == 0)
+    if (h == nullptr)
         return s;
 
     const char* sp = h + 7;
@@ -179,7 +179,7 @@ RamLog* RamLog::get(const std::string& name) {
         _named = new RM();
     }
 
-    RamLog* result = mapFindWithDefault(*_named, name, static_cast<RamLog*>(NULL));
+    RamLog* result = mapFindWithDefault(*_named, name, static_cast<RamLog*>(nullptr));
     if (!result) {
         result = new RamLog(name);
         (*_named)[name] = result;
@@ -189,9 +189,9 @@ RamLog* RamLog::get(const std::string& name) {
 
 RamLog* RamLog::getIfExists(const std::string& name) {
     if (!_named)
-        return NULL;
+        return nullptr;
     stdx::lock_guard<stdx::mutex> lk(*_namedLock);
-    return mapFindWithDefault(*_named, name, static_cast<RamLog*>(NULL));
+    return mapFindWithDefault(*_named, name, static_cast<RamLog*>(nullptr));
 }
 
 void RamLog::getNames(std::vector<string>& names) {
diff --git a/src/mongo/logger/rotatable_file_manager.cpp b/src/mongo/logger/rotatable_file_manager.cpp
index f5eb9ebe73f..4ba06af6f5c 100644
--- a/src/mongo/logger/rotatable_file_manager.cpp
+++ b/src/mongo/logger/rotatable_file_manager.cpp
@@ -61,7 +61,7 @@ StatusWithRotatableFileWriter RotatableFileManager::openFile(const std::string&
 }
 
 RotatableFileWriter* RotatableFileManager::getFile(const std::string& name) {
-    return mapFindWithDefault(_writers, name, static_cast<RotatableFileWriter*>(NULL));
+    return mapFindWithDefault(_writers, name, static_cast<RotatableFileWriter*>(nullptr));
 }
 
 RotatableFileManager::FileNameStatusPairVector RotatableFileManager::rotateAll(
diff --git a/src/mongo/s/chunk_manager_index_bounds_test.cpp b/src/mongo/s/chunk_manager_index_bounds_test.cpp
index ecb46584090..c551d06a29a 100644
--- a/src/mongo/s/chunk_manager_index_bounds_test.cpp
+++ b/src/mongo/s/chunk_manager_index_bounds_test.cpp
@@ -74,7 +74,7 @@ protected:
                                  const char* queryStr,
                                  const IndexBounds& expectedBounds) {
         auto query(canonicalize(queryStr));
-        ASSERT(query.get() != NULL);
+        ASSERT(query.get() != nullptr);
 
         BSONObj key = fromjson(keyStr);
 
@@ -98,7 +98,7 @@ protected:
     // Assume shard key is { a: 1 }
     void checkIndexBounds(const char* queryStr, const OrderedIntervalList& expectedOil) {
         auto query(canonicalize(queryStr));
-        ASSERT(query.get() != NULL);
+        ASSERT(query.get() != nullptr);
 
         BSONObj key = fromjson("{a: 1}");
 
@@ -284,7 +284,7 @@ TEST_F(CMCollapseTreeTest, BasicAllElemMatch) {
 
     const char* queryStr = "{foo: {$all: [ {$elemMatch: {a:1, b:1}} ]}}";
     auto query(canonicalize(queryStr));
-    ASSERT(query.get() != NULL);
+    ASSERT(query.get() != nullptr);
 
     BSONObj key = fromjson("{'foo.a': 1}");
 
@@ -365,7 +365,7 @@ TEST_F(CMCollapseTreeTest, TextWithQuery) {
 TEST_F(CMCollapseTreeTest, HashedSinglePoint) {
     const char* queryStr = "{ a: 0 }";
     auto query(canonicalize(queryStr));
-    ASSERT(query.get() != NULL);
+    ASSERT(query.get() != nullptr);
 
     BSONObj key = fromjson("{a: 'hashed'}");
 
diff --git a/src/mongo/s/client/parallel.cpp b/src/mongo/s/client/parallel.cpp
index 7903b2c48e5..3320e4517b7 100644
--- a/src/mongo/s/client/parallel.cpp
+++ b/src/mongo/s/client/parallel.cpp
@@ -198,7 +198,7 @@ ParallelSortClusteredCursor::~ParallelSortClusteredCursor() {
     }
 
     delete[] _cursors;
-    _cursors = 0;
+    _cursors = nullptr;
 
     // Clear out our metadata after removing legacy cursor data
     _cursorMap.clear();
@@ -224,11 +224,11 @@ void ParallelSortClusteredCursor::init(OperationContext* opCtx) {
 void ParallelSortClusteredCursor::_finishCons() {
     _numServers = _servers.size();
     _lastFrom = 0;
-    _cursors = 0;
+    _cursors = nullptr;
 
     if (!_qSpec.isEmpty()) {
         _needToSkip = _qSpec.ntoskip();
-        _cursors = 0;
+        _cursors = nullptr;
         _sortKey = _qSpec.sort();
         _fields = _qSpec.fields();
     }
@@ -552,8 +552,9 @@ void ParallelSortClusteredCursor::startInit(OperationContext* opCtx) {
                         isCommand() ? 1 : 0,  // nToReturn (0 if query indicates multi)
                         0,                    // nToSkip
                         // Does this need to be a ptr?
-                        _qSpec.fields().isEmpty() ? 0 : _qSpec.fieldsData(),  // fieldsToReturn
-                        _qSpec.options(),                                     // options
+                        _qSpec.fields().isEmpty() ? nullptr
+                                                  : _qSpec.fieldsData(),  // fieldsToReturn
+                        _qSpec.options(),                                 // options
                         // NtoReturn is weird.
                         // If zero, it means use default size, so we do that for all cursors
                         // If positive, it's the batch size (we don't want this cursor limiting
@@ -579,9 +580,10 @@ void ParallelSortClusteredCursor::startInit(OperationContext* opCtx) {
                         _qSpec.ntoreturn(),  // nToReturn
                         _qSpec.ntoskip(),    // nToSkip
                         // Does this need to be a ptr?
-                        _qSpec.fields().isEmpty() ? 0 : _qSpec.fieldsData(),  // fieldsToReturn
-                        _qSpec.options(),                                     // options
-                        0));                                                  // batchSize
+                        _qSpec.fields().isEmpty() ? nullptr
+                                                  : _qSpec.fieldsData(),  // fieldsToReturn
+                        _qSpec.options(),                                 // options
+                        0));                                              // batchSize
                 }
             }
 
@@ -1005,25 +1007,25 @@ void ParallelSortClusteredCursor::_oldInit(OperationContext* opCtx) {
                     new DBClientCursor(conns[i]->get(),
                                        NamespaceString(_ns),
                                        _query,
-                                       0,                                 // nToReturn
-                                       0,                                 // nToSkip
-                                       _fields.isEmpty() ? 0 : &_fields,  // fieldsToReturn
+                                       0,                                       // nToReturn
+                                       0,                                       // nToSkip
+                                       _fields.isEmpty() ? nullptr : &_fields,  // fieldsToReturn
                                        _options,
                                        _batchSize == 0 ? 0 : _batchSize + _needToSkip  // batchSize
                                        ),
-                    NULL);
+                    nullptr);
 
             try {
                 _cursors[i].get()->initLazy(!firstPass);
             } catch (NetworkException& e) {
                 socketExs.push_back(e.what() + errLoc);
-                _cursors[i].reset(NULL, NULL);
+                _cursors[i].reset(nullptr, nullptr);
                 conns[i]->done();
                 if (!returnPartial)
                     break;
             } catch (std::exception& e) {
                 otherExs.push_back(e.what() + errLoc);
-                _cursors[i].reset(NULL, NULL);
+                _cursors[i].reset(nullptr, nullptr);
                 conns[i]->done();
                 break;
             }
@@ -1051,7 +1053,7 @@ void ParallelSortClusteredCursor::_oldInit(OperationContext* opCtx) {
                 if (!_cursors[i].get()->initLazyFinish(retry)) {
                     warning() << "invalid result from " << conns[i]->getHost()
                               << (retry ? ", retrying" : "");
-                    _cursors[i].reset(NULL, NULL);
+                    _cursors[i].reset(nullptr, nullptr);
 
                     if (!retry) {
                         socketExs.push_back(str::stream() << "error querying server: "
@@ -1071,17 +1073,17 @@ void ParallelSortClusteredCursor::_oldInit(OperationContext* opCtx) {
                 staleConfigExs.push_back(
                     (string) "stale config detected when receiving response for " + e.toString() +
                     errLoc);
-                _cursors[i].reset(NULL, NULL);
+                _cursors[i].reset(nullptr, nullptr);
                 conns[i]->done();
                 continue;
             } catch (NetworkException& e) {
                 socketExs.push_back(e.what() + errLoc);
-                _cursors[i].reset(NULL, NULL);
+                _cursors[i].reset(nullptr, nullptr);
                 conns[i]->done();
                 continue;
             } catch (std::exception& e) {
                 otherExs.push_back(e.what() + errLoc);
-                _cursors[i].reset(NULL, NULL);
+                _cursors[i].reset(nullptr, nullptr);
                 conns[i]->done();
                 continue;
             }
@@ -1100,12 +1102,12 @@ void ParallelSortClusteredCursor::_oldInit(OperationContext* opCtx) {
 
                 staleConfigExs.push_back((string) "stale config detected for " + e.toString() +
                                          errLoc);
-                _cursors[i].reset(NULL, NULL);
+                _cursors[i].reset(nullptr, nullptr);
                 conns[i]->done();
                 continue;
             } catch (std::exception& e) {
                 otherExs.push_back(e.what() + errLoc);
-                _cursors[i].reset(NULL, NULL);
+                _cursors[i].reset(nullptr, nullptr);
                 conns[i]->done();
                 continue;
             }
diff --git a/src/mongo/s/client/shard_connection.cpp b/src/mongo/s/client/shard_connection.cpp
index e5698ef5f69..2cc44c44a1f 100644
--- a/src/mongo/s/client/shard_connection.cpp
+++ b/src/mongo/s/client/shard_connection.cpp
@@ -127,7 +127,7 @@ public:
         std::unique_ptr<DBClientBase> c;
         if (s->avail) {
             c.reset(s->avail);
-            s->avail = 0;
+            s->avail = nullptr;
 
             // May throw an exception
             shardConnectionPool.onHandedOut(c.get());
@@ -162,7 +162,7 @@ public:
                     release(addr, ss->avail);
                 }
 
-                ss->avail = 0;
+                ss->avail = nullptr;
             }
 
             if (fromDestructor) {
@@ -181,7 +181,7 @@ public:
 
         const bool isConnGood = shardConnectionPool.isConnectionGood(addr, conn);
 
-        if (s->avail != NULL) {
+        if (s->avail != nullptr) {
             warning() << "Detected additional sharded connection in the "
                       << "thread local pool for " << addr;
 
@@ -193,7 +193,7 @@ public:
 
             if (!isConnGood) {
                 delete s->avail;
-                s->avail = NULL;
+                s->avail = nullptr;
             }
 
             // Let the internal pool handle the bad connection, this can also
@@ -268,7 +268,7 @@ public:
      */
     void clearPool() {
         for (HostMap::iterator iter = _hosts.begin(); iter != _hosts.end(); ++iter) {
-            if (iter->second->avail != NULL) {
+            if (iter->second->avail != nullptr) {
                 delete iter->second->avail;
             }
             delete iter->second;
@@ -443,7 +443,7 @@ void ShardConnection::kill() {
             delete _conn;
         }
 
-        _conn = 0;
+        _conn = nullptr;
         _finishedInit = true;
     }
 }
diff --git a/src/mongo/s/client/shard_connection.h b/src/mongo/s/client/shard_connection.h
index 2b28aff0e18..c23c03964bb 100644
--- a/src/mongo/s/client/shard_connection.h
+++ b/src/mongo/s/client/shard_connection.h
@@ -110,7 +110,7 @@ public:
     }
 
     bool ok() const {
-        return _conn != NULL;
+        return _conn != nullptr;
     }
 
     /** reports all thread local connections on this instance */
diff --git a/src/mongo/s/client/version_manager.cpp b/src/mongo/s/client/version_manager.cpp
index 75c235d6cc6..f1cdfbc5e6b 100644
--- a/src/mongo/s/client/version_manager.cpp
+++ b/src/mongo/s/client/version_manager.cpp
@@ -196,7 +196,7 @@ bool initShardVersionEmptyNS(OperationContext* opCtx, DBClientBase* conn_in) {
                             "",
                             Grid::get(opCtx)->shardRegistry()->getConfigServerConnectionString(),
                             ChunkVersion(),
-                            NULL,
+                            nullptr,
                             true,
                             result);
 
diff --git a/src/mongo/s/commands/cluster_get_last_error_cmd.cpp b/src/mongo/s/commands/cluster_get_last_error_cmd.cpp
index ec7f151302c..aabd696f845 100644
--- a/src/mongo/s/commands/cluster_get_last_error_cmd.cpp
+++ b/src/mongo/s/commands/cluster_get_last_error_cmd.cpp
@@ -277,7 +277,7 @@ public:
         BSONArrayBuilder errorRawGLE;
 
         int numWCErrors = 0;
-        const LegacyWCResponse* lastErrResponse = NULL;
+        const LegacyWCResponse* lastErrResponse = nullptr;
 
         for (std::vector<LegacyWCResponse>::const_iterator it = wcResponses.begin();
              it != wcResponses.end();
diff --git a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
index 6f169e55140..39ec9ddae0f 100644
--- a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
+++ b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
@@ -70,7 +70,7 @@ const Milliseconds kNoDistLockTimeout(-1);
  * Generates a unique name for the temporary M/R output collection.
  */
 std::string getTmpName(StringData coll) {
-    return str::stream() << "tmp.mrs." << coll << "_" << time(0) << "_"
+    return str::stream() << "tmp.mrs." << coll << "_" << time(nullptr) << "_"
                          << JOB_NUMBER.fetchAndAdd(1);
 }
 
diff --git a/src/mongo/s/write_ops/batch_write_op.cpp b/src/mongo/s/write_ops/batch_write_op.cpp
index 79abd418faf..5efce61128d 100644
--- a/src/mongo/s/write_ops/batch_write_op.cpp
+++ b/src/mongo/s/write_ops/batch_write_op.cpp
@@ -363,7 +363,7 @@ Status BatchWriteOp::targetBatch(const NSTargeter& targeter,
         if (ordered && !batchMap.empty()) {
             dassert(batchMap.size() == 1u);
             if (isNewBatchRequiredOrdered(writes, batchMap)) {
-                writeOp.cancelWrites(NULL);
+                writeOp.cancelWrites(nullptr);
                 break;
             }
         }
@@ -591,7 +591,7 @@ void BatchWriteOp::noteBatchResponse(const TargetedWriteBatch& targetedBatch,
 
     vector<WriteErrorDetail*>::iterator itemErrorIt = itemErrors.begin();
     int index = 0;
-    WriteErrorDetail* lastError = NULL;
+    WriteErrorDetail* lastError = nullptr;
     for (vector<TargetedWrite *>::const_iterator it = targetedBatch.getWrites().begin();
          it != targetedBatch.getWrites().end();
          ++it, ++index) {
@@ -601,7 +601,7 @@ void BatchWriteOp::noteBatchResponse(const TargetedWriteBatch& targetedBatch,
         dassert(writeOp.getWriteState() == WriteOpState_Pending);
 
         // See if we have an error for the write
-        WriteErrorDetail* writeError = NULL;
+        WriteErrorDetail* writeError = nullptr;
 
         if (itemErrorIt != itemErrors.end() && (*itemErrorIt)->getIndex() == index) {
             // We have an per-item error for this write op's index
@@ -610,7 +610,7 @@ void BatchWriteOp::noteBatchResponse(const TargetedWriteBatch& targetedBatch,
         }
 
         // Finish the response (with error, if needed)
-        if (NULL == writeError) {
+        if (nullptr == writeError) {
             if (!ordered || !lastError) {
                 writeOp.noteWriteComplete(*write);
             } else {
@@ -625,7 +625,7 @@ void BatchWriteOp::noteBatchResponse(const TargetedWriteBatch& targetedBatch,
     }
 
     // Track errors we care about, whether batch or individual errors
-    if (NULL != trackedErrors) {
+    if (nullptr != trackedErrors) {
         trackErrors(targetedBatch.getEndpoint(), itemErrors, trackedErrors);
     }
 
@@ -723,7 +723,7 @@ void BatchWriteOp::buildClientResponse(BatchedCommandResponse* batchResp) {
 
     // For non-verbose, it's all we need.
     if (!_clientRequest.isVerboseWC()) {
-        dassert(batchResp->isValid(NULL));
+        dassert(batchResp->isValid(nullptr));
         return;
     }
 
@@ -802,7 +802,7 @@ void BatchWriteOp::buildClientResponse(BatchedCommandResponse* batchResp) {
         batchResp->setNModified(_numModified);
     }
 
-    dassert(batchResp->isValid(NULL));
+    dassert(batchResp->isValid(nullptr));
 }
 
 int BatchWriteOp::numWriteOpsIn(WriteOpState opState) const {
diff --git a/src/mongo/s/write_ops/batch_write_op_test.cpp b/src/mongo/s/write_ops/batch_write_op_test.cpp
index 85a289bf6d4..49b586fc58a 100644
--- a/src/mongo/s/write_ops/batch_write_op_test.cpp
+++ b/src/mongo/s/write_ops/batch_write_op_test.cpp
@@ -92,14 +92,14 @@ void buildResponse(int n, BatchedCommandResponse* response) {
     response->clear();
     response->setStatus(Status::OK());
     response->setN(n);
-    ASSERT(response->isValid(NULL));
+    ASSERT(response->isValid(nullptr));
 }
 
 void buildErrResponse(int code, const std::string& message, BatchedCommandResponse* response) {
     response->clear();
     response->setN(0);
     response->setStatus({ErrorCodes::Error(code), message});
-    ASSERT(response->isValid(NULL));
+    ASSERT(response->isValid(nullptr));
 }
 
 void addError(int code, const std::string& message, int index, BatchedCommandResponse* response) {
@@ -154,7 +154,7 @@ TEST_F(BatchWriteOpTest, SingleOp) {
     BatchedCommandResponse response;
     buildResponse(1, &response);
 
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -187,7 +187,7 @@ TEST_F(BatchWriteOpTest, SingleError) {
     BatchedCommandResponse response;
     buildErrResponse(ErrorCodes::UnknownError, "message", &response);
 
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -266,7 +266,7 @@ TEST_F(BatchWriteOpTest, SingleWriteConcernErrorOrdered) {
     addWCError(&response);
 
     // First stale response comes back, we should retry
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -301,14 +301,14 @@ TEST_F(BatchWriteOpTest, SingleStaleError) {
     addError(ErrorCodes::StaleShardVersion, "mock stale error", 0, &response);
 
     // First stale response comes back, we should retry
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
     ASSERT_OK(batchOp.targetBatch(targeter, false, &targeted));
 
     // Respond again with a stale response
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
@@ -317,7 +317,7 @@ TEST_F(BatchWriteOpTest, SingleStaleError) {
     buildResponse(1, &response);
 
     // Respond with an 'ok' response
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -359,7 +359,7 @@ TEST_F(BatchWriteOpTest, MultiOpSameShardOrdered) {
     BatchedCommandResponse response;
     buildResponse(2, &response);
 
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -401,7 +401,7 @@ TEST_F(BatchWriteOpTest, MultiOpSameShardUnordered) {
     BatchedCommandResponse response;
     buildResponse(2, &response);
 
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -440,7 +440,7 @@ TEST_F(BatchWriteOpTest, MultiOpTwoShardsOrdered) {
     buildResponse(1, &response);
 
     // Respond to first targeted batch
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
@@ -452,7 +452,7 @@ TEST_F(BatchWriteOpTest, MultiOpTwoShardsOrdered) {
     assertEndpointsEqual(targeted.begin()->second->getEndpoint(), endpointB);
 
     // Respond to second targeted batch
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -513,7 +513,7 @@ TEST_F(BatchWriteOpTest, MultiOpTwoShardsUnordered) {
     // Respond to both targeted batches
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(batchOp.isFinished());
 
@@ -555,7 +555,7 @@ TEST_F(BatchWriteOpTest, MultiOpTwoShardsEachOrdered) {
     // Respond to both targeted batches for first multi-delete
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(!batchOp.isFinished());
 
@@ -569,7 +569,7 @@ TEST_F(BatchWriteOpTest, MultiOpTwoShardsEachOrdered) {
     // Respond to second targeted batches for second multi-delete
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(batchOp.isFinished());
 
@@ -616,7 +616,7 @@ TEST_F(BatchWriteOpTest, MultiOpTwoShardsEachUnordered) {
     // Respond to both targeted batches, each containing two ops
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(batchOp.isFinished());
 
@@ -667,7 +667,7 @@ TEST_F(BatchWriteOpTest, MultiOpOneOrTwoShardsOrdered) {
     buildResponse(2, &response);
 
     // Respond to first targeted batch containing the two single-host deletes
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
@@ -683,7 +683,7 @@ TEST_F(BatchWriteOpTest, MultiOpOneOrTwoShardsOrdered) {
     // Respond to two targeted batches for first multi-delete
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(!batchOp.isFinished());
 
@@ -697,7 +697,7 @@ TEST_F(BatchWriteOpTest, MultiOpOneOrTwoShardsOrdered) {
     // Respond to two targeted batches for second multi-delete
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(!batchOp.isFinished());
 
@@ -713,7 +713,7 @@ TEST_F(BatchWriteOpTest, MultiOpOneOrTwoShardsOrdered) {
     buildResponse(2, &response);
 
     // Respond to final targeted batch containing the last two single-host deletes
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -766,7 +766,7 @@ TEST_F(BatchWriteOpTest, MultiOpOneOrTwoShardsUnordered) {
     // Respond to first targeted batch containing the two single-host deletes
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(batchOp.isFinished());
 
@@ -812,7 +812,7 @@ TEST_F(BatchWriteOpTest, MultiOpSingleShardErrorUnordered) {
     auto targetedIt = targeted.begin();
 
     // No error on first shard
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     buildResponse(0, &response);
@@ -820,7 +820,7 @@ TEST_F(BatchWriteOpTest, MultiOpSingleShardErrorUnordered) {
 
     // Error on second write on second shard
     ++targetedIt;
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(batchOp.isFinished());
     ASSERT(++targetedIt == targeted.end());
 
@@ -873,7 +873,7 @@ TEST_F(BatchWriteOpTest, MultiOpTwoShardErrorsUnordered) {
     // Error on first write on first shard and second write on second shard.
     for (auto it = targeted.begin(); it != targeted.end(); ++it) {
         ASSERT(!batchOp.isFinished());
-        batchOp.noteBatchResponse(*it->second, response, NULL);
+        batchOp.noteBatchResponse(*it->second, response, nullptr);
     }
     ASSERT(batchOp.isFinished());
 
@@ -932,7 +932,7 @@ TEST_F(BatchWriteOpTest, MultiOpPartialSingleShardErrorUnordered) {
     buildResponse(2, &response);
 
     // No errors on first shard
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     buildResponse(1, &response);
@@ -940,7 +940,7 @@ TEST_F(BatchWriteOpTest, MultiOpPartialSingleShardErrorUnordered) {
 
     // Error on second write on second shard
     ++targetedIt;
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(batchOp.isFinished());
     ASSERT(++targetedIt == targeted.end());
 
@@ -990,7 +990,7 @@ TEST_F(BatchWriteOpTest, MultiOpPartialSingleShardErrorOrdered) {
     buildResponse(1, &response);
 
     // No errors on first shard
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     buildResponse(0, &response);
@@ -998,7 +998,7 @@ TEST_F(BatchWriteOpTest, MultiOpPartialSingleShardErrorOrdered) {
 
     // Error on second write on second shard
     ++targetedIt;
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(batchOp.isFinished());
     ASSERT(++targetedIt == targeted.end());
 
@@ -1052,7 +1052,7 @@ TEST_F(BatchWriteOpTest, MultiOpErrorAndWriteConcernErrorUnordered) {
     addWCError(&response);
 
     // First stale response comes back, we should retry
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     // Unordered reports write concern error
@@ -1099,7 +1099,7 @@ TEST_F(BatchWriteOpTest, SingleOpErrorAndWriteConcernErrorOrdered) {
     addWCError(&response);
 
     // First response comes back with write concern error
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     buildResponse(0, &response);
@@ -1107,7 +1107,7 @@ TEST_F(BatchWriteOpTest, SingleOpErrorAndWriteConcernErrorOrdered) {
 
     // Second response comes back with write error
     ++targetedIt;
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(batchOp.isFinished());
     ASSERT(++targetedIt == targeted.end());
 
@@ -1157,7 +1157,7 @@ TEST_F(BatchWriteOpTest, MultiOpFailedTargetOrdered) {
     buildResponse(1, &response);
 
     // First response ok
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
@@ -1217,7 +1217,7 @@ TEST_F(BatchWriteOpTest, MultiOpFailedTargetUnordered) {
     buildResponse(2, &response);
 
     // Response is ok for first and third write
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -1254,7 +1254,7 @@ TEST_F(BatchWriteOpTest, MultiOpFailedBatchOrdered) {
     buildResponse(1, &response);
 
     // First shard batch is ok
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
@@ -1263,7 +1263,7 @@ TEST_F(BatchWriteOpTest, MultiOpFailedBatchOrdered) {
     buildErrResponse(ErrorCodes::UnknownError, "mock error", &response);
 
     // Second shard batch fails
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     // We should have recorded an error for the second write
@@ -1310,14 +1310,14 @@ TEST_F(BatchWriteOpTest, MultiOpFailedBatchUnordered) {
     buildResponse(1, &response);
 
     // First shard batch is ok
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     buildErrResponse(ErrorCodes::UnknownError, "mock error", &response);
 
     // Second shard batch fails
     ++targetedIt;
-    batchOp.noteBatchResponse(*targetedIt->second, response, NULL);
+    batchOp.noteBatchResponse(*targetedIt->second, response, nullptr);
     ASSERT(batchOp.isFinished());
     ASSERT(++targetedIt == targeted.end());
 
@@ -1359,7 +1359,7 @@ TEST_F(BatchWriteOpTest, MultiOpAbortOrdered) {
     buildResponse(1, &response);
 
     // First shard batch is ok
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     WriteErrorDetail abortError;
@@ -1447,14 +1447,14 @@ TEST_F(BatchWriteOpTest, MultiOpTwoWCErrors) {
     addWCError(&response);
 
     // First shard write write concern fails.
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
     ASSERT_OK(batchOp.targetBatch(targeter, true, &targeted));
 
     // Second shard write write concern fails.
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 
     BatchedCommandResponse clientResponse;
@@ -1503,7 +1503,7 @@ TEST_F(BatchWriteOpLimitTests, OneBigDoc) {
     BatchedCommandResponse response;
     buildResponse(1, &response);
 
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 }
 
@@ -1535,7 +1535,7 @@ TEST_F(BatchWriteOpLimitTests, OneBigOneSmall) {
     BatchedCommandResponse response;
     buildResponse(1, &response);
 
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(!batchOp.isFinished());
 
     targetedOwned.clear();
@@ -1543,7 +1543,7 @@ TEST_F(BatchWriteOpLimitTests, OneBigOneSmall) {
     ASSERT_EQUALS(targeted.size(), 1u);
     ASSERT_EQUALS(targeted.begin()->second->getWrites().size(), 1u);
 
-    batchOp.noteBatchResponse(*targeted.begin()->second, response, NULL);
+    batchOp.noteBatchResponse(*targeted.begin()->second, response, nullptr);
     ASSERT(batchOp.isFinished());
 }
 
diff --git a/src/mongo/s/write_ops/batched_command_response.cpp b/src/mongo/s/write_ops/batched_command_response.cpp
index 9ec01a62e61..0c2396f7499 100644
--- a/src/mongo/s/write_ops/batched_command_response.cpp
+++ b/src/mongo/s/write_ops/batched_command_response.cpp
@@ -66,7 +66,7 @@ BatchedCommandResponse::~BatchedCommandResponse() {
 
 bool BatchedCommandResponse::isValid(std::string* errMsg) const {
     std::string dummy;
-    if (errMsg == NULL) {
+    if (errMsg == nullptr) {
         errMsg = &dummy;
     }
 
@@ -195,7 +195,7 @@ bool BatchedCommandResponse::parseBSON(const BSONObj& source, string* errMsg) {
         _nModified = intNModified;
     }
 
-    std::vector<BatchedUpsertDetail*>* tempUpsertDetails = NULL;
+    std::vector<BatchedUpsertDetail*>* tempUpsertDetails = nullptr;
     fieldState = FieldParser::extract(source, upsertDetails, &tempUpsertDetails, errMsg);
     if (fieldState == FieldParser::FIELD_INVALID)
         return false;
@@ -223,12 +223,12 @@ bool BatchedCommandResponse::parseBSON(const BSONObj& source, string* errMsg) {
         return false;
     _isElectionIdSet = fieldState == FieldParser::FIELD_SET;
 
-    std::vector<WriteErrorDetail*>* tempErrDetails = NULL;
+    std::vector<WriteErrorDetail*>* tempErrDetails = nullptr;
     fieldState = FieldParser::extract(source, writeErrors, &tempErrDetails, errMsg);
     if (fieldState == FieldParser::FIELD_INVALID)
         return false;
     _writeErrorDetails.reset(tempErrDetails);
-    WriteConcernErrorDetail* wcError = NULL;
+    WriteConcernErrorDetail* wcError = nullptr;
     fieldState = FieldParser::extract(source, writeConcernError, &wcError, errMsg);
     if (fieldState == FieldParser::FIELD_INVALID)
         return false;
@@ -347,14 +347,14 @@ void BatchedCommandResponse::setUpsertDetails(
 }
 
 void BatchedCommandResponse::addToUpsertDetails(BatchedUpsertDetail* upsertDetails) {
-    if (_upsertDetails.get() == NULL) {
+    if (_upsertDetails.get() == nullptr) {
         _upsertDetails.reset(new std::vector<BatchedUpsertDetail*>);
     }
     _upsertDetails->push_back(upsertDetails);
 }
 
 void BatchedCommandResponse::unsetUpsertDetails() {
-    if (_upsertDetails.get() != NULL) {
+    if (_upsertDetails.get() != nullptr) {
         for (std::vector<BatchedUpsertDetail*>::iterator it = _upsertDetails->begin();
              it != _upsertDetails->end();
              ++it) {
@@ -365,7 +365,7 @@ void BatchedCommandResponse::unsetUpsertDetails() {
 }
 
 bool BatchedCommandResponse::isUpsertDetailsSet() const {
-    return _upsertDetails.get() != NULL;
+    return _upsertDetails.get() != nullptr;
 }
 
 size_t BatchedCommandResponse::sizeUpsertDetails() const {
@@ -432,14 +432,14 @@ void BatchedCommandResponse::setErrDetails(const std::vector<WriteErrorDetail*>&
 }
 
 void BatchedCommandResponse::addToErrDetails(WriteErrorDetail* errDetails) {
-    if (_writeErrorDetails.get() == NULL) {
+    if (_writeErrorDetails.get() == nullptr) {
         _writeErrorDetails.reset(new std::vector<WriteErrorDetail*>);
     }
     _writeErrorDetails->push_back(errDetails);
 }
 
 void BatchedCommandResponse::unsetErrDetails() {
-    if (_writeErrorDetails.get() != NULL) {
+    if (_writeErrorDetails.get() != nullptr) {
         for (std::vector<WriteErrorDetail*>::iterator it = _writeErrorDetails->begin();
              it != _writeErrorDetails->end();
              ++it) {
@@ -450,7 +450,7 @@ void BatchedCommandResponse::unsetErrDetails() {
 }
 
 bool BatchedCommandResponse::isErrDetailsSet() const {
-    return _writeErrorDetails.get() != NULL;
+    return _writeErrorDetails.get() != nullptr;
 }
 
 size_t BatchedCommandResponse::sizeErrDetails() const {
diff --git a/src/mongo/s/write_ops/cluster_write.cpp b/src/mongo/s/write_ops/cluster_write.cpp
index 3955cf5bce2..4e3aa4c7e3b 100644
--- a/src/mongo/s/write_ops/cluster_write.cpp
+++ b/src/mongo/s/write_ops/cluster_write.cpp
@@ -58,7 +58,7 @@ namespace {
 void toBatchError(const Status& status, BatchedCommandResponse* response) {
     response->clear();
     response->setStatus(status);
-    dassert(response->isValid(NULL));
+    dassert(response->isValid(nullptr));
 }
 
 }  // namespace
diff --git a/src/mongo/s/write_ops/write_error_detail.cpp b/src/mongo/s/write_ops/write_error_detail.cpp
index 5d4e5b84cfc..d51618fe25b 100644
--- a/src/mongo/s/write_ops/write_error_detail.cpp
+++ b/src/mongo/s/write_ops/write_error_detail.cpp
@@ -50,7 +50,7 @@ WriteErrorDetail::WriteErrorDetail() {
 
 bool WriteErrorDetail::isValid(std::string* errMsg) const {
     std::string dummy;
-    if (errMsg == NULL) {
+    if (errMsg == nullptr) {
         errMsg = &dummy;
     }
 
diff --git a/src/mongo/s/write_ops/write_op.cpp b/src/mongo/s/write_ops/write_op.cpp
index 1d647c0ce30..97e5b1d1795 100644
--- a/src/mongo/s/write_ops/write_op.cpp
+++ b/src/mongo/s/write_ops/write_op.cpp
@@ -228,7 +228,7 @@ void WriteOp::noteWriteComplete(const TargetedWrite& targetedWrite) {
     const WriteOpRef& ref = targetedWrite.writeOpRef;
     auto& childOp = _childOps[ref.second];
 
-    childOp.pendingWrite = NULL;
+    childOp.pendingWrite = nullptr;
     childOp.endpoint.reset(new ShardEndpoint(targetedWrite.endpoint));
     childOp.state = WriteOpState_Completed;
     _updateOpState();
@@ -238,7 +238,7 @@ void WriteOp::noteWriteError(const TargetedWrite& targetedWrite, const WriteErro
     const WriteOpRef& ref = targetedWrite.writeOpRef;
     auto& childOp = _childOps[ref.second];
 
-    childOp.pendingWrite = NULL;
+    childOp.pendingWrite = nullptr;
     childOp.endpoint.reset(new ShardEndpoint(targetedWrite.endpoint));
     childOp.error.reset(new WriteErrorDetail);
     error.cloneTo(childOp.error.get());
diff --git a/src/mongo/s/write_ops/write_op_test.cpp b/src/mongo/s/write_ops/write_op_test.cpp
index 21499683120..3110a74c909 100644
--- a/src/mongo/s/write_ops/write_op_test.cpp
+++ b/src/mongo/s/write_ops/write_op_test.cpp
@@ -441,7 +441,7 @@ TEST(WriteOpTests, CancelSingle) {
     ASSERT_EQUALS(targeted.size(), 1u);
     assertEndpointsEqual(targeted.front()->endpoint, endpoint);
 
-    writeOp.cancelWrites(NULL);
+    writeOp.cancelWrites(nullptr);
 
     ASSERT_EQUALS(writeOp.getWriteState(), WriteOpState_Ready);
 }
diff --git a/src/mongo/scripting/deadline_monitor_test.cpp b/src/mongo/scripting/deadline_monitor_test.cpp
index a9dd1a546ce..1ad1fb70cdb 100644
--- a/src/mongo/scripting/deadline_monitor_test.cpp
+++ b/src/mongo/scripting/deadline_monitor_test.cpp
@@ -66,7 +66,7 @@ private:
 
 class Task {
 public:
-    Task() : _group(NULL), _killed(0) {}
+    Task() : _group(nullptr), _killed(0) {}
     explicit Task(TaskGroup* group) : _group(group), _killed(0) {}
     void kill() {
         _killed = curTimeMillis64();
diff --git a/src/mongo/scripting/engine.cpp b/src/mongo/scripting/engine.cpp
index 28cb06c949e..93f70408757 100644
--- a/src/mongo/scripting/engine.cpp
+++ b/src/mongo/scripting/engine.cpp
@@ -225,7 +225,7 @@ void Scope::loadStored(OperationContext* opCtx, bool ignoreNotConnected) {
     auto directDBClient = DBDirectClientFactory::get(opCtx).create(opCtx);
 
     unique_ptr<DBClientCursor> c =
-        directDBClient->query(coll, Query(), 0, 0, NULL, QueryOption_SlaveOk, 0);
+        directDBClient->query(coll, Query(), 0, 0, nullptr, QueryOption_SlaveOk, 0);
     massert(16669, "unable to get db client cursor from query", c.get());
 
     set<string> thisTime;
@@ -560,7 +560,7 @@ unique_ptr<Scope> ScriptEngine::getPooledScope(OperationContext* opCtx,
     return p;
 }
 
-void (*ScriptEngine::_connectCallback)(DBClientBase&) = 0;
+void (*ScriptEngine::_connectCallback)(DBClientBase&) = nullptr;
 
 ScriptEngine* getGlobalScriptEngine() {
     if (hasGlobalServiceContext())
diff --git a/src/mongo/scripting/engine.h b/src/mongo/scripting/engine.h
index f5a85d44f3e..a1f02724ee2 100644
--- a/src/mongo/scripting/engine.h
+++ b/src/mongo/scripting/engine.h
@@ -140,7 +140,7 @@ public:
         uasserted(9005, std::string("invoke failed: ") + getError());
     }
 
-    virtual void injectNative(const char* field, NativeFunction func, void* data = 0) = 0;
+    virtual void injectNative(const char* field, NativeFunction func, void* data = nullptr) = 0;
 
     virtual bool exec(StringData code,
                       const std::string& name,
diff --git a/src/mongo/scripting/mozjs/implscope.h b/src/mongo/scripting/mozjs/implscope.h
index b0eb7c55c14..5c428528544 100644
--- a/src/mongo/scripting/mozjs/implscope.h
+++ b/src/mongo/scripting/mozjs/implscope.h
@@ -153,7 +153,7 @@ public:
               bool assertOnError,
               int timeoutMs) override;
 
-    void injectNative(const char* field, NativeFunction func, void* data = 0) override;
+    void injectNative(const char* field, NativeFunction func, void* data = nullptr) override;
 
     ScriptingFunction _createFunction(const char* code) override;
 
diff --git a/src/mongo/scripting/mozjs/mongo.cpp b/src/mongo/scripting/mozjs/mongo.cpp
index a2ef99c93f7..e86f0582bb4 100644
--- a/src/mongo/scripting/mozjs/mongo.cpp
+++ b/src/mongo/scripting/mozjs/mongo.cpp
@@ -365,7 +365,7 @@ void MongoBase::Functions::find::call(JSContext* cx, JS::CallArgs args) {
                                                        q,
                                                        nToReturn,
                                                        nToSkip,
-                                                       haveFields ? &fields : NULL,
+                                                       haveFields ? &fields : nullptr,
                                                        options,
                                                        batchSize));
     if (!cursor.get()) {
diff --git a/src/mongo/scripting/mozjs/proxyscope.h b/src/mongo/scripting/mozjs/proxyscope.h
index 9d11a857923..e4948a6bc9f 100644
--- a/src/mongo/scripting/mozjs/proxyscope.h
+++ b/src/mongo/scripting/mozjs/proxyscope.h
@@ -170,7 +170,7 @@ public:
               bool assertOnError,
               int timeoutMs) override;
 
-    void injectNative(const char* field, NativeFunction func, void* data = 0) override;
+    void injectNative(const char* field, NativeFunction func, void* data = nullptr) override;
 
     ScriptingFunction _createFunction(const char* code) override;
 
diff --git a/src/mongo/shell/dbshell.cpp b/src/mongo/shell/dbshell.cpp
index 9ee4527f86c..4282d05a525 100644
--- a/src/mongo/shell/dbshell.cpp
+++ b/src/mongo/shell/dbshell.cpp
@@ -184,7 +184,7 @@ void generateCompletions(const std::string& prefix, std::vector<std::string>& al
     try {
         BSONObj args = BSON("0" << prefix);
         shellMainScope->invokeSafe(
-            "function callShellAutocomplete(x) {shellAutocomplete(x)}", &args, NULL);
+            "function callShellAutocomplete(x) {shellAutocomplete(x)}", &args, nullptr);
         BSONObjBuilder b;
         shellMainScope->append(b, "", "__autocomplete__");
         BSONObj res = b.obj();
@@ -543,7 +543,7 @@ static void edit(const std::string& whatToEdit) {
         GetTempPathA(sizeof tempFolder, tempFolder);
         sb << tempFolder << "mongo_edit" << time(0) + i << ".js";
 #else
-        sb << "/tmp/mongo_edit" << time(0) + i << ".js";
+        sb << "/tmp/mongo_edit" << time(nullptr) + i << ".js";
 #endif
         filename = sb.str();
         if (!::mongo::shell_utils::fileExists(filename))
@@ -834,7 +834,7 @@ int _main(int argc, char* argv[], char** envp) {
                 "function() { return typeof TestData === 'object' && TestData !== null && "
                 "TestData.hasOwnProperty('failIfUnterminatedProcesses') && "
                 "TestData.failIfUnterminatedProcesses; }"_sd;
-            shellMainScope->invokeSafe(code.rawData(), 0, 0);
+            shellMainScope->invokeSafe(code.rawData(), nullptr, nullptr);
             failIfUnterminatedProcesses = shellMainScope->getBoolean("__returnValue");
 
             if (failIfUnterminatedProcesses) {
@@ -858,7 +858,7 @@ int _main(int argc, char* argv[], char** envp) {
         std::string rcLocation;
         if (!shellGlobalParams.norc) {
 #ifndef _WIN32
-            if (getenv("HOME") != NULL)
+            if (getenv("HOME") != nullptr)
                 rcLocation = str::stream() << getenv("HOME") << "/.mongorc.js";
 #else
             if (getenv("HOMEDRIVE") != NULL && getenv("HOMEPATH") != NULL)
diff --git a/src/mongo/shell/linenoise.cpp b/src/mongo/shell/linenoise.cpp
index bc3373def85..f4fdc340e79 100644
--- a/src/mongo/shell/linenoise.cpp
+++ b/src/mongo/shell/linenoise.cpp
@@ -385,12 +385,12 @@ public:
     }
 
     Utf32String* yank() {
-        return (size > 0) ? &theRing[indexToSlot[index]] : 0;
+        return (size > 0) ? &theRing[indexToSlot[index]] : nullptr;
     }
 
     Utf32String* yankPop() {
         if (size == 0) {
-            return 0;
+            return nullptr;
         }
         ++index;
         if (index == size) {
@@ -467,8 +467,8 @@ static const int DELETE_KEY = 0x10E00000;
 static const int PAGE_UP_KEY = 0x11000000;
 static const int PAGE_DOWN_KEY = 0x11200000;
 
-static const char* unsupported_term[] = {"dumb", "cons25", "emacs", NULL};
-static linenoiseCompletionCallback* completionCallback = NULL;
+static const char* unsupported_term[] = {"dumb", "cons25", "emacs", nullptr};
+static linenoiseCompletionCallback* completionCallback = nullptr;
 
 #ifdef _WIN32
 static HANDLE console_in, console_out;
@@ -485,7 +485,7 @@ static int atexit_registered = 0; /* register atexit just 1 time */
 static int historyMaxLen = LINENOISE_DEFAULT_HISTORY_MAX_LEN;
 static int historyLen = 0;
 static int historyIndex = 0;
-static UChar8** history = NULL;
+static UChar8** history = nullptr;
 
 // used to emulate Windows command prompt on down-arrow after a recall
 // we use -2 as our "not set" value because we add 1 to the previous index on down-arrow,
@@ -497,7 +497,7 @@ static void linenoiseAtExit(void);
 
 static bool isUnsupportedTerm(void) {
     char* term = getenv("TERM");
-    if (term == NULL)
+    if (term == nullptr)
         return false;
     for (int j = 0; unsupported_term[j]; ++j)
         if (!strcasecmp(term, unsupported_term[j])) {
@@ -517,7 +517,7 @@ void linenoiseHistoryFree(void) {
             free(history[j]);
         historyLen = 0;
         free(history);
-        history = 0;
+        history = nullptr;
     }
 }
 
@@ -1754,7 +1754,7 @@ int InputBuffer::incrementalHistorySearch(PromptBase& pi, int startChar) {
     bool keepLooping = true;
     bool useSearchedLine = true;
     bool searchAgain = false;
-    UChar32* activeHistoryLine = 0;
+    UChar32* activeHistoryLine = nullptr;
     while (keepLooping) {
         c = linenoiseReadChar();
         c = cleanupCtrl(c);  // convert CTRL + <char> into normal ctrl
@@ -2639,12 +2639,12 @@ char* linenoise(const char* prompt) {
         PromptInfo pi(reinterpret_cast<const UChar8*>(prompt), getScreenColumns());
         if (isUnsupportedTerm()) {
             if (write32(1, pi.promptText.get(), pi.promptChars) == -1)
-                return 0;
+                return nullptr;
             fflush(stdout);
             if (preloadedBufferContents.empty()) {
                 unique_ptr<char[]> buf8(new char[LINENOISE_MAX_LINE]);
-                if (fgets(buf8.get(), LINENOISE_MAX_LINE, stdin) == NULL) {
-                    return NULL;
+                if (fgets(buf8.get(), LINENOISE_MAX_LINE, stdin) == nullptr) {
+                    return nullptr;
                 }
                 size_t len = strlen(buf8.get());
                 while (len && (buf8[len - 1] == '\n' || buf8[len - 1] == '\r')) {
@@ -2659,7 +2659,7 @@ char* linenoise(const char* prompt) {
             }
         } else {
             if (enableRawMode() == -1) {
-                return NULL;
+                return nullptr;
             }
             InputBuffer ib(buf32, charWidths, LINENOISE_MAX_LINE);
             if (!preloadedBufferContents.empty()) {
@@ -2670,7 +2670,7 @@ char* linenoise(const char* prompt) {
             disableRawMode();
             printf("\n");
             if (count == -1) {
-                return NULL;
+                return nullptr;
             }
             size_t bufferSize = sizeof(UChar32) * ib.length() + 1;
             unique_ptr<UChar8[]> buf8(new UChar8[bufferSize]);
@@ -2679,8 +2679,8 @@ char* linenoise(const char* prompt) {
         }
     } else {  // input not from a terminal, we should work with piped input, i.e. redirected stdin
         unique_ptr<char[]> buf8(new char[LINENOISE_MAX_LINE]);
-        if (fgets(buf8.get(), LINENOISE_MAX_LINE, stdin) == NULL) {
-            return NULL;
+        if (fgets(buf8.get(), LINENOISE_MAX_LINE, stdin) == nullptr) {
+            return nullptr;
         }
 
         // if fgets() gave us the newline, remove it
@@ -2706,9 +2706,9 @@ int linenoiseHistoryAdd(const char* line) {
     if (historyMaxLen == 0) {
         return 0;
     }
-    if (history == NULL) {
+    if (history == nullptr) {
         history = reinterpret_cast<UChar8**>(malloc(sizeof(UChar8*) * historyMaxLen));
-        if (history == NULL) {
+        if (history == nullptr) {
             return 0;
         }
         memset(history, 0, (sizeof(char*) * historyMaxLen));
@@ -2746,7 +2746,7 @@ int linenoiseHistorySetMaxLen(int len) {
     if (history) {
         int tocopy = historyLen;
         UChar8** newHistory = reinterpret_cast<UChar8**>(malloc(sizeof(UChar8*) * len));
-        if (newHistory == NULL) {
+        if (newHistory == nullptr) {
             return 0;
         }
         if (len < tocopy) {
@@ -2784,7 +2784,7 @@ mongo::Status linenoiseHistorySave(const char* filename) {
         return linenoiseFileError(mongo::ErrorCodes::FileOpenFailed, "open()", filename, ewd);
     }
     fp = fdopen(fd, "wt");
-    if (fp == NULL) {
+    if (fp == nullptr) {
         const auto ewd = mongo::errnoWithDescription();
         // We've already failed, so no need to report any close() failure.
         (void)close(fd);
@@ -2820,7 +2820,7 @@ mongo::Status linenoiseHistorySave(const char* filename) {
 /* Load the history from the specified file. */
 mongo::Status linenoiseHistoryLoad(const char* filename) {
     FILE* fp = fopen(filename, "rt");
-    if (fp == NULL) {
+    if (fp == nullptr) {
         if (errno == ENOENT) {
             // Not having a history file isn't an error condition.
             // For example, it's always the case when the shell is run for the first time.
@@ -2831,7 +2831,7 @@ mongo::Status linenoiseHistoryLoad(const char* filename) {
     }
 
     char buf[LINENOISE_MAX_LINE];
-    while (fgets(buf, LINENOISE_MAX_LINE, fp) != NULL) {
+    while (fgets(buf, LINENOISE_MAX_LINE, fp) != nullptr) {
         char* p = strchr(buf, '\r');
         if (!p) {
             p = strchr(buf, '\n');
diff --git a/src/mongo/shell/shell_utils.cpp b/src/mongo/shell/shell_utils.cpp
index af46190753f..b97e6358b14 100644
--- a/src/mongo/shell/shell_utils.cpp
+++ b/src/mongo/shell/shell_utils.cpp
@@ -264,7 +264,7 @@ bool isBalanced(const std::string& code) {
 
 std::string dbConnect;
 
-static const char* argv0 = 0;
+static const char* argv0 = nullptr;
 EnterpriseShellCallback* enterpriseCallback = nullptr;
 
 void RecordMyLocation(const char* _argv0) {
diff --git a/src/mongo/shell/shell_utils_launcher.cpp b/src/mongo/shell/shell_utils_launcher.cpp
index 51b266dc9ed..c25acf297f7 100644
--- a/src/mongo/shell/shell_utils_launcher.cpp
+++ b/src/mongo/shell/shell_utils_launcher.cpp
@@ -119,7 +119,7 @@ void safeClose(int fd) {
         }
 
         ~ScopedSignalBlocker() {
-            pthread_sigmask(SIG_SETMASK, &_oldMask, NULL);
+            pthread_sigmask(SIG_SETMASK, &_oldMask, nullptr);
         }
 
     private:
@@ -314,7 +314,7 @@ ProgramRunner::ProgramRunner(const BSONObj& args, const BSONObj& env, bool isMon
             if (str == "--port") {
                 _port = -2;
             } else if (_port == -2) {
-                _port = strtol(str.c_str(), 0, 10);
+                _port = strtol(str.c_str(), nullptr, 10);
             } else if (isMongodProgram && str == "--configsvr") {
                 _name = "c";
             }
@@ -428,7 +428,7 @@ void ProgramRunner::start() {
         }
 #endif
 
-        fflush(0);
+        fflush(nullptr);
 
         launchProcess(pipeEnds[1]);  // sets _pid
 
@@ -692,7 +692,7 @@ void ProgramRunner::launchProcess(int child_stdout) {
 // returns true if process exited
 // If this function returns true, it will always call `registry.unregisterProgram(pid);`
 // If block is true, this will throw if it cannot wait for the processes to exit.
-bool wait_for_pid(ProcessId pid, bool block = true, int* exit_code = NULL) {
+bool wait_for_pid(ProcessId pid, bool block = true, int* exit_code = nullptr) {
 #ifdef _WIN32
     verify(registry.countHandleForPid(pid));
     HANDLE h = registry.getHandleForPid(pid);
@@ -1100,7 +1100,7 @@ std::vector<ProcessId> getRunningMongoChildProcessIds() {
 }
 
 MongoProgramScope::~MongoProgramScope() {
-    DESTRUCTOR_GUARD(KillMongoProgramInstances(); ClearRawMongoProgramOutput(BSONObj(), 0);)
+    DESTRUCTOR_GUARD(KillMongoProgramInstances(); ClearRawMongoProgramOutput(BSONObj(), nullptr);)
 }
 
 void installShellUtilsLauncher(Scope& scope) {
diff --git a/src/mongo/unittest/system_resource_canary_bm.cpp b/src/mongo/unittest/system_resource_canary_bm.cpp
index beaba9aa585..f2f09bc162b 100644
--- a/src/mongo/unittest/system_resource_canary_bm.cpp
+++ b/src/mongo/unittest/system_resource_canary_bm.cpp
@@ -137,7 +137,7 @@ BENCHMARK_DEFINE_F(CacheLatencyTest, BM_CacheLatency)(benchmark::State& state) {
     size_t counter = arrLength / (kStrideBytes * 100) + 1;
 
     for (auto keepRunning : state) {
-        char** dummyResult = 0;  // Dummy result to prevent the loop from being optimized out.
+        char** dummyResult = nullptr;  // Dummy result to prevent the loop from being optimized out.
         char** ptrToNextLinkedListNode = reinterpret_cast<char**>(data.get()[0]);
 
         for (size_t i = 0; i < counter; ++i) {
diff --git a/src/mongo/unittest/unittest.cpp b/src/mongo/unittest/unittest.cpp
index 764be0908d0..3cce9bf868d 100644
--- a/src/mongo/unittest/unittest.cpp
+++ b/src/mongo/unittest/unittest.cpp
@@ -138,7 +138,7 @@ public:
     static Result* cur;
 };
 
-Result* Result::cur = 0;
+Result* Result::cur = nullptr;
 
 namespace {
 
@@ -390,7 +390,7 @@ int Suite::run(const std::vector<std::string>& suites, const std::string& filter
 
     for (std::string name : torun) {
         std::shared_ptr<Suite>& s = _allSuites()[name];
-        fassert(16145, s != NULL);
+        fassert(16145, s != nullptr);
 
         log() << "going to run suite: " << name << std::endl;
         results.emplace_back(s->run(filter, runsPerTest));
@@ -407,7 +407,7 @@ int Suite::run(const std::vector<std::string>& suites, const std::string& filter
     Result totals("TOTALS");
     std::vector<std::string> failedSuites;
 
-    Result::cur = NULL;
+    Result::cur = nullptr;
     for (const auto& r : results) {
         log().setIsTruncatable(false) << r->toString();
         if (abs(r->rc()) > abs(rc))
diff --git a/src/mongo/util/allocator.cpp b/src/mongo/util/allocator.cpp
index 358689a0655..66e87518b59 100644
--- a/src/mongo/util/allocator.cpp
+++ b/src/mongo/util/allocator.cpp
@@ -37,7 +37,7 @@ namespace mongo {
 
 void* mongoMalloc(size_t size) {
     void* x = std::malloc(size);
-    if (x == NULL) {
+    if (x == nullptr) {
         reportOutOfMemoryErrorAndExit();
     }
     return x;
@@ -45,7 +45,7 @@ void* mongoMalloc(size_t size) {
 
 void* mongoRealloc(void* ptr, size_t size) {
     void* x = std::realloc(ptr, size);
-    if (x == NULL) {
+    if (x == nullptr) {
         reportOutOfMemoryErrorAndExit();
     }
     return x;
diff --git a/src/mongo/util/assert_util.cpp b/src/mongo/util/assert_util.cpp
index 2167b2849ec..dcf2b580d42 100644
--- a/src/mongo/util/assert_util.cpp
+++ b/src/mongo/util/assert_util.cpp
@@ -223,7 +223,7 @@ std::string demangleName(const std::type_info& typeinfo) {
 #else
     int status;
 
-    char* niceName = abi::__cxa_demangle(typeinfo.name(), 0, 0, &status);
+    char* niceName = abi::__cxa_demangle(typeinfo.name(), nullptr, nullptr, &status);
     if (!niceName)
         return typeinfo.name();
 
diff --git a/src/mongo/util/background.cpp b/src/mongo/util/background.cpp
index 441cdab0e53..e5b40238230 100644
--- a/src/mongo/util/background.cpp
+++ b/src/mongo/util/background.cpp
@@ -276,7 +276,7 @@ void PeriodicTaskRunner::remove(PeriodicTask* task) {
     stdx::lock_guard<stdx::mutex> lock(_mutex);
     for (size_t i = 0; i != _tasks.size(); i++) {
         if (_tasks[i] == task) {
-            _tasks[i] = NULL;
+            _tasks[i] = nullptr;
             break;
         }
     }
diff --git a/src/mongo/util/concurrency/mutex.h b/src/mongo/util/concurrency/mutex.h
index 8674fe269a4..30ee48f8a30 100644
--- a/src/mongo/util/concurrency/mutex.h
+++ b/src/mongo/util/concurrency/mutex.h
@@ -79,7 +79,7 @@ class SimpleMutex {
 
 public:
     SimpleMutex() {
-        verify(pthread_mutex_init(&_lock, 0) == 0);
+        verify(pthread_mutex_init(&_lock, nullptr) == 0);
     }
 
     ~SimpleMutex() {
diff --git a/src/mongo/util/concurrency/ticketholder.h b/src/mongo/util/concurrency/ticketholder.h
index 51c232bc5d1..8ab3d4a39d9 100644
--- a/src/mongo/util/concurrency/ticketholder.h
+++ b/src/mongo/util/concurrency/ticketholder.h
@@ -118,7 +118,7 @@ class TicketHolderReleaser {
 
 public:
     TicketHolderReleaser() {
-        _holder = NULL;
+        _holder = nullptr;
     }
 
     explicit TicketHolderReleaser(TicketHolder* holder) {
@@ -132,10 +132,10 @@ public:
     }
 
     bool hasTicket() const {
-        return _holder != NULL;
+        return _holder != nullptr;
     }
 
-    void reset(TicketHolder* holder = NULL) {
+    void reset(TicketHolder* holder = nullptr) {
         if (_holder) {
             _holder->release();
         }
diff --git a/src/mongo/util/heap_profiler.cpp b/src/mongo/util/heap_profiler.cpp
index 3edb8717f79..05a8a59f03a 100644
--- a/src/mongo/util/heap_profiler.cpp
+++ b/src/mongo/util/heap_profiler.cpp
@@ -481,7 +481,7 @@ private:
             if (dladdr(stack.frames[j], &dli)) {
                 if (dli.dli_sname) {
                     int status;
-                    demangled = abi::__cxa_demangle(dli.dli_sname, 0, 0, &status);
+                    demangled = abi::__cxa_demangle(dli.dli_sname, nullptr, nullptr, &status);
                     if (demangled) {
                         // strip off function parameters as they are very verbose and not useful
                         char* p = strchr(demangled, '(');
diff --git a/src/mongo/util/log.h b/src/mongo/util/log.h
index bca7c87a33a..68a16c34493 100644
--- a/src/mongo/util/log.h
+++ b/src/mongo/util/log.h
@@ -236,7 +236,7 @@ extern Tee* const startupWarningsLog;  // Things put here get reported in MMS
 /**
  * Write the current context (backtrace), along with the optional "msg".
  */
-void logContext(const char* msg = NULL);
+void logContext(const char* msg = nullptr);
 
 /**
  * Turns the global log manager into a plain console logger (no adornments).
diff --git a/src/mongo/util/md5.cpp b/src/mongo/util/md5.cpp
index 383b046c9ac..6a2867f0007 100644
--- a/src/mongo/util/md5.cpp
+++ b/src/mongo/util/md5.cpp
@@ -159,7 +159,7 @@ static void md5_process(md5_state_t* pms, const md5_byte_t* data /*[64]*/) {
              * On little-endian machines, we can process properly aligned
              * data without copying it.
              */
-            if (!((data - (const md5_byte_t*)0) & 3)) {
+            if (!((data - (const md5_byte_t*)nullptr) & 3)) {
                 /* data are properly aligned */
                 X = (const md5_word_t*)data;
             } else {
diff --git a/src/mongo/util/net/sock.cpp b/src/mongo/util/net/sock.cpp
index 6d7b2d1e8f7..bb616b4452e 100644
--- a/src/mongo/util/net/sock.cpp
+++ b/src/mongo/util/net/sock.cpp
@@ -190,7 +190,7 @@ Socket::Socket(int fd, const SockAddr& remote)
     : _fd(fd),
       _remote(remote),
       _timeout(0),
-      _lastValidityCheckAtSecs(time(0)),
+      _lastValidityCheckAtSecs(time(nullptr)),
       _logLevel(logger::LogSeverity::Log()) {
     _init();
     if (fd >= 0) {
@@ -201,7 +201,7 @@ Socket::Socket(int fd, const SockAddr& remote)
 Socket::Socket(double timeout, logger::LogSeverity ll) : _logLevel(ll) {
     _fd = INVALID_SOCKET;
     _timeout = timeout;
-    _lastValidityCheckAtSecs = time(0);
+    _lastValidityCheckAtSecs = time(nullptr);
     _init();
 }
 
@@ -214,7 +214,7 @@ void Socket::_init() {
     _bytesIn = 0;
     _awaitingHandshake = true;
 #ifdef MONGO_CONFIG_SSL
-    _sslManager = 0;
+    _sslManager = nullptr;
 #endif
 }
 
@@ -612,7 +612,7 @@ bool Socket::isStillConnected() {
     if (!isPollSupported())
         return true;  // nothing we can do
 
-    time_t now = time(0);
+    time_t now = time(nullptr);
     time_t idleTimeSecs = now - _lastValidityCheckAtSecs;
 
     // Only check once every 5 secs
diff --git a/src/mongo/util/net/sock.h b/src/mongo/util/net/sock.h
index 561cd1cd9e4..a9edfc71de6 100644
--- a/src/mongo/util/net/sock.h
+++ b/src/mongo/util/net/sock.h
@@ -196,7 +196,7 @@ public:
      *
      * This function may throw SocketException.
      */
-    SSLPeerInfo doSSLHandshake(const char* firstBytes = NULL, int len = 0);
+    SSLPeerInfo doSSLHandshake(const char* firstBytes = nullptr, int len = 0);
 
     /**
      * @return the time when the socket was opened.
diff --git a/src/mongo/util/net/sock_test.cpp b/src/mongo/util/net/sock_test.cpp
index 14cc5721e29..bb246175eef 100644
--- a/src/mongo/util/net/sock_test.cpp
+++ b/src/mongo/util/net/sock_test.cpp
@@ -210,7 +210,7 @@ public:
     SocketFailPointTest()
         : _failPoint(getGlobalFailPointRegistry()->getFailPoint(kSocketFailPointName)),
           _sockets(socketPair(SOCK_STREAM)) {
-        ASSERT_TRUE(_failPoint != NULL);
+        ASSERT_TRUE(_failPoint != nullptr);
         ASSERT_TRUE(_sockets.first);
         ASSERT_TRUE(_sockets.second);
     }
diff --git a/src/mongo/util/net/sockaddr.cpp b/src/mongo/util/net/sockaddr.cpp
index be88e9c206e..9efa10ca409 100644
--- a/src/mongo/util/net/sockaddr.cpp
+++ b/src/mongo/util/net/sockaddr.cpp
@@ -280,7 +280,7 @@ std::string SockAddr::getAddr() const {
         case AF_INET6: {
             const int buflen = 128;
             char buffer[buflen];
-            int ret = getnameinfo(raw(), addressSize, buffer, buflen, NULL, 0, NI_NUMERICHOST);
+            int ret = getnameinfo(raw(), addressSize, buffer, buflen, nullptr, 0, NI_NUMERICHOST);
             massert(
                 13082, str::stream() << "getnameinfo error " << getAddrInfoStrError(ret), ret == 0);
             return buffer;
diff --git a/src/mongo/util/net/ssl/detail/impl/engine_openssl.ipp b/src/mongo/util/net/ssl/detail/impl/engine_openssl.ipp
index d143a358253..fc0ff1128b7 100644
--- a/src/mongo/util/net/ssl/detail/impl/engine_openssl.ipp
+++ b/src/mongo/util/net/ssl/detail/impl/engine_openssl.ipp
@@ -42,14 +42,14 @@ engine::engine(SSL_CTX* context, const std::string& remoteHostName)
     ::SSL_set_mode(ssl_, SSL_MODE_ENABLE_PARTIAL_WRITE);
     ::SSL_set_mode(ssl_, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
-    ::BIO* int_bio = 0;
+    ::BIO* int_bio = nullptr;
     ::BIO_new_bio_pair(&int_bio, 0, &ext_bio_, 0);
     ::SSL_set_bio(ssl_, int_bio, int_bio);
 }
 
 engine::~engine() {
     if (SSL_get_app_data(ssl_)) {
-        SSL_set_app_data(ssl_, 0);
+        SSL_set_app_data(ssl_, nullptr);
     }
 
     ::BIO_free(ext_bio_);
@@ -63,14 +63,14 @@ SSL* engine::native_handle() {
 engine::want engine::handshake(stream_base::handshake_type type, asio::error_code& ec) {
     return perform((type == asio::ssl::stream_base::client) ? &engine::do_connect
                                                             : &engine::do_accept,
-                   0,
+                   nullptr,
                    0,
                    ec,
-                   0);
+                   nullptr);
 }
 
 engine::want engine::shutdown(asio::error_code& ec) {
-    return perform(&engine::do_shutdown, 0, 0, ec, 0);
+    return perform(&engine::do_shutdown, nullptr, 0, ec, nullptr);
 }
 
 engine::want engine::write(const asio::const_buffer& data,
diff --git a/src/mongo/util/net/ssl/impl/context_openssl.ipp b/src/mongo/util/net/ssl/impl/context_openssl.ipp
index b0b48910b4a..ef3ba9cb992 100644
--- a/src/mongo/util/net/ssl/impl/context_openssl.ipp
+++ b/src/mongo/util/net/ssl/impl/context_openssl.ipp
@@ -29,7 +29,7 @@
 namespace asio {
 namespace ssl {
 
-context::context(context::method m) : handle_(0) {
+context::context(context::method m) : handle_(nullptr) {
     ::ERR_clear_error();
 
     switch (m) {
@@ -257,11 +257,11 @@ context::context(context::method m) : handle_(0) {
 #endif  // (OPENSSL_VERSION_NUMBER >= 0x10100000L)
 
         default:
-            handle_ = ::SSL_CTX_new(0);
+            handle_ = ::SSL_CTX_new(nullptr);
             break;
     }
 
-    if (handle_ == 0) {
+    if (handle_ == nullptr) {
         asio::error_code ec(static_cast<int>(::ERR_get_error()), asio::error::get_ssl_category());
         asio::detail::throw_error(ec, "context");
     }
@@ -270,13 +270,13 @@ context::context(context::method m) : handle_(0) {
 #if defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
 context::context(context&& other) {
     handle_ = other.handle_;
-    other.handle_ = 0;
+    other.handle_ = nullptr;
 }
 
 context& context::operator=(context&& other) {
     context tmp(ASIO_MOVE_CAST(context)(*this));
     handle_ = other.handle_;
-    other.handle_ = 0;
+    other.handle_ = nullptr;
     return *this;
 }
 #endif  // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
@@ -284,7 +284,7 @@ context& context::operator=(context&& other) {
 context::~context() {
     if (handle_) {
         if (SSL_CTX_get_app_data(handle_)) {
-            SSL_CTX_set_app_data(handle_, 0);
+            SSL_CTX_set_app_data(handle_, nullptr);
         }
 
         ::SSL_CTX_free(handle_);
diff --git a/src/mongo/util/net/ssl_manager_openssl.cpp b/src/mongo/util/net/ssl_manager_openssl.cpp
index 59695f00504..3c178b9f0b2 100644
--- a/src/mongo/util/net/ssl_manager_openssl.cpp
+++ b/src/mongo/util/net/ssl_manager_openssl.cpp
@@ -738,7 +738,7 @@ SSLConnectionOpenSSL::SSLConnectionOpenSSL(SSL_CTX* context,
     ssl = SSL_new(context);
 
     std::string sslErr =
-        NULL != getSSLManager() ? getSSLManager()->getSSLErrorMessage(ERR_get_error()) : "";
+        nullptr != getSSLManager() ? getSSLManager()->getSSLErrorMessage(ERR_get_error()) : "";
     massert(15861, "Error creating new SSL object " + sslErr, ssl);
 
     BIO_new_bio_pair(&internalBIO, BUFFER_SIZE, &networkBIO, BUFFER_SIZE);
@@ -794,7 +794,7 @@ SSLManagerOpenSSL::SSLManagerOpenSSL(const SSLParams& params, bool isServer)
 
     if (!clientPEM.empty()) {
         if (!_parseAndValidateCertificate(
-                clientPEM, clientPassword, &_sslConfiguration.clientSubjectName, NULL)) {
+                clientPEM, clientPassword, &_sslConfiguration.clientSubjectName, nullptr)) {
             uasserted(16941, "ssl initialization problem");
         }
     }
@@ -1069,7 +1069,7 @@ bool SSLManagerOpenSSL::_parseAndValidateCertificate(const std::string& keyFile,
                                                      SSLX509Name* subjectName,
                                                      Date_t* serverCertificateExpirationDate) {
     BIO* inBIO = BIO_new(BIO_s_file());
-    if (inBIO == NULL) {
+    if (inBIO == nullptr) {
         error() << "failed to allocate BIO object: " << getSSLErrorMessage(ERR_get_error());
         return false;
     }
@@ -1082,8 +1082,8 @@ bool SSLManagerOpenSSL::_parseAndValidateCertificate(const std::string& keyFile,
     }
 
     X509* x509 = PEM_read_bio_X509(
-        inBIO, NULL, &SSLManagerOpenSSL::password_cb, static_cast<void*>(&keyPassword));
-    if (x509 == NULL) {
+        inBIO, nullptr, &SSLManagerOpenSSL::password_cb, static_cast<void*>(&keyPassword));
+    if (x509 == nullptr) {
         error() << "cannot retrieve certificate from keyfile: " << keyFile << ' '
                 << getSSLErrorMessage(ERR_get_error());
         return false;
@@ -1091,7 +1091,7 @@ bool SSLManagerOpenSSL::_parseAndValidateCertificate(const std::string& keyFile,
     ON_BLOCK_EXIT([&] { X509_free(x509); });
 
     *subjectName = getCertificateSubjectX509Name(x509);
-    if (serverCertificateExpirationDate != NULL) {
+    if (serverCertificateExpirationDate != nullptr) {
         unsigned long long notBeforeMillis = _convertASN1ToMillis(X509_get_notBefore(x509));
         if (notBeforeMillis == 0) {
             error() << "date conversion failed";
@@ -1166,7 +1166,7 @@ bool SSLManagerOpenSSL::_setupPEM(SSL_CTX* context,
 Status SSLManagerOpenSSL::_setupCA(SSL_CTX* context, const std::string& caFile) {
     // Set the list of CAs sent to clients
     STACK_OF(X509_NAME)* certNames = SSL_load_client_CA_file(caFile.c_str());
-    if (certNames == NULL) {
+    if (certNames == nullptr) {
         return Status(ErrorCodes::InvalidSSLConfiguration,
                       str::stream() << "cannot read certificate authority file: " << caFile << " "
                                     << getSSLErrorMessage(ERR_get_error()));
@@ -1174,7 +1174,7 @@ Status SSLManagerOpenSSL::_setupCA(SSL_CTX* context, const std::string& caFile)
     SSL_CTX_set_client_CA_list(context, certNames);
 
     // Load trusted CA
-    if (SSL_CTX_load_verify_locations(context, caFile.c_str(), NULL) != 1) {
+    if (SSL_CTX_load_verify_locations(context, caFile.c_str(), nullptr) != 1) {
         return Status(ErrorCodes::InvalidSSLConfiguration,
                       str::stream() << "cannot read certificate authority file: " << caFile << " "
                                     << getSSLErrorMessage(ERR_get_error()));
@@ -1426,8 +1426,8 @@ bool SSLManagerOpenSSL::_doneWithSSLOp(SSLConnectionOpenSSL* conn, int status) {
 }
 
 SSLConnectionInterface* SSLManagerOpenSSL::connect(Socket* socket) {
-    std::unique_ptr<SSLConnectionOpenSSL> sslConn =
-        std::make_unique<SSLConnectionOpenSSL>(_clientContext.get(), socket, (const char*)NULL, 0);
+    std::unique_ptr<SSLConnectionOpenSSL> sslConn = std::make_unique<SSLConnectionOpenSSL>(
+        _clientContext.get(), socket, (const char*)nullptr, 0);
 
     const auto undotted = removeFQDNRoot(socket->remoteAddr().hostOrIp());
     int ret = ::SSL_set_tlsext_host_name(sslConn->ssl, undotted.c_str());
@@ -1497,7 +1497,7 @@ StatusWith<SSLPeerInfo> SSLManagerOpenSSL::parseAndValidatePeerCertificate(
 
     X509* peerCert = SSL_get_peer_certificate(conn);
 
-    if (NULL == peerCert) {  // no certificate presented by peer
+    if (nullptr == peerCert) {  // no certificate presented by peer
         if (_weakValidation) {
             // do not give warning if certificate warnings are  suppressed
             if (!_suppressNoCertificateWarning) {
@@ -1561,9 +1561,9 @@ StatusWith<SSLPeerInfo> SSLManagerOpenSSL::parseAndValidatePeerCertificate(
     StringBuilder certificateNames;
 
     STACK_OF(GENERAL_NAME)* sanNames = static_cast<STACK_OF(GENERAL_NAME)*>(
-        X509_get_ext_d2i(peerCert, NID_subject_alt_name, NULL, NULL));
+        X509_get_ext_d2i(peerCert, NID_subject_alt_name, nullptr, nullptr));
 
-    if (sanNames != NULL) {
+    if (sanNames != nullptr) {
         int sanNamesList = sk_GENERAL_NAME_num(sanNames);
         certificateNames << "SAN(s): ";
         for (int i = 0; i < sanNamesList; i++) {
diff --git a/src/mongo/util/processinfo_linux.cpp b/src/mongo/util/processinfo_linux.cpp
index c9bd249d478..32e98f7fc1d 100644
--- a/src/mongo/util/processinfo_linux.cpp
+++ b/src/mongo/util/processinfo_linux.cpp
@@ -255,8 +255,8 @@ public:
         char fstr[1024] = {0};
 
         f = fopen(fname, "r");
-        if (f != NULL) {
-            if (fgets(fstr, 1023, f) != NULL)
+        if (f != nullptr) {
+            if (fgets(fstr, 1023, f) != nullptr)
                 fstr[strlen(fstr) < 1 ? 0 : strlen(fstr) - 1] = '\0';
             fclose(f);
         }
@@ -272,10 +272,10 @@ public:
         procCount = 0;
 
         f = fopen("/proc/cpuinfo", "r");
-        if (f == NULL)
+        if (f == nullptr)
             return;
 
-        while (fgets(fstr, 1023, f) != NULL && !feof(f)) {
+        while (fgets(fstr, 1023, f) != nullptr && !feof(f)) {
             // until the end of the file
             fstr[strlen(fstr) < 1 ? 0 : strlen(fstr) - 1] = '\0';
             if (strncmp(fstr, "processor ", 10) == 0 || strncmp(fstr, "processor\t:", 11) == 0)
diff --git a/src/mongo/util/progress_meter.cpp b/src/mongo/util/progress_meter.cpp
index 9ad977581ec..6287cbd7552 100644
--- a/src/mongo/util/progress_meter.cpp
+++ b/src/mongo/util/progress_meter.cpp
@@ -45,7 +45,7 @@ void ProgressMeter::reset(unsigned long long total, int secondsBetween, int chec
 
     _done = 0;
     _hits = 0;
-    _lastTime = (int)time(0);
+    _lastTime = (int)time(nullptr);
 
     _active = true;
 }
@@ -62,7 +62,7 @@ bool ProgressMeter::hit(int n) {
     if (_hits % _checkInterval)
         return false;
 
-    int t = (int)time(0);
+    int t = (int)time(nullptr);
     if (t - _lastTime < _secondsBetween)
         return false;
 
diff --git a/src/mongo/util/shared_buffer.h b/src/mongo/util/shared_buffer.h
index 00000d0a3d5..c026f92f848 100644
--- a/src/mongo/util/shared_buffer.h
+++ b/src/mongo/util/shared_buffer.h
@@ -95,7 +95,7 @@ public:
     }
 
     char* get() const {
-        return _holder ? _holder->data() : NULL;
+        return _holder ? _holder->data() : nullptr;
     }
 
     explicit operator bool() const {
diff --git a/src/mongo/util/signal_handlers.cpp b/src/mongo/util/signal_handlers.cpp
index 707a76f3233..f6f81234c11 100644
--- a/src/mongo/util/signal_handlers.cpp
+++ b/src/mongo/util/signal_handlers.cpp
@@ -180,7 +180,7 @@ void signalProcessingThread(LogFileStatus rotate) {
         switch (actualSignal) {
             case SIGUSR1:
                 // log rotate signal
-                signalTimeSeconds = time(0);
+                signalTimeSeconds = time(nullptr);
                 if (signalTimeSeconds <= lastSignalTimeSeconds) {
                     // ignore multiple signals in the same or earlier second.
                     break;
@@ -227,7 +227,7 @@ void startSignalProcessingThread(LogFileStatus rotate) {
     stdx::thread(eventProcessingThread).detach();
 #else
     // Mask signals in the current (only) thread. All new threads will inherit this mask.
-    invariant(pthread_sigmask(SIG_SETMASK, &asyncSignals, 0) == 0);
+    invariant(pthread_sigmask(SIG_SETMASK, &asyncSignals, nullptr) == 0);
     // Spawn a thread to capture the signals we just masked off.
     stdx::thread(signalProcessingThread, rotate).detach();
 #endif
diff --git a/src/mongo/util/stacktrace_posix.cpp b/src/mongo/util/stacktrace_posix.cpp
index 9eaed27e06c..996cdb52b16 100644
--- a/src/mongo/util/stacktrace_posix.cpp
+++ b/src/mongo/util/stacktrace_posix.cpp
@@ -61,7 +61,7 @@ const int maxBackTraceFrames = 100;
 
 /// Optional string containing extra unwinding information.  Should take the form of a
 /// JSON document.
-std::string* soMapJson = NULL;
+std::string* soMapJson = nullptr;
 
 /**
  * Returns the "basename" of a path.  The returned StringData is valid until the data referenced
@@ -188,9 +188,9 @@ void printStackTrace(std::ostream& os) {
         Dl_info& dlinfo(dlinfoForFrames[i]);
         if (!dladdr(addresses[i], &dlinfo)) {
             dlinfo.dli_fname = unknownFileName;
-            dlinfo.dli_fbase = NULL;
-            dlinfo.dli_sname = NULL;
-            dlinfo.dli_saddr = NULL;
+            dlinfo.dli_fbase = nullptr;
+            dlinfo.dli_sname = nullptr;
+            dlinfo.dli_saddr = nullptr;
         }
         os << ' ' << addresses[i];
     }
diff --git a/src/mongo/util/str.h b/src/mongo/util/str.h
index b2ee26dbbdb..f36aa3b0f6d 100644
--- a/src/mongo/util/str.h
+++ b/src/mongo/util/str.h
@@ -128,7 +128,7 @@ inline bool endsWith(const char* p, const char* suffix) {
 /** find char x, and return rest of the string thereafter, or an empty string if not found */
 inline const char* after(const char* s, char x) {
     const char* p = strchr(s, x);
-    return (p != 0) ? p + 1 : "";
+    return (p != nullptr) ? p + 1 : "";
 }
 inline mongo::StringData after(mongo::StringData s, char x) {
     auto pos = s.find(x);
@@ -138,7 +138,7 @@ inline mongo::StringData after(mongo::StringData s, char x) {
 /** find string x, and return rest of the string thereafter, or an empty string if not found */
 inline const char* after(const char* s, const char* x) {
     const char* p = strstr(s, x);
-    return (p != 0) ? p + strlen(x) : "";
+    return (p != nullptr) ? p + strlen(x) : "";
 }
 inline mongo::StringData after(mongo::StringData s, mongo::StringData x) {
     auto pos = s.find(x);
diff --git a/src/mongo/util/text_test.cpp b/src/mongo/util/text_test.cpp
index cee43fd57cc..77d6561e795 100644
--- a/src/mongo/util/text_test.cpp
+++ b/src/mongo/util/text_test.cpp
@@ -43,7 +43,7 @@ static std::vector<std::string> svec(const char* first, ...) {
         va_list ap;
         va_start(ap, first);
         const char* curr;
-        while (NULL != (curr = va_arg(ap, const char*))) {
+        while (nullptr != (curr = va_arg(ap, const char*))) {
             result.push_back(curr);
         }
         va_end(ap);
@@ -52,7 +52,7 @@ static std::vector<std::string> svec(const char* first, ...) {
 }
 
 TEST(WindowsCommandLineConstruction, EmptyCommandLine) {
-    ASSERT_EQUALS("", constructUtf8WindowsCommandLine(svec(NULL)));
+    ASSERT_EQUALS("", constructUtf8WindowsCommandLine(svec(nullptr)));
 }
 
 TEST(WindowsCommandLineConstruction, NothingToQuote) {
diff --git a/src/mongo/util/time_support.cpp b/src/mongo/util/time_support.cpp
index f3c1fee7a33..b40ebcb19ee 100644
--- a/src/mongo/util/time_support.cpp
+++ b/src/mongo/util/time_support.cpp
@@ -143,7 +143,7 @@ std::string time_t_to_String_short(time_t t) {
 // colonsOk should be false when creating filenames
 string terseCurrentTime(bool colonsOk) {
     struct tm t;
-    time_t_to_Struct(time(0), &t);
+    time_t_to_Struct(time(nullptr), &t);
 
     const char* fmt = (colonsOk ? "%Y-%m-%dT%H:%M:%S" : "%Y-%m-%dT%H-%M-%S");
     char buf[32];
@@ -921,13 +921,13 @@ unsigned long long curTimeMicros64() {
 #include <sys/time.h>
 unsigned long long curTimeMillis64() {
     timeval tv;
-    gettimeofday(&tv, NULL);
+    gettimeofday(&tv, nullptr);
     return ((unsigned long long)tv.tv_sec) * 1000 + tv.tv_usec / 1000;
 }
 
 unsigned long long curTimeMicros64() {
     timeval tv;
-    gettimeofday(&tv, NULL);
+    gettimeofday(&tv, nullptr);
     return (((unsigned long long)tv.tv_sec) * 1000 * 1000) + tv.tv_usec;
 }
 #endif
diff --git a/src/mongo/util/unowned_ptr_test.cpp b/src/mongo/util/unowned_ptr_test.cpp
index ac1bf86067f..4a6ec0b1d34 100644
--- a/src/mongo/util/unowned_ptr_test.cpp
+++ b/src/mongo/util/unowned_ptr_test.cpp
@@ -46,7 +46,7 @@ TEST(UnownedPtr, Construction) {
     ASSERT_EQUALS(aNullPtr, unowned_ptr<int>());
     ASSERT_EQUALS(aNullPtr, unowned_ptr<int>({}));
     ASSERT_EQUALS(aNullPtr, unowned_ptr<int>(nullptr));
-    ASSERT_EQUALS(aNullPtr, unowned_ptr<int>(NULL));
+    ASSERT_EQUALS(aNullPtr, unowned_ptr<int>(nullptr));
     ASSERT_EQUALS(p1.get(), unowned_ptr<int>(p1.get()));
     ASSERT_EQUALS(p1.get(), unowned_ptr<int>(p1));
     ASSERT_EQUALS(p2.get(), unowned_ptr<int>(p2));
@@ -59,7 +59,7 @@ TEST(UnownedPtr, Construction) {
     ASSERT_EQUALS(aNullPtr, unowned_ptr<const int>());
     ASSERT_EQUALS(aNullPtr, unowned_ptr<const int>({}));
     ASSERT_EQUALS(aNullPtr, unowned_ptr<const int>(nullptr));
-    ASSERT_EQUALS(aNullPtr, unowned_ptr<const int>(NULL));
+    ASSERT_EQUALS(aNullPtr, unowned_ptr<const int>(nullptr));
     ASSERT_EQUALS(p1.get(), unowned_ptr<const int>(p1.get()));
     ASSERT_EQUALS(cp1.get(), unowned_ptr<const int>(cp1.get()));
     ASSERT_EQUALS(p1.get(), unowned_ptr<const int>(p1));
@@ -86,7 +86,7 @@ TEST(UnownedPtr, Assignment) {
 
     ASSERT_EQUALS(aNullPtr, (unowned_ptr<int>() = {}));
     ASSERT_EQUALS(aNullPtr, (unowned_ptr<int>() = nullptr));
-    ASSERT_EQUALS(aNullPtr, (unowned_ptr<int>() = NULL));
+    ASSERT_EQUALS(aNullPtr, (unowned_ptr<int>() = nullptr));
     ASSERT_EQUALS(p1.get(), (unowned_ptr<int>() = p1.get()));
     ASSERT_EQUALS(p1.get(), (unowned_ptr<int>() = p1));
     ASSERT_EQUALS(p2.get(), (unowned_ptr<int>() = p2));
@@ -98,7 +98,7 @@ TEST(UnownedPtr, Assignment) {
 
     ASSERT_EQUALS(aNullPtr, (unowned_ptr<const int>() = {}));
     ASSERT_EQUALS(aNullPtr, (unowned_ptr<const int>() = nullptr));
-    ASSERT_EQUALS(aNullPtr, (unowned_ptr<const int>() = NULL));
+    ASSERT_EQUALS(aNullPtr, (unowned_ptr<const int>() = nullptr));
     ASSERT_EQUALS(p1.get(), (unowned_ptr<const int>() = p1.get()));
     ASSERT_EQUALS(cp1.get(), (unowned_ptr<const int>() = cp1.get()));
     ASSERT_EQUALS(p1.get(), (unowned_ptr<const int>() = p1));