SERVER-39506 destroying delete for RCString

6 files changed, 72 insertions, 115 deletions

diff --git a/src/mongo/db/SConscript b/src/mongo/db/SConscript
index d0debcf9e1f..2d5d9447d8e 100644
--- a/src/mongo/db/SConscript
+++ b/src/mongo/db/SConscript
@@ -1657,7 +1657,6 @@ env.Library(
         '$BUILD_DIR/mongo/crypto/fle_crypto',
         '$BUILD_DIR/mongo/scripting/scripting',
         '$BUILD_DIR/mongo/scripting/scripting_common',
-        '$BUILD_DIR/mongo/util/intrusive_counter',
         '$BUILD_DIR/mongo/util/pcre_util',
         '$BUILD_DIR/mongo/util/pcre_wrapper',
         '$BUILD_DIR/mongo/util/summation',
diff --git a/src/mongo/db/exec/document_value/SConscript b/src/mongo/db/exec/document_value/SConscript
index 9d0947da749..5899cb089fc 100644
--- a/src/mongo/db/exec/document_value/SConscript
+++ b/src/mongo/db/exec/document_value/SConscript
@@ -15,7 +15,6 @@ env.Library(
         '$BUILD_DIR/mongo/base',
         '$BUILD_DIR/mongo/db/pipeline/field_path',
         '$BUILD_DIR/mongo/db/query/datetime/date_time_support',
-        '$BUILD_DIR/mongo/util/intrusive_counter',
     ],
 )
 
diff --git a/src/mongo/db/exec/document_value/value_internal.h b/src/mongo/db/exec/document_value/value_internal.h
index b19af0e728f..8f36c8f800e 100644
--- a/src/mongo/db/exec/document_value/value_internal.h
+++ b/src/mongo/db/exec/document_value/value_internal.h
@@ -30,14 +30,20 @@
 #pragma once
 
 #include <algorithm>
+#include <cstdlib>
+#include <new>
+
 #include <boost/intrusive_ptr.hpp>
 
 #include "mongo/base/static_assert.h"
+#include "mongo/base/string_data.h"
 #include "mongo/bson/bsonmisc.h"
 #include "mongo/bson/bsonobj.h"
 #include "mongo/bson/bsontypes.h"
 #include "mongo/bson/oid.h"
 #include "mongo/bson/timestamp.h"
+#include "mongo/bson/util/builder.h"
+#include "mongo/util/assert_util.h"
 #include "mongo/util/debug_util.h"
 #include "mongo/util/intrusive_counter.h"
 
@@ -47,6 +53,67 @@ class Document;
 class DocumentStorage;
 class Value;
 
+
+/** An immutable reference-counted string of inline data. */
+class RCString final : public RefCountable {
+public:
+    static boost::intrusive_ptr<const RCString> create(StringData s) {
+        using namespace fmt::literals;
+        static constexpr size_t sizeLimit = BSONObjMaxUserSize;
+        uassert(16493,
+                "RCString too large. Requires size={} < limit={}"_format(s.size(), sizeLimit),
+                s.size() < sizeLimit);
+        return boost::intrusive_ptr{new (s) RCString{s}};
+    }
+
+    explicit operator StringData() const noexcept {
+        return StringData{_data(), _size};
+    }
+
+    void* operator new(size_t, StringData s) {
+        return ::operator new(_allocSize(s.size()));
+    }
+
+    /** Used if constructor fails after placement `new (StringData)`. */
+    void operator delete(void* ptr, StringData s) {
+        ::operator delete(ptr, _allocSize(s.size()));
+    }
+
+#if __cpp_lib_destroying_delete >= 201806L
+    void operator delete(RCString* ptr, std::destroying_delete_t) {
+        size_t sz = _allocSize(ptr->_size);
+        ptr->~RCString();
+        ::operator delete(ptr, sz);
+    }
+#else   // !__cpp_lib_destroying_delete
+    /** Invoked by virtual destructor. */
+    void operator delete(void* ptr) {
+        ::operator delete(ptr);
+    }
+#endif  // __cpp_lib_destroying_delete
+
+private:
+    static size_t _allocSize(size_t stringSize) {
+        return sizeof(RCString) + stringSize + 1;  // Incl. '\0'-terminator
+    }
+
+    /** Use static `create()` instead. */
+    explicit RCString(StringData s) : _size{s.size()} {
+        if (_size)
+            memcpy(_data(), s.rawData(), _size);
+        _data()[_size] = '\0';
+    }
+
+    const char* _data() const noexcept {
+        return reinterpret_cast<const char*>(this + 1);
+    }
+    char* _data() noexcept {
+        return const_cast<char*>(std::as_const(*this)._data());
+    }
+
+    size_t _size; /** Excluding '\0' terminator. */
+};
+
 // TODO: a MutableVector, similar to MutableDocument
 /// A heap-allocated reference-counted std::vector
 class RCVector : public RefCountable {
@@ -268,7 +335,7 @@ public:
         } else {
             dassert(typeid(*genericRCPtr) == typeid(const RCString));
             const RCString* stringPtr = static_cast<const RCString*>(genericRCPtr);
-            return StringData(stringPtr->c_str(), stringPtr->size());
+            return StringData{*stringPtr};
         }
     }
 
diff --git a/src/mongo/util/SConscript b/src/mongo/util/SConscript
index 4f92d284478..aff0ed44fef 100644
--- a/src/mongo/util/SConscript
+++ b/src/mongo/util/SConscript
@@ -115,16 +115,6 @@ env.Library(
 )
 
 env.Library(
-    target='intrusive_counter',
-    source=[
-        'intrusive_counter.cpp',
-    ],
-    LIBDEPS=[
-        '$BUILD_DIR/mongo/base',
-    ],
-)
-
-env.Library(
     target='log_and_backoff',
     source=[
         'log_and_backoff.cpp',
diff --git a/src/mongo/util/intrusive_counter.cpp b/src/mongo/util/intrusive_counter.cpp
deleted file mode 100644
index e33cbc87da5..00000000000
--- a/src/mongo/util/intrusive_counter.cpp
+++ /dev/null
@@ -1,60 +0,0 @@
-/**
- *    Copyright (C) 2018-present MongoDB, Inc.
- *
- *    This program is free software: you can redistribute it and/or modify
- *    it under the terms of the Server Side Public License, version 1,
- *    as published by MongoDB, Inc.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    Server Side Public License for more details.
- *
- *    You should have received a copy of the Server Side Public License
- *    along with this program. If not, see
- *    <http://www.mongodb.com/licensing/server-side-public-license>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the Server Side Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#include "mongo/platform/basic.h"
-
-#include "mongo/util/intrusive_counter.h"
-
-#include "mongo/util/str.h"
-
-namespace mongo {
-using boost::intrusive_ptr;
-
-intrusive_ptr<const RCString> RCString::create(StringData s) {
-    uassert(16493,
-            str::stream() << "Tried to create string longer than "
-                          << (BSONObjMaxUserSize / 1024 / 1024) << "MB",
-            s.size() < static_cast<size_t>(BSONObjMaxUserSize));
-
-    const size_t sizeWithNUL = s.size() + 1;
-    const size_t bytesNeeded = sizeof(RCString) + sizeWithNUL;
-
-#pragma warning(push)
-#pragma warning(disable : 4291)
-    intrusive_ptr<RCString> ptr = new (bytesNeeded) RCString();  // uses custom operator new
-#pragma warning(pop)
-
-    ptr->_size = s.size();
-    char* stringStart = reinterpret_cast<char*>(ptr.get()) + sizeof(RCString);
-    s.copyTo(stringStart, true);
-
-    return ptr;
-}
-
-}  // namespace mongo
diff --git a/src/mongo/util/intrusive_counter.h b/src/mongo/util/intrusive_counter.h
index 38d024ddea6..9041f50d937 100644
--- a/src/mongo/util/intrusive_counter.h
+++ b/src/mongo/util/intrusive_counter.h
@@ -29,12 +29,11 @@
 
 #pragma once
 
+#include <atomic>  // NOLINT
 #include <boost/intrusive_ptr.hpp>
 #include <cstdlib>
 
-#include "mongo/base/string_data.h"
-#include "mongo/platform/atomic_word.h"
-#include "mongo/util/allocator.h"
+#include "mongo/util/assert_util_core.h"
 
 namespace mongo {
 
@@ -67,13 +66,13 @@ public:
         // See this for a description of why relaxed is OK here. It is also used in libc++.
         // http://www.boost.org/doc/libs/1_66_0/doc/html/atomic/usage_examples.html#boost_atomic.usage_examples.example_reference_counters.discussion
         ptr->_count.fetch_add(1, std::memory_order_relaxed);
-    };
+    }
 
     friend void intrusive_ptr_release(const RefCountable* ptr) {
         if (ptr->_count.fetch_sub(1, std::memory_order_acq_rel) == 1) {
             delete ptr;
         }
-    };
+    }
 
 protected:
     /**
@@ -101,41 +100,4 @@ boost::intrusive_ptr<T> make_intrusive(Args&&... args) {
     ptr->threadUnsafeIncRefCountTo(1);
     return boost::intrusive_ptr<T>(ptr, /*add ref*/ false);
 }
-
-/// This is an immutable reference-counted string
-class RCString : public RefCountable {
-public:
-    const char* c_str() const {
-        return reinterpret_cast<const char*>(this) + sizeof(RCString);
-    }
-    int size() const {
-        return _size;
-    }
-    StringData stringData() const {
-        return StringData(c_str(), _size);
-    }
-
-    static boost::intrusive_ptr<const RCString> create(StringData s);
-
-// MSVC: C4291: 'declaration' : no matching operator delete found; memory will not be freed if
-// initialization throws an exception
-// We simply rely on the default global placement delete since a local placement delete would be
-// ambiguous for some compilers
-#pragma warning(push)
-#pragma warning(disable : 4291)
-    void operator delete(void* ptr) {
-        free(ptr);
-    }
-#pragma warning(pop)
-
-private:
-    // these can only be created by calling create()
-    RCString(){};
-    void* operator new(size_t objSize, size_t realSize) {
-        return mongoMalloc(realSize);
-    }
-
-    int _size;  // does NOT include trailing NUL byte.
-    // char[_size+1] array allocated past end of class
-};
 }  // namespace mongo