Fix Clang/GCC compilation warnings.

This makes it easier to adopt snappy in other projects.

PiperOrigin-RevId: 309958249

6 files changed, 141 insertions, 53 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0dde8f3..7d9f542 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,6 +37,49 @@ if(NOT CMAKE_CXX_STANDARD)
   set(CMAKE_CXX_EXTENSIONS OFF)
 endif(NOT CMAKE_CXX_STANDARD)
 
+# https://github.com/izenecloud/cmake/blob/master/SetCompilerWarningAll.cmake
+if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  # Use the highest warning level for Visual Studio.
+  set(CMAKE_CXX_WARNING_LEVEL 4)
+  if(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
+    string(REGEX REPLACE "/W[0-4]" "/W4" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  else(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4")
+  endif(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
+
+  # Disable C++ exceptions.
+  string(REGEX REPLACE "/EH[a-z]+" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHs-c-")
+  add_definitions(-D_HAS_EXCEPTIONS=0)
+
+  # Disable RTTI.
+  string(REGEX REPLACE "/GR" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /GR-")
+else(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  # Use -Wall for clang and gcc.
+  if(NOT CMAKE_CXX_FLAGS MATCHES "-Wall")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
+  endif(NOT CMAKE_CXX_FLAGS MATCHES "-Wall")
+
+  # Use -Wextra for clang and gcc.
+  if(NOT CMAKE_CXX_FLAGS MATCHES "-Wextra")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wextra")
+  endif(NOT CMAKE_CXX_FLAGS MATCHES "-Wextra")
+
+  # Use -Werror for clang and gcc.
+  if(NOT CMAKE_CXX_FLAGS MATCHES "-Werror")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
+  endif(NOT CMAKE_CXX_FLAGS MATCHES "-Werror")
+
+  # Disable C++ exceptions.
+  string(REGEX REPLACE "-fexceptions" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-exceptions")
+
+  # Disable RTTI.
+  string(REGEX REPLACE "-frtti" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
+endif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+
 # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to make
 # it prominent in the GUI.
 option(BUILD_SHARED_LIBS "Build shared libraries(DLLs)." OFF)
diff --git a/snappy-sinksource.cc b/snappy-sinksource.cc
index 605a2cb..8214964 100644
--- a/snappy-sinksource.cc
+++ b/snappy-sinksource.cc
@@ -33,17 +33,24 @@
 
 namespace snappy {
 
-Source::~Source() { }
+Source::~Source() = default;
 
-Sink::~Sink() { }
+Sink::~Sink() = default;
 
 char* Sink::GetAppendBuffer(size_t length, char* scratch) {
+  // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+  (void)length;
+
   return scratch;
 }
 
 char* Sink::GetAppendBufferVariable(
       size_t min_size, size_t desired_size_hint, char* scratch,
       size_t scratch_size, size_t* allocated_size) {
+  // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+  (void)min_size;
+  (void)desired_size_hint;
+
   *allocated_size = scratch_size;
   return scratch;
 }
@@ -56,7 +63,7 @@ void Sink::AppendAndTakeOwnership(
   (*deleter)(deleter_arg, bytes, n);
 }
 
-ByteArraySource::~ByteArraySource() { }
+ByteArraySource::~ByteArraySource() = default;
 
 size_t ByteArraySource::Available() const { return left_; }
 
@@ -81,16 +88,20 @@ void UncheckedByteArraySink::Append(const char* data, size_t n) {
 }
 
 char* UncheckedByteArraySink::GetAppendBuffer(size_t len, char* scratch) {
+  // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+  (void)len;
+  (void)scratch;
+
   return dest_;
 }
 
 void UncheckedByteArraySink::AppendAndTakeOwnership(
-    char* data, size_t n,
+    char* bytes, size_t n,
     void (*deleter)(void*, const char*, size_t),
     void *deleter_arg) {
-  if (data != dest_) {
-    std::memcpy(dest_, data, n);
-    (*deleter)(deleter_arg, data, n);
+  if (bytes != dest_) {
+    std::memcpy(dest_, bytes, n);
+    (*deleter)(deleter_arg, bytes, n);
   }
   dest_ += n;
 }
@@ -98,6 +109,11 @@ void UncheckedByteArraySink::AppendAndTakeOwnership(
 char* UncheckedByteArraySink::GetAppendBufferVariable(
       size_t min_size, size_t desired_size_hint, char* scratch,
       size_t scratch_size, size_t* allocated_size) {
+  // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+  (void)min_size;
+  (void)scratch;
+  (void)scratch_size;
+
   *allocated_size = desired_size_hint;
   return dest_;
 }
diff --git a/snappy-stubs-internal.h b/snappy-stubs-internal.h
index 0e62e73..7a44848 100644
--- a/snappy-stubs-internal.h
+++ b/snappy-stubs-internal.h
@@ -95,7 +95,7 @@
 #ifdef ARRAYSIZE
 #undef ARRAYSIZE
 #endif
-#define ARRAYSIZE(a) (sizeof(a) / sizeof(*(a)))
+#define ARRAYSIZE(a) int{sizeof(a) / sizeof(*(a))}
 
 // Static prediction hints.
 #ifdef HAVE_BUILTIN_EXPECT
@@ -439,28 +439,28 @@ inline const char* Varint::Parse32WithLimit(const char* p,
 
 inline char* Varint::Encode32(char* sptr, uint32_t v) {
   // Operate on characters as unsigneds
-  unsigned char* ptr = reinterpret_cast<unsigned char*>(sptr);
-  static const int B = 128;
-  if (v < (1<<7)) {
-    *(ptr++) = v;
-  } else if (v < (1<<14)) {
-    *(ptr++) = v | B;
-    *(ptr++) = v>>7;
-  } else if (v < (1<<21)) {
-    *(ptr++) = v | B;
-    *(ptr++) = (v>>7) | B;
-    *(ptr++) = v>>14;
-  } else if (v < (1<<28)) {
-    *(ptr++) = v | B;
-    *(ptr++) = (v>>7) | B;
-    *(ptr++) = (v>>14) | B;
-    *(ptr++) = v>>21;
+  uint8_t* ptr = reinterpret_cast<uint8_t*>(sptr);
+  static const uint8_t B = 128;
+  if (v < (1 << 7)) {
+    *(ptr++) = static_cast<uint8_t>(v);
+  } else if (v < (1 << 14)) {
+    *(ptr++) = static_cast<uint8_t>(v | B);
+    *(ptr++) = static_cast<uint8_t>(v >> 7);
+  } else if (v < (1 << 21)) {
+    *(ptr++) = static_cast<uint8_t>(v | B);
+    *(ptr++) = static_cast<uint8_t>((v >> 7) | B);
+    *(ptr++) = static_cast<uint8_t>(v >> 14);
+  } else if (v < (1 << 28)) {
+    *(ptr++) = static_cast<uint8_t>(v | B);
+    *(ptr++) = static_cast<uint8_t>((v >> 7) | B);
+    *(ptr++) = static_cast<uint8_t>((v >> 14) | B);
+    *(ptr++) = static_cast<uint8_t>(v >> 21);
   } else {
-    *(ptr++) = v | B;
-    *(ptr++) = (v>>7) | B;
-    *(ptr++) = (v>>14) | B;
-    *(ptr++) = (v>>21) | B;
-    *(ptr++) = v>>28;
+    *(ptr++) = static_cast<uint8_t>(v | B);
+    *(ptr++) = static_cast<uint8_t>((v>>7) | B);
+    *(ptr++) = static_cast<uint8_t>((v>>14) | B);
+    *(ptr++) = static_cast<uint8_t>((v>>21) | B);
+    *(ptr++) = static_cast<uint8_t>(v >> 28);
   }
   return reinterpret_cast<char*>(ptr);
 }
diff --git a/snappy-test.h b/snappy-test.h
index c9a777d..b5a53b5 100644
--- a/snappy-test.h
+++ b/snappy-test.h
@@ -118,7 +118,7 @@ namespace file {
   };
 
   DummyStatus GetContents(
-      const std::string& filename, std::string* data, int unused) {
+      const std::string& filename, std::string* data, int /*unused*/) {
     FILE* fp = std::fopen(filename.c_str(), "rb");
     if (fp == NULL) {
       std::perror(filename.c_str());
@@ -142,7 +142,7 @@ namespace file {
   }
 
   inline DummyStatus SetContents(
-      const std::string& filename, const std::string& str, int unused) {
+      const std::string& filename, const std::string& str, int /*unused*/) {
     FILE* fp = std::fopen(filename.c_str(), "wb");
     if (fp == NULL) {
       std::perror(filename.c_str());
diff --git a/snappy.cc b/snappy.cc
index e378c2a..90bdd48 100644
--- a/snappy.cc
+++ b/snappy.cc
@@ -96,7 +96,7 @@ static inline uint32_t HashBytes(uint32_t bytes, int shift) {
   return (bytes * kMul) >> shift;
 }
 
-size_t MaxCompressedLength(size_t source_len) {
+size_t MaxCompressedLength(size_t source_bytes) {
   // Compressed data can be defined as:
   //    compressed := item* literal*
   //    item       := literal* copy
@@ -117,7 +117,7 @@ size_t MaxCompressedLength(size_t source_len) {
   // I.e., 6 bytes of input turn into 7 bytes of "compressed" data.
   //
   // This last factor dominates the blowup, so the final estimate is:
-  return 32 + source_len + source_len/6;
+  return 32 + source_bytes + source_bytes / 6;
 }
 
 namespace {
@@ -563,7 +563,7 @@ char* CompressFragment(const char* input,
             // These for-loops are meant to be unrolled. So we can freely
             // special case the first iteration to use the value already
             // loaded in preload.
-            uint32_t dword = i == 0 ? preload : data;
+            uint32_t dword = i == 0 ? preload : static_cast<uint32_t>(data);
             assert(dword == LittleEndian::Load32(ip + i));
             uint32_t hash = HashBytes(dword, shift);
             candidate = base_ip + table[hash];
@@ -680,7 +680,12 @@ char* CompressFragment(const char* input,
 
 // Called back at avery compression call to trace parameters and sizes.
 static inline void Report(const char *algorithm, size_t compressed_size,
-                          size_t uncompressed_size) {}
+                          size_t uncompressed_size) {
+  // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+  (void)algorithm;
+  (void)compressed_size;
+  (void)uncompressed_size;
+}
 
 // Signature of output types needed by decompression code.
 // The decompression code is templatized on a type that obeys this
@@ -1170,7 +1175,10 @@ class SnappyIOVecWriter {
   }
 
   char* GetOutputPtr() { return nullptr; }
-  void SetOutputPtr(char* op) {}
+  void SetOutputPtr(char* op) {
+    // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+    (void)op;
+  }
 
   inline bool AppendNoCheck(const char* ip, size_t len) {
     while (len > 0) {
@@ -1360,10 +1368,13 @@ class SnappyArrayWriter {
   SNAPPY_ATTRIBUTE_ALWAYS_INLINE
   inline bool AppendFromSelf(size_t offset, size_t len, char** op_p) {
     char* const op = *op_p;
+    assert(op >= base_);
     char* const op_end = op + len;
 
     // Check if we try to append from before the start of the buffer.
-    if (SNAPPY_PREDICT_FALSE(op - base_ < offset)) return false;
+    if (SNAPPY_PREDICT_FALSE(static_cast<size_t>(op - base_) < offset))
+      return false;
+
     if (SNAPPY_PREDICT_FALSE((kSlopBytes < 64 && len > kSlopBytes) ||
                             op >= op_limit_min_slop_ || offset < len)) {
       if (op_end > op_limit_ || offset == 0) return false;
@@ -1381,8 +1392,9 @@ class SnappyArrayWriter {
   inline void Flush() {}
 };
 
-bool RawUncompress(const char* compressed, size_t n, char* uncompressed) {
-  ByteArraySource reader(compressed, n);
+bool RawUncompress(const char* compressed, size_t compressed_length,
+                   char* uncompressed) {
+  ByteArraySource reader(compressed, compressed_length);
   return RawUncompress(&reader, uncompressed);
 }
 
@@ -1391,9 +1403,10 @@ bool RawUncompress(Source* compressed, char* uncompressed) {
   return InternalUncompress(compressed, &output);
 }
 
-bool Uncompress(const char* compressed, size_t n, std::string* uncompressed) {
+bool Uncompress(const char* compressed, size_t compressed_length,
+                std::string* uncompressed) {
   size_t ulength;
-  if (!GetUncompressedLength(compressed, n, &ulength)) {
+  if (!GetUncompressedLength(compressed, compressed_length, &ulength)) {
     return false;
   }
   // On 32-bit builds: max_size() < kuint32max.  Check for that instead
@@ -1402,7 +1415,8 @@ bool Uncompress(const char* compressed, size_t n, std::string* uncompressed) {
     return false;
   }
   STLStringResizeUninitialized(uncompressed, ulength);
-  return RawUncompress(compressed, n, string_as_array(uncompressed));
+  return RawUncompress(compressed, compressed_length,
+                       string_as_array(uncompressed));
 }
 
 // A Writer that drops everything on the floor and just does validation
@@ -1422,11 +1436,20 @@ class SnappyDecompressionValidator {
     return expected_ == produced_;
   }
   inline bool Append(const char* ip, size_t len, size_t* produced) {
+    // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+    (void)ip;
+
     *produced += len;
     return *produced <= expected_;
   }
   inline bool TryFastAppend(const char* ip, size_t available, size_t length,
                             size_t* produced) {
+    // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+    (void)ip;
+    (void)available;
+    (void)length;
+    (void)produced;
+
     return false;
   }
   inline bool AppendFromSelf(size_t offset, size_t len, size_t* produced) {
@@ -1439,8 +1462,8 @@ class SnappyDecompressionValidator {
   inline void Flush() {}
 };
 
-bool IsValidCompressedBuffer(const char* compressed, size_t n) {
-  ByteArraySource reader(compressed, n);
+bool IsValidCompressedBuffer(const char* compressed, size_t compressed_length) {
+  ByteArraySource reader(compressed, compressed_length);
   SnappyDecompressionValidator writer;
   return InternalUncompress(&reader, &writer);
 }
@@ -1567,13 +1590,15 @@ class SnappyScatteredWriter {
 
   inline bool AppendFromSelf(size_t offset, size_t len, char** op_p) {
     char* op = *op_p;
+    assert(op >= op_base_);
     // Check if we try to append from before the start of the buffer.
     if (SNAPPY_PREDICT_FALSE((kSlopBytes < 64 && len > kSlopBytes) ||
-                            op - op_base_ < offset ||
-                            op >= op_limit_min_slop_ || offset < len)) {
+                             static_cast<size_t>(op - op_base_) < offset ||
+                             op >= op_limit_min_slop_ || offset < len)) {
       if (offset == 0) return false;
       char* const op_end = op + len;
-      if (SNAPPY_PREDICT_FALSE(op - op_base_ < offset || op_end > op_limit_)) {
+      if (SNAPPY_PREDICT_FALSE(static_cast<size_t>(op - op_base_) < offset ||
+                               op_end > op_limit_)) {
         op_ptr_ = op;
         bool res = SlowAppendFromSelf(offset, len);
         *op_p = op_ptr_;
@@ -1692,6 +1717,10 @@ class SnappySinkAllocator {
   };
 
   static void Deleter(void* arg, const char* bytes, size_t size) {
+    // TODO: Switch to [[maybe_unused]] when we can assume C++17.
+    (void)arg;
+    (void)size;
+
     delete[] bytes;
   }
 
diff --git a/snappy_unittest.cc b/snappy_unittest.cc
index d39be43..d14c56b 100644
--- a/snappy_unittest.cc
+++ b/snappy_unittest.cc
@@ -415,7 +415,7 @@ static void VerifyIOVec(const std::string& input) {
     num = input.size();
   }
   struct iovec* iov = new iovec[num];
-  int used_so_far = 0;
+  size_t used_so_far = 0;
   std::bernoulli_distribution one_in_five(1.0 / 5);
   for (size_t i = 0; i < num; ++i) {
     assert(used_so_far < input.size());
@@ -742,7 +742,7 @@ TEST(Snappy, FourByteOffset) {
   // How many times each fragment is emitted.
   const int n1 = 2;
   const int n2 = 100000 / fragment2.size();
-  const int length = n1 * fragment1.size() + n2 * fragment2.size();
+  const size_t length = n1 * fragment1.size() + n2 * fragment2.size();
 
   std::string compressed;
   Varint::Append32(&compressed, length);
@@ -1078,12 +1078,12 @@ TEST(Snappy, FindMatchLengthRandom) {
     }
     DataEndingAtUnreadablePage u(s);
     DataEndingAtUnreadablePage v(t);
-    int matched = TestFindMatchLength(u.data(), v.data(), t.size());
+    size_t matched = TestFindMatchLength(u.data(), v.data(), t.size());
     if (matched == t.size()) {
       EXPECT_EQ(s, t);
     } else {
       EXPECT_NE(s[matched], t[matched]);
-      for (int j = 0; j < matched; ++j) {
+      for (size_t j = 0; j < matched; ++j) {
         EXPECT_EQ(s[j], t[j]);
       }
     }
@@ -1323,7 +1323,7 @@ static void BM_UIOVec(int iters, int arg) {
   const int kNumEntries = 10;
   struct iovec iov[kNumEntries];
   char *dst = new char[contents.size()];
-  int used_so_far = 0;
+  size_t used_so_far = 0;
   for (int i = 0; i < kNumEntries; ++i) {
     iov[i].iov_base = dst + used_so_far;
     if (used_so_far == contents.size()) {
@@ -1475,7 +1475,7 @@ static void BM_ZFlatIncreasingTableSize(int iters, int arg) {
   SetBenchmarkBytesProcessed(static_cast<int64_t>(iters) * total_contents_size);
   StartBenchmarkTiming();
   while (iters-- > 0) {
-    for (int i = 0; i < contents.size(); ++i) {
+    for (size_t i = 0; i < contents.size(); ++i) {
       snappy::RawCompress(contents[i].data(), contents[i].size(), dst[i],
                           &zsize);
     }