Fix Cygwin build.

src/google/protobuf/compiler/command_line_interface_unittest.cc

@@ -146,6 +146,8 @@ class CommandLineInterfaceTest : public testing::Test {
                                      const string& proto_name,
                                      const string& message_name);
 
+  void ExpectNullCodeGeneratorCalled(const string& parameter);
+
   void ReadDescriptorSet(const string& filename,
                          FileDescriptorSet* descriptor_set);
 
@@ -170,6 +172,8 @@ class CommandLineInterfaceTest : public testing::Test {
 
   // Pointers which need to be deleted later.
   vector<CodeGenerator*> mock_generators_to_delete_;
+
+  NullCodeGenerator* null_generator_;
 };
 
 class CommandLineInterfaceTest::NullCodeGenerator : public CodeGenerator {
@@ -220,7 +224,7 @@ void CommandLineInterfaceTest::SetUp() {
   mock_generators_to_delete_.push_back(generator);
   cli_.RegisterGenerator("--alt_out", generator, "Alt output.");
 
-  generator = new NullCodeGenerator();
+  generator = null_generator_ = new NullCodeGenerator();
   mock_generators_to_delete_.push_back(generator);
   cli_.RegisterGenerator("--null_out", generator, "Null output.");
 
@@ -338,6 +342,12 @@ void CommandLineInterfaceTest::ExpectGeneratedWithInsertions(
       temp_directory_);
 }
 
+void CommandLineInterfaceTest::ExpectNullCodeGeneratorCalled(
+    const string& parameter) {
+  EXPECT_TRUE(null_generator_->called_);
+  EXPECT_EQ(parameter, null_generator_->parameter_);
+}
+
 void CommandLineInterfaceTest::ReadDescriptorSet(
     const string& filename, FileDescriptorSet* descriptor_set) {
   string path = temp_directory_ + "/" + filename;
@@ -481,8 +491,7 @@ TEST_F(CommandLineInterfaceTest, WindowsOutputPath) {
       "--proto_path=$tmpdir foo.proto");
 
   ExpectNoErrors();
-  EXPECT_TRUE(generator->called_);
-  EXPECT_EQ("", generator->parameter_);
+  ExpectNullCodeGeneratorCalled("");
 }
 
 TEST_F(CommandLineInterfaceTest, WindowsOutputPathAndParameter) {
@@ -495,8 +504,7 @@ TEST_F(CommandLineInterfaceTest, WindowsOutputPathAndParameter) {
       "--proto_path=$tmpdir foo.proto");
 
   ExpectNoErrors();
-  EXPECT_TRUE(generator->called_);
-  EXPECT_EQ("bar", generator->parameter_);
+  ExpectNullCodeGeneratorCalled("bar");
 }
 
 TEST_F(CommandLineInterfaceTest, TrailingBackslash) {

src/google/protobuf/compiler/subprocess.cc

@@ -115,8 +115,11 @@ bool Subprocess::Communicate(const Message& input, Message* output,
 
   GOOGLE_CHECK_NE(child_stdin_, -1) << "Must call Start() first.";
 
+  // The "sighandler_t" typedef is GNU-specific, so define our own.
+  typedef void SignalHandler(int);
+
   // Make sure SIGPIPE is disabled so that if the child dies it doesn't kill us.
-  sighandler_t old_pipe_handler = signal(SIGPIPE, SIG_IGN);
+  SignalHandler* old_pipe_handler = signal(SIGPIPE, SIG_IGN);
 
   string input_data = input.SerializeAsString();
   string output_data;

src/google/protobuf/extension_set.cc

@@ -120,7 +120,14 @@ void ExtensionSet::RegisterExtension(const MessageLite* containing_type,
 }
 
 static bool CallNoArgValidityFunc(const void* arg, int number) {
-  return reinterpret_cast<const EnumValidityFunc*>(arg)(number);
+  // Note:  Must use C-style cast here rather than reinterpret_cast because
+  //   the C++ standard at one point did not allow casts between function and
+  //   data pointers and some compilers enforce this for C++-style casts.  No
+  //   compiler enforces it for C-style casts since lots of C-style code has
+  //   relied on these kinds of casts for a long time, despite being
+  //   technically undefined.  See:
+  //     http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#195
+  return ((const EnumValidityFunc*)arg)(number);
 }
 
 void ExtensionSet::RegisterEnumExtension(const MessageLite* containing_type,
@@ -130,7 +137,8 @@ void ExtensionSet::RegisterEnumExtension(const MessageLite* containing_type,
   GOOGLE_CHECK_EQ(type, WireFormatLite::TYPE_ENUM);
   ExtensionInfo info(type, is_repeated, is_packed);
   info.enum_is_valid = CallNoArgValidityFunc;
-  info.enum_is_valid_arg = reinterpret_cast<void*>(is_valid);
+  // See comment in CallNoArgValidityFunc() about why we use a c-style cast.
+  info.enum_is_valid_arg = (void*)is_valid;
   Register(containing_type, number, info);
 }