Add a --fatal_warnings flag that requests that protoc exit with a
failing status code if any warnings are generated during compilation.
Partially address #3980.
This change refactors util::Status to have a similar shape as the
recently open-sourced absl::Status. This will allow Protobuf to
eventually use absl::Status and reduce the codesize.
Note that there is more work required before absl::Status can be used.
This fixes the following build error:
In file included from no_warning_test.cc:7:
../../src/google/protobuf/parse_context.h: In instantiation of 'const char* google::protobuf::internal::EpsCopyInputStream::AppendUntilEnd(const char*, const A&) [with A = google::protobuf::internal::EpsCopyInputStream::AppendString(const char*, std::string*)::<lambda(const char*, ptrdiff_t)>]':
../../src/google/protobuf/parse_context.h:366:70: required from here
../../src/google/protobuf/stubs/logging.h:161:48: error: comparison of unsigned expression in '>= 0' is always true [-Werror=type-limits]
161 | #define GOOGLE_CHECK_GE(A, B) GOOGLE_CHECK((A) >= (B))
| ^
../../src/google/protobuf/stubs/logging.h:151:5: note: in definition of macro 'GOOGLE_LOG_IF'
151 | !(CONDITION) ? (void)0 : GOOGLE_LOG(LEVEL)
| ^~~~~~~~~
../../src/google/protobuf/stubs/logging.h:161:31: note: in expansion of macro 'GOOGLE_CHECK'
161 | #define GOOGLE_CHECK_GE(A, B) GOOGLE_CHECK((A) >= (B))
| ^~~~~~~~~~~~
../../src/google/protobuf/stubs/logging.h:201:26: note: in expansion of macro 'GOOGLE_CHECK_GE'
201 | #define GOOGLE_DCHECK_GE GOOGLE_CHECK_GE
| ^~~~~~~~~~~~~~~
../../src/google/protobuf/parse_context.h:351:7: note: in expansion of macro 'GOOGLE_DCHECK_GE'
351 | GOOGLE_DCHECK_GE(chunk_size, static_cast<size_t>(0));
| ^~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
The #ifdef block is duplicated with the above (which was fixed in 3.15.1).
It would be great to have this fix backported to 3.15.1 (and released as 3.15.2).
Our use of constinit does not seem to work with GCC yet (see
https://github.com/protocolbuffers/protobuf/issues/8310), so this
commit disables it on GCC for now.
This commit also updates mutex.h to work around the fact that MinGW's
std::mutex apparently does not have a constexpr constructor. We already
have this kind of workaround for MSVC, so we can just use the same
workaround.
