GCC_CXXFLAGS was generated for GCC 15.1.0, but ci_test_gcc and
ci_test_gcc_cxx{11..26} now run in gcc:latest, currently GCC 16.2.0,
so the "maximal warnings" job was missing warnings introduced since
15.1.0 while carrying entries GCC 16 treats as duplicates or no-ops.
Regenerated with https://github.com/nlohmann/gcc_flags (patched
locally to not crash on an option whose "-x c++ <opt> -" probe fails
before it reads stdin, e.g. -Wabi=; the tool otherwise raises
BrokenPipeError instead of recording the option as an error) run
against g++ 16.2.0 in the official gcc:16 Docker image, keeping the
documented -Wno-* exclusions and the same alphabetical placement
scheme as before.
Also added three GCC 16 warnings the generator cannot discover on its
own because it only probes value ranges/lists it finds in the -Q
option name itself, not in the enum choices --help=warnings documents
separately:
- -Wbidi-chars=any, -Wleading-whitespace=spaces: manually verified
these compile cleanly with g++ 16.2.0.
- -Wstrict-flex-arrays: deliberately NOT added, unlike the other two.
Without -fstrict-flex-arrays (which the library does not enable, as
it would change codegen for flexible array members), GCC prints
"'-Wstrict-flex-arrays' is ignored when '-fstrict-flex-arrays' is
not present" on every translation unit, and under our -Werror that
note itself aborts the build. This differs from the harmless
no-op warnings already kept in the file (-Whsa, -Wsynth,
-Wunreachable-code, -Wunsafe-loop-optimizations), which emit
nothing; #5725 item 7 named -Wstrict-flex-arrays as one of the
flags GCC 16 adds, but did not anticipate this failure mode.
Verified: compiled the library header and a representative set of
test translation units (including ones touched by items 1, 3, 8, 9,
10 of this issue) with the regenerated GCC_CXXFLAGS plus -Werror
under g++ 16.2.0 at -std=c++11 through -std=c++26, with zero warnings;
ran the full local test suite (129/129 passing, unrelated to this
compiler) as a regression check. CI must still confirm the actual
ci_test_gcc / ci_test_standards_gcc targets end to end, since this was
verified with direct g++ invocations rather than through the CMake/
CXXFLAGS environment-variable plumbing in ci.cmake.
#5725 item 7
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann