C11 provides static assertions via _Static_assert and provides static_assert as a convenience define for this in assert.h. Our codebase uses the latter, as _Static_assert has actually already been deprecated in C23.
Not all toolchains that declare support for C11 actually support it; e.g. MSVC 19.27 does not support _Static_assert, but somehow supports static_assert. MSVC 19.27 admits to be a "preview implementation of the ISO C11 standard", so this is not surprising (MSVC 19.28 does not come with this caveat). Furthermore some FATE boxes [1] use old GCC toolchains (with only experimental support for C11) where _Static_assert is supported, but assert.h does not provide the fallback define. They are broken since the first usage of static_assert. This commit therefore checks whether static_assert and _Static_assert work with assert.h included; if not, configure errors out. This intentionally drops support for MSVC 19.27. Users like the old FATE boxes above can still add -Dstatic_assert=_Static_assert to cflags as a workaround if desired. [1]: https://fate.ffmpeg.org/report.cgi?time=20240321123620&slot=sh4-debian-qemu-gcc-4.7 Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com> --- configure | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/configure b/configure index 343edb38ab..fc366549bc 100755 --- a/configure +++ b/configure @@ -5589,6 +5589,19 @@ check_cxxflags_cc -std=$stdcxx ctype.h "__cplusplus >= 201103L" || check_cflags_cc -std=$stdc ctype.h "__STDC_VERSION__ >= 201112L" || { check_cflags_cc -std=c11 ctype.h "__STDC_VERSION__ >= 201112L" && stdc="c11" || die "Compiler lacks C11 support"; } +test_cc <<EOF || die "Compiler lacks support for C11 static assertions" +#include <assert.h> +#include <stddef.h> +struct Foo { + int a; + void *ptr; +} obj; +static_assert(offsetof(struct Foo, a) == 0, + "First element of struct does not have offset 0"); +_Static_assert(offsetof(struct Foo, ptr) >= offsetof(struct Foo, a) + sizeof(obj.a), + "elements not properly ordered in struct"); +EOF + check_cppflags -D_FILE_OFFSET_BITS=64 check_cppflags -D_LARGEFILE_SOURCE -- 2.40.1 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
