Andreas Rheinhardt: > C11 provides static assertions via _Static_assert and > provides static_assert as a convenience define for this > in assert.h. MSVC 19.27 declares support for C11, but does > not support _Static_assert, but somehow supports > static_assert. That's therefore what we use. > > But apparently there are some old GCC toolchains where > _Static_assert is supported, but assert.h does not provide > the fallback define. Some fate boxes are affected by this > [1]. > > This commit therefore checks whether static_assert works > with assert.h included; if not, it errors out. Users like > the above can still add -Dstatic_assert=_Static_assert > to cflags as a workaround. > > [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> > --- > This is what a test without fallback looks like. > Posted to gather opinions on what people prefer. > > configure | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/configure b/configure > index 6d7b33b0ff..c2d2c70c20 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_assert" > +#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 >
Jan has tested old toolchains and found out that his GCC 4.7 has proper C11 headers; so this seems to be unique to Michael's setup. This makes me prefer this patch instead of the version with the fallback. (Michael can simply add -Dstatic_assert=_Static_assert to his cflags.) Of course others are still invited to share their opinions. - Andreas _______________________________________________ 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".
