On Tue, Jan 18 2022, Junio C Hamano wrote: > Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> writes: > >> The inherent problem is that __has_extension() is a way to ask >> Clang (and GCC) whether the compiler supports that feature, but the >> -Wc11-extensions warning will be issued on the basis of the selected >> __STDC_VERSION__. With -std=gnu99 the __has_extension() built-in will >> return true, but the warning will still fire. >> >> Let's narrowly work around this by checking whether: > > The end result, if and when a change along this line proves OK for > all versions of FreeBSD we care about, may be narrow, but as a band > aid to discuss just before the final release, I do not know if > anybody can sensibly assess the ramifications of such a change, > except for somebody whose primary development environment has been > FreeBSD for the past 6 months or more. libgen.h is a trivially sized header (~20 lines of non-comment non-whitespace), and uses __generic for exactly one thing. If you'd like to go with your patch instead that's fair enough, but I don't see what using FreeBSD as a primary development environment for an extended time would buy anyone in understanding this narrow issue causing the C11 warning. > This looks way more than we can take comfortably at this point in > the release cycle, compared to "fixing" the developer build by > kicking developers on FreeBSD out of the "we are C99 or below at > this point" enforcement mechanism. > >> A. We are under FreeBSD >> B. We are using a C standard older than C11 >> >> In that case we'll include sys/cdefs.h, and undefine FreeBSD's >> __generic() wrapper if it's been defined. We'll then load libgen.h, >> and restore whatever __generic definition we temporarily undefined >> earlier. >> >> An alternate solution would be to simply define NO_LIBGEN_H=Y in >> config.mak.uname for FreeBSD, but this way we'll use its OS-provided >> basename() and dirname(), and in the general case ensure that nothing >> changes outside of DEVELOPER=1 builds. >> >> 1. https://github.com/freebsd/freebsd-src/commit/62b7f85d4749 >> >> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> >> --- >> git-compat-util.h | 18 ++++++++++++++++++ >> 1 file changed, 18 insertions(+) >> >> diff --git a/git-compat-util.h b/git-compat-util.h >> index 1229c8296b9..69d9b5f202f 100644 >> --- a/git-compat-util.h >> +++ b/git-compat-util.h >> @@ -318,7 +318,25 @@ static inline int setitimer(int which, const struct itimerval *value, struct iti >> #endif >> >> #ifndef NO_LIBGEN_H >> +/* >> + * FreeBSD's libgen.h inadvertently requires C11 features, due to its >> + * sys/cdefs.h using _Generic() if >> + * __has_extension(c_generic_selections) is true, regardless of >> + * __STDC_VERSION__.... >> + */ >> +#if defined(__FreeBSD__) && __STDC_VERSION__ - 0 < 201112L >> +#include <sys/cdefs.h> >> +#ifdef __generic >> +#define __fbsd_generic __generic >> +#endif >> +#undef __generic >> +#endif >> #include <libgen.h> >> +/* ...continue FreeBSD-specific hack above */ >> +#ifdef __fbsd_generic >> +#define __generic __fbsd_generic >> +#undef __fbsd_generic >> +#endif >> #else >> #define basename gitbasename >> char *gitbasename(char *);
