On Wed, Sep 26, 2012 at 08:09:48PM -0700, Paul Eggert wrote: > >> C11 is not incompatible with C99, the way that C99 was incompatible with > >> C89. >... > > The CC="gcc -std=gnu99" is needed in my example, it is not a part of the > > scenario when the compiler defaults to C99 - which is neither for gcc > > nor for other compilers that implausible. > > Yes, that's plausible.
And now I also found a case where the difference between gnu99 and gnu11 matters today: glibc 2.16 has the following protected by what boils down to #if defined _GNU_SOURCE || defined _ISOC11_SOURCE || \ (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L) - timespec_get() and TIME_UTC - aligned_alloc() - at_quick_exit() - quick_exit() - CMPLX/CMPLXF/CMPLXL - static_assert > But having '-std=gnu11' break things doesn't > sound plausible. Sorry, I shouldn't have started talking about a separate different thing in one email with my "does -std=gnu11 break anything?" remark. >... > > So autoconf is now trying an option that will fail the test with the > > current compiler, and will likely be deprecated > > Perhaps we should back off on how many C11 features we're checking, so > that IBM XL C V12.1 passes too? That might be more useful. On a downside, that requires users to check for more features. It's a policy decision which features should be guaranteed to be available when ac_cv_prog_cc_c11 is not "no", and for which features autoconf should provide separate tests and autoconf users then have to check separately. cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed