[Bug libstdc++/54847] --enable-libstdcxx-time=yes doesn't find the function nanosleep() on darwin

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54847

--- Comment #44 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-08 20:42:22 UTC ---
(In reply to comment #42)
> You want to find an test such that:
> 
> (your test) <=> (nanosleep is the one you want)

That's why I was asking about other feature test macros that would allow us to
detect systems supporting the POSIX.1b-1993 Realtime Extensions, but not the
later Timers option, or the POSIX-2008 Base.


> Ok, what about just using _POSIX_TIMERS > 0 || defined(__APPLE__)?  That may
> miss some other OSs in the same boat, but they can always add similar checks.

Because we generally try to avoid littering acinclude.m4 with such checks.  The
other OSs can add defines to their own os_defines.h files if needed.


(In reply to comment #43)
> will effectively default darwin to --enable-libstdcxx-time=yes and eliminates a
> configure option.

That's a *good* thing. If the platform unconditionally supports the feature and
doesn't need a configure check why would you want to prevent using it?  All
that achieves is an incomplete libstdc++ with missing functionality.