[Bug libstdc++/54847] --enable-libstdcxx-time=yes non-functional 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 #30 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-08 14:47:20 UTC ---
Can we take a step back and determine what exactly this PR is about?  Several
of the comments make incorrect statements about the status quo, so I want to
get the report clear.

I don't understand comment 1. 

Contrary to comment 2, the configure check for sched_yield does *not* check
_POSIX_TIMERS, so sched_yield should be used on darwin when
--enable-libstdcxx-time is used.  Is _GLIBCXX_USE_SCHED_YIELD defined on darwin
when the --enable-libstdcxx-time option is used?

That option *doesn't* enable the use of clock_gettime on darwin, because the
function isn't available. That's unavoidable.

That option does enable checking for nanosleep, but the check fails on darwin
because nanosleep is available but darwin doesn't identify itself as supporting
the Timers option (presumably because the rest of the option isn't supported.)

If that's correct, could we change the bug description to be more accurate?