http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54847
--- Comment #27 from Jack Howarth <howarth at nitro dot med.uc.edu> 2012-10-08
13:47:32 UTC ---
The unistd.h header on darwin12 defines...
#define _POSIX_TIMERS (-1) /* [TMR] */
>From the documentation on --enable-libstdcxx-time...
dnl Check for clock_gettime, nanosleep and sched_yield, used in the
dnl implementation of 20.11.7 [time.clock], and 30.3.2 [thread.thread.this]
dnl in the C++11 standard.
dnl
dnl --enable-libstdcxx-time
dnl --enable-libstdcxx-time=yes
dnl checks for the availability of monotonic and realtime clocks,
dnl nanosleep and sched_yield in libc and libposix4 and, if needed,
dnl links in the latter.
dnl --enable-libstdcxx-time=rt
dnl also searches (and, if needed, links) librt. Note that this is
dnl not always desirable because, in glibc, for example, in turn it
dnl triggers the linking of libpthread too, which activates locking,
dnl a large overhead for single-thread programs.
dnl --enable-libstdcxx-time=no
dnl --disable-libstdcxx-time
dnl disables the checks completely
it seems that --enable-libstdcxx-time defaults to 'no' which would seem to
imply that it is effectively --disable-libstdcxx-time. The
--enable-libstdcxx-time=yes check is too strict for darwin because it doesn't
handle the case of _POSIX_TIMER defined to -1 for testing pre-POSIX 2008
nanosleep(). What would you consider to be an acceptable change to the test
at...
AC_MSG_CHECKING([for nanosleep])
AC_TRY_LINK(
[#include <unistd.h>
#include <time.h>
],
[#if _POSIX_TIMERS > 0
timespec tp;
#endif
nanosleep(&tp, 0);
], [ac_has_nanosleep=yes], [ac_has_nanosleep=no])
AC_MSG_RESULT($ac_has_nanosleep)
in libstdc++-v3/acinclude.m4 to solve this limitation? Again I would note that
short-circuiting this test for _POSIX_TIMERS > 0 introduces no regressions in
the libstdc++-v3 test suite so the darwin nanosleep() appears to be sufficient.
Or is the libstdc++-v3 testsuite currently incapable of properly testing this
feature?
