[gcc r17-462] libstdc++: vxworks: enable clock_gettime

[Alexandre Oliva]

https://gcc.gnu.org/g:8633b886e6b894524c632f35c2920f71eaad4a71

commit r17-462-g8633b886e6b894524c632f35c2920f71eaad4a71
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Mon May 11 03:46:46 2026 -0300

    libstdc++: vxworks: enable clock_gettime
    
    We've been using gettimeofday() on VxWorks, because configury didn't
    state clock_gettime was available.  It has been since at least
    vxworks6.9, possibly earlier.  Indeed, it's been available for longer
    than gettimeofday(), so this enables libstdc++'s chrono.cc to work
    with earlier 6.9 releases.
    
    We've used clock_gettime unconditionally in __gthread_cond_timedwait
    for a very long time, so it's not like this brings in a new
    dependency, but it allows clocks and deadlines to work with the same
    precision.  Before this change, we'd use gettimeofday's coarser
    clocks, and finer timed waits, which makes room for imprecisions.
    
    
    for  libstdc++-v3/ChangeLog
    
            * acinclude.m4 (GLIBXX_ENABLE_LIBSTDCXX_TIME) [vxworks*]:
            Enable monotonic and realtime clocks.
            * configure: Rebuilt.

Diff:
---
 libstdc++-v3/acinclude.m4 | 2 ++
 libstdc++-v3/configure    | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 8dc9e17b214c..e7bc4fbf90c7 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -1785,6 +1785,8 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
       # VxWorks has nanosleep as soon as the kernel is configured with
       # INCLUDE_POSIX_TIMERS, which is normally/most-often the case.
       vxworks*)
+        ac_has_clock_monotonic=yes
+        ac_has_clock_realtime=yes
         ac_has_nanosleep=yes
         ;;
       gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 6713e4504b1c..3785ad94f330 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -21473,6 +21473,8 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
       # VxWorks has nanosleep as soon as the kernel is configured with
       # INCLUDE_POSIX_TIMERS, which is normally/most-often the case.
       vxworks*)
+        ac_has_clock_monotonic=yes
+        ac_has_clock_realtime=yes
         ac_has_nanosleep=yes
         ;;
       gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)