From 92b47a321e14f98c524f6e67e7ecabad5afa7886 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Mon, 23 Nov 2020 17:17:09 +0000
Subject: [PATCH] libstdc++: Add configure checks for semaphores
This moves the checks for POSIX semaphores to configure time. As well as
requiring <semaphore.h> and SEM_VALUE_MAX, we also require the
sem_timedwait function. That was only optional in POSIX 2001 (and is
absent on Darwin).
libstdc++-v3/ChangeLog:
* acinclude.m4 (GLIBCXX_CHECK_GTHREADS): Check for
* config.h.in: Regenerate.
* configure: Regenerate.
* include/bits/semaphore_base.h (_GLIBCXX_HAVE_POSIX_SEMAPHORE):
Check autoconf macro instead of defining it here.
---
libstdc++-v3/acinclude.m4 | 37 ++++++++++++++
libstdc++-v3/config.h.in | 4 ++
libstdc++-v3/configure | 58 ++++++++++++++++++++++
libstdc++-v3/include/bits/semaphore_base.h | 6 +--
4 files changed, 101 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 486347b34d94..a4a0bb840181 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4089,6 +4089,43 @@ AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
fi
fi
+ AC_CHECK_HEADER(semaphore.h, [
+ AC_MSG_CHECKING([for POSIX Semaphores and sem_timedwait])
+ AC_TRY_COMPILE([
+ #include <unistd.h>
+ #include <semaphore.h>
+ #include <limits.h>
+ ],
+ [
+ #if !defined _POSIX_TIMEOUTS || _POSIX_TIMEOUTS <= 0
+ # error "POSIX Timeouts option not supported"
+ #elif !defined _POSIX_SEMAPHORES || _POSIX_SEMAPHORES <= 0
+ # error "POSIX Semaphores option not supported"
+ #else
+ #if defined SEM_VALUE_MAX
+ constexpr int sem_value_max = SEM_VALUE_MAX;
+ #elif defined _POSIX_SEM_VALUE_MAX
+ constexpr int sem_value_max = _POSIX_SEM_VALUE_MAX;
+ #else
+ # error "SEM_VALUE_MAX not available"
+ #endif
+ sem_t sem;
+ sem_init(&sem, 0, sem_value_max);
+ struct timespec ts = { 0 };
+ sem_timedwait(&sem, &ts);
+ #endif
+ ],
+ [ac_have_posix_semaphore=yes],
+ [ac_have_posix_semaphore=no])],
+ [ac_have_posix_semaphore=no])
+
+ if test $ac_have_posix_semaphore = yes ; then
+ AC_DEFINE(_GLIBCXX_HAVE_POSIX_SEMAPHORE,
+ 1,
+ [Define to 1 if POSIX Semaphores with sem_timedwait are available in <semaphore.h>.])
+ fi
+ AC_MSG_RESULT([$ac_have_posix_semaphore])
+
CXXFLAGS="$ac_save_CXXFLAGS"
AC_LANG_RESTORE
])
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index 8ae3e0fc4bf8..72faabfb2c10 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -872,6 +872,10 @@
/* Define if gthreads library is available. */
#undef _GLIBCXX_HAS_GTHREADS
+/* Define to 1 if POSIX Semaphores with sem_timedwait are available in
+ <semaphore.h>. */
+#undef _GLIBCXX_HAVE_POSIX_SEMAPHORE
+
/* Define to 1 if a full hosted library is built, or 0 if freestanding. */
#undef _GLIBCXX_HOSTED
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index d9ed414cc773..a3d08310cf13 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -76363,6 +76363,64 @@ fi
fi
fi
+ ac_fn_cxx_check_header_mongrel "$LINENO" "semaphore.h" "ac_cv_header_semaphore_h" "$ac_includes_default"
+if test "x$ac_cv_header_semaphore_h" = xyes; then :
+
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking for POSIX Semaphores and sem_timedwait" >&5
+$as_echo_n "checking for POSIX Semaphores and sem_timedwait... " >&6; }
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+ #include <unistd.h>
+ #include <semaphore.h>
+ #include <limits.h>
+
+int
+main ()
+{
+
+ #if !defined _POSIX_TIMEOUTS || _POSIX_TIMEOUTS <= 0
+ # error "POSIX Timeouts option not supported"
+ #elif !defined _POSIX_SEMAPHORES || _POSIX_SEMAPHORES <= 0
+ # error "POSIX Semaphores option not supported"
+ #else
+ #if defined SEM_VALUE_MAX
+ constexpr int sem_value_max = SEM_VALUE_MAX;
+ #elif defined _POSIX_SEM_VALUE_MAX
+ constexpr int sem_value_max = _POSIX_SEM_VALUE_MAX;
+ #else
+ # error "SEM_VALUE_MAX not available"
+ #endif
+ sem_t sem;
+ sem_init(&sem, 0, sem_value_max);
+ struct timespec ts = { 0 };
+ sem_timedwait(&sem, &ts);
+ #endif
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+ ac_have_posix_semaphore=yes
+else
+ ac_have_posix_semaphore=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+else
+ ac_have_posix_semaphore=no
+fi
+
+
+
+ if test $ac_have_posix_semaphore = yes ; then
+
+$as_echo "#define _GLIBCXX_HAVE_POSIX_SEMAPHORE 1" >>confdefs.h
+
+ fi
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_have_posix_semaphore" >&5
+$as_echo "$ac_have_posix_semaphore" >&6; }
+
CXXFLAGS="$ac_save_CXXFLAGS"
ac_ext=c
ac_cpp='$CPP $CPPFLAGS'
diff --git a/libstdc++-v3/include/bits/semaphore_base.h b/libstdc++-v3/include/bits/semaphore_base.h
index 5e29d3783fe1..0692f95f24f2 100644
--- a/libstdc++-v3/include/bits/semaphore_base.h
+++ b/libstdc++-v3/include/bits/semaphore_base.h
@@ -39,11 +39,9 @@
#include <ext/numeric_traits.h>
-#if __has_include(<semaphore.h>)
+#ifdef _GLIBCXX_HAVE_POSIX_SEMAPHORE
+# include <limits.h>
# include <semaphore.h>
-# if defined SEM_VALUE_MAX || _POSIX_SEM_VALUE_MAX
-# define _GLIBCXX_HAVE_POSIX_SEMAPHORE 1
-# endif
#endif
#include <chrono>
--
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