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# semaphore.m4 serial 2
dnl Copyright (C) 2019-2024 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
# Sets LIB_SEMAPHORE to the library needed, in addition to $(LIBMULTITHREAD),
# for getting the <semaphore.h> functions.
AC_DEFUN([gl_SEMAPHORE],
[
AC_REQUIRE([gl_THREADLIB])
dnl sem_post is
dnl - in libc on macOS, FreeBSD, AIX, IRIX, Solaris 11, Haiku, Cygwin,
dnl - in libpthread on glibc systems, OpenBSD,
dnl - in libpthread or librt on NetBSD,
dnl - in librt on HP-UX 11, OSF/1, Solaris 10.
dnl On the platforms where -lpthread is needed, it is contained in
dnl $LIBMULTITHREAD. Therefore, the only library we need to test for is -lrt.
AC_CACHE_CHECK([for library needed for semaphore functions],
[gl_cv_semaphore_lib],
[saved_LIBS="$LIBS"
LIBS="$LIBS $LIBMULTITHREAD"
AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#include <semaphore.h>]],
[[sem_post ((sem_t *)0);]])],
[gl_cv_semaphore_lib=none],
[LIBS="$LIBS -lrt"
AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#include <semaphore.h>]],
[[sem_post ((sem_t *)0);]])],
[gl_cv_semaphore_lib='-lrt'],
[gl_cv_semaphore_lib=none])
])
LIBS="$saved_LIBS"
])
if test "x$gl_cv_semaphore_lib" = xnone; then
LIB_SEMAPHORE=
else
LIB_SEMAPHORE="$gl_cv_semaphore_lib"
fi
AC_SUBST([LIB_SEMAPHORE])
])
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