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# pthread-once.m4
# serial 6
dnl Copyright (C) 2019-2025 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.
dnl This file is offered as-is, without any warranty.
AC_DEFUN([gl_PTHREAD_ONCE],
[
AC_REQUIRE([gl_PTHREAD_H])
AC_REQUIRE([AC_CANONICAL_HOST])
AC_REQUIRE([gl_PTHREADLIB])
if { case "$host_os" in mingw* | windows*) true;; *) false;; esac; } \
&& test $gl_threads_api = windows; then
dnl Choose function names that don't conflict with the mingw-w64 winpthreads
dnl library.
REPLACE_PTHREAD_ONCE=1
PTHREAD_ONCE_LIB=
else
if test $HAVE_PTHREAD_H = 0; then
HAVE_PTHREAD_ONCE=0
PTHREAD_ONCE_LIB=
else
dnl Work around Cygwin 3.5.3 bug.
AC_CACHE_CHECK([whether pthread_once works],
[gl_cv_func_pthread_once_works],
[case "$host_os" in
cygwin*) gl_cv_func_pthread_once_works="guessing no" ;;
*) gl_cv_func_pthread_once_works="yes" ;;
esac
])
case "$gl_cv_func_pthread_once_works" in
*yes) ;;
*) REPLACE_PTHREAD_ONCE=1 ;;
esac
dnl Determine whether linking requires $(LIBPMULTITHREAD) or only
dnl $(LIBPTHREAD).
if test -z "$LIBPTHREAD" && test -n "$LIBPMULTITHREAD"; then
AC_CACHE_CHECK([whether pthread_once can be used without linking with libpthread],
[gl_cv_func_pthread_once_no_lib],
[AC_RUN_IFELSE(
[AC_LANG_PROGRAM(
[[#include <pthread.h>
static pthread_once_t a_once = PTHREAD_ONCE_INIT;
static int a;
static void a_init (void) { a = 8647; }
]],
[[if (pthread_once (&a_once, a_init)) return 1;
if (a != 8647) return 2;
return 0;
]])],
[gl_cv_func_pthread_once_no_lib=yes],
[gl_cv_func_pthread_once_no_lib=no],
[case "$host_os" in
# Guess no on glibc.
*-gnu* | gnu*)
gl_cv_func_pthread_once_no_lib="guessing no" ;;
# Guess no on FreeBSD.
freebsd* | dragonfly* | midnightbsd*)
gl_cv_func_pthread_once_no_lib="guessing no" ;;
# Guess yes otherwise.
*)
gl_cv_func_pthread_once_no_lib="guessing yes" ;;
esac
])
])
case "$gl_cv_func_pthread_once_no_lib" in
*yes) PTHREAD_ONCE_LIB="$LIBPTHREAD" ;;
*) PTHREAD_ONCE_LIB="$LIBPMULTITHREAD" ;;
esac
dnl Expected result:
dnl PTHREAD_ONCE_LIB is $(LIBPMULTITHREAD) on glibc < 2.34, FreeBSD.
dnl PTHREAD_ONCE_LIB is $(LIBPTHREAD) in particular on
dnl musl libc, macOS, NetBSD, Solaris, Cygwin, Haiku, Android.
else
PTHREAD_ONCE_LIB="$LIBPTHREAD"
fi
fi
fi
AC_SUBST([PTHREAD_ONCE_LIB])
])
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