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# threads.m4 serial 8
dnl Copyright (C) 2019-2021 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 Tests whether the <threads.h> facility is available.
dnl Sets the variable LIBSTDTHREAD to the linker options for use in a Makefile
dnl for a program that uses the <threads.h> functions.
dnl Sets the variable LIBTHREADLOCAL to the linker options for use in a Makefile
dnl for a program that uses the 'thread_local' macro.
AC_DEFUN([gl_THREADS_H],
[
AC_REQUIRE([gl_THREADS_H_DEFAULTS])
AC_REQUIRE([AC_CANONICAL_HOST])
AC_REQUIRE([gl_STDTHREADLIB])
gl_CHECK_NEXT_HEADERS([threads.h])
if test $ac_cv_header_threads_h = yes; then
HAVE_THREADS_H=1
else
HAVE_THREADS_H=0
fi
AC_SUBST([HAVE_THREADS_H])
if test $HAVE_THREADS_H = 1; then
dnl AIX 7.1..7.2 defines thrd_start_t incorrectly, namely as
dnl 'void * (*) (void *)' instead of 'int (*) (void *)'.
AC_CACHE_CHECK([whether thrd_start_t is correct],
[gl_cv_thrd_start_t_correct],
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM([[
#include <threads.h>
#ifdef __cplusplus
extern "C" {
#endif
extern void foo (thrd_start_t);
extern void foo (int (*) (void *));
#ifdef __cplusplus
}
#endif
]], [[]])],
[gl_cv_thrd_start_t_correct=yes],
[gl_cv_thrd_start_t_correct=no])
])
if test $gl_cv_thrd_start_t_correct != yes; then
BROKEN_THRD_START_T=1
fi
fi
dnl Define _Thread_local.
dnl GCC, for example, supports '__thread' since version 3.3, but it supports
dnl '_Thread_local' only starting with version 4.9.
AH_VERBATIM([thread_local], gl_THREAD_LOCAL_DEFINITION)
dnl Test whether _Thread_local is supported in the compiler and linker.
AC_CACHE_CHECK([whether _Thread_local works],
[gl_cv_thread_local_works],
[dnl On AIX 7.1 with GCC 4.8.1, this test program compiles fine, but the
dnl 'test-thread-local' test misbehaves.
dnl On Android 4.3, this test program compiles fine, but the
dnl 'test-thread-local' test crashes.
if case "$host_os" in
aix*) test -n "$GCC" ;;
linux*-android*) true ;;
*) false ;;
esac
then
gl_cv_thread_local_works="guessing no"
else
AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM([gl_THREAD_LOCAL_DEFINITION[
int _Thread_local x;
]], [[
x = 42;
]])],
[if test "$cross_compiling" != yes; then
gl_cv_thread_local_works=yes
else
gl_cv_thread_local_works="guessing yes"
fi
],
[if test "$cross_compiling" != yes; then
gl_cv_thread_local_works=no
else
gl_cv_thread_local_works="guessing no"
fi
])
fi
])
case "$gl_cv_thread_local_works" in
*yes) ;;
*) HAVE_THREAD_LOCAL=0 ;;
esac
dnl Determine the link dependencies of '_Thread_local'.
LIBTHREADLOCAL=
dnl On AIX 7.2 with "xlc -qthreaded -qtls", programs that use _Thread_local
dnl as defined above produce link errors regarding the symbols
dnl '.__tls_get_mod' and '__tls_get_addr'. Similarly, on AIX 7.2 with gcc,
dnl 32-bit programs that use _Thread_local produce link errors regarding the
dnl symbol '__get_tpointer'. The fix is to link with -lpthread.
case "$host_os" in
aix*)
LIBTHREADLOCAL=-lpthread
;;
esac
AC_SUBST([LIBTHREADLOCAL])
dnl Check for declarations of anything we want to poison if the
dnl corresponding gnulib module is not in use, and which is not
dnl guaranteed by C89.
gl_WARN_ON_USE_PREPARE([[#include <threads.h>
]], [call_once
cnd_broadcast cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait
mtx_destroy mtx_init mtx_lock mtx_timedlock mtx_trylock mtx_unlock
thrd_create thrd_current thrd_detach thrd_equal thrd_exit thrd_join
thrd_sleep thrd_yield
tss_create tss_delete tss_get tss_set])
])
dnl Expands to C preprocessor statements that define _Thread_local.
AC_DEFUN([gl_THREAD_LOCAL_DEFINITION],
[[/* The _Thread_local keyword of C11. */
/* GNU C: <https://gcc.gnu.org/onlinedocs/gcc-3.3.1/gcc/Thread-Local.html> */
/* ARM C: <https://developer.arm.com/docs/dui0472/latest/compiler-specific-features/__declspecthread> */
/* IBM C: supported only with compiler option -qtls, see
<https://www.ibm.com/support/knowledgecenter/SSGH2K_12.1.0/com.ibm.xlc121.aix.doc/compiler_ref/opt_tls.html> */
/* Oracle Solaris Studio C: <https://docs.oracle.com/cd/E18659_01/html/821-1384/bjabr.html> */
/* MSVC: <https://docs.microsoft.com/en-us/cpp/parallel/thread-local-storage-tls> */
#ifndef _Thread_local
# if defined __GNUC__ || defined __CC_ARM || defined __xlC__ || defined __SUNPRO_C
# define _Thread_local __thread
# elif defined _MSC_VER
# define _Thread_local __declspec (thread)
# endif
#endif
]])
AC_DEFUN([gl_THREADS_MODULE_INDICATOR],
[
dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
AC_REQUIRE([gl_THREADS_H_DEFAULTS])
gl_MODULE_INDICATOR_SET_VARIABLE([$1])
dnl Define it also as a C macro, for the benefit of the unit tests.
gl_MODULE_INDICATOR_FOR_TESTS([$1])
])
AC_DEFUN([gl_THREADS_H_DEFAULTS],
[
gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CND])
gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MTX])
gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_THRD])
gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TSS])
dnl Assume proper GNU behavior unless another module says otherwise.
HAVE_THREAD_LOCAL=1; AC_SUBST([HAVE_THREAD_LOCAL])
BROKEN_THRD_START_T=0; AC_SUBST([BROKEN_THRD_START_T])
REPLACE_THRD_CREATE=0; AC_SUBST([REPLACE_THRD_CREATE])
REPLACE_THRD_CURRENT=0; AC_SUBST([REPLACE_THRD_CURRENT])
REPLACE_THRD_DETACH=0; AC_SUBST([REPLACE_THRD_DETACH])
REPLACE_THRD_EQUAL=0; AC_SUBST([REPLACE_THRD_EQUAL])
REPLACE_THRD_JOIN=0; AC_SUBST([REPLACE_THRD_JOIN])
])
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