1 # threadlib.m4 serial 31
2 dnl Copyright (C) 2005-2021 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
11 dnl The general structure of the multithreading modules in gnulib is that we
12 dnl have three set of modules:
15 dnl pthread, which combines
27 dnl threads, which combines
34 dnl * Gnulib API, with an implementation that can be chosen at configure
35 dnl time through the option --enable-threads=...
42 dnl They are independent, except for the fact that
43 dnl - the implementation of the ISO C API may use the POSIX (or some other
44 dnl platform dependent) API,
45 dnl - the implementation of the Gnulib API may use the POSIX or ISO C or
46 dnl some other platform dependent API, depending on the --enable-threads
49 dnl This file contains macros for all of these APIs!
51 dnl ============================================================================
52 dnl Macros for all thread APIs
54 AC_DEFUN([gl_ANYTHREADLIB_EARLY],
56 AC_REQUIRE([AC_CANONICAL_HOST])
57 if test -z "$gl_anythreadlib_early_done"; then
60 # On OSF/1, the compiler needs the flag -D_REENTRANT so that it
61 # groks <pthread.h>. cc also understands the flag -pthread, but
62 # we don't use it because 1. gcc-2.95 doesn't understand -pthread,
63 # 2. putting a flag into CPPFLAGS that has an effect on the linker
64 # causes the AC_LINK_IFELSE test below to succeed unexpectedly,
65 # leading to wrong values of LIBTHREAD and LTLIBTHREAD.
66 CPPFLAGS="$CPPFLAGS -D_REENTRANT"
69 # Some systems optimize for single-threaded programs by default, and
70 # need special flags to disable these optimizations. For example, the
71 # definition of 'errno' in <errno.h>.
73 aix* | freebsd*) CPPFLAGS="$CPPFLAGS -D_THREAD_SAFE" ;;
74 solaris*) CPPFLAGS="$CPPFLAGS -D_REENTRANT" ;;
76 gl_anythreadlib_early_done=done
80 dnl Checks whether the compiler and linker support weak declarations of symbols.
82 AC_DEFUN([gl_WEAK_SYMBOLS],
84 AC_REQUIRE([AC_CANONICAL_HOST])
85 AC_CACHE_CHECK([whether imported symbols can be declared weak],
88 dnl First, test whether the compiler accepts it syntactically.
91 [[extern void xyzzy ();
94 [gl_cv_have_weak=maybe])
95 if test $gl_cv_have_weak = maybe; then
96 dnl Second, test whether it actually works. On Cygwin 1.7.2, with
97 dnl gcc 4.3, symbols declared weak always evaluate to the address 0.
104 return (fputs == NULL);
106 [gl_cv_have_weak=yes],
107 [gl_cv_have_weak=no],
108 [dnl When cross-compiling, assume that only ELF platforms support
110 AC_EGREP_CPP([Extensible Linking Format],
112 Extensible Linking Format
115 [gl_cv_have_weak="guessing yes"],
116 [gl_cv_have_weak="guessing no"])
119 dnl But when linking statically, weak symbols don't work.
121 *" -static "*) gl_cv_have_weak=no ;;
123 dnl Test for a bug in FreeBSD 11: A link error occurs when using a weak
124 dnl symbol and linking against a shared library that has a dependency on
125 dnl the shared library that defines the symbol.
126 case "$gl_cv_have_weak" in
129 freebsd* | dragonfly* | midnightbsd*)
131 $CC $CPPFLAGS $CFLAGS $LDFLAGS -fPIC -shared -o libempty.so conftest1.c -lpthread >&AS_MESSAGE_LOG_FD 2>&1
132 cat <<EOF > conftest2.c
134 #pragma weak pthread_mutexattr_gettype
137 return (pthread_mutexattr_gettype != NULL);
140 $CC $CPPFLAGS $CFLAGS $LDFLAGS -o conftest conftest2.c libempty.so >&AS_MESSAGE_LOG_FD 2>&1 \
141 || gl_cv_have_weak=no
142 rm -f conftest1.c libempty.so conftest2.c conftest
148 case "$gl_cv_have_weak" in
150 AC_DEFINE([HAVE_WEAK_SYMBOLS], [1],
151 [Define to 1 if the compiler and linker support weak declarations of symbols.])
156 dnl ============================================================================
157 dnl Macros for the POSIX API
161 dnl Tests for the libraries needs for using the POSIX threads API.
162 dnl Sets the variable LIBPTHREAD to the linker options for use in a Makefile.
163 dnl Sets the variable LIBPMULTITHREAD, for programs that really need
164 dnl multithread functionality. The difference between LIBPTHREAD and
165 dnl LIBPMULTITHREAD is that on platforms supporting weak symbols, typically
166 dnl LIBPTHREAD is empty whereas LIBPMULTITHREAD is not.
167 dnl Sets the variable LIB_SCHED_YIELD to the linker options needed to use the
168 dnl sched_yield() function.
169 dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
170 dnl multithread-safe programs.
171 dnl Defines the C macro HAVE_PTHREAD_API if (at least parts of) the POSIX
172 dnl threads API is available.
174 dnl The guts of gl_PTHREADLIB. Needs to be expanded only once.
176 AC_DEFUN([gl_PTHREADLIB_BODY],
178 AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
179 if test -z "$gl_pthreadlib_body_done"; then
183 # On OSF/1, the compiler needs the flag -pthread or -D_REENTRANT so that
184 # it groks <pthread.h>. It's added above, in gl_ANYTHREADLIB_EARLY.
185 AC_CHECK_HEADER([pthread.h],
186 [gl_have_pthread_h=yes], [gl_have_pthread_h=no])
187 if test "$gl_have_pthread_h" = yes; then
188 # Other possible tests:
189 # -lpthreads (FSU threads, PCthreads)
191 # Test whether both pthread_mutex_lock and pthread_mutexattr_init exist
192 # in libc. IRIX 6.5 has the first one in both libc and libpthread, but
193 # the second one only in libpthread, and lock.c needs it.
195 # If -pthread works, prefer it to -lpthread, since Ubuntu 14.04
196 # needs -pthread for some reason. See:
197 # https://lists.gnu.org/r/bug-gnulib/2014-09/msg00023.html
199 for gl_pthread in '' '-pthread'; do
200 LIBS="$LIBS $gl_pthread"
203 [[#include <pthread.h>
205 pthread_mutexattr_t ma;
207 [[pthread_mutex_lock (&m);
208 pthread_mutexattr_init (&ma);]])],
210 LIBPTHREAD=$gl_pthread
211 LIBPMULTITHREAD=$gl_pthread])
213 test $gl_pthread_api = yes && break
215 echo "$as_me:__oline__: gl_pthread_api=$gl_pthread_api" >&AS_MESSAGE_LOG_FD
216 echo "$as_me:__oline__: LIBPTHREAD=$LIBPTHREAD" >&AS_MESSAGE_LOG_FD
218 gl_pthread_in_glibc=no
219 # On Linux with glibc >= 2.34, libc contains the fully functional
223 AC_EGREP_CPP([Lucky user],
224 [#include <features.h>
225 #ifdef __GNU_LIBRARY__
226 #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 34) || (__GLIBC__ > 2)
231 [gl_pthread_in_glibc=yes],
235 echo "$as_me:__oline__: gl_pthread_in_glibc=$gl_pthread_in_glibc" >&AS_MESSAGE_LOG_FD
237 # Test for libpthread by looking for pthread_kill. (Not pthread_self,
238 # since it is defined as a macro on OSF/1.)
239 if test $gl_pthread_api = yes && test -z "$LIBPTHREAD"; then
240 # The program links fine without libpthread. But it may actually
241 # need to link with libpthread in order to create multiple threads.
242 AC_CHECK_LIB([pthread], [pthread_kill],
243 [if test $gl_pthread_in_glibc = yes; then
246 LIBPMULTITHREAD=-lpthread
247 # On Solaris and HP-UX, most pthread functions exist also in libc.
248 # Therefore pthread_in_use() needs to actually try to create a
249 # thread: pthread_create from libc will fail, whereas
250 # pthread_create will actually create a thread.
251 # On Solaris 10 or newer, this test is no longer needed, because
252 # libc contains the fully functional pthread functions.
254 solaris | solaris2.[1-9] | solaris2.[1-9].* | hpux*)
255 AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
256 [Define if the pthread_in_use() detection is hard.])
260 elif test $gl_pthread_api != yes; then
261 # Some library is needed. Try libpthread and libc_r.
262 AC_CHECK_LIB([pthread], [pthread_kill],
265 LIBPMULTITHREAD=-lpthread])
266 if test $gl_pthread_api != yes; then
268 AC_CHECK_LIB([c_r], [pthread_kill],
271 LIBPMULTITHREAD=-lc_r])
274 echo "$as_me:__oline__: LIBPMULTITHREAD=$LIBPMULTITHREAD" >&AS_MESSAGE_LOG_FD
276 AC_MSG_CHECKING([whether POSIX threads API is available])
277 AC_MSG_RESULT([$gl_pthread_api])
278 AC_SUBST([LIBPTHREAD])
279 AC_SUBST([LIBPMULTITHREAD])
280 if test $gl_pthread_api = yes; then
281 AC_DEFINE([HAVE_PTHREAD_API], [1],
282 [Define if you have the <pthread.h> header and the POSIX threads API.])
285 dnl On some systems, sched_yield is in librt, rather than in libpthread.
288 [[#include <sched.h>]],
289 [[sched_yield ();]])],
292 [dnl Solaris 7...10 has sched_yield in librt, not in libpthread or libc.
293 AC_CHECK_LIB([rt], [sched_yield], [LIB_SCHED_YIELD=-lrt],
294 [dnl Solaris 2.5.1, 2.6 has sched_yield in libposix4, not librt.
295 AC_CHECK_LIB([posix4], [sched_yield], [LIB_SCHED_YIELD=-lposix4])])
297 AC_SUBST([LIB_SCHED_YIELD])
299 gl_pthreadlib_body_done=done
303 AC_DEFUN([gl_PTHREADLIB],
305 AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
309 dnl ============================================================================
310 dnl Macros for the ISO C API
314 dnl Tests for the libraries needs for using the ISO C threads API.
315 dnl Sets the variable LIBSTDTHREAD to the linker options for use in a Makefile.
316 dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
317 dnl multithread-safe programs.
318 dnl Defines the C macro HAVE_THREADS_H if (at least parts of) the ISO C threads
319 dnl API is available.
321 dnl The guts of gl_STDTHREADLIB. Needs to be expanded only once.
323 AC_DEFUN([gl_STDTHREADLIB_BODY],
325 AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
326 AC_REQUIRE([AC_CANONICAL_HOST])
327 if test -z "$gl_stdthreadlib_body_done"; then
328 AC_CHECK_HEADERS_ONCE([threads.h])
336 if test $ac_cv_header_threads_h = yes; then
337 dnl glibc >= 2.29 has thrd_create in libpthread.
338 dnl FreeBSD >= 10 has thrd_create in libstdthreads; this library depends
339 dnl on libpthread (for the symbol 'pthread_mutexattr_gettype').
340 dnl glibc >= 2.34, AIX >= 7.1, and Solaris >= 11.4 have thrd_create in
342 AC_CHECK_FUNCS([thrd_create])
343 if test $ac_cv_func_thrd_create = yes; then
346 AC_CHECK_LIB([stdthreads], [thrd_create], [
347 LIBSTDTHREAD='-lstdthreads -lpthread'
349 dnl Guess that thrd_create is in libpthread.
350 LIBSTDTHREAD="$LIBPMULTITHREAD"
354 dnl Libraries needed by thrd.c, mtx.c, cnd.c, tss.c.
355 LIBSTDTHREAD="$LIBPMULTITHREAD $LIB_SCHED_YIELD"
359 AC_SUBST([LIBSTDTHREAD])
361 AC_MSG_CHECKING([whether ISO C threads API is available])
362 AC_MSG_RESULT([$ac_cv_header_threads_h])
363 gl_stdthreadlib_body_done=done
367 AC_DEFUN([gl_STDTHREADLIB],
369 AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
373 dnl ============================================================================
374 dnl Macros for the Gnulib API
378 dnl Tests for a multithreading library to be used.
379 dnl If the configure.ac contains a definition of the gl_THREADLIB_DEFAULT_NO
380 dnl (it must be placed before the invocation of gl_THREADLIB_EARLY!), then the
381 dnl default is 'no', otherwise it is system dependent. In both cases, the user
382 dnl can change the choice through the options --enable-threads=choice or
383 dnl --disable-threads.
384 dnl Defines at most one of the macros USE_ISOC_THREADS, USE_POSIX_THREADS,
385 dnl USE_ISOC_AND_POSIX_THREADS, USE_WINDOWS_THREADS.
386 dnl The choice --enable-threads=isoc+posix is available only on platforms that
387 dnl have both the ISO C and the POSIX threads APIs. It has the effect of using
388 dnl the ISO C API for most things and the POSIX API only for creating and
389 dnl controlling threads (because there is no equivalent to pthread_atfork in
391 dnl Sets the variables LIBTHREAD and LTLIBTHREAD to the linker options for use
392 dnl in a Makefile (LIBTHREAD for use without libtool, LTLIBTHREAD for use with
394 dnl Sets the variables LIBMULTITHREAD and LTLIBMULTITHREAD similarly, for
395 dnl programs that really need multithread functionality. The difference
396 dnl between LIBTHREAD and LIBMULTITHREAD is that on platforms supporting weak
397 dnl symbols, typically LIBTHREAD is empty whereas LIBMULTITHREAD is not.
398 dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
399 dnl multithread-safe programs.
400 dnl Since support for GNU pth was removed, $LTLIBTHREAD and $LIBTHREAD have the
401 dnl same value, and similarly $LTLIBMULTITHREAD and $LIBMULTITHREAD have the
402 dnl same value. Only system libraries are needed.
404 AC_DEFUN([gl_THREADLIB_EARLY],
406 AC_REQUIRE([gl_THREADLIB_EARLY_BODY])
409 dnl The guts of gl_THREADLIB_EARLY. Needs to be expanded only once.
411 AC_DEFUN([gl_THREADLIB_EARLY_BODY],
413 dnl Ordering constraints: This macro modifies CPPFLAGS in a way that
414 dnl influences the result of the autoconf tests that test for *_unlocked
415 dnl declarations, on AIX 5 at least. Therefore it must come early.
416 AC_BEFORE([$0], [gl_FUNC_GLIBC_UNLOCKED_IO])dnl
417 AC_BEFORE([$0], [gl_ARGP])dnl
419 AC_REQUIRE([AC_CANONICAL_HOST])
420 dnl _GNU_SOURCE is needed for pthread_rwlock_t on glibc systems.
421 AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
422 dnl Check for multithreading.
423 m4_ifdef([gl_THREADLIB_DEFAULT_NO],
424 [m4_divert_text([DEFAULTS], [gl_use_threads_default=no])],
425 [m4_divert_text([DEFAULTS], [gl_use_threads_default=])])
426 m4_divert_text([DEFAULTS], [gl_use_winpthreads_default=])
427 AC_ARG_ENABLE([threads],
428 AS_HELP_STRING([--enable-threads={isoc|posix|isoc+posix|windows}], [specify multithreading API])m4_ifdef([gl_THREADLIB_DEFAULT_NO], [], [
429 AS_HELP_STRING([--disable-threads], [build without multithread safety])]),
430 [gl_use_threads=$enableval],
431 [if test -n "$gl_use_threads_default"; then
432 gl_use_threads="$gl_use_threads_default"
436 dnl Disable multithreading by default on OSF/1, because it interferes
437 dnl with fork()/exec(): When msgexec is linked with -lpthread, its
438 dnl child process gets an endless segmentation fault inside execvp().
439 osf*) gl_use_threads=no ;;
440 dnl Disable multithreading by default on Cygwin 1.5.x, because it has
441 dnl bugs that lead to endless loops or crashes. See
442 dnl <https://cygwin.com/ml/cygwin/2009-08/msg00283.html>.
445 1.[0-5].*) gl_use_threads=no ;;
446 *) gl_use_threads=yes ;;
449 dnl Obey gl_AVOID_WINPTHREAD on mingw.
451 case "$gl_use_winpthreads_default" in
452 yes) gl_use_threads=posix ;;
453 no) gl_use_threads=windows ;;
454 *) gl_use_threads=yes ;;
457 *) gl_use_threads=yes ;;
462 if test "$gl_use_threads" = yes \
463 || test "$gl_use_threads" = isoc \
464 || test "$gl_use_threads" = posix \
465 || test "$gl_use_threads" = isoc+posix; then
466 # For using <threads.h> or <pthread.h>:
467 gl_ANYTHREADLIB_EARLY
471 dnl The guts of gl_THREADLIB. Needs to be expanded only once.
473 AC_DEFUN([gl_THREADLIB_BODY],
475 AC_REQUIRE([gl_THREADLIB_EARLY_BODY])
481 if test "$gl_use_threads" != no; then
482 dnl Check whether the compiler and linker support weak declarations.
484 if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
485 dnl If we use weak symbols to implement pthread_in_use / pth_in_use /
486 dnl thread_in_use, we also need to test whether the ISO C 11 thrd_create
487 dnl facility is in use.
488 AC_CHECK_HEADERS_ONCE([threads.h])
491 if test "$gl_use_threads" = isoc || test "$gl_use_threads" = isoc+posix; then
492 AC_CHECK_HEADERS_ONCE([threads.h])
493 gl_have_isoc_threads="$ac_cv_header_threads_h"
495 if test "$gl_use_threads" = yes \
496 || test "$gl_use_threads" = posix \
497 || test "$gl_use_threads" = isoc+posix; then
499 LIBTHREAD=$LIBPTHREAD LTLIBTHREAD=$LIBPTHREAD
500 LIBMULTITHREAD=$LIBPMULTITHREAD LTLIBMULTITHREAD=$LIBPMULTITHREAD
501 if test $gl_pthread_api = yes; then
502 if test "$gl_use_threads" = isoc+posix && test "$gl_have_isoc_threads" = yes; then
503 gl_threads_api='isoc+posix'
504 AC_DEFINE([USE_ISOC_AND_POSIX_THREADS], [1],
505 [Define if the combination of the ISO C and POSIX multithreading APIs can be used.])
506 LIBTHREAD= LTLIBTHREAD=
509 AC_DEFINE([USE_POSIX_THREADS], [1],
510 [Define if the POSIX multithreading library can be used.])
511 if test -z "$LIBMULTITHREAD" && test -z "$LTLIBMULTITHREAD"; then
512 AC_DEFINE([USE_POSIX_THREADS_FROM_LIBC], [1],
513 [Define if references to the POSIX multithreading library are satisfied by libc.])
515 if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
516 AC_DEFINE([USE_POSIX_THREADS_WEAK], [1],
517 [Define if references to the POSIX multithreading library should be made weak.])
518 LIBTHREAD= LTLIBTHREAD=
521 freebsd* | dragonfly* | midnightbsd*)
522 if test "x$LIBTHREAD" != "x$LIBMULTITHREAD"; then
523 dnl If weak symbols can't tell whether pthread_create(), pthread_key_create()
524 dnl etc. will succeed, we need a runtime test.
525 AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
526 [Define if the pthread_in_use() detection is hard.])
535 if test $gl_threads_api = none; then
536 if test "$gl_use_threads" = isoc && test "$gl_have_isoc_threads" = yes; then
538 LIBTHREAD=$LIBSTDTHREAD LTLIBTHREAD=$LIBSTDTHREAD
539 LIBMULTITHREAD=$LIBSTDTHREAD LTLIBMULTITHREAD=$LIBSTDTHREAD
541 AC_DEFINE([USE_ISOC_THREADS], [1],
542 [Define if the ISO C multithreading library can be used.])
545 if test $gl_threads_api = none; then
546 case "$gl_use_threads" in
547 yes | windows | win32) # The 'win32' is for backward compatibility.
548 if { case "$host_os" in
553 gl_threads_api=windows
554 AC_DEFINE([USE_WINDOWS_THREADS], [1],
555 [Define if the native Windows multithreading API can be used.])
561 AC_MSG_CHECKING([for multithread API to use])
562 AC_MSG_RESULT([$gl_threads_api])
563 AC_SUBST([LIBTHREAD])
564 AC_SUBST([LTLIBTHREAD])
565 AC_SUBST([LIBMULTITHREAD])
566 AC_SUBST([LTLIBMULTITHREAD])
569 AC_DEFUN([gl_THREADLIB],
571 AC_REQUIRE([gl_THREADLIB_EARLY])
572 AC_REQUIRE([gl_THREADLIB_BODY])
576 dnl gl_DISABLE_THREADS
577 dnl ------------------
578 dnl Sets the gl_THREADLIB default so that threads are not used by default.
579 dnl The user can still override it at installation time, by using the
580 dnl configure option '--enable-threads'.
582 AC_DEFUN([gl_DISABLE_THREADS], [
583 m4_divert_text([INIT_PREPARE], [gl_use_threads_default=no])
587 dnl gl_AVOID_WINPTHREAD
588 dnl -------------------
589 dnl Sets the gl_THREADLIB default so that on mingw, a dependency to the
590 dnl libwinpthread DLL (mingw-w64 winpthreads library) is avoided.
591 dnl The user can still override it at installation time, by using the
592 dnl configure option '--enable-threads'.
594 AC_DEFUN([gl_AVOID_WINPTHREAD], [
595 m4_divert_text([INIT_PREPARE], [gl_use_winpthreads_default=no])
599 dnl ============================================================================
602 dnl Survey of platforms:
604 dnl Platform Available Compiler Supports test-lock
605 dnl flavours option weak result
606 dnl --------------- --------- --------- -------- ---------
607 dnl Linux 2.4/glibc posix -lpthread Y OK
609 dnl Linux/glibc 2.34 posix Y OK
611 dnl GNU Hurd/glibc posix -lpthread Y OK
613 dnl Ubuntu 14.04 posix -pthread Y OK
615 dnl FreeBSD 5.3 posix -lc_r Y
617 dnl posix -lpthread ? Y
620 dnl FreeBSD 5.2 posix -lc_r Y
624 dnl FreeBSD 4.0,4.10 posix -lc_r Y OK
628 dnl OpenBSD 3.4 posix -lpthread Y OK
630 dnl Mac OS X 10.[123] posix -lpthread Y OK
632 dnl Solaris 7,8,9 posix -lpthread Y Sol 7,8: 0.0; Sol 9: OK
634 dnl HP-UX 11 posix -lpthread N (cc) OK
637 dnl IRIX 6.5 posix -lpthread Y 0.5
639 dnl AIX 4.3,5.1 posix -lpthread N AIX 4: 0.5; AIX 5: OK
641 dnl OSF/1 4.0,5.1 posix -pthread (cc) N OK
642 dnl -lpthread (gcc) Y
644 dnl Cygwin posix -lpthread Y OK
646 dnl Mingw windows N OK
650 dnl The test-lock result shows what happens if in test-lock.c EXPLICIT_YIELD is
652 dnl OK if all three tests terminate OK,
653 dnl 0.5 if the first test terminates OK but the second one loops endlessly,
654 dnl 0.0 if the first test already loops endlessly.