1 # SPDX-License-Identifier: GPL-2.0-or-later WITH LicenseRef-Autoconf-exception-macro
2 # ===========================================================================
3 # https://www.gnu.org/software/autoconf-archive/ax_pthread.html
4 # ===========================================================================
8 # AX_PTHREAD([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])
12 # This macro figures out how to build C programs using POSIX threads. It
13 # sets the PTHREAD_LIBS output variable to the threads library and linker
14 # flags, and the PTHREAD_CFLAGS output variable to any special C compiler
15 # flags that are needed. (The user can also force certain compiler
16 # flags/libs to be tested by setting these environment variables.)
18 # Also sets PTHREAD_CC and PTHREAD_CXX to any special C compiler that is
19 # needed for multi-threaded programs (defaults to the value of CC
20 # respectively CXX otherwise). (This is necessary on e.g. AIX to use the
21 # special cc_r/CC_r compiler alias.)
23 # NOTE: You are assumed to not only compile your program with these flags,
24 # but also to link with them as well. For example, you might link with
25 # $PTHREAD_CC $CFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS
26 # $PTHREAD_CXX $CXXFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS
28 # If you are only building threaded programs, you may wish to use these
29 # variables in your default LIBS, CFLAGS, and CC:
31 # LIBS="$PTHREAD_LIBS $LIBS"
32 # CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
33 # CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS"
37 # In addition, if the PTHREAD_CREATE_JOINABLE thread-attribute constant
38 # has a nonstandard name, this macro defines PTHREAD_CREATE_JOINABLE to
39 # that name (e.g. PTHREAD_CREATE_UNDETACHED on AIX).
41 # Also HAVE_PTHREAD_PRIO_INHERIT is defined if pthread is found and the
42 # PTHREAD_PRIO_INHERIT symbol is defined when compiling with
45 # ACTION-IF-FOUND is a list of shell commands to run if a threads library
46 # is found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it
47 # is not found. If ACTION-IF-FOUND is not specified, the default action
48 # will define HAVE_PTHREAD.
50 # Please let the authors know if this macro fails on any platform, or if
51 # you have any other suggestions or comments. This macro was based on work
52 # by SGJ on autoconf scripts for FFTW (http://www.fftw.org/) (with help
53 # from M. Frigo), as well as ac_pthread and hb_pthread macros posted by
54 # Alejandro Forero Cuervo to the autoconf macro repository. We are also
55 # grateful for the helpful feedback of numerous users.
57 # Updated for Autoconf 2.68 by Daniel Richard G.
61 # Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
62 # Copyright (c) 2011 Daniel Richard G. <skunk@iSKUNK.ORG>
63 # Copyright (c) 2019 Marc Stevens <marc.stevens@cwi.nl>
65 # This program is free software: you can redistribute it and/or modify it
66 # under the terms of the GNU General Public License as published by the
67 # Free Software Foundation, either version 3 of the License, or (at your
68 # option) any later version.
70 # This program is distributed in the hope that it will be useful, but
71 # WITHOUT ANY WARRANTY; without even the implied warranty of
72 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
73 # Public License for more details.
75 # You should have received a copy of the GNU General Public License along
76 # with this program. If not, see <https://www.gnu.org/licenses/>.
78 # As a special exception, the respective Autoconf Macro's copyright owner
79 # gives unlimited permission to copy, distribute and modify the configure
80 # scripts that are the output of Autoconf when processing the Macro. You
81 # need not follow the terms of the GNU General Public License when using
82 # or distributing such scripts, even though portions of the text of the
83 # Macro appear in them. The GNU General Public License (GPL) does govern
84 # all other use of the material that constitutes the Autoconf Macro.
86 # This special exception to the GPL applies to versions of the Autoconf
87 # Macro released by the Autoconf Archive. When you make and distribute a
88 # modified version of the Autoconf Macro, you may extend this special
89 # exception to the GPL to apply to your modified version as well.
93 AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
94 AC_DEFUN([AX_PTHREAD], [
95 AC_REQUIRE([AC_CANONICAL_HOST])
96 AC_REQUIRE([AC_PROG_CC])
97 AC_REQUIRE([AC_PROG_SED])
101 # We used to check for pthread.h first, but this fails if pthread.h
102 # requires special compiler flags (e.g. on Tru64 or Sequent).
103 # It gets checked for in the link test anyway.
105 # First of all, check if the user has set any of the PTHREAD_LIBS,
106 # etcetera environment variables, and if threads linking works using
108 if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
109 ax_pthread_save_CC="$CC"
110 ax_pthread_save_CFLAGS="$CFLAGS"
111 ax_pthread_save_LIBS="$LIBS"
112 AS_IF([test "x$PTHREAD_CC" != "x"], [CC="$PTHREAD_CC"])
113 AS_IF([test "x$PTHREAD_CXX" != "x"], [CXX="$PTHREAD_CXX"])
114 CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
115 LIBS="$PTHREAD_LIBS $LIBS"
116 AC_MSG_CHECKING([for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS])
117 AC_LINK_IFELSE([AC_LANG_CALL([], [pthread_join])], [ax_pthread_ok=yes])
118 AC_MSG_RESULT([$ax_pthread_ok])
119 if test "x$ax_pthread_ok" = "xno"; then
123 CC="$ax_pthread_save_CC"
124 CFLAGS="$ax_pthread_save_CFLAGS"
125 LIBS="$ax_pthread_save_LIBS"
128 # We must check for the threads library under a number of different
129 # names; the ordering is very important because some systems
130 # (e.g. DEC) have both -lpthread and -lpthreads, where one of the
131 # libraries is broken (non-POSIX).
133 # Create a list of thread flags to try. Items with a "," contain both
134 # C compiler flags (before ",") and linker flags (after ","). Other items
135 # starting with a "-" are C compiler flags, and remaining items are
136 # library names, except for "none" which indicates that we try without
137 # any flags at all, and "pthread-config" which is a program returning
138 # the flags for the Pth emulation library.
140 ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"
142 # The ordering *is* (sometimes) important. Some notes on the
143 # individual items follow:
145 # pthreads: AIX (must check this before -lpthread)
146 # none: in case threads are in libc; should be tried before -Kthread and
147 # other compiler flags to prevent continual compiler warnings
148 # -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)
149 # -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
150 # (Note: HP C rejects this with "bad form for `-t' option")
151 # -pthreads: Solaris/gcc (Note: HP C also rejects)
152 # -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
153 # doesn't hurt to check since this sometimes defines pthreads and
154 # -D_REENTRANT too), HP C (must be checked before -lpthread, which
155 # is present but should not be used directly; and before -mthreads,
156 # because the compiler interprets this as "-mt" + "-hreads")
157 # -mthreads: Mingw32/gcc, Lynx/gcc
158 # pthread: Linux, etcetera
159 # --thread-safe: KAI C++
160 # pthread-config: use pthread-config program (for GNU Pth library)
166 # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
167 # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
169 ax_pthread_flags="-kthread lthread $ax_pthread_flags"
174 # From the cc(1) man page: "[-mt] Sets various -D flags to enable
175 # multi-threading and also sets -lpthread."
177 ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
182 # IBM z/OS requires a feature-test macro to be defined in order to
183 # enable POSIX threads at all, so give the user a hint if this is
184 # not set. (We don't define these ourselves, as they can affect
185 # other portions of the system API in unpredictable ways.)
187 AC_EGREP_CPP([AX_PTHREAD_ZOS_MISSING],
189 # if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
190 AX_PTHREAD_ZOS_MISSING
193 [AC_MSG_WARN([IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support.])])
198 # On Solaris (at least, for some versions), libc contains stubbed
199 # (non-functional) versions of the pthreads routines, so link-based
200 # tests will erroneously succeed. (N.B.: The stubs are missing
201 # pthread_cleanup_push, or rather a function called by this macro,
202 # so we could check for that, but who knows whether they'll stub
203 # that too in a future libc.) So we'll check first for the
204 # standard Solaris way of linking pthreads (-mt -lpthread).
206 ax_pthread_flags="-mt,-lpthread pthread $ax_pthread_flags"
210 # Are we compiling with Clang?
212 AC_CACHE_CHECK([whether $CC is Clang],
213 [ax_cv_PTHREAD_CLANG],
214 [ax_cv_PTHREAD_CLANG=no
215 # Note that Autoconf sets GCC=yes for Clang as well as GCC
216 if test "x$GCC" = "xyes"; then
217 AC_EGREP_CPP([AX_PTHREAD_CC_IS_CLANG],
218 [/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
219 # if defined(__clang__) && defined(__llvm__)
220 AX_PTHREAD_CC_IS_CLANG
223 [ax_cv_PTHREAD_CLANG=yes])
226 ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
229 # GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
231 # Note that for GCC and Clang -pthread generally implies -lpthread,
232 # except when -nostdlib is passed.
233 # This is problematic using libtool to build C++ shared libraries with pthread:
234 # [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460
235 # [2] https://bugzilla.redhat.com/show_bug.cgi?id=661333
236 # [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=468555
237 # To solve this, first try -pthread together with -lpthread for GCC
239 AS_IF([test "x$GCC" = "xyes"],
240 [ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"])
242 # Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first
244 AS_IF([test "x$ax_pthread_clang" = "xyes"],
245 [ax_pthread_flags="-pthread,-lpthread -pthread"])
248 # The presence of a feature test macro requesting re-entrant function
249 # definitions is, on some systems, a strong hint that pthreads support is
253 darwin* | hpux* | linux* | osf* | solaris*)
254 ax_pthread_check_macro="_REENTRANT"
258 ax_pthread_check_macro="_THREAD_SAFE"
262 ax_pthread_check_macro="--"
265 AS_IF([test "x$ax_pthread_check_macro" = "x--"],
266 [ax_pthread_check_cond=0],
267 [ax_pthread_check_cond="!defined($ax_pthread_check_macro)"])
270 if test "x$ax_pthread_ok" = "xno"; then
271 for ax_pthread_try_flag in $ax_pthread_flags; do
273 case $ax_pthread_try_flag in
275 AC_MSG_CHECKING([whether pthreads work without any flags])
279 PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"`
280 PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"`
281 AC_MSG_CHECKING([whether pthreads work with "$PTHREAD_CFLAGS" and "$PTHREAD_LIBS"])
285 AC_MSG_CHECKING([whether pthreads work with $ax_pthread_try_flag])
286 PTHREAD_CFLAGS="$ax_pthread_try_flag"
290 AC_CHECK_PROG([ax_pthread_config], [pthread-config], [yes], [no])
291 AS_IF([test "x$ax_pthread_config" = "xno"], [continue])
292 PTHREAD_CFLAGS="`pthread-config --cflags`"
293 PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
297 AC_MSG_CHECKING([for the pthreads library -l$ax_pthread_try_flag])
298 PTHREAD_LIBS="-l$ax_pthread_try_flag"
302 ax_pthread_save_CFLAGS="$CFLAGS"
303 ax_pthread_save_LIBS="$LIBS"
304 CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
305 LIBS="$PTHREAD_LIBS $LIBS"
307 # Check for various functions. We must include pthread.h,
308 # since some functions may be macros. (On the Sequent, we
309 # need a special flag -Kthread to make this header compile.)
310 # We check for pthread_join because it is in -lpthread on IRIX
311 # while pthread_create is in libc. We check for pthread_attr_init
312 # due to DEC craziness with -lpthreads. We check for
313 # pthread_cleanup_push because it is one of the few pthread
314 # functions on Solaris that doesn't have a non-functional libc stub.
315 # We try pthread_create on general principles.
317 AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>
318 # if $ax_pthread_check_cond
319 # error "$ax_pthread_check_macro must be defined"
321 static void *some_global = NULL;
322 static void routine(void *a)
324 /* To avoid any unused-parameter or
325 unused-but-set-parameter warning. */
328 static void *start_routine(void *a) { return a; }],
329 [pthread_t th; pthread_attr_t attr;
330 pthread_create(&th, 0, start_routine, 0);
332 pthread_attr_init(&attr);
333 pthread_cleanup_push(routine, 0);
334 pthread_cleanup_pop(0) /* ; */])],
338 CFLAGS="$ax_pthread_save_CFLAGS"
339 LIBS="$ax_pthread_save_LIBS"
341 AC_MSG_RESULT([$ax_pthread_ok])
342 AS_IF([test "x$ax_pthread_ok" = "xyes"], [break])
350 # Clang needs special handling, because older versions handle the -pthread
351 # option in a rather... idiosyncratic way
353 if test "x$ax_pthread_clang" = "xyes"; then
355 # Clang takes -pthread; it has never supported any other flag
357 # (Note 1: This will need to be revisited if a system that Clang
358 # supports has POSIX threads in a separate library. This tends not
359 # to be the way of modern systems, but it's conceivable.)
361 # (Note 2: On some systems, notably Darwin, -pthread is not needed
362 # to get POSIX threads support; the API is always present and
363 # active. We could reasonably leave PTHREAD_CFLAGS empty. But
364 # -pthread does define _REENTRANT, and while the Darwin headers
365 # ignore this macro, third-party headers might not.)
367 # However, older versions of Clang make a point of warning the user
368 # that, in an invocation where only linking and no compilation is
369 # taking place, the -pthread option has no effect ("argument unused
370 # during compilation"). They expect -pthread to be passed in only
371 # when source code is being compiled.
373 # Problem is, this is at odds with the way Automake and most other
374 # C build frameworks function, which is that the same flags used in
375 # compilation (CFLAGS) are also used in linking. Many systems
376 # supported by AX_PTHREAD require exactly this for POSIX threads
377 # support, and in fact it is often not straightforward to specify a
378 # flag that is used only in the compilation phase and not in
379 # linking. Such a scenario is extremely rare in practice.
381 # Even though use of the -pthread flag in linking would only print
382 # a warning, this can be a nuisance for well-run software projects
383 # that build with -Werror. So if the active version of Clang has
384 # this misfeature, we search for an option to squash it.
386 AC_CACHE_CHECK([whether Clang needs flag to prevent "argument unused" warning when linking with -pthread],
387 [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG],
388 [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
389 # Create an alternate version of $ac_link that compiles and
390 # links in two steps (.c -> .o, .o -> exe) instead of one
391 # (.c -> exe), because the warning occurs only in the second
393 ax_pthread_save_ac_link="$ac_link"
394 ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
395 ax_pthread_link_step=`AS_ECHO(["$ac_link"]) | sed "$ax_pthread_sed"`
396 ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
397 ax_pthread_save_CFLAGS="$CFLAGS"
398 for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
399 AS_IF([test "x$ax_pthread_try" = "xunknown"], [break])
400 CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
401 ac_link="$ax_pthread_save_ac_link"
402 AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
403 [ac_link="$ax_pthread_2step_ac_link"
404 AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
408 ac_link="$ax_pthread_save_ac_link"
409 CFLAGS="$ax_pthread_save_CFLAGS"
410 AS_IF([test "x$ax_pthread_try" = "x"], [ax_pthread_try=no])
411 ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
414 case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
416 *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
419 fi # $ax_pthread_clang = yes
423 # Various other checks:
424 if test "x$ax_pthread_ok" = "xyes"; then
425 ax_pthread_save_CFLAGS="$CFLAGS"
426 ax_pthread_save_LIBS="$LIBS"
427 CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
428 LIBS="$PTHREAD_LIBS $LIBS"
430 # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
431 AC_CACHE_CHECK([for joinable pthread attribute],
432 [ax_cv_PTHREAD_JOINABLE_ATTR],
433 [ax_cv_PTHREAD_JOINABLE_ATTR=unknown
434 for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
435 AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>],
436 [int attr = $ax_pthread_attr; return attr /* ; */])],
437 [ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break],
441 AS_IF([test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
442 test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
443 test "x$ax_pthread_joinable_attr_defined" != "xyes"],
444 [AC_DEFINE_UNQUOTED([PTHREAD_CREATE_JOINABLE],
445 [$ax_cv_PTHREAD_JOINABLE_ATTR],
446 [Define to necessary symbol if this constant
447 uses a non-standard name on your system.])
448 ax_pthread_joinable_attr_defined=yes
451 AC_CACHE_CHECK([whether more special flags are required for pthreads],
452 [ax_cv_PTHREAD_SPECIAL_FLAGS],
453 [ax_cv_PTHREAD_SPECIAL_FLAGS=no
456 ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
460 AS_IF([test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
461 test "x$ax_pthread_special_flags_added" != "xyes"],
462 [PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
463 ax_pthread_special_flags_added=yes])
465 AC_CACHE_CHECK([for PTHREAD_PRIO_INHERIT],
466 [ax_cv_PTHREAD_PRIO_INHERIT],
467 [AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <pthread.h>]],
468 [[int i = PTHREAD_PRIO_INHERIT;
470 [ax_cv_PTHREAD_PRIO_INHERIT=yes],
471 [ax_cv_PTHREAD_PRIO_INHERIT=no])
473 AS_IF([test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
474 test "x$ax_pthread_prio_inherit_defined" != "xyes"],
475 [AC_DEFINE([HAVE_PTHREAD_PRIO_INHERIT], [1], [Have PTHREAD_PRIO_INHERIT.])
476 ax_pthread_prio_inherit_defined=yes
479 CFLAGS="$ax_pthread_save_CFLAGS"
480 LIBS="$ax_pthread_save_LIBS"
482 # More AIX lossage: compile with *_r variant
483 if test "x$GCC" != "xyes"; then
487 [x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6],
488 [#handle absolute path differently from PATH based program lookup
492 AS_IF([AS_EXECUTABLE_P([${CC}_r])],[PTHREAD_CC="${CC}_r"])
493 AS_IF([test "x${CXX}" != "x"], [AS_IF([AS_EXECUTABLE_P([${CXX}_r])],[PTHREAD_CXX="${CXX}_r"])])
496 AC_CHECK_PROGS([PTHREAD_CC],[${CC}_r],[$CC])
497 AS_IF([test "x${CXX}" != "x"], [AC_CHECK_PROGS([PTHREAD_CXX],[${CXX}_r],[$CXX])])
506 test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
507 test -n "$PTHREAD_CXX" || PTHREAD_CXX="$CXX"
509 AC_SUBST([PTHREAD_LIBS])
510 AC_SUBST([PTHREAD_CFLAGS])
511 AC_SUBST([PTHREAD_CC])
512 AC_SUBST([PTHREAD_CXX])
514 # Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
515 if test "x$ax_pthread_ok" = "xyes"; then
516 ifelse([$1],,[AC_DEFINE([HAVE_PTHREAD],[1],[Define if you have POSIX threads libraries and header files.])],[$1])