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+++ b/m4/threadlib.m4
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+# threadlib.m4 serial 32
+dnl Copyright (C) 2005-2022 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 From Bruno Haible.
+
+AC_PREREQ([2.60])
+
+dnl The general structure of the multithreading modules in gnulib is that we
+dnl have three set of modules:
+dnl
+dnl * POSIX API:
+dnl pthread, which combines
+dnl pthread-h
+dnl pthread-thread
+dnl pthread-once
+dnl pthread-mutex
+dnl pthread-rwlock
+dnl pthread-cond
+dnl pthread-tss
+dnl pthread-spin
+dnl sched_yield
+dnl
+dnl * ISO C API:
+dnl threads, which combines
+dnl threads-h
+dnl thrd
+dnl mtx
+dnl cnd
+dnl tss
+dnl
+dnl * Gnulib API, with an implementation that can be chosen at configure
+dnl time through the option --enable-threads=...
+dnl thread
+dnl lock
+dnl cond
+dnl tls
+dnl yield
+dnl
+dnl They are independent, except for the fact that
+dnl - the implementation of the ISO C API may use the POSIX (or some other
+dnl platform dependent) API,
+dnl - the implementation of the Gnulib API may use the POSIX or ISO C or
+dnl some other platform dependent API, depending on the --enable-threads
+dnl option.
+dnl
+dnl This file contains macros for all of these APIs!
+
+dnl ============================================================================
+dnl Macros for all thread APIs
+
+AC_DEFUN([gl_ANYTHREADLIB_EARLY],
+[
+ AC_REQUIRE([AC_CANONICAL_HOST])
+ if test -z "$gl_anythreadlib_early_done"; then
+ case "$host_os" in
+ osf*)
+ # On OSF/1, the compiler needs the flag -D_REENTRANT so that it
+ # groks <pthread.h>. cc also understands the flag -pthread, but
+ # we don't use it because 1. gcc-2.95 doesn't understand -pthread,
+ # 2. putting a flag into CPPFLAGS that has an effect on the linker
+ # causes the AC_LINK_IFELSE test below to succeed unexpectedly,
+ # leading to wrong values of LIBTHREAD and LTLIBTHREAD.
+ CPPFLAGS="$CPPFLAGS -D_REENTRANT"
+ ;;
+ esac
+ # Some systems optimize for single-threaded programs by default, and
+ # need special flags to disable these optimizations. For example, the
+ # definition of 'errno' in <errno.h>.
+ case "$host_os" in
+ aix* | freebsd*) CPPFLAGS="$CPPFLAGS -D_THREAD_SAFE" ;;
+ solaris*) CPPFLAGS="$CPPFLAGS -D_REENTRANT" ;;
+ esac
+ gl_anythreadlib_early_done=done
+ fi
+])
+
+dnl Checks whether the compiler and linker support weak declarations of symbols.
+
+AC_DEFUN([gl_WEAK_SYMBOLS],
+[
+ AC_REQUIRE([AC_CANONICAL_HOST])
+ AC_CACHE_CHECK([whether imported symbols can be declared weak],
+ [gl_cv_have_weak],
+ [case "$host_os" in
+ cygwin*)
+ dnl On Cygwin 3.2.0 with gcc 10.2, the test below would succeed, but
+ dnl programs that use pthread_in_use() with weak symbol references
+ dnl crash miserably at runtime.
+ gl_cv_have_weak="guessing no"
+ ;;
+ *)
+ gl_cv_have_weak=no
+ dnl First, test whether the compiler accepts it syntactically.
+ AC_LINK_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[extern void xyzzy ();
+#pragma weak xyzzy]],
+ [[xyzzy();]])],
+ [gl_cv_have_weak=maybe])
+ if test $gl_cv_have_weak = maybe; then
+ dnl Second, test whether it actually works. On Cygwin 1.7.2, with
+ dnl gcc 4.3, symbols declared weak always evaluate to the address 0.
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#include <stdio.h>
+#pragma weak fputs
+int main ()
+{
+ return (fputs == NULL);
+}]])],
+ [gl_cv_have_weak=yes],
+ [gl_cv_have_weak=no],
+ [dnl When cross-compiling, assume that only ELF platforms support
+ dnl weak symbols.
+ AC_EGREP_CPP([Extensible Linking Format],
+ [#ifdef __ELF__
+ Extensible Linking Format
+ #endif
+ ],
+ [gl_cv_have_weak="guessing yes"],
+ [gl_cv_have_weak="guessing no"])
+ ])
+ fi
+ ;;
+ esac
+ dnl But when linking statically, weak symbols don't work.
+ case " $LDFLAGS " in
+ *" -static "*) gl_cv_have_weak=no ;;
+ esac
+ dnl Test for a bug in FreeBSD 11: A link error occurs when using a weak
+ dnl symbol and linking against a shared library that has a dependency on
+ dnl the shared library that defines the symbol.
+ case "$gl_cv_have_weak" in
+ *yes)
+ case "$host_os" in
+ freebsd* | dragonfly* | midnightbsd*)
+ : > conftest1.c
+ $CC $CPPFLAGS $CFLAGS $LDFLAGS -fPIC -shared -o libempty.so conftest1.c -lpthread >&AS_MESSAGE_LOG_FD 2>&1
+ cat <<EOF > conftest2.c
+#include <pthread.h>
+#pragma weak pthread_mutexattr_gettype
+int main ()
+{
+ return (pthread_mutexattr_gettype != NULL);
+}
+EOF
+ $CC $CPPFLAGS $CFLAGS $LDFLAGS -o conftest conftest2.c libempty.so >&AS_MESSAGE_LOG_FD 2>&1 \
+ || gl_cv_have_weak=no
+ rm -f conftest1.c libempty.so conftest2.c conftest
+ ;;
+ esac
+ ;;
+ esac
+ ])
+ case "$gl_cv_have_weak" in
+ *yes)
+ AC_DEFINE([HAVE_WEAK_SYMBOLS], [1],
+ [Define to 1 if the compiler and linker support weak declarations of symbols.])
+ ;;
+ esac
+])
+
+dnl ============================================================================
+dnl Macros for the POSIX API
+
+dnl gl_PTHREADLIB
+dnl -------------
+dnl Tests for the libraries needs for using the POSIX threads API.
+dnl Sets the variable LIBPTHREAD to the linker options for use in a Makefile.
+dnl Sets the variable LIBPMULTITHREAD, for programs that really need
+dnl multithread functionality. The difference between LIBPTHREAD and
+dnl LIBPMULTITHREAD is that on platforms supporting weak symbols, typically
+dnl LIBPTHREAD is empty whereas LIBPMULTITHREAD is not.
+dnl Sets the variable LIB_SCHED_YIELD to the linker options needed to use the
+dnl sched_yield() function.
+dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
+dnl multithread-safe programs.
+dnl Defines the C macro HAVE_PTHREAD_API if (at least parts of) the POSIX
+dnl threads API is available.
+
+dnl The guts of gl_PTHREADLIB. Needs to be expanded only once.
+
+AC_DEFUN([gl_PTHREADLIB_BODY],
+[
+ AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+ if test -z "$gl_pthreadlib_body_done"; then
+ gl_pthread_api=no
+ LIBPTHREAD=
+ LIBPMULTITHREAD=
+ # On OSF/1, the compiler needs the flag -pthread or -D_REENTRANT so that
+ # it groks <pthread.h>. It's added above, in gl_ANYTHREADLIB_EARLY.
+ AC_CHECK_HEADER([pthread.h],
+ [gl_have_pthread_h=yes], [gl_have_pthread_h=no])
+ if test "$gl_have_pthread_h" = yes; then
+ # Other possible tests:
+ # -lpthreads (FSU threads, PCthreads)
+ # -lgthreads
+ # Test whether both pthread_mutex_lock and pthread_mutexattr_init exist
+ # in libc. IRIX 6.5 has the first one in both libc and libpthread, but
+ # the second one only in libpthread, and lock.c needs it.
+ #
+ # If -pthread works, prefer it to -lpthread, since Ubuntu 14.04
+ # needs -pthread for some reason. See:
+ # https://lists.gnu.org/r/bug-gnulib/2014-09/msg00023.html
+ save_LIBS=$LIBS
+ for gl_pthread in '' '-pthread'; do
+ LIBS="$LIBS $gl_pthread"
+ AC_LINK_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <pthread.h>
+ pthread_mutex_t m;
+ pthread_mutexattr_t ma;
+ ]],
+ [[pthread_mutex_lock (&m);
+ pthread_mutexattr_init (&ma);]])],
+ [gl_pthread_api=yes
+ LIBPTHREAD=$gl_pthread
+ LIBPMULTITHREAD=$gl_pthread])
+ LIBS=$save_LIBS
+ test $gl_pthread_api = yes && break
+ done
+ echo "$as_me:__oline__: gl_pthread_api=$gl_pthread_api" >&AS_MESSAGE_LOG_FD
+ echo "$as_me:__oline__: LIBPTHREAD=$LIBPTHREAD" >&AS_MESSAGE_LOG_FD
+
+ gl_pthread_in_glibc=no
+ # On Linux with glibc >= 2.34, libc contains the fully functional
+ # pthread functions.
+ case "$host_os" in
+ linux*)
+ AC_EGREP_CPP([Lucky user],
+ [#include <features.h>
+ #ifdef __GNU_LIBRARY__
+ #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 34) || (__GLIBC__ > 2)
+ Lucky user
+ #endif
+ #endif
+ ],
+ [gl_pthread_in_glibc=yes],
+ [])
+ ;;
+ esac
+ echo "$as_me:__oline__: gl_pthread_in_glibc=$gl_pthread_in_glibc" >&AS_MESSAGE_LOG_FD
+
+ # Test for libpthread by looking for pthread_kill. (Not pthread_self,
+ # since it is defined as a macro on OSF/1.)
+ if test $gl_pthread_api = yes && test -z "$LIBPTHREAD"; then
+ # The program links fine without libpthread. But it may actually
+ # need to link with libpthread in order to create multiple threads.
+ AC_CHECK_LIB([pthread], [pthread_kill],
+ [if test $gl_pthread_in_glibc = yes; then
+ LIBPMULTITHREAD=
+ else
+ LIBPMULTITHREAD=-lpthread
+ # On Solaris and HP-UX, most pthread functions exist also in libc.
+ # Therefore pthread_in_use() needs to actually try to create a
+ # thread: pthread_create from libc will fail, whereas
+ # pthread_create will actually create a thread.
+ # On Solaris 10 or newer, this test is no longer needed, because
+ # libc contains the fully functional pthread functions.
+ case "$host_os" in
+ solaris | solaris2.[1-9] | solaris2.[1-9].* | hpux*)
+ AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
+ [Define if the pthread_in_use() detection is hard.])
+ esac
+ fi
+ ])
+ elif test $gl_pthread_api != yes; then
+ # Some library is needed. Try libpthread and libc_r.
+ AC_CHECK_LIB([pthread], [pthread_kill],
+ [gl_pthread_api=yes
+ LIBPTHREAD=-lpthread
+ LIBPMULTITHREAD=-lpthread])
+ if test $gl_pthread_api != yes; then
+ # For FreeBSD 4.
+ AC_CHECK_LIB([c_r], [pthread_kill],
+ [gl_pthread_api=yes
+ LIBPTHREAD=-lc_r
+ LIBPMULTITHREAD=-lc_r])
+ fi
+ fi
+ echo "$as_me:__oline__: LIBPMULTITHREAD=$LIBPMULTITHREAD" >&AS_MESSAGE_LOG_FD
+ fi
+ AC_MSG_CHECKING([whether POSIX threads API is available])
+ AC_MSG_RESULT([$gl_pthread_api])
+ AC_SUBST([LIBPTHREAD])
+ AC_SUBST([LIBPMULTITHREAD])
+ if test $gl_pthread_api = yes; then
+ AC_DEFINE([HAVE_PTHREAD_API], [1],
+ [Define if you have the <pthread.h> header and the POSIX threads API.])
+ fi
+
+ dnl On some systems, sched_yield is in librt, rather than in libpthread.
+ AC_LINK_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <sched.h>]],
+ [[sched_yield ();]])],
+ [LIB_SCHED_YIELD=
+ ],
+ [dnl Solaris 7...10 has sched_yield in librt, not in libpthread or libc.
+ AC_CHECK_LIB([rt], [sched_yield], [LIB_SCHED_YIELD=-lrt],
+ [dnl Solaris 2.5.1, 2.6 has sched_yield in libposix4, not librt.
+ AC_CHECK_LIB([posix4], [sched_yield], [LIB_SCHED_YIELD=-lposix4])])
+ ])
+ AC_SUBST([LIB_SCHED_YIELD])
+
+ gl_pthreadlib_body_done=done
+ fi
+])
+
+AC_DEFUN([gl_PTHREADLIB],
+[
+ AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+ gl_PTHREADLIB_BODY
+])
+
+dnl ============================================================================
+dnl Macros for the ISO C API
+
+dnl gl_STDTHREADLIB
+dnl ---------------
+dnl Tests for the libraries needs for using the ISO C threads API.
+dnl Sets the variable LIBSTDTHREAD to the linker options for use in a Makefile.
+dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
+dnl multithread-safe programs.
+dnl Defines the C macro HAVE_THREADS_H if (at least parts of) the ISO C threads
+dnl API is available.
+
+dnl The guts of gl_STDTHREADLIB. Needs to be expanded only once.
+
+AC_DEFUN([gl_STDTHREADLIB_BODY],
+[
+ AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+ AC_REQUIRE([AC_CANONICAL_HOST])
+ if test -z "$gl_stdthreadlib_body_done"; then
+ AC_CHECK_HEADERS_ONCE([threads.h])
+
+ case "$host_os" in
+ mingw*)
+ LIBSTDTHREAD=
+ ;;
+ *)
+ gl_PTHREADLIB_BODY
+ if test $ac_cv_header_threads_h = yes; then
+ dnl glibc >= 2.29 has thrd_create in libpthread.
+ dnl FreeBSD >= 10 has thrd_create in libstdthreads; this library depends
+ dnl on libpthread (for the symbol 'pthread_mutexattr_gettype').
+ dnl glibc >= 2.34, AIX >= 7.1, and Solaris >= 11.4 have thrd_create in
+ dnl libc.
+ AC_CHECK_FUNCS([thrd_create])
+ if test $ac_cv_func_thrd_create = yes; then
+ LIBSTDTHREAD=
+ else
+ AC_CHECK_LIB([stdthreads], [thrd_create], [
+ LIBSTDTHREAD='-lstdthreads -lpthread'
+ ], [
+ dnl Guess that thrd_create is in libpthread.
+ LIBSTDTHREAD="$LIBPMULTITHREAD"
+ ])
+ fi
+ else
+ dnl Libraries needed by thrd.c, mtx.c, cnd.c, tss.c.
+ LIBSTDTHREAD="$LIBPMULTITHREAD $LIB_SCHED_YIELD"
+ fi
+ ;;
+ esac
+ AC_SUBST([LIBSTDTHREAD])
+
+ AC_MSG_CHECKING([whether ISO C threads API is available])
+ AC_MSG_RESULT([$ac_cv_header_threads_h])
+ gl_stdthreadlib_body_done=done
+ fi
+])
+
+AC_DEFUN([gl_STDTHREADLIB],
+[
+ AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+ gl_STDTHREADLIB_BODY
+])
+
+dnl ============================================================================
+dnl Macros for the Gnulib API
+
+dnl gl_THREADLIB
+dnl ------------
+dnl Tests for a multithreading library to be used.
+dnl If the configure.ac contains a definition of the gl_THREADLIB_DEFAULT_NO
+dnl (it must be placed before the invocation of gl_THREADLIB_EARLY!), then the
+dnl default is 'no', otherwise it is system dependent. In both cases, the user
+dnl can change the choice through the options --enable-threads=choice or
+dnl --disable-threads.
+dnl Defines at most one of the macros USE_ISOC_THREADS, USE_POSIX_THREADS,
+dnl USE_ISOC_AND_POSIX_THREADS, USE_WINDOWS_THREADS.
+dnl The choice --enable-threads=isoc+posix is available only on platforms that
+dnl have both the ISO C and the POSIX threads APIs. It has the effect of using
+dnl the ISO C API for most things and the POSIX API only for creating and
+dnl controlling threads (because there is no equivalent to pthread_atfork in
+dnl the ISO C API).
+dnl Sets the variables LIBTHREAD and LTLIBTHREAD to the linker options for use
+dnl in a Makefile (LIBTHREAD for use without libtool, LTLIBTHREAD for use with
+dnl libtool).
+dnl Sets the variables LIBMULTITHREAD and LTLIBMULTITHREAD similarly, for
+dnl programs that really need multithread functionality. The difference
+dnl between LIBTHREAD and LIBMULTITHREAD is that on platforms supporting weak
+dnl symbols, typically LIBTHREAD is empty whereas LIBMULTITHREAD is not.
+dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
+dnl multithread-safe programs.
+dnl Since support for GNU pth was removed, $LTLIBTHREAD and $LIBTHREAD have the
+dnl same value, and similarly $LTLIBMULTITHREAD and $LIBMULTITHREAD have the
+dnl same value. Only system libraries are needed.
+
+AC_DEFUN([gl_THREADLIB_EARLY],
+[
+ AC_REQUIRE([gl_THREADLIB_EARLY_BODY])
+])
+
+dnl The guts of gl_THREADLIB_EARLY. Needs to be expanded only once.
+
+AC_DEFUN([gl_THREADLIB_EARLY_BODY],
+[
+ dnl Ordering constraints: This macro modifies CPPFLAGS in a way that
+ dnl influences the result of the autoconf tests that test for *_unlocked
+ dnl declarations, on AIX 5 at least. Therefore it must come early.
+ AC_BEFORE([$0], [gl_FUNC_GLIBC_UNLOCKED_IO])dnl
+ AC_BEFORE([$0], [gl_ARGP])dnl
+
+ AC_REQUIRE([AC_CANONICAL_HOST])
+ dnl _GNU_SOURCE is needed for pthread_rwlock_t on glibc systems.
+ AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+ dnl Check for multithreading.
+ m4_ifdef([gl_THREADLIB_DEFAULT_NO],
+ [m4_divert_text([DEFAULTS], [gl_use_threads_default=no])],
+ [m4_divert_text([DEFAULTS], [gl_use_threads_default=])])
+ m4_divert_text([DEFAULTS], [gl_use_winpthreads_default=])
+ AC_ARG_ENABLE([threads],
+AS_HELP_STRING([--enable-threads={isoc|posix|isoc+posix|windows}], [specify multithreading API])m4_ifdef([gl_THREADLIB_DEFAULT_NO], [], [
+AS_HELP_STRING([--disable-threads], [build without multithread safety])]),
+ [gl_use_threads=$enableval],
+ [if test -n "$gl_use_threads_default"; then
+ gl_use_threads="$gl_use_threads_default"
+ else
+changequote(,)dnl
+ case "$host_os" in
+ dnl Disable multithreading by default on OSF/1, because it interferes
+ dnl with fork()/exec(): When msgexec is linked with -lpthread, its
+ dnl child process gets an endless segmentation fault inside execvp().
+ osf*) gl_use_threads=no ;;
+ dnl Disable multithreading by default on Cygwin 1.5.x, because it has
+ dnl bugs that lead to endless loops or crashes. See
+ dnl <https://cygwin.com/ml/cygwin/2009-08/msg00283.html>.
+ cygwin*)
+ case `uname -r` in
+ 1.[0-5].*) gl_use_threads=no ;;
+ *) gl_use_threads=yes ;;
+ esac
+ ;;
+ dnl Obey gl_AVOID_WINPTHREAD on mingw.
+ mingw*)
+ case "$gl_use_winpthreads_default" in
+ yes) gl_use_threads=posix ;;
+ no) gl_use_threads=windows ;;
+ *) gl_use_threads=yes ;;
+ esac
+ ;;
+ *) gl_use_threads=yes ;;
+ esac
+changequote([,])dnl
+ fi
+ ])
+ if test "$gl_use_threads" = yes \
+ || test "$gl_use_threads" = isoc \
+ || test "$gl_use_threads" = posix \
+ || test "$gl_use_threads" = isoc+posix; then
+ # For using <threads.h> or <pthread.h>:
+ gl_ANYTHREADLIB_EARLY
+ fi
+])
+
+dnl The guts of gl_THREADLIB. Needs to be expanded only once.
+
+AC_DEFUN([gl_THREADLIB_BODY],
+[
+ AC_REQUIRE([gl_THREADLIB_EARLY_BODY])
+ gl_threads_api=none
+ LIBTHREAD=
+ LTLIBTHREAD=
+ LIBMULTITHREAD=
+ LTLIBMULTITHREAD=
+ if test "$gl_use_threads" != no; then
+ dnl Check whether the compiler and linker support weak declarations.
+ gl_WEAK_SYMBOLS
+ if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
+ dnl If we use weak symbols to implement pthread_in_use / pth_in_use /
+ dnl thread_in_use, we also need to test whether the ISO C 11 thrd_create
+ dnl facility is in use.
+ AC_CHECK_HEADERS_ONCE([threads.h])
+ :
+ fi
+ if test "$gl_use_threads" = isoc || test "$gl_use_threads" = isoc+posix; then
+ AC_CHECK_HEADERS_ONCE([threads.h])
+ gl_have_isoc_threads="$ac_cv_header_threads_h"
+ fi
+ if test "$gl_use_threads" = yes \
+ || test "$gl_use_threads" = posix \
+ || test "$gl_use_threads" = isoc+posix; then
+ gl_PTHREADLIB_BODY
+ LIBTHREAD=$LIBPTHREAD LTLIBTHREAD=$LIBPTHREAD
+ LIBMULTITHREAD=$LIBPMULTITHREAD LTLIBMULTITHREAD=$LIBPMULTITHREAD
+ if test $gl_pthread_api = yes; then
+ if test "$gl_use_threads" = isoc+posix && test "$gl_have_isoc_threads" = yes; then
+ gl_threads_api='isoc+posix'
+ AC_DEFINE([USE_ISOC_AND_POSIX_THREADS], [1],
+ [Define if the combination of the ISO C and POSIX multithreading APIs can be used.])
+ LIBTHREAD= LTLIBTHREAD=
+ else
+ gl_threads_api=posix
+ AC_DEFINE([USE_POSIX_THREADS], [1],
+ [Define if the POSIX multithreading library can be used.])
+ if test -z "$LIBMULTITHREAD" && test -z "$LTLIBMULTITHREAD"; then
+ AC_DEFINE([USE_POSIX_THREADS_FROM_LIBC], [1],
+ [Define if references to the POSIX multithreading library are satisfied by libc.])
+ else
+ if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
+ AC_DEFINE([USE_POSIX_THREADS_WEAK], [1],
+ [Define if references to the POSIX multithreading library should be made weak.])
+ LIBTHREAD= LTLIBTHREAD=
+ else
+ case "$host_os" in
+ freebsd* | dragonfly* | midnightbsd*)
+ if test "x$LIBTHREAD" != "x$LIBMULTITHREAD"; then
+ dnl If weak symbols can't tell whether pthread_create(), pthread_key_create()
+ dnl etc. will succeed, we need a runtime test.
+ AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
+ [Define if the pthread_in_use() detection is hard.])
+ fi
+ ;;
+ esac
+ fi
+ fi
+ fi
+ fi
+ fi
+ if test $gl_threads_api = none; then
+ if test "$gl_use_threads" = isoc && test "$gl_have_isoc_threads" = yes; then
+ gl_STDTHREADLIB_BODY
+ LIBTHREAD=$LIBSTDTHREAD LTLIBTHREAD=$LIBSTDTHREAD
+ LIBMULTITHREAD=$LIBSTDTHREAD LTLIBMULTITHREAD=$LIBSTDTHREAD
+ gl_threads_api=isoc
+ AC_DEFINE([USE_ISOC_THREADS], [1],
+ [Define if the ISO C multithreading library can be used.])
+ fi
+ fi
+ if test $gl_threads_api = none; then
+ case "$gl_use_threads" in
+ yes | windows | win32) # The 'win32' is for backward compatibility.
+ if { case "$host_os" in
+ mingw*) true;;
+ *) false;;
+ esac
+ }; then
+ gl_threads_api=windows
+ AC_DEFINE([USE_WINDOWS_THREADS], [1],
+ [Define if the native Windows multithreading API can be used.])
+ fi
+ ;;
+ esac
+ fi
+ fi
+ AC_MSG_CHECKING([for multithread API to use])
+ AC_MSG_RESULT([$gl_threads_api])
+ AC_SUBST([LIBTHREAD])
+ AC_SUBST([LTLIBTHREAD])
+ AC_SUBST([LIBMULTITHREAD])
+ AC_SUBST([LTLIBMULTITHREAD])
+])
+
+AC_DEFUN([gl_THREADLIB],
+[
+ AC_REQUIRE([gl_THREADLIB_EARLY])
+ AC_REQUIRE([gl_THREADLIB_BODY])
+])
+
+
+dnl gl_DISABLE_THREADS
+dnl ------------------
+dnl Sets the gl_THREADLIB default so that threads are not used by default.
+dnl The user can still override it at installation time, by using the
+dnl configure option '--enable-threads'.
+
+AC_DEFUN([gl_DISABLE_THREADS], [
+ m4_divert_text([INIT_PREPARE], [gl_use_threads_default=no])
+])
+
+
+dnl gl_AVOID_WINPTHREAD
+dnl -------------------
+dnl Sets the gl_THREADLIB default so that on mingw, a dependency to the
+dnl libwinpthread DLL (mingw-w64 winpthreads library) is avoided.
+dnl The user can still override it at installation time, by using the
+dnl configure option '--enable-threads'.
+
+AC_DEFUN([gl_AVOID_WINPTHREAD], [
+ m4_divert_text([INIT_PREPARE], [gl_use_winpthreads_default=no])
+])
+
+
+dnl ============================================================================
+
+
+dnl Survey of platforms:
+dnl
+dnl Platform Available Compiler Supports test-lock
+dnl flavours option weak result
+dnl --------------- --------- --------- -------- ---------
+dnl Linux 2.4/glibc posix -lpthread Y OK
+dnl
+dnl Linux/glibc 2.34 posix Y OK
+dnl
+dnl GNU Hurd/glibc posix -lpthread Y OK
+dnl
+dnl Ubuntu 14.04 posix -pthread Y OK
+dnl
+dnl FreeBSD 5.3 posix -lc_r Y
+dnl posix -lkse ? Y
+dnl posix -lpthread ? Y
+dnl posix -lthr Y
+dnl
+dnl FreeBSD 5.2 posix -lc_r Y
+dnl posix -lkse Y
+dnl posix -lthr Y
+dnl
+dnl FreeBSD 4.0,4.10 posix -lc_r Y OK
+dnl
+dnl NetBSD 1.6 --
+dnl
+dnl OpenBSD 3.4 posix -lpthread Y OK
+dnl
+dnl Mac OS X 10.[123] posix -lpthread Y OK
+dnl
+dnl Solaris 7,8,9 posix -lpthread Y Sol 7,8: 0.0; Sol 9: OK
+dnl
+dnl HP-UX 11 posix -lpthread N (cc) OK
+dnl Y (gcc)
+dnl
+dnl IRIX 6.5 posix -lpthread Y 0.5
+dnl
+dnl AIX 4.3,5.1 posix -lpthread N AIX 4: 0.5; AIX 5: OK
+dnl
+dnl OSF/1 4.0,5.1 posix -pthread (cc) N OK
+dnl -lpthread (gcc) Y
+dnl
+dnl Cygwin posix -lpthread Y OK
+dnl
+dnl Mingw windows N OK
+dnl
+dnl BeOS 5 --
+dnl
+dnl The test-lock result shows what happens if in test-lock.c EXPLICIT_YIELD is
+dnl turned off:
+dnl OK if all three tests terminate OK,
+dnl 0.5 if the first test terminates OK but the second one loops endlessly,
+dnl 0.0 if the first test already loops endlessly.