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 # ===========================================================================

 #           http://www.nongnu.org/autoconf-archive/ax_pthread.html

 # ===========================================================================

 #

 # SYNOPSIS

 #

 #   AX_PTHREAD([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])

 #

 # DESCRIPTION

 #

 #   This macro figures out how to build C programs using POSIX threads. It

 #   sets the PTHREAD_LIBS output variable to the threads library and linker

 #   flags, and the PTHREAD_CFLAGS output variable to any special C compiler

 #   flags that are needed. (The user can also force certain compiler

 #   flags/libs to be tested by setting these environment variables.)

 #

 #   Also sets PTHREAD_CC to any special C compiler that is needed for

 #   multi-threaded programs (defaults to the value of CC otherwise). (This

 #   is necessary on AIX to use the special cc_r compiler alias.)

 #

 #   NOTE: You are assumed to not only compile your program with these flags,

 #   but also link it with them as well. e.g. you should link with

 #   $PTHREAD_CC $CFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS

 #

 #   If you are only building threads programs, you may wish to use these

 #   variables in your default LIBS, CFLAGS, and CC:

 #

 #     LIBS="$PTHREAD_LIBS $LIBS"

 #     CFLAGS="$CFLAGS $PTHREAD_CFLAGS"

 #     CC="$PTHREAD_CC"

 #

 #   In addition, if the PTHREAD_CREATE_JOINABLE thread-attribute constant

 #   has a nonstandard name, defines PTHREAD_CREATE_JOINABLE to that name

 #   (e.g. PTHREAD_CREATE_UNDETACHED on AIX).

 #

 #   ACTION-IF-FOUND is a list of shell commands to run if a threads library

 #   is found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it

 #   is not found. If ACTION-IF-FOUND is not specified, the default action

 #   will define HAVE_PTHREAD.

 #

 #   Please let the authors know if this macro fails on any platform, or if

 #   you have any other suggestions or comments. This macro was based on work

 #   by SGJ on autoconf scripts for FFTW (http://www.fftw.org/) (with help

 #   from M. Frigo), as well as ac_pthread and hb_pthread macros posted by

 #   Alejandro Forero Cuervo to the autoconf macro repository. We are also

 #   grateful for the helpful feedback of numerous users.

 #

 # LICENSE

 #

 #   Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>

 #

 #   This program is free software: you can redistribute it and/or modify it

 #   under the terms of the GNU General Public License as published by the

 #   Free Software Foundation, either version 3 of the License, or (at your

 #   option) any later version.

 #

 #   This program is distributed in the hope that it will be useful, but

 #   WITHOUT ANY WARRANTY; without even the implied warranty of

 #   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General

 #   Public License for more details.

 #

 #   You should have received a copy of the GNU General Public License along

 #   with this program. If not, see <http://www.gnu.org/licenses/>.

 #

 #   As a special exception, the respective Autoconf Macro's copyright owner

 #   gives unlimited permission to copy, distribute and modify the configure

 #   scripts that are the output of Autoconf when processing the Macro. You

 #   need not follow the terms of the GNU General Public License when using

 #   or distributing such scripts, even though portions of the text of the

 #   Macro appear in them. The GNU General Public License (GPL) does govern

 #   all other use of the material that constitutes the Autoconf Macro.

 #

 #   This special exception to the GPL applies to versions of the Autoconf

 #   Macro released by the Autoconf Archive. When you make and distribute a

 #   modified version of the Autoconf Macro, you may extend this special

 #   exception to the GPL to apply to your modified version as well.

 #serial 6

 AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])

 AC_DEFUN([AX_PTHREAD], [

 AC_REQUIRE([AC_CANONICAL_HOST])

 AC_LANG_SAVE

 AC_LANG_C

 ax_pthread_ok=no

 # We used to check for pthread.h first, but this fails if pthread.h

 # requires special compiler flags (e.g. on True64 or Sequent).

 # It gets checked for in the link test anyway.

 # First of all, check if the user has set any of the PTHREAD_LIBS,

 # etcetera environment variables, and if threads linking works using

 # them:

 if test x"$PTHREAD_LIBS$PTHREAD_CFLAGS" != x; then

         save_CFLAGS="$CFLAGS"

         CFLAGS="$CFLAGS $PTHREAD_CFLAGS"

         save_LIBS="$LIBS"

         LIBS="$PTHREAD_LIBS $LIBS"

         AC_MSG_CHECKING([for pthread_join in LIBS=$PTHREAD_LIBS with CFLAGS=$PTHREAD_CFLAGS])

         AC_TRY_LINK_FUNC(pthread_join, ax_pthread_ok=yes)

         AC_MSG_RESULT($ax_pthread_ok)

         if test x"$ax_pthread_ok" = xno; then

                 PTHREAD_LIBS=""

                 PTHREAD_CFLAGS=""

         fi

         LIBS="$save_LIBS"

         CFLAGS="$save_CFLAGS"

 fi

 # We must check for the threads library under a number of different

 # names; the ordering is very important because some systems

 # (e.g. DEC) have both -lpthread and -lpthreads, where one of the

 # libraries is broken (non-POSIX).

 # Create a list of thread flags to try.  Items starting with a "-" are

 # C compiler flags, and other items are library names, except for "none"

 # which indicates that we try without any flags at all, and "pthread-config"

 # which is a program returning the flags for the Pth emulation library.

 ax_pthread_flags="pthreads none -Kthread -kthread lthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"

 # The ordering *is* (sometimes) important.  Some notes on the

 # individual items follow:

 # pthreads: AIX (must check this before -lpthread)

 # none: in case threads are in libc; should be tried before -Kthread and

 #       other compiler flags to prevent continual compiler warnings

 # -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)

 # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)

 # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)

 # -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads)

 # -pthreads: Solaris/gcc

 # -mthreads: Mingw32/gcc, Lynx/gcc

 # -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it

 #      doesn't hurt to check since this sometimes defines pthreads too;

 #      also defines -D_REENTRANT)

 #      ... -mt is also the pthreads flag for HP/aCC

 # pthread: Linux, etcetera

 # --thread-safe: KAI C++

 # pthread-config: use pthread-config program (for GNU Pth library)

 case "${host_cpu}-${host_os}" in

         *solaris*)

         # On Solaris (at least, for some versions), libc contains stubbed

         # (non-functional) versions of the pthreads routines, so link-based

         # tests will erroneously succeed.  (We need to link with -pthreads/-mt/

         # -lpthread.)  (The stubs are missing pthread_cleanup_push, or rather

         # a function called by this macro, so we could check for that, but

         # who knows whether they'll stub that too in a future libc.)  So,

         # we'll just look for -pthreads and -lpthread first:

         ax_pthread_flags="-pthreads pthread -mt -pthread $ax_pthread_flags"

         ;;

 	*-darwin*)

 	acx_pthread_flags="-pthread $acx_pthread_flags"

 	;;

 esac

 if test x"$ax_pthread_ok" = xno; then

 for flag in $ax_pthread_flags; do

         case $flag in

                 none)

                 AC_MSG_CHECKING([whether pthreads work without any flags])

                 ;;

                 -*)

                 AC_MSG_CHECKING([whether pthreads work with $flag])

                 PTHREAD_CFLAGS="$flag"

                 ;;

 		pthread-config)

 		AC_CHECK_PROG(ax_pthread_config, pthread-config, yes, no)

 		if test x"$ax_pthread_config" = xno; then continue; fi

 		PTHREAD_CFLAGS="`pthread-config --cflags`"

 		PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"

 		;;

                 *)

                 AC_MSG_CHECKING([for the pthreads library -l$flag])

                 PTHREAD_LIBS="-l$flag"

                 ;;

         esac

         save_LIBS="$LIBS"

         save_CFLAGS="$CFLAGS"

         LIBS="$PTHREAD_LIBS $LIBS"

         CFLAGS="$CFLAGS $PTHREAD_CFLAGS"

         # Check for various functions.  We must include pthread.h,

         # since some functions may be macros.  (On the Sequent, we

         # need a special flag -Kthread to make this header compile.)

         # We check for pthread_join because it is in -lpthread on IRIX

         # while pthread_create is in libc.  We check for pthread_attr_init

         # due to DEC craziness with -lpthreads.  We check for

         # pthread_cleanup_push because it is one of the few pthread

         # functions on Solaris that doesn't have a non-functional libc stub.

         # We try pthread_create on general principles.

         AC_TRY_LINK([#include <pthread.h>

 	             static void routine(void* a) {a=0;}

 	             static void* start_routine(void* a) {return a;}],

                     [pthread_t th; pthread_attr_t attr;

                      pthread_join(th, 0);

                      pthread_attr_init(&attr);

                      pthread_cleanup_push(routine, 0);

                      pthread_create(&th,0,start_routine,0);

                      pthread_cleanup_pop(0); ],

                     [ax_pthread_ok=yes])

         LIBS="$save_LIBS"

         CFLAGS="$save_CFLAGS"

         AC_MSG_RESULT($ax_pthread_ok)

         if test "x$ax_pthread_ok" = xyes; then

                 break;

         fi

         PTHREAD_LIBS=""

         PTHREAD_CFLAGS=""

 done

 fi

 # Various other checks:

 if test "x$ax_pthread_ok" = xyes; then

         save_LIBS="$LIBS"

         LIBS="$PTHREAD_LIBS $LIBS"

         save_CFLAGS="$CFLAGS"

         CFLAGS="$CFLAGS $PTHREAD_CFLAGS"

         # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.

 	AC_MSG_CHECKING([for joinable pthread attribute])

 	attr_name=unknown

 	for attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do

 	    AC_TRY_LINK([#include <pthread.h>], [int attr=$attr; return attr;],

                         [attr_name=$attr; break])

 	done

         AC_MSG_RESULT($attr_name)

         if test "$attr_name" != PTHREAD_CREATE_JOINABLE; then

             AC_DEFINE_UNQUOTED(PTHREAD_CREATE_JOINABLE, $attr_name,

                                [Define to necessary symbol if this constant

                                 uses a non-standard name on your system.])

         fi

         AC_MSG_CHECKING([if more special flags are required for pthreads])

         flag=no

         case "${host_cpu}-${host_os}" in

             *-aix* | *-freebsd* | *-darwin*) flag="-D_THREAD_SAFE";;

             *solaris* | *-osf* | *-hpux*) flag="-D_REENTRANT";;

         esac

         AC_MSG_RESULT(${flag})

         if test "x$flag" != xno; then

             PTHREAD_CFLAGS="$flag $PTHREAD_CFLAGS"

         fi

         LIBS="$save_LIBS"

         CFLAGS="$save_CFLAGS"

         # More AIX lossage: must compile with xlc_r or cc_r

 	if test x"$GCC" != xyes; then

           AC_CHECK_PROGS(PTHREAD_CC, xlc_r cc_r, ${CC})

         else

           PTHREAD_CC=$CC

 	fi

 else

         PTHREAD_CC="$CC"

 fi

 AC_SUBST(PTHREAD_LIBS)

 AC_SUBST(PTHREAD_CFLAGS)

 AC_SUBST(PTHREAD_CC)

 # Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:

 if test x"$ax_pthread_ok" = xyes; then

         ifelse([$1],,AC_DEFINE(HAVE_PTHREAD,1,[Define if you have POSIX threads libraries and header files.]),[$1])

         :

 else

         ax_pthread_ok=no

         $2

 fi

 AC_LANG_RESTORE

 ])dnl AX_PTHREAD