# threadlib.m4 serial 12

dnl Copyright (C) 2005-2017 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.

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_POSIX_THREADS, USE_SOLARIS_THREADS,

dnl USE_PTH_THREADS, USE_WINDOWS_THREADS

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.

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.

  dnl AC_USE_SYSTEM_EXTENSIONS was introduced in autoconf 2.60 and obsoletes

  dnl AC_GNU_SOURCE.

  m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],

    [AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])],

    [AC_REQUIRE([AC_GNU_SOURCE])])

  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=])])

  AC_ARG_ENABLE([threads],

AC_HELP_STRING([--enable-threads={posix|solaris|pth|windows}], [specify multithreading API])m4_ifdef([gl_THREADLIB_DEFAULT_NO], [], [

AC_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().

         dnl Disable multithreading by default on Cygwin 1.5.x, because it has

         dnl bugs that lead to endless loops or crashes. See

         dnl <http://cygwin.com/ml/cygwin/2009-08/msg00283.html>.

         osf*) gl_use_threads=no ;;

         cygwin*)

               case `uname -r` in

                 1.[0-5].*) gl_use_threads=no ;;

                 *)         gl_use_threads=yes ;;

               esac

               ;;

         *)    gl_use_threads=yes ;;

       esac

changequote([,])dnl

     fi

    ])

  if test "$gl_use_threads" = yes || test "$gl_use_threads" = posix; then

    # For using <pthread.h>:

    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

  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.

    AC_CACHE_CHECK([whether imported symbols can be declared weak],

      [gl_cv_have_weak],

      [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

      ])

    if test "$gl_use_threads" = yes || test "$gl_use_threads" = posix; then

      # On OSF/1, the compiler needs the flag -pthread or -D_REENTRANT so that

      # it groks <pthread.h>. It's added above, in gl_THREADLIB_EARLY_BODY.

      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

        gl_have_pthread=

        # 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:

        # http://lists.gnu.org/archive/html/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_have_pthread=yes

             LIBTHREAD=$gl_pthread LTLIBTHREAD=$gl_pthread

             LIBMULTITHREAD=$gl_pthread LTLIBMULTITHREAD=$gl_pthread])

          LIBS=$save_LIBS

          test -n "$gl_have_pthread" && break

        done

        # Test for libpthread by looking for pthread_kill. (Not pthread_self,

        # since it is defined as a macro on OSF/1.)

        if test -n "$gl_have_pthread" && test -z "$LIBTHREAD"; 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],

            [LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-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

            ])

        elif test -z "$gl_have_pthread"; then

          # Some library is needed. Try libpthread and libc_r.

          AC_CHECK_LIB([pthread], [pthread_kill],

            [gl_have_pthread=yes

             LIBTHREAD=-lpthread LTLIBTHREAD=-lpthread

             LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-lpthread])

          if test -z "$gl_have_pthread"; then

            # For FreeBSD 4.

            AC_CHECK_LIB([c_r], [pthread_kill],

              [gl_have_pthread=yes

               LIBTHREAD=-lc_r LTLIBTHREAD=-lc_r

               LIBMULTITHREAD=-lc_r LTLIBMULTITHREAD=-lc_r])

          fi

        fi

        if test -n "$gl_have_pthread"; then

          gl_threads_api=posix

          AC_DEFINE([USE_POSIX_THREADS], [1],

            [Define if the POSIX multithreading library can be used.])

          if test -n "$LIBMULTITHREAD" || test -n "$LTLIBMULTITHREAD"; then

            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=

            fi

          fi

        fi

      fi

    fi

    if test -z "$gl_have_pthread"; then

      if test "$gl_use_threads" = yes || test "$gl_use_threads" = solaris; then

        gl_have_solaristhread=

        gl_save_LIBS="$LIBS"

        LIBS="$LIBS -lthread"

        AC_LINK_IFELSE(

          [AC_LANG_PROGRAM(

             [[

#include <thread.h>

#include <synch.h>

             ]],

             [[thr_self();]])],

          [gl_have_solaristhread=yes])

        LIBS="$gl_save_LIBS"

        if test -n "$gl_have_solaristhread"; then

          gl_threads_api=solaris

          LIBTHREAD=-lthread

          LTLIBTHREAD=-lthread

          LIBMULTITHREAD="$LIBTHREAD"

          LTLIBMULTITHREAD="$LTLIBTHREAD"

          AC_DEFINE([USE_SOLARIS_THREADS], [1],

            [Define if the old Solaris multithreading library can be used.])

          if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then

            AC_DEFINE([USE_SOLARIS_THREADS_WEAK], [1],

              [Define if references to the old Solaris multithreading library should be made weak.])

            LIBTHREAD=

            LTLIBTHREAD=

          fi

        fi

      fi

    fi

    if test "$gl_use_threads" = pth; then

      gl_save_CPPFLAGS="$CPPFLAGS"

      AC_LIB_LINKFLAGS([pth])

      gl_have_pth=

      gl_save_LIBS="$LIBS"

      LIBS="$LIBS $LIBPTH"

      AC_LINK_IFELSE(

        [AC_LANG_PROGRAM([[#include <pth.h>]], [[pth_self();]])],

        [gl_have_pth=yes])

      LIBS="$gl_save_LIBS"

      if test -n "$gl_have_pth"; then

        gl_threads_api=pth

        LIBTHREAD="$LIBPTH"

        LTLIBTHREAD="$LTLIBPTH"

        LIBMULTITHREAD="$LIBTHREAD"

        LTLIBMULTITHREAD="$LTLIBTHREAD"

        AC_DEFINE([USE_PTH_THREADS], [1],

          [Define if the GNU Pth multithreading library can be used.])

        if test -n "$LIBMULTITHREAD" || test -n "$LTLIBMULTITHREAD"; then

          if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then

            AC_DEFINE([USE_PTH_THREADS_WEAK], [1],

              [Define if references to the GNU Pth multithreading library should be made weak.])

            LIBTHREAD=

            LTLIBTHREAD=

          fi

        fi

      else

        CPPFLAGS="$gl_save_CPPFLAGS"

      fi

    fi

    if test -z "$gl_have_pthread"; 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 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 GNU Hurd/glibc     posix

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                    solaris    -lthread        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 Any of the above   pth        -lpth                  0.0

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.