path: root/m4/threadlib.m4

# threadlib.m4 serial 15
dnl Copyright (C) 2005-2019 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 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.
  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=])])
  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 <https://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
       dnl But when linking statically, weak symbols don't work.
       case " $LDFLAGS " in
         *" -static "*) gl_cv_have_weak=no ;;
       esac
      ])
    dnl Check whether the linker supports the --as-needed/--no-as-needed options.
    dnl Assume GCC, so that we can use the -Wl option.
    AC_CACHE_CHECK([whether the linker supports --as-needed],
      [gl_cv_linker_have_as_needed],
      [if test -n "$GCC"; then
         gl_saved_ldflags="$LDFLAGS"
         LDFLAGS="$gl_saved_ldflags -Wl,--as-needed -Wl,--no-as-needed"
         AC_LINK_IFELSE([AC_LANG_PROGRAM()],
           [gl_cv_linker_have_as_needed=yes],
           [gl_cv_linker_have_as_needed=no])
         LDFLAGS="$gl_saved_ldflags"
       else
         gl_cv_linker_have_as_needed=no
       fi
      ])
    dnl Check whether the linker supports the --push-state/--pop-state options.
    dnl Assume GCC, so that we can use the -Wl option.
    AC_CACHE_CHECK([whether the linker supports --push-state],
      [gl_cv_linker_have_push_state],
      [if test -n "$GCC"; then
         gl_saved_ldflags="$LDFLAGS"
         LDFLAGS="$gl_saved_ldflags -Wl,--push-state -Wl,--pop-state"
         AC_LINK_IFELSE([AC_LANG_PROGRAM()],
           [gl_cv_linker_have_push_state=yes],
           [gl_cv_linker_have_push_state=no])
         LDFLAGS="$gl_saved_ldflags"
       else
         gl_cv_linker_have_push_state=no
       fi
      ])
    if test "$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:
        # https://lists.gnu.org/r/bug-gnulib/2014-09/msg00023.html
        save_LIBS=$LIBS
        for gl_pthread in '' '-pthread'; do
          LIBS="$LIBS $gl_pthread"
          AC_LINK_IFELSE(
            [AC_LANG_PROGRAM(
               [[#include <pthread.h>
                 pthread_mutex_t m;
                 pthread_mutexattr_t ma;
               ]],
               [[pthread_mutex_lock (&m);
                 pthread_mutexattr_init (&ma);]])],
            [gl_have_pthread=yes
             LIBTHREAD=$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 "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
              AC_DEFINE([USE_POSIX_THREADS_WEAK], [1],
                [Define if references to the POSIX multithreading library should be made weak.])
              LIBTHREAD=
              LTLIBTHREAD=
              dnl On platforms where GCC enables --as-needed by default, attempt
              dnl to make sure that LIBMULTITHREAD really links with -lpthread.
              dnl Otherwise linking with LIBMULTITHREAD has no effect; then
              dnl the weak symbols are not defined and thus evaluate to NULL.
              case "$LIBMULTITHREAD" in
                "") ;;
                -pthread)
                  if test $gl_cv_linker_have_as_needed = yes; then
                    if test $gl_cv_linker_have_push_state = yes; then
                      LIBMULTITHREAD="$LIBMULTITHREAD -Wl,--push-state -Wl,--no-as-needed -lpthread -Wl,--pop-state"
                    else
                      LIBMULTITHREAD="$LIBMULTITHREAD -Wl,--no-as-needed -lpthread"
                    fi
                  fi
                  ;;
                *)
                  if test $gl_cv_linker_have_as_needed = yes; then
                    if test $gl_cv_linker_have_push_state = yes; then
                      LIBMULTITHREAD="-Wl,--push-state -Wl,--no-as-needed $LIBMULTITHREAD -Wl,--pop-state"
                    else
                      LIBMULTITHREAD="-Wl,--no-as-needed $LIBMULTITHREAD"
                    fi
                  fi
                  ;;
              esac
              # TODO: May need to modify LTLIBMULTITHREAD similarly.
            fi
          fi
        fi
      fi
    fi
    if test -z "$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=
            dnl On platforms where GCC enables --as-needed by default, attempt
            dnl to make sure that LIBMULTITHREAD really links with -lthread.
            dnl Otherwise linking with LIBMULTITHREAD has no effect; then
            dnl the weak symbols are not defined and thus evaluate to NULL.
            if test $gl_cv_linker_have_as_needed = yes; then
              if test $gl_cv_linker_have_push_state = yes; then
                LIBMULTITHREAD="-Wl,--push-state -Wl,--no-as-needed $LIBMULTITHREAD -Wl,--pop-state"
              else
                LIBMULTITHREAD="-Wl,--no-as-needed $LIBMULTITHREAD"
              fi
            fi
            # TODO: May need to modify LTLIBMULTITHREAD similarly.
          fi
        fi
      fi
    fi
    if test "$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=
            dnl On platforms where GCC enables --as-needed by default, attempt
            dnl to make sure that LIBMULTITHREAD really links with -lpth.
            dnl Otherwise linking with LIBMULTITHREAD has no effect; then
            dnl the weak symbols are not defined and thus evaluate to NULL.
            if test $gl_cv_linker_have_as_needed = yes; then
              if test $gl_cv_linker_have_push_state = yes; then
                LIBMULTITHREAD="-Wl,--push-state -Wl,--no-as-needed $LIBMULTITHREAD -Wl,--pop-state"
              else
                LIBMULTITHREAD="-Wl,--no-as-needed $LIBMULTITHREAD"
              fi
            fi
            # TODO: May need to modify LTLIBMULTITHREAD similarly.
          fi
        fi
      else
        CPPFLAGS="$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.