# ===========================================================================
#        https://www.gnu.org/software/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 to link with them as well. For example, you might link with
#   $PTHREAD_CC $CFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS
#
#   If you are only building threaded programs, you may wish to use these
#   variables in your default LIBS, CFLAGS, and CC:
#
#     LIBS="$PTHREAD_LIBS $LIBS"
#     CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
#     CC="$PTHREAD_CC"
#
#   In addition, if the PTHREAD_CREATE_JOINABLE thread-attribute constant
#   has a nonstandard name, this macro defines PTHREAD_CREATE_JOINABLE to
#   that name (e.g. PTHREAD_CREATE_UNDETACHED on AIX).
#
#   Also HAVE_PTHREAD_PRIO_INHERIT is defined if pthread is found and the
#   PTHREAD_PRIO_INHERIT symbol is defined when compiling with
#   PTHREAD_CFLAGS.
#
#   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.
#
#   Updated for Autoconf 2.68 by Daniel Richard G.
#
# LICENSE
#
#   Copyright (c) 2008 Steven G. Johnson <[email protected]>
#   Copyright (c) 2011 Daniel Richard G. <[email protected]>
#
#   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 <https://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 24

AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
AC_DEFUN([AX_PTHREAD], [
AC_REQUIRE([AC_CANONICAL_HOST])
AC_REQUIRE([AC_PROG_CC])
AC_REQUIRE([AC_PROG_SED])
AC_LANG_PUSH([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 Tru64 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$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
       ax_pthread_save_CC="$CC"
       ax_pthread_save_CFLAGS="$CFLAGS"
       ax_pthread_save_LIBS="$LIBS"
       AS_IF([test "x$PTHREAD_CC" != "x"], [CC="$PTHREAD_CC"])
       CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
       LIBS="$PTHREAD_LIBS $LIBS"
       AC_MSG_CHECKING([for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS])
       AC_LINK_IFELSE([AC_LANG_CALL([], [pthread_join])], [ax_pthread_ok=yes])
       AC_MSG_RESULT([$ax_pthread_ok])
       if test "x$ax_pthread_ok" = "xno"; then
               PTHREAD_LIBS=""
               PTHREAD_CFLAGS=""
       fi
       CC="$ax_pthread_save_CC"
       CFLAGS="$ax_pthread_save_CFLAGS"
       LIBS="$ax_pthread_save_LIBS"
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 -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)
# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
#           (Note: HP C rejects this with "bad form for `-t' option")
# -pthreads: Solaris/gcc (Note: HP C also rejects)
# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
#      doesn't hurt to check since this sometimes defines pthreads and
#      -D_REENTRANT too), HP C (must be checked before -lpthread, which
#      is present but should not be used directly; and before -mthreads,
#      because the compiler interprets this as "-mt" + "-hreads")
# -mthreads: Mingw32/gcc, Lynx/gcc
# pthread: Linux, etcetera
# --thread-safe: KAI C++
# pthread-config: use pthread-config program (for GNU Pth library)

case $host_os in

       freebsd*)

       # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
       # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)

       ax_pthread_flags="-kthread lthread $ax_pthread_flags"
       ;;

       hpux*)

       # From the cc(1) man page: "[-mt] Sets various -D flags to enable
       # multi-threading and also sets -lpthread."

       ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
       ;;

       openedition*)

       # IBM z/OS requires a feature-test macro to be defined in order to
       # enable POSIX threads at all, so give the user a hint if this is
       # not set. (We don't define these ourselves, as they can affect
       # other portions of the system API in unpredictable ways.)

       AC_EGREP_CPP([AX_PTHREAD_ZOS_MISSING],
           [
#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
            AX_PTHREAD_ZOS_MISSING
#            endif
           ],
           [AC_MSG_WARN([IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support.])])
       ;;

       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. (N.B.: 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 check first for the
       # standard Solaris way of linking pthreads (-mt -lpthread).

       ax_pthread_flags="-mt,pthread pthread $ax_pthread_flags"
       ;;
esac

# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)

AS_IF([test "x$GCC" = "xyes"],
     [ax_pthread_flags="-pthread -pthreads $ax_pthread_flags"])

# The presence of a feature test macro requesting re-entrant function
# definitions is, on some systems, a strong hint that pthreads support is
# correctly enabled

case $host_os in
       darwin* | hpux* | linux* | osf* | solaris*)
       ax_pthread_check_macro="_REENTRANT"
       ;;

       aix*)
       ax_pthread_check_macro="_THREAD_SAFE"
       ;;

       *)
       ax_pthread_check_macro="--"
       ;;
esac
AS_IF([test "x$ax_pthread_check_macro" = "x--"],
     [ax_pthread_check_cond=0],
     [ax_pthread_check_cond="!defined($ax_pthread_check_macro)"])

# Are we compiling with Clang?

AC_CACHE_CHECK([whether $CC is Clang],
   [ax_cv_PTHREAD_CLANG],
   [ax_cv_PTHREAD_CLANG=no
    # Note that Autoconf sets GCC=yes for Clang as well as GCC
    if test "x$GCC" = "xyes"; then
       AC_EGREP_CPP([AX_PTHREAD_CC_IS_CLANG],
           [/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
#            if defined(__clang__) && defined(__llvm__)
            AX_PTHREAD_CC_IS_CLANG
#            endif
           ],
           [ax_cv_PTHREAD_CLANG=yes])
    fi
   ])
ax_pthread_clang="$ax_cv_PTHREAD_CLANG"

ax_pthread_clang_warning=no

# Clang needs special handling, because older versions handle the -pthread
# option in a rather... idiosyncratic way

if test "x$ax_pthread_clang" = "xyes"; then

       # Clang takes -pthread; it has never supported any other flag

       # (Note 1: This will need to be revisited if a system that Clang
       # supports has POSIX threads in a separate library.  This tends not
       # to be the way of modern systems, but it's conceivable.)

       # (Note 2: On some systems, notably Darwin, -pthread is not needed
       # to get POSIX threads support; the API is always present and
       # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
       # -pthread does define _REENTRANT, and while the Darwin headers
       # ignore this macro, third-party headers might not.)

       PTHREAD_CFLAGS="-pthread"
       PTHREAD_LIBS=

       ax_pthread_ok=yes

       # However, older versions of Clang make a point of warning the user
       # that, in an invocation where only linking and no compilation is
       # taking place, the -pthread option has no effect ("argument unused
       # during compilation").  They expect -pthread to be passed in only
       # when source code is being compiled.
       #
       # Problem is, this is at odds with the way Automake and most other
       # C build frameworks function, which is that the same flags used in
       # compilation (CFLAGS) are also used in linking.  Many systems
       # supported by AX_PTHREAD require exactly this for POSIX threads
       # support, and in fact it is often not straightforward to specify a
       # flag that is used only in the compilation phase and not in
       # linking.  Such a scenario is extremely rare in practice.
       #
       # Even though use of the -pthread flag in linking would only print
       # a warning, this can be a nuisance for well-run software projects
       # that build with -Werror.  So if the active version of Clang has
       # this misfeature, we search for an option to squash it.

       AC_CACHE_CHECK([whether Clang needs flag to prevent "argument unused" warning when linking with -pthread],
           [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG],
           [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
            # Create an alternate version of $ac_link that compiles and
            # links in two steps (.c -> .o, .o -> exe) instead of one
            # (.c -> exe), because the warning occurs only in the second
            # step
            ax_pthread_save_ac_link="$ac_link"
            ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
            ax_pthread_link_step=`$as_echo "$ac_link" | sed "$ax_pthread_sed"`
            ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
            ax_pthread_save_CFLAGS="$CFLAGS"
            for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
               AS_IF([test "x$ax_pthread_try" = "xunknown"], [break])
               CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
               ac_link="$ax_pthread_save_ac_link"
               AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
                   [ac_link="$ax_pthread_2step_ac_link"
                    AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
                        [break])
                   ])
            done
            ac_link="$ax_pthread_save_ac_link"
            CFLAGS="$ax_pthread_save_CFLAGS"
            AS_IF([test "x$ax_pthread_try" = "x"], [ax_pthread_try=no])
            ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
           ])

       case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
               no | unknown) ;;
               *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
       esac

fi # $ax_pthread_clang = yes

if test "x$ax_pthread_ok" = "xno"; then
for ax_pthread_try_flag in $ax_pthread_flags; do

       case $ax_pthread_try_flag in
               none)
               AC_MSG_CHECKING([whether pthreads work without any flags])
               ;;

               -mt,pthread)
               AC_MSG_CHECKING([whether pthreads work with -mt -lpthread])
               PTHREAD_CFLAGS="-mt"
               PTHREAD_LIBS="-lpthread"
               ;;

               -*)
               AC_MSG_CHECKING([whether pthreads work with $ax_pthread_try_flag])
               PTHREAD_CFLAGS="$ax_pthread_try_flag"
               ;;

               pthread-config)
               AC_CHECK_PROG([ax_pthread_config], [pthread-config], [yes], [no])
               AS_IF([test "x$ax_pthread_config" = "xno"], [continue])
               PTHREAD_CFLAGS="`pthread-config --cflags`"
               PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
               ;;

               *)
               AC_MSG_CHECKING([for the pthreads library -l$ax_pthread_try_flag])
               PTHREAD_LIBS="-l$ax_pthread_try_flag"
               ;;
       esac

       ax_pthread_save_CFLAGS="$CFLAGS"
       ax_pthread_save_LIBS="$LIBS"
       CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
       LIBS="$PTHREAD_LIBS $LIBS"

       # 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_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>
#                       if $ax_pthread_check_cond
#                        error "$ax_pthread_check_macro must be defined"
#                       endif
                       static void routine(void *a) { a = 0; }
                       static void *start_routine(void *a) { return a; }],
                      [pthread_t th; pthread_attr_t attr;
                       pthread_create(&th, 0, start_routine, 0);
                       pthread_join(th, 0);
                       pthread_attr_init(&attr);
                       pthread_cleanup_push(routine, 0);
                       pthread_cleanup_pop(0) /* ; */])],
           [ax_pthread_ok=yes],
           [])

       CFLAGS="$ax_pthread_save_CFLAGS"
       LIBS="$ax_pthread_save_LIBS"

       AC_MSG_RESULT([$ax_pthread_ok])
       AS_IF([test "x$ax_pthread_ok" = "xyes"], [break])

       PTHREAD_LIBS=""
       PTHREAD_CFLAGS=""
done
fi

# Various other checks:
if test "x$ax_pthread_ok" = "xyes"; then
       ax_pthread_save_CFLAGS="$CFLAGS"
       ax_pthread_save_LIBS="$LIBS"
       CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
       LIBS="$PTHREAD_LIBS $LIBS"

       # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
       AC_CACHE_CHECK([for joinable pthread attribute],
           [ax_cv_PTHREAD_JOINABLE_ATTR],
           [ax_cv_PTHREAD_JOINABLE_ATTR=unknown
            for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
                AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>],
                                                [int attr = $ax_pthread_attr; return attr /* ; */])],
                               [ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break],
                               [])
            done
           ])
       AS_IF([test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
              test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
              test "x$ax_pthread_joinable_attr_defined" != "xyes"],
             [AC_DEFINE_UNQUOTED([PTHREAD_CREATE_JOINABLE],
                                 [$ax_cv_PTHREAD_JOINABLE_ATTR],
                                 [Define to necessary symbol if this constant
                                  uses a non-standard name on your system.])
              ax_pthread_joinable_attr_defined=yes
             ])

       AC_CACHE_CHECK([whether more special flags are required for pthreads],
           [ax_cv_PTHREAD_SPECIAL_FLAGS],
           [ax_cv_PTHREAD_SPECIAL_FLAGS=no
            case $host_os in
            solaris*)
            ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
            ;;
            esac
           ])
       AS_IF([test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
              test "x$ax_pthread_special_flags_added" != "xyes"],
             [PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
              ax_pthread_special_flags_added=yes])

       AC_CACHE_CHECK([for PTHREAD_PRIO_INHERIT],
           [ax_cv_PTHREAD_PRIO_INHERIT],
           [AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <pthread.h>]],
                                            [[int i = PTHREAD_PRIO_INHERIT;]])],
                           [ax_cv_PTHREAD_PRIO_INHERIT=yes],
                           [ax_cv_PTHREAD_PRIO_INHERIT=no])
           ])
       AS_IF([test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
              test "x$ax_pthread_prio_inherit_defined" != "xyes"],
             [AC_DEFINE([HAVE_PTHREAD_PRIO_INHERIT], [1], [Have PTHREAD_PRIO_INHERIT.])
              ax_pthread_prio_inherit_defined=yes
             ])

       CFLAGS="$ax_pthread_save_CFLAGS"
       LIBS="$ax_pthread_save_LIBS"

       # More AIX lossage: compile with *_r variant
       if test "x$GCC" != "xyes"; then
           case $host_os in
               aix*)
               AS_CASE(["x/$CC"],
                   [x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6],
                   [#handle absolute path differently from PATH based program lookup
                    AS_CASE(["x$CC"],
                        [x/*],
                        [AS_IF([AS_EXECUTABLE_P([${CC}_r])],[PTHREAD_CC="${CC}_r"])],
                        [AC_CHECK_PROGS([PTHREAD_CC],[${CC}_r],[$CC])])])
               ;;
           esac
       fi
fi

test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"

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_POP
])dnl AX_PTHREAD

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