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

#        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 <stevenj@alum.mit.edu>

#   Copyright (c) 2011 Daniel Richard G. <skunk@iSKUNK.ORG>

#

#   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