gold: Use autotools pthread macro

Message ID 20180216033531.23726-1-JPEWhacker@gmail.com
State New
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Series
  • gold: Use autotools pthread macro
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Commit Message

Joshua Watt Feb. 16, 2018, 3:35 a.m.
The autotools library macro (AX_PTHREAD) is now used to detect if
pthreads is present and multi-threaded linking in gold is automatically
enabled if it is found. This enables multi-threaded gold on platforms
where pthreads is enabled via other methods than just -lpthread (e.g.
MinGW)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>

---
 config/ax_pthread.m4       | 485 ++++++++++++++++++++++++++++
 gold/Makefile.am           |  11 +-
 gold/Makefile.in           |  22 +-
 gold/aclocal.m4            |   1 +
 gold/configure             | 767 +++++++++++++++++++++++++++++++++++++++++++--
 gold/configure.ac          |  23 +-
 gold/testsuite/Makefile.in |   8 +-
 7 files changed, 1254 insertions(+), 63 deletions(-)
 create mode 100644 config/ax_pthread.m4

-- 
2.14.3

Comments

Cary Coutant Feb. 17, 2018, 10:42 p.m. | #1
> The autotools library macro (AX_PTHREAD) is now used to detect if

> pthreads is present and multi-threaded linking in gold is automatically

> enabled if it is found. This enables multi-threaded gold on platforms

> where pthreads is enabled via other methods than just -lpthread (e.g.

> MinGW)

>

> Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>

> ---

>  config/ax_pthread.m4       | 485 ++++++++++++++++++++++++++++

>  gold/Makefile.am           |  11 +-

>  gold/Makefile.in           |  22 +-

>  gold/aclocal.m4            |   1 +

>  gold/configure             | 767 +++++++++++++++++++++++++++++++++++++++++++--

>  gold/configure.ac          |  23 +-

>  gold/testsuite/Makefile.in |   8 +-

>  7 files changed, 1254 insertions(+), 63 deletions(-)


Thanks for the patch! I have a few preliminary questions and comments...

First, do you or your company have a copyright assignment on file with FSF?

I could be wrong, but I believe adding to config/ will require
approval from a GCC config/ maintainer. The normal process, as I
understand it, would be to add the file to the GCC tree, then sync it
into the binutils tree. I'm not in a position to approve that, nor can
I judge on the acceptability of the copyright notice in that file.

I'd like to retain the ability to use --disable-threads as a configure option.

If this is just to get MinGW on board, is there a lighter-weight way
of doing that? Could we just add a configure option that switches
between -lpthread and -pthread (or whatever option is needed)? I like
the idea of fully automating it, but that's a pretty big m4 file!

Anyway, I'd like to hear what the GCC folks think of adding
ax_pthread.m4 to the config/ directory.

(BTW, In the future, please omit diffs from generated files from your patch.)

-cary
Joshua Watt Feb. 19, 2018, 3:01 a.m. | #2
On Sat, Feb 17, 2018 at 4:42 PM, Cary Coutant <ccoutant@gmail.com> wrote:
>> The autotools library macro (AX_PTHREAD) is now used to detect if

>> pthreads is present and multi-threaded linking in gold is automatically

>> enabled if it is found. This enables multi-threaded gold on platforms

>> where pthreads is enabled via other methods than just -lpthread (e.g.

>> MinGW)

>>

>> Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>

>> ---

>>  config/ax_pthread.m4       | 485 ++++++++++++++++++++++++++++

>>  gold/Makefile.am           |  11 +-

>>  gold/Makefile.in           |  22 +-

>>  gold/aclocal.m4            |   1 +

>>  gold/configure             | 767 +++++++++++++++++++++++++++++++++++++++++++--

>>  gold/configure.ac          |  23 +-

>>  gold/testsuite/Makefile.in |   8 +-

>>  7 files changed, 1254 insertions(+), 63 deletions(-)

>

> Thanks for the patch! I have a few preliminary questions and comments...

>

> First, do you or your company have a copyright assignment on file with FSF?


I do not. What is the process for that? I don't need a company
assignment, an individual contributor for me will be fine.

If I sign that for this project, would it also cover GCC, or do I need
one for each?

>

> I could be wrong, but I believe adding to config/ will require

> approval from a GCC config/ maintainer. The normal process, as I

> understand it, would be to add the file to the GCC tree, then sync it

> into the binutils tree. I'm not in a position to approve that, nor can

> I judge on the acceptability of the copyright notice in that file.


Ok. I didn't realize the config/ directory came from GCC. I'll look
into getting it submitted there.... How does that get "synced" to
binutils? Would I make a patch to add it here after it is added there?

FWIW, it is the same license as the ax_check_define macro (also from
the autotools macro archive) that is already in config/

>

> I'd like to retain the ability to use --disable-threads as a configure option.

>


I will add that back in.

> If this is just to get MinGW on board, is there a lighter-weight way

> of doing that? Could we just add a configure option that switches

> between -lpthread and -pthread (or whatever option is needed)? I like

> the idea of fully automating it, but that's a pretty big m4 file!


It is pretty large.... I pulled it straight from the autoconf macro
archive. IMHO, its much better quality than anything I would be able
to come up with otherwise, and pretty brain-dead easy for the end
user. It should "just work" without any special switches (although the
user *can* configure it with some env-vars I think).

>

> Anyway, I'd like to hear what the GCC folks think of adding

> ax_pthread.m4 to the config/ directory.

>

> (BTW, In the future, please omit diffs from generated files from your patch.)


Will do. I couldn't find a lot of examples of config changes in
binutils, but I thought the one that I did updated the generated files
also. I must have been mistaken.

>

> -cary


Thanks,
Joshua Watt
Cary Coutant Feb. 19, 2018, 8:39 p.m. | #3
>> First, do you or your company have a copyright assignment on file with FSF?

>

> I do not. What is the process for that? I don't need a company

> assignment, an individual contributor for me will be fine.

>

> If I sign that for this project, would it also cover GCC, or do I need

> one for each?


It will cover all FSF contributions.

If config/ax_pthread.m4 is accepted by the config maintainers, I doubt
you'd need an assignment for that, since it's already licensed and
it's not actually your contribution.

That leaves a fairly small change to gold sources (not counting
auto-regenerated files) -- small enough that I don't think you need to
complete an assignment.

If  you do want to file a copyright assignment for future changes,
I'll forward you a copy of the form and instructions separately.

>> I could be wrong, but I believe adding to config/ will require

>> approval from a GCC config/ maintainer. The normal process, as I

>> understand it, would be to add the file to the GCC tree, then sync it

>> into the binutils tree. I'm not in a position to approve that, nor can

>> I judge on the acceptability of the copyright notice in that file.

>

> Ok. I didn't realize the config/ directory came from GCC. I'll look

> into getting it submitted there.... How does that get "synced" to

> binutils? Would I make a patch to add it here after it is added there?


I've added config-patches to the conversation, so I'm hoping that was
sufficient to get that going. Once added in the GCC tree, I think one
can either wait for an automatic sync, or go ahead and submit a patch
to do the sync (but I'm not completely versed on how the shared
directories really operate).

> FWIW, it is the same license as the ax_check_define macro (also from

> the autotools macro archive) that is already in config/


That suggests to me that there shouldn't be a problem adding this new file.

>> I'd like to retain the ability to use --disable-threads as a configure option.

>

> I will add that back in.


Thanks.

>> If this is just to get MinGW on board, is there a lighter-weight way

>> of doing that? Could we just add a configure option that switches

>> between -lpthread and -pthread (or whatever option is needed)? I like

>> the idea of fully automating it, but that's a pretty big m4 file!

>

> It is pretty large.... I pulled it straight from the autoconf macro

> archive. IMHO, its much better quality than anything I would be able

> to come up with otherwise, and pretty brain-dead easy for the end

> user. It should "just work" without any special switches (although the

> user *can* configure it with some env-vars I think).


Sounds good to me if others agree.

>> (BTW, In the future, please omit diffs from generated files from your patch.)

>

> Will do. I couldn't find a lot of examples of config changes in

> binutils, but I thought the one that I did updated the generated files

> also. I must have been mistaken.


It's a convention that makes reviewing and applying patches easier for
us maintainers, but it's easy to forget to strip out those diffs.

-cary
Ben Elliston Feb. 19, 2018, 9:09 p.m. | #4
On Mon, Feb 19, 2018 at 12:39:47PM -0800, Cary Coutant wrote:

> I've added config-patches to the conversation, so I'm hoping that

> was sufficient to get that going. Once added in the GCC tree, I

> think one can either wait for an automatic sync, or go ahead and

> submit a patch to do the sync (but I'm not completely versed on how

> the shared directories really operate).


config-patches has nothing to do with the GCC config/ directory. It is
the place to send patches for config.{guess,sub}. Taking if off the
cc: line.

Ben

Patch

diff --git a/config/ax_pthread.m4 b/config/ax_pthread.m4
new file mode 100644
index 0000000000..5fbf9fe0d6
--- /dev/null
+++ b/config/ax_pthread.m4
@@ -0,0 +1,485 @@ 
+# ===========================================================================
+#        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
diff --git a/gold/Makefile.am b/gold/Makefile.am
index 675deecb47..f87067aab4 100644
--- a/gold/Makefile.am
+++ b/gold/Makefile.am
@@ -31,8 +31,11 @@  ACLOCAL_AMFLAGS = -I ../bfd -I ../config
 ZLIB = @zlibdir@ -lz
 ZLIBINC = @zlibinc@
 
-AM_CFLAGS = $(WARN_CFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC)
-AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC)
+THREADFLAGS = @PTHREAD_CFLAGS@
+THREADLIBS = @PTHREAD_LIBS@
+
+AM_CFLAGS = $(WARN_CFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
+AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
 
 AM_CPPFLAGS = \
 	-I$(srcdir) -I$(srcdir)/../include -I$(srcdir)/../elfcpp \
@@ -46,10 +49,6 @@  if PLUGINS
 LIBDL = @DLOPEN_LIBS@
 endif
 
-if THREADS
-THREADSLIB = -lpthread
-endif
-
 AM_YFLAGS = -d
 
 # Automake 1.10+ disables lex and yacc output file regeneration if
diff --git a/gold/Makefile.in b/gold/Makefile.in
index 1f4f7ea2c7..8a3962e311 100644
--- a/gold/Makefile.in
+++ b/gold/Makefile.in
@@ -87,11 +87,12 @@  subdir = .
 DIST_COMMON = NEWS README ChangeLog $(srcdir)/Makefile.in \
 	$(srcdir)/Makefile.am $(top_srcdir)/configure \
 	$(am__configure_deps) $(srcdir)/config.in \
-	$(srcdir)/../mkinstalldirs $(top_srcdir)/po/Make-in ffsll.c \
-	ftruncate.c mremap.c pread.c yyscript.h yyscript.c \
+	$(srcdir)/../mkinstalldirs $(top_srcdir)/po/Make-in pread.c \
+	ffsll.c ftruncate.c mremap.c yyscript.h yyscript.c \
 	$(srcdir)/../depcomp $(srcdir)/../ylwrap
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
-am__aclocal_m4_deps = $(top_srcdir)/../config/depstand.m4 \
+am__aclocal_m4_deps = $(top_srcdir)/../config/ax_pthread.m4 \
+	$(top_srcdir)/../config/depstand.m4 \
 	$(top_srcdir)/../config/gettext-sister.m4 \
 	$(top_srcdir)/../config/lcmessage.m4 \
 	$(top_srcdir)/../config/lead-dot.m4 \
@@ -152,8 +153,7 @@  am_ld_new_OBJECTS = $(am__objects_4)
 ld_new_OBJECTS = $(am_ld_new_OBJECTS)
 am__DEPENDENCIES_2 = $(am__DEPENDENCIES_1) libgold.a $(LIBIBERTY) \
 	$(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1) \
-	$(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1) \
-	$(am__DEPENDENCIES_1)
+	$(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1)
 ld_new_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) $(ld_new_LDFLAGS) \
 	$(LDFLAGS) -o $@
 @GCC_TRUE@@NATIVE_LINKER_TRUE@am_ld1_OBJECTS = $(am__objects_4)
@@ -400,8 +400,12 @@  PACKAGE_URL = @PACKAGE_URL@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 PATH_SEPARATOR = @PATH_SEPARATOR@
 POSUB = @POSUB@
+PTHREAD_CC = @PTHREAD_CC@
+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_LIBS = @PTHREAD_LIBS@
 RANDOM_SEED_CFLAGS = @RANDOM_SEED_CFLAGS@
 RANLIB = @RANLIB@
+SED = @SED@
 SET_MAKE = @SET_MAKE@
 SHELL = @SHELL@
 STRIP = @STRIP@
@@ -426,6 +430,7 @@  am__leading_dot = @am__leading_dot@
 am__quote = @am__quote@
 am__tar = @am__tar@
 am__untar = @am__untar@
+ax_pthread_config = @ax_pthread_config@
 bindir = @bindir@
 build = @build@
 build_alias = @build_alias@
@@ -484,8 +489,10 @@  ACLOCAL_AMFLAGS = -I ../bfd -I ../config
 # case both are empty.
 ZLIB = @zlibdir@ -lz
 ZLIBINC = @zlibinc@
-AM_CFLAGS = $(WARN_CFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC)
-AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC)
+THREADFLAGS = @PTHREAD_CFLAGS@
+THREADLIBS = @PTHREAD_LIBS@
+AM_CFLAGS = $(WARN_CFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
+AM_CXXFLAGS = $(WARN_CXXFLAGS) $(LFS_CFLAGS) $(RANDOM_SEED_CFLAGS) $(ZLIBINC) $(THREADFLAGS)
 AM_CPPFLAGS = \
 	-I$(srcdir) -I$(srcdir)/../include -I$(srcdir)/../elfcpp \
 	-DLOCALEDIR="\"$(datadir)/locale\"" \
@@ -494,7 +501,6 @@  AM_CPPFLAGS = \
 
 LIBIBERTY = ../libiberty/libiberty.a
 @PLUGINS_TRUE@LIBDL = @DLOPEN_LIBS@
-@THREADS_TRUE@THREADSLIB = -lpthread
 AM_YFLAGS = -d
 
 # Automake 1.10+ disables lex and yacc output file regeneration if
diff --git a/gold/aclocal.m4 b/gold/aclocal.m4
index 47cb21fc5a..2f34365173 100644
--- a/gold/aclocal.m4
+++ b/gold/aclocal.m4
@@ -1000,6 +1000,7 @@  AC_SUBST([am__tar])
 AC_SUBST([am__untar])
 ]) # _AM_PROG_TAR
 
+m4_include([../config/ax_pthread.m4])
 m4_include([../config/depstand.m4])
 m4_include([../config/gettext-sister.m4])
 m4_include([../config/lcmessage.m4])
diff --git a/gold/configure b/gold/configure
index 90a706dc51..4a9e5faa1a 100755
--- a/gold/configure
+++ b/gold/configure
@@ -600,6 +600,13 @@  HAVE_NO_USE_LINKER_PLUGIN_FALSE
 HAVE_NO_USE_LINKER_PLUGIN_TRUE
 HAVE_PUBNAMES_FALSE
 HAVE_PUBNAMES_TRUE
+THREADS_FALSE
+THREADS_TRUE
+PTHREAD_CFLAGS
+PTHREAD_LIBS
+PTHREAD_CC
+ax_pthread_config
+SED
 zlibinc
 zlibdir
 LIBOBJS
@@ -711,8 +718,6 @@  DEFAULT_TARGET_AARCH64_FALSE
 DEFAULT_TARGET_AARCH64_TRUE
 PLUGINS_FALSE
 PLUGINS_TRUE
-THREADS_FALSE
-THREADS_TRUE
 installed_linker
 install_as_default
 am__untar
@@ -793,7 +798,6 @@  ac_user_opts='
 enable_option_checking
 with_sysroot
 enable_gold
-enable_threads
 enable_plugins
 enable_relro
 enable_targets
@@ -1444,7 +1448,6 @@  Optional Features:
   --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)
   --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]
   --enable-gold[=ARG]     build gold [ARG={default,yes,no}]
-  --enable-threads        multi-threaded linking
   --enable-plugins        linker plugins
   --enable-relro          enable -z relro in ELF linker by default
   --enable-targets        alternative target configurations
@@ -3311,31 +3314,6 @@  fi
 
 
 
-# Check whether --enable-threads was given.
-if test "${enable_threads+set}" = set; then :
-  enableval=$enable_threads; case "${enableval}" in
-  yes | "") threads=yes ;;
-  no) threads=no ;;
-  *) threads=yes ;;
- esac
-else
-  threads=no
-fi
-
-if test "$threads" = "yes"; then
-
-$as_echo "#define ENABLE_THREADS 1" >>confdefs.h
-
-fi
- if test "$threads" = "yes"; then
-  THREADS_TRUE=
-  THREADS_FALSE='#'
-else
-  THREADS_TRUE='#'
-  THREADS_FALSE=
-fi
-
-
 # Check whether --enable-plugins was given.
 if test "${enable_plugins+set}" = set; then :
   enableval=$enable_plugins; case "${enableval}" in
@@ -7043,6 +7021,729 @@  fi
 
 
 
+# Check for pthreads. If available, enable multi-threaded linking
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for a sed that does not truncate output" >&5
+$as_echo_n "checking for a sed that does not truncate output... " >&6; }
+if test "${ac_cv_path_SED+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+            ac_script=s/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/
+     for ac_i in 1 2 3 4 5 6 7; do
+       ac_script="$ac_script$as_nl$ac_script"
+     done
+     echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
+     { ac_script=; unset ac_script;}
+     if test -z "$SED"; then
+  ac_path_SED_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in sed gsed; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_SED="$as_dir/$ac_prog$ac_exec_ext"
+      { test -f "$ac_path_SED" && $as_test_x "$ac_path_SED"; } || continue
+# Check for GNU ac_path_SED and select it if it is found.
+  # Check for GNU $ac_path_SED
+case `"$ac_path_SED" --version 2>&1` in
+*GNU*)
+  ac_cv_path_SED="$ac_path_SED" ac_path_SED_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo '' >> "conftest.nl"
+    "$ac_path_SED" -f conftest.sed < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_SED_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_SED="$ac_path_SED"
+      ac_path_SED_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_SED_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_SED"; then
+    as_fn_error "no acceptable sed could be found in \$PATH" "$LINENO" 5
+  fi
+else
+  ac_cv_path_SED=$SED
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_SED" >&5
+$as_echo "$ac_cv_path_SED" >&6; }
+ SED="$ac_cv_path_SED"
+  rm -f conftest.sed
+
+
+
+
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+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="$LIBS"
+        if test "x$PTHREAD_CC" != "x"; then :
+  CC="$PTHREAD_CC"
+fi
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS" >&5
+$as_echo_n "checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS... " >&6; }
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char pthread_join ();
+int
+main ()
+{
+return pthread_join ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$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 $ax_pthread_flags"
+        ;;
+
+        openedition*)
+
+        # IBM z/OS requires a feature-test macro to be defined in order to
+        # enable POSIX threads at all, so give the user a hint if this is
+        # not set. (We don't define these ourselves, as they can affect
+        # other portions of the system API in unpredictable ways.)
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
+             AX_PTHREAD_ZOS_MISSING
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_ZOS_MISSING" >/dev/null 2>&1; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&5
+$as_echo "$as_me: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&2;}
+fi
+rm -f conftest*
+
+        ;;
+
+        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 $ax_pthread_flags"
+        ;;
+esac
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+if test "x$GCC" = "xyes"; then :
+  ax_pthread_flags="-pthread -pthreads $ax_pthread_flags"
+fi
+
+# 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 $host_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
+
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+if test "x$ax_pthread_check_macro" = "x--"; then :
+  ax_pthread_check_cond=0
+else
+  ax_pthread_check_cond="!defined($ax_pthread_check_macro)"
+fi
+
+# Are we compiling with Clang?
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC is Clang" >&5
+$as_echo_n "checking whether $CC is Clang... " >&6; }
+if test "${ax_cv_PTHREAD_CLANG+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$GCC" = "xyes"; then
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+#            if defined(__clang__) && defined(__llvm__)
+             AX_PTHREAD_CC_IS_CLANG
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_CC_IS_CLANG" >/dev/null 2>&1; then :
+  ax_cv_PTHREAD_CLANG=yes
+fi
+rm -f conftest*
+
+     fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG" >&6; }
+ax_pthread_clang="$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.
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread" >&5
+$as_echo_n "checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread... " >&6; }
+if test "${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  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="$CFLAGS"
+             for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
+                if test "x$ax_pthread_try" = "xunknown"; then :
+  break
+fi
+                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                ac_link="$ax_pthread_save_ac_link"
+                cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_link="$ax_pthread_2step_ac_link"
+                     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+             ac_link="$ax_pthread_save_ac_link"
+             CFLAGS="$ax_pthread_save_CFLAGS"
+             if test "x$ax_pthread_try" = "x"; then :
+  ax_pthread_try=no
+fi
+             ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&6; }
+
+        case "$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)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work without any flags" >&5
+$as_echo_n "checking whether pthreads work without any flags... " >&6; }
+                ;;
+
+                -mt,pthread)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with -mt -lpthread" >&5
+$as_echo_n "checking whether pthreads work with -mt -lpthread... " >&6; }
+                PTHREAD_CFLAGS="-mt"
+                PTHREAD_LIBS="-lpthread"
+                ;;
+
+                -*)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with $ax_pthread_try_flag" >&5
+$as_echo_n "checking whether pthreads work with $ax_pthread_try_flag... " >&6; }
+                PTHREAD_CFLAGS="$ax_pthread_try_flag"
+                ;;
+
+                pthread-config)
+                # Extract the first word of "pthread-config", so it can be a program name with args.
+set dummy pthread-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if test "${ac_cv_prog_ax_pthread_config+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$ax_pthread_config"; then
+  ac_cv_prog_ax_pthread_config="$ax_pthread_config" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+    ac_cv_prog_ax_pthread_config="yes"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  test -z "$ac_cv_prog_ax_pthread_config" && ac_cv_prog_ax_pthread_config="no"
+fi
+fi
+ax_pthread_config=$ac_cv_prog_ax_pthread_config
+if test -n "$ax_pthread_config"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_config" >&5
+$as_echo "$ax_pthread_config" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+                if test "x$ax_pthread_config" = "xno"; then :
+  continue
+fi
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking for the pthreads library -l$ax_pthread_try_flag" >&5
+$as_echo_n "checking for the pthreads library -l$ax_pthread_try_flag... " >&6; }
+                PTHREAD_LIBS="-l$ax_pthread_try_flag"
+                ;;
+        esac
+
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Check for various functions.  We must include pthread.h,
+        # since some functions may be macros.  (On the Sequent, we
+        # need a special flag -Kthread to make this header compile.)
+        # We check for pthread_join because it is in -lpthread on IRIX
+        # while pthread_create is in libc.  We check for pthread_attr_init
+        # due to DEC craziness with -lpthreads.  We check for
+        # pthread_cleanup_push because it is one of the few pthread
+        # functions on Solaris that doesn't have a non-functional libc stub.
+        # We try pthread_create on general principles.
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#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; }
+int
+main ()
+{
+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) /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xyes"; then :
+  break
+fi
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+# Various other checks:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for joinable pthread attribute" >&5
+$as_echo_n "checking for joinable pthread attribute... " >&6; }
+if test "${ax_cv_PTHREAD_JOINABLE_ATTR+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int attr = $ax_pthread_attr; return attr /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_JOINABLE_ATTR" >&5
+$as_echo "$ax_cv_PTHREAD_JOINABLE_ATTR" >&6; }
+        if test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
+               test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
+               test "x$ax_pthread_joinable_attr_defined" != "xyes"; then :
+
+cat >>confdefs.h <<_ACEOF
+#define PTHREAD_CREATE_JOINABLE $ax_cv_PTHREAD_JOINABLE_ATTR
+_ACEOF
+
+               ax_pthread_joinable_attr_defined=yes
+
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether more special flags are required for pthreads" >&5
+$as_echo_n "checking whether more special flags are required for pthreads... " >&6; }
+if test "${ax_cv_PTHREAD_SPECIAL_FLAGS+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_SPECIAL_FLAGS" >&5
+$as_echo "$ax_cv_PTHREAD_SPECIAL_FLAGS" >&6; }
+        if test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
+               test "x$ax_pthread_special_flags_added" != "xyes"; then :
+  PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for PTHREAD_PRIO_INHERIT" >&5
+$as_echo_n "checking for PTHREAD_PRIO_INHERIT... " >&6; }
+if test "${ax_cv_PTHREAD_PRIO_INHERIT+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int i = PTHREAD_PRIO_INHERIT;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_PRIO_INHERIT=yes
+else
+  ax_cv_PTHREAD_PRIO_INHERIT=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_PRIO_INHERIT" >&5
+$as_echo "$ax_cv_PTHREAD_PRIO_INHERIT" >&6; }
+        if test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"; then :
+
+$as_echo "#define HAVE_PTHREAD_PRIO_INHERIT 1" >>confdefs.h
+
+               ax_pthread_prio_inherit_defined=yes
+
+fi
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        # More AIX lossage: compile with *_r variant
+        if test "x$GCC" != "xyes"; then
+            case $host_os in
+                aix*)
+                case "x/$CC" in #(
+  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
+                     case "x$CC" in #(
+  x/*) :
+    if { test -f ${CC}_r && $as_test_x ${CC}_r; }; then :
+  PTHREAD_CC="${CC}_r"
+fi ;; #(
+  *) :
+    for ac_prog in ${CC}_r
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if test "${ac_cv_prog_PTHREAD_CC+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$PTHREAD_CC"; then
+  ac_cv_prog_PTHREAD_CC="$PTHREAD_CC" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+    ac_cv_prog_PTHREAD_CC="$ac_prog"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+PTHREAD_CC=$ac_cv_prog_PTHREAD_CC
+if test -n "$PTHREAD_CC"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PTHREAD_CC" >&5
+$as_echo "$PTHREAD_CC" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+  test -n "$PTHREAD_CC" && break
+done
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+ ;;
+esac ;; #(
+  *) :
+     ;;
+esac
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+
+
+
+
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+        threads=yes
+        :
+else
+        ax_pthread_ok=no
+        threads=no
+fi
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+if test "$threads" = "yes"; then
+
+$as_echo "#define ENABLE_THREADS 1" >>confdefs.h
+
+fi
+ if test "$threads" = "yes"; then
+  THREADS_TRUE=
+  THREADS_FALSE='#'
+else
+  THREADS_TRUE='#'
+  THREADS_FALSE=
+fi
+
+
 ac_fn_c_check_decl "$LINENO" "basename" "ac_cv_have_decl_basename" "$ac_includes_default"
 if test "x$ac_cv_have_decl_basename" = x""yes; then :
   ac_have_decl=1
@@ -7878,10 +8579,6 @@  else
   am__EXEEXT_FALSE=
 fi
 
-if test -z "${THREADS_TRUE}" && test -z "${THREADS_FALSE}"; then
-  as_fn_error "conditional \"THREADS\" was never defined.
-Usually this means the macro was only invoked conditionally." "$LINENO" 5
-fi
 if test -z "${PLUGINS_TRUE}" && test -z "${PLUGINS_FALSE}"; then
   as_fn_error "conditional \"PLUGINS\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
@@ -7995,6 +8692,10 @@  if test -z "${IFUNC_STATIC_TRUE}" && test -z "${IFUNC_STATIC_FALSE}"; then
   as_fn_error "conditional \"IFUNC_STATIC\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
+if test -z "${THREADS_TRUE}" && test -z "${THREADS_FALSE}"; then
+  as_fn_error "conditional \"THREADS\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
 if test -z "${HAVE_PUBNAMES_TRUE}" && test -z "${HAVE_PUBNAMES_FALSE}"; then
   as_fn_error "conditional \"HAVE_PUBNAMES\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
diff --git a/gold/configure.ac b/gold/configure.ac
index 5ba43f2f95..c46b455fda 100644
--- a/gold/configure.ac
+++ b/gold/configure.ac
@@ -85,21 +85,6 @@  AC_ARG_ENABLE(gold,
 AC_SUBST(install_as_default)
 AC_SUBST(installed_linker)
 
-dnl For now threads are a configure time option.
-AC_ARG_ENABLE([threads],
-[  --enable-threads        multi-threaded linking],
-[case "${enableval}" in
-  yes | "") threads=yes ;;
-  no) threads=no ;;
-  *) threads=yes ;;
- esac],
-[threads=no])
-if test "$threads" = "yes"; then
-  AC_DEFINE(ENABLE_THREADS, 1,
-	    [Define to do multi-threaded linking])
-fi
-AM_CONDITIONAL(THREADS, test "$threads" = "yes")
-
 AC_ARG_ENABLE([plugins],
 [  --enable-plugins        linker plugins],
 [case "${enableval}" in
@@ -570,6 +555,14 @@  fi
 # Link in zlib if we can.  This allows us to write compressed sections.
 AM_ZLIB
 
+# Check for pthreads. If available, enable multi-threaded linking
+AX_PTHREAD([threads=yes], [threads=no])
+if test "$threads" = "yes"; then
+  AC_DEFINE(ENABLE_THREADS, 1,
+	    [Define to do multi-threaded linking])
+fi
+AM_CONDITIONAL(THREADS, test "$threads" = "yes")
+
 dnl We have to check these in C, not C++, because autoconf generates
 dnl tests which have no type information, and current glibc provides
 dnl multiple declarations of functions like basename when compiling
diff --git a/gold/testsuite/Makefile.in b/gold/testsuite/Makefile.in
index bbf8dc146b..96f3a08b9f 100644
--- a/gold/testsuite/Makefile.in
+++ b/gold/testsuite/Makefile.in
@@ -1054,7 +1054,8 @@  check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 subdir = testsuite
 DIST_COMMON = $(srcdir)/Makefile.in $(srcdir)/Makefile.am
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
-am__aclocal_m4_deps = $(top_srcdir)/../config/depstand.m4 \
+am__aclocal_m4_deps = $(top_srcdir)/../config/ax_pthread.m4 \
+	$(top_srcdir)/../config/depstand.m4 \
 	$(top_srcdir)/../config/gettext-sister.m4 \
 	$(top_srcdir)/../config/lcmessage.m4 \
 	$(top_srcdir)/../config/lead-dot.m4 \
@@ -2711,8 +2712,12 @@  PACKAGE_URL = @PACKAGE_URL@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 PATH_SEPARATOR = @PATH_SEPARATOR@
 POSUB = @POSUB@
+PTHREAD_CC = @PTHREAD_CC@
+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_LIBS = @PTHREAD_LIBS@
 RANDOM_SEED_CFLAGS = @RANDOM_SEED_CFLAGS@
 RANLIB = @RANLIB@
+SED = @SED@
 SET_MAKE = @SET_MAKE@
 SHELL = @SHELL@
 STRIP = @STRIP@
@@ -2737,6 +2742,7 @@  am__leading_dot = @am__leading_dot@
 am__quote = @am__quote@
 am__tar = @am__tar@
 am__untar = @am__untar@
+ax_pthread_config = @ax_pthread_config@
 bindir = @bindir@
 build = @build@
 build_alias = @build_alias@