updated ax_pthread.m4

moo/bin/Makefile.am

@@ -10,7 +10,7 @@ CPPFLAGS_ALL_COMMON = \
 LDFLAGS_ALL_COMMON = -L$(abs_builddir) -L$(abs_builddir)/../lib -L$(libdir)
 
 CPPFLAGS_BIN_COMMON = $(CPPFLAGS_ALL_COMMON)
-LDFLAGS_BIN_COMMON = $(LDFLAGS_ALL_COMMON) -version-info 1:0:0 -no-undefined
+LDFLAGS_BIN_COMMON = $(LDFLAGS_ALL_COMMON) -no-undefined
 LIBADD_BIN_COMMON = $(LIBM) 
 
 bin_PROGRAMS = moo

moo/bin/Makefile.in

@@ -358,7 +358,7 @@ CPPFLAGS_ALL_COMMON = \
 
 LDFLAGS_ALL_COMMON = -L$(abs_builddir) -L$(abs_builddir)/../lib -L$(libdir)
 CPPFLAGS_BIN_COMMON = $(CPPFLAGS_ALL_COMMON)
-LDFLAGS_BIN_COMMON = $(LDFLAGS_ALL_COMMON) -version-info 1:0:0 -no-undefined
+LDFLAGS_BIN_COMMON = $(LDFLAGS_ALL_COMMON) -no-undefined
 LIBADD_BIN_COMMON = $(LIBM) 
 
 ##################################################

moo/configure

@@ -17612,10 +17612,12 @@ fi
 # (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
+# Create a list of thread flags to try. Items with a "," contain both
-# C compiler flags, and other items are library names, except for "none"
+# C compiler flags (before ",") and linker flags (after ","). Other items
-# which indicates that we try without any flags at all, and "pthread-config"
+# starting with a "-" are C compiler flags, and remaining items are
-# which is a program returning the flags for the Pth emulation library.
+# 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"
 
@@ -17691,39 +17693,10 @@ rm -f conftest*
         # 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"
+        ax_pthread_flags="-mt,-lpthread 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
@@ -17755,107 +17728,51 @@ fi
 $as_echo "$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
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
-# option in a rather... idiosyncratic way
 
-if test "x$ax_pthread_clang" = "xyes"; then
+# Note that for GCC and Clang -pthread generally implies -lpthread,
+# except when -nostdlib is passed.
+# This is problematic using libtool to build C++ shared libraries with pthread:
+# [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460
+# [2] https://bugzilla.redhat.com/show_bug.cgi?id=661333
+# [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=468555
+# To solve this, first try -pthread together with -lpthread for GCC
 
-        # Clang takes -pthread; it has never supported any other flag
+if test "x$GCC" = "xyes"; then :
+  ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"
+fi
 
-        # (Note 1: This will need to be revisited if a system that Clang
+# Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first
-        # 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
+if test "x$ax_pthread_clang" = "xyes"; then :
-        # to get POSIX threads support; the API is always present and
+  ax_pthread_flags="-pthread,-lpthread -pthread"
-        # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
+fi
-        # -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
+# 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
 
-        # However, older versions of Clang make a point of warning the user
+case $host_os in
-        # that, in an invocation where only linking and no compilation is
+        darwin* | hpux* | linux* | osf* | solaris*)
-        # taking place, the -pthread option has no effect ("argument unused
+        ax_pthread_check_macro="_REENTRANT"
-        # 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
+        aix*)
-$as_echo_n "checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread... " >&6; }
+        ax_pthread_check_macro="_THREAD_SAFE"
-if ${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+:} false; then :
+        ;;
-  $as_echo_n "(cached) " >&6
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+if test "x$ax_pthread_check_macro" = "x--"; then :
+  ax_pthread_check_cond=0
 else
-  ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
+  ax_pthread_check_cond="!defined($ax_pthread_check_macro)"
-             # 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
@@ -17866,11 +17783,11 @@ for ax_pthread_try_flag in $ax_pthread_flags; do
 $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
+                PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"`
-$as_echo_n "checking whether pthreads work with -mt -lpthread... " >&6; }
+                PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"`
-                PTHREAD_CFLAGS="-mt"
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with \"$PTHREAD_CFLAGS\" and \"$PTHREAD_LIBS\"" >&5
-                PTHREAD_LIBS="-lpthread"
+$as_echo_n "checking whether pthreads work with \"$PTHREAD_CFLAGS\" and \"$PTHREAD_LIBS\"... " >&6; }
                 ;;
 
                 -*)
@@ -17953,7 +17870,13 @@ $as_echo_n "checking for the pthreads library -l$ax_pthread_try_flag... " >&6; }
 #                       if $ax_pthread_check_cond
 #                        error "$ax_pthread_check_macro must be defined"
 #                       endif
-                        static void routine(void *a) { a = 0; }
+                        static void *some_global = NULL;
+                        static void routine(void *a)
+                          {
+                             /* To avoid any unused-parameter or
+                                unused-but-set-parameter warning.  */
+                             some_global = a;
+                          }
                         static void *start_routine(void *a) { return a; }
 int
 main ()
@@ -17988,6 +17911,104 @@ fi
 done
 fi
 
+
+# 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.)
+
+        # 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 ${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+:} false; 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 # $ax_pthread_clang = yes
+
+
+
 # Various other checks:
 if test "x$ax_pthread_ok" = "xyes"; then
         ax_pthread_save_CFLAGS="$CFLAGS"
@@ -18069,6 +18090,7 @@ int
 main ()
 {
 int i = PTHREAD_PRIO_INHERIT;
+                                               return i;
   ;
   return 0;
 }

moo/lib/Makefile.am

@@ -1,7 +1,5 @@
 AUTOMAKE_OPTIONS = nostdinc
 
-AM_CFLAGS = $(PTHREAD_CFLAGS)
-
 CPPFLAGS_ALL_COMMON = \
 	-I$(abs_builddir) \
 	-I$(abs_srcdir) \
@@ -13,7 +11,7 @@ else
 LDFLAGS_ALL_COMMON = -L$(abs_builddir) -L$(libdir)
 endif
 
-CPPFLAGS_LIB_COMMON = $(CPPFLAGS_ALL_COMMON) 
+CPPFLAGS_LIB_COMMON = $(CPPFLAGS_ALL_COMMON) $(PTHREAD_CFLAGS)
 LDFLAGS_LIB_COMMON = $(LDFLAGS_ALL_COMMON) -version-info 1:0:0 -no-undefined
 LIBADD_LIB_COMMON =
 
@@ -139,7 +137,7 @@ libmoox_la_SOURCES += poll-msw.c poll-msw.h
 endif
 libmoox_la_CPPFLAGS = $(CPPFLAGS_LIB_COMMON) $(CPPFLAGS_PFMOD)
 libmoox_la_LDFLAGS = $(LDFLAGS_LIB_COMMON)
-libmoox_la_LIBADD = $(LIBADD_LIB_COMMON) -lmoo $(LIBM) $(PTHREAD_LIBS)
+libmoox_la_LIBADD = -lmoo $(LIBADD_LIB_COMMON) $(LIBM) $(PTHREAD_LIBS)
 
 if ENABLE_LIBLTDL
 libmoox_la_LIBADD += $(LTDL_LIBS)

moo/lib/Makefile.in

@@ -429,7 +429,6 @@ top_build_prefix = @top_build_prefix@
 top_builddir = @top_builddir@
 top_srcdir = @top_srcdir@
 AUTOMAKE_OPTIONS = nostdinc
-AM_CFLAGS = $(PTHREAD_CFLAGS)
 CPPFLAGS_ALL_COMMON = \
 	-I$(abs_builddir) \
 	-I$(abs_srcdir) \
@@ -437,7 +436,7 @@ CPPFLAGS_ALL_COMMON = \
 
 @ENABLE_STATIC_MODULE_FALSE@LDFLAGS_ALL_COMMON = -L$(abs_builddir) -L$(libdir)
 @ENABLE_STATIC_MODULE_TRUE@LDFLAGS_ALL_COMMON = -L$(abs_builddir)/../mod -L$(abs_builddir) -L$(libdir)
-CPPFLAGS_LIB_COMMON = $(CPPFLAGS_ALL_COMMON) 
+CPPFLAGS_LIB_COMMON = $(CPPFLAGS_ALL_COMMON) $(PTHREAD_CFLAGS)
 LDFLAGS_LIB_COMMON = $(LDFLAGS_ALL_COMMON) -version-info 1:0:0 -no-undefined
 LIBADD_LIB_COMMON = 
 @WIN32_FALSE@CPPFLAGS_PFMOD =  \
@@ -518,7 +517,7 @@ libmoox_la_SOURCES = moo-opt.h moo-std.h opt-imp.h opt.c std.c \
 	$(am__append_15)
 libmoox_la_CPPFLAGS = $(CPPFLAGS_LIB_COMMON) $(CPPFLAGS_PFMOD)
 libmoox_la_LDFLAGS = $(LDFLAGS_LIB_COMMON)
-libmoox_la_LIBADD = $(LIBADD_LIB_COMMON) -lmoo $(LIBM) $(PTHREAD_LIBS) \
+libmoox_la_LIBADD = -lmoo $(LIBADD_LIB_COMMON) $(LIBM) $(PTHREAD_LIBS) \
 	$(am__append_16) $(am__append_17) $(am__append_18) \
 	$(am__append_19)
 libmoox_la_DEPENDENCIES = libmoo.la

moo/m4/ax_pthread.m4

@@ -55,6 +55,7 @@
 #
 #   Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
 #   Copyright (c) 2011 Daniel Richard G. <skunk@iSKUNK.ORG>
+#   Copyright (c) 2019 Marc Stevens <marc.stevens@cwi.nl>
 #
 #   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
@@ -82,7 +83,7 @@
 #   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
+#serial 27
 
 AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
 AC_DEFUN([AX_PTHREAD], [
@@ -123,10 +124,12 @@ fi
 # (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
+# Create a list of thread flags to try. Items with a "," contain both
-# C compiler flags, and other items are library names, except for "none"
+# C compiler flags (before ",") and linker flags (after ","). Other items
-# which indicates that we try without any flags at all, and "pthread-config"
+# starting with a "-" are C compiler flags, and remaining items are
-# which is a program returning the flags for the Pth emulation library.
+# 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"
 
@@ -194,14 +197,47 @@ case $host_os in
         # 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"
+        ax_pthread_flags="-mt,-lpthread pthread $ax_pthread_flags"
         ;;
 esac
 
+# 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"
+
+
 # GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
 
+# Note that for GCC and Clang -pthread generally implies -lpthread,
+# except when -nostdlib is passed.
+# This is problematic using libtool to build C++ shared libraries with pthread:
+# [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460
+# [2] https://bugzilla.redhat.com/show_bug.cgi?id=661333
+# [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=468555
+# To solve this, first try -pthread together with -lpthread for GCC
+
 AS_IF([test "x$GCC" = "xyes"],
-      [ax_pthread_flags="-pthread -pthreads $ax_pthread_flags"])
+      [ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"])
+
+# Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first
+
+AS_IF([test "x$ax_pthread_clang" = "xyes"],
+      [ax_pthread_flags="-pthread,-lpthread -pthread"])
+
 
 # The presence of a feature test macro requesting re-entrant function
 # definitions is, on some systems, a strong hint that pthreads support is
@@ -224,25 +260,86 @@ 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 $CC is Clang],
+if test "x$ax_pthread_ok" = "xno"; then
-    [ax_cv_PTHREAD_CLANG],
+for ax_pthread_try_flag in $ax_pthread_flags; do
-    [ax_cv_PTHREAD_CLANG=no
+
-     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+        case $ax_pthread_try_flag in
-     if test "x$GCC" = "xyes"; then
+                none)
-        AC_EGREP_CPP([AX_PTHREAD_CC_IS_CLANG],
+                AC_MSG_CHECKING([whether pthreads work without any flags])
-            [/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+                ;;
-#            if defined(__clang__) && defined(__llvm__)
+
-             AX_PTHREAD_CC_IS_CLANG
+                *,*)
-#            endif
+                PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"`
-            ],
+                PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"`
-            [ax_cv_PTHREAD_CLANG=yes])
+                AC_MSG_CHECKING([whether pthreads work with "$PTHREAD_CFLAGS" and "$PTHREAD_LIBS"])
-     fi
+                ;;
-    ])
+
-ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+                -*)
+                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 *some_global = NULL;
+                        static void routine(void *a)
+                          {
+                             /* To avoid any unused-parameter or
+                                unused-but-set-parameter warning.  */
+                             some_global = a;
+                          }
+                        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
 
-ax_pthread_clang_warning=no
 
 # Clang needs special handling, because older versions handle the -pthread
 # option in a rather... idiosyncratic way
@@ -261,11 +358,6 @@ if test "x$ax_pthread_clang" = "xyes"; then
         # -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
@@ -320,78 +412,7 @@ if test "x$ax_pthread_clang" = "xyes"; then
 
 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$ax_pthread_ok" = "xyes"; then
@@ -438,7 +459,8 @@ if test "x$ax_pthread_ok" = "xyes"; then
         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;]])],
+                                             [[int i = PTHREAD_PRIO_INHERIT;
+                                               return i;]])],
                             [ax_cv_PTHREAD_PRIO_INHERIT=yes],
                             [ax_cv_PTHREAD_PRIO_INHERIT=no])
             ])