diff --git a/Makefile.in b/Makefile.in
index 522ca305c..e38f265e8 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -90,6 +90,7 @@ host_triplet = @host@
 subdir = .
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps = $(top_srcdir)/config/ax_check_openssl.m4 \
+	$(top_srcdir)/config/ax_pthread.m4 \
 	$(top_srcdir)/config/iperf_config_static_bin.m4 \
 	$(top_srcdir)/configure.ac
 am__configure_deps = $(am__aclocal_m4_deps) $(CONFIGURE_DEPENDENCIES) \
@@ -219,6 +220,7 @@ AWK = @AWK@
 CC = @CC@
 CCDEPMODE = @CCDEPMODE@
 CFLAGS = @CFLAGS@
+CPP = @CPP@
 CPPFLAGS = @CPPFLAGS@
 CSCOPE = @CSCOPE@
 CTAGS = @CTAGS@
@@ -273,6 +275,10 @@ PACKAGE_URL = @PACKAGE_URL@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 PATH_SEPARATOR = @PATH_SEPARATOR@
 PKG_CONFIG = @PKG_CONFIG@
+PTHREAD_CC = @PTHREAD_CC@
+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_CXX = @PTHREAD_CXX@
+PTHREAD_LIBS = @PTHREAD_LIBS@
 RANLIB = @RANLIB@
 SED = @SED@
 SET_MAKE = @SET_MAKE@
@@ -291,6 +297,7 @@ 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@
diff --git a/configure b/configure
index a539d16bc..76ab0cc69 100755
--- a/configure
+++ b/configure
@@ -666,6 +666,12 @@ OPENSSL_LDFLAGS
 OPENSSL_LIBS
 OPENSSL_INCLUDES
 PKG_CONFIG
+PTHREAD_CFLAGS
+PTHREAD_LIBS
+PTHREAD_CXX
+PTHREAD_CC
+ax_pthread_config
+CPP
 ENABLE_PROFILING_FALSE
 ENABLE_PROFILING_TRUE
 MAINT
@@ -817,7 +823,8 @@ CFLAGS
 LDFLAGS
 LIBS
 CPPFLAGS
-LT_SYS_LIBRARY_PATH'
+LT_SYS_LIBRARY_PATH
+CPP'
 
 
 # Initialize some variables set by options.
@@ -1486,6 +1493,7 @@ Some influential environment variables:
               you have headers in a nonstandard directory <include dir>
   LT_SYS_LIBRARY_PATH
               User-defined run-time library search path.
+  CPP         C preprocessor
 
 Use these variables to override the choices made by `configure' or to help
 it to find libraries and programs with nonstandard names/locations.
@@ -1750,6 +1758,44 @@ printf "%s\n" "$ac_res" >&6; }
 
 } # ac_fn_c_check_func
 
+# ac_fn_c_try_cpp LINENO
+# ----------------------
+# Try to preprocess conftest.$ac_ext, and return whether this succeeded.
+ac_fn_c_try_cpp ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  if { { ac_try="$ac_cpp conftest.$ac_ext"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+printf "%s\n" "$ac_try_echo"; } >&5
+  (eval "$ac_cpp conftest.$ac_ext") 2>conftest.err
+  ac_status=$?
+  if test -s conftest.err; then
+    grep -v '^ *+' conftest.err >conftest.er1
+    cat conftest.er1 >&5
+    mv -f conftest.er1 conftest.err
+  fi
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; } > conftest.i && {
+	 test -z "$ac_c_preproc_warn_flag$ac_c_werror_flag" ||
+	 test ! -s conftest.err
+       }
+then :
+  ac_retval=0
+else $as_nop
+  printf "%s\n" "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+    ac_retval=1
+fi
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+  as_fn_set_status $ac_retval
+
+} # ac_fn_c_try_cpp
+
 # ac_fn_c_check_member LINENO AGGR MEMBER VAR INCLUDES
 # ----------------------------------------------------
 # Tries to find if the field MEMBER exists in type AGGR, after including
@@ -2647,6 +2693,119 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
+# ===========================================================================
+#        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 and PTHREAD_CXX to any special C compiler that is
+#   needed for multi-threaded programs (defaults to the value of CC
+#   respectively CXX otherwise). (This is necessary on e.g. AIX to use the
+#   special cc_r/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
+#   $PTHREAD_CXX $CXXFLAGS $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 $PTHREAD_CFLAGS"
+#     CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS"
+#     CC="$PTHREAD_CC"
+#     CXX="$PTHREAD_CXX"
+#
+#   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>
+#   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
+#   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 31
+
+# This is what autoupdate's m4 run will expand.  It fires the warning
+# (with _au_warn_XXX), outputs it into the updated configure.ac (with
+# m4_warn), and then outputs the replacement expansion.  We need extra
+# quotation around the m4_warn and dnl so they will be written
+# unexpanded into the updated configure.ac.
+
+
+# This is an auxiliary macro that is also run when
+# autoupdate runs m4.  It simply calls m4_warning, but
+# we need a wrapper so that each warning is emitted only
+# once.  We break the quoting in m4_warning's argument in
+# order to expand this macro's arguments, not AU_DEFUN's.
+
+
+# Finally, this is the expansion that is picked up by
+# autoconf, causing NAME to expand to NEW-CODE, plus
+# (if SILENT is not "silent") a m4_warning telling the
+# maintainer to run autoupdate.  We don't issue MESSAGE
+# from autoconf, because that's instructions for what
+# to do *after* running autoupdate.
+
+
 # Also link binaries as static
 # Check whether --enable-static-bin was given.
 if test ${enable_static_bin+y}
@@ -13707,108 +13866,6 @@ else
 fi
 
 
-if test -n "$ac_tool_prefix"; then
-  # Extract the first word of "${ac_tool_prefix}ranlib", so it can be a program name with args.
-set dummy ${ac_tool_prefix}ranlib; ac_word=$2
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-printf %s "checking for $ac_word... " >&6; }
-if test ${ac_cv_prog_RANLIB+y}
-then :
-  printf %s "(cached) " >&6
-else $as_nop
-  if test -n "$RANLIB"; then
-  ac_cv_prog_RANLIB="$RANLIB" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  case $as_dir in #(((
-    '') as_dir=./ ;;
-    */) ;;
-    *) as_dir=$as_dir/ ;;
-  esac
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
-    ac_cv_prog_RANLIB="${ac_tool_prefix}ranlib"
-    printf "%s\n" "$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
-RANLIB=$ac_cv_prog_RANLIB
-if test -n "$RANLIB"; then
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $RANLIB" >&5
-printf "%s\n" "$RANLIB" >&6; }
-else
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
-printf "%s\n" "no" >&6; }
-fi
-
-
-fi
-if test -z "$ac_cv_prog_RANLIB"; then
-  ac_ct_RANLIB=$RANLIB
-  # Extract the first word of "ranlib", so it can be a program name with args.
-set dummy ranlib; ac_word=$2
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-printf %s "checking for $ac_word... " >&6; }
-if test ${ac_cv_prog_ac_ct_RANLIB+y}
-then :
-  printf %s "(cached) " >&6
-else $as_nop
-  if test -n "$ac_ct_RANLIB"; then
-  ac_cv_prog_ac_ct_RANLIB="$ac_ct_RANLIB" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  case $as_dir in #(((
-    '') as_dir=./ ;;
-    */) ;;
-    *) as_dir=$as_dir/ ;;
-  esac
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
-    ac_cv_prog_ac_ct_RANLIB="ranlib"
-    printf "%s\n" "$as_me:${as_lineno-$LINENO}: found $as_dir$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-fi
-fi
-ac_ct_RANLIB=$ac_cv_prog_ac_ct_RANLIB
-if test -n "$ac_ct_RANLIB"; then
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_ct_RANLIB" >&5
-printf "%s\n" "$ac_ct_RANLIB" >&6; }
-else
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
-printf "%s\n" "no" >&6; }
-fi
-
-  if test "x$ac_ct_RANLIB" = x; then
-    RANLIB=":"
-  else
-    case $cross_compiling:$ac_tool_warned in
-yes:)
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
-printf "%s\n" "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
-ac_tool_warned=yes ;;
-esac
-    RANLIB=$ac_ct_RANLIB
-  fi
-else
-  RANLIB="$ac_cv_prog_RANLIB"
-fi
-
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether ln -s works" >&5
 printf %s "checking whether ln -s works... " >&6; }
 LN_S=$as_ln_s
@@ -13821,7 +13878,6 @@ printf "%s\n" "no, using $LN_S" >&6; }
 fi
 
 
-
 # Add -Wall if we are using GCC.
 if test "x$GCC" = "xyes"; then
   CFLAGS="$CFLAGS -Wall"
@@ -14126,60 +14182,972 @@ printf "%s\n" "#define const /**/" >>confdefs.h
 fi
 
 
-# Check for poll.h (it's in POSIX so everyone should have it?)
-ac_fn_c_check_header_compile "$LINENO" "poll.h" "ac_cv_header_poll_h" "$ac_includes_default"
-if test "x$ac_cv_header_poll_h" = xyes
+ac_ext=c
+ac_cpp='$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
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking how to run the C preprocessor" >&5
+printf %s "checking how to run the C preprocessor... " >&6; }
+# On Suns, sometimes $CPP names a directory.
+if test -n "$CPP" && test -d "$CPP"; then
+  CPP=
+fi
+if test -z "$CPP"; then
+  if test ${ac_cv_prog_CPP+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+      # Double quotes because $CC needs to be expanded
+    for CPP in "$CC -E" "$CC -E -traditional-cpp" cpp /lib/cpp
+    do
+      ac_preproc_ok=false
+for ac_c_preproc_warn_flag in '' yes
+do
+  # Use a header file that comes with gcc, so configuring glibc
+  # with a fresh cross-compiler works.
+  # On the NeXT, cc -E runs the code through the compiler's parser,
+  # not just through cpp. "Syntax error" is here to catch this case.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <limits.h>
+		     Syntax error
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"
 then :
-  printf "%s\n" "#define HAVE_POLL_H 1" >>confdefs.h
 
+else $as_nop
+  # Broken: fails on valid input.
+continue
 fi
+rm -f conftest.err conftest.i conftest.$ac_ext
 
-
-# SCTP.  Allow user to disable SCTP support with --without-sctp.
-# Otherwise we try to find whatever support is required.
-try_sctp=true
-
-# Check whether --with-sctp was given.
-if test ${with_sctp+y}
+  # OK, works on sane cases.  Now check whether nonexistent headers
+  # can be detected and how.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <ac_nonexistent.h>
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"
 then :
-  withval=$with_sctp;
-        case "$withval" in
-	y | ye | yes)
-	  ;;
-	n | no)
-	try_sctp=false
-	  ;;
-	*)
-	as_fn_error $? "Invalid --with-sctp value" "$LINENO" 5
-	  ;;
-	esac
-
+  # Broken: success on invalid input.
+continue
 else $as_nop
+  # Passes both tests.
+ac_preproc_ok=:
+break
+fi
+rm -f conftest.err conftest.i conftest.$ac_ext
 
-        try_sctp=true
-
-
+done
+# Because of `break', _AC_PREPROC_IFELSE's cleaning code was skipped.
+rm -f conftest.i conftest.err conftest.$ac_ext
+if $ac_preproc_ok
+then :
+  break
 fi
 
+    done
+    ac_cv_prog_CPP=$CPP
 
-ac_fn_c_check_header_compile "$LINENO" "linux/tcp.h" "ac_cv_header_linux_tcp_h" "$ac_includes_default"
-if test "x$ac_cv_header_linux_tcp_h" = xyes
+fi
+  CPP=$ac_cv_prog_CPP
+else
+  ac_cv_prog_CPP=$CPP
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $CPP" >&5
+printf "%s\n" "$CPP" >&6; }
+ac_preproc_ok=false
+for ac_c_preproc_warn_flag in '' yes
+do
+  # Use a header file that comes with gcc, so configuring glibc
+  # with a fresh cross-compiler works.
+  # On the NeXT, cc -E runs the code through the compiler's parser,
+  # not just through cpp. "Syntax error" is here to catch this case.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <limits.h>
+		     Syntax error
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"
 then :
-  printf "%s\n" "#define HAVE_LINUX_TCP_H 1" >>confdefs.h
 
+else $as_nop
+  # Broken: fails on valid input.
+continue
 fi
+rm -f conftest.err conftest.i conftest.$ac_ext
 
-
-# Check for SCTP support
-if $try_sctp; then
-ac_fn_c_check_header_compile "$LINENO" "sys/socket.h" "ac_cv_header_sys_socket_h" "$ac_includes_default"
-if test "x$ac_cv_header_sys_socket_h" = xyes
+  # OK, works on sane cases.  Now check whether nonexistent headers
+  # can be detected and how.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <ac_nonexistent.h>
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"
 then :
-  printf "%s\n" "#define HAVE_SYS_SOCKET_H 1" >>confdefs.h
-
+  # Broken: success on invalid input.
+continue
+else $as_nop
+  # Passes both tests.
+ac_preproc_ok=:
+break
 fi
+rm -f conftest.err conftest.i conftest.$ac_ext
 
-       for ac_header in netinet/sctp.h
+done
+# Because of `break', _AC_PREPROC_IFELSE's cleaning code was skipped.
+rm -f conftest.i conftest.err conftest.$ac_ext
+if $ac_preproc_ok
+then :
+
+else $as_nop
+  { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "C preprocessor \"$CPP\" fails sanity check
+See \`config.log' for more details" "$LINENO" 5; }
+fi
+
+ac_ext=c
+ac_cpp='$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
+
+
+
+
+
+
+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="$PTHREAD_CC"
+fi
+        if test "x$PTHREAD_CXX" != "x"
+then :
+  CXX="$PTHREAD_CXX"
+fi
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS" >&5
+printf %s "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.  */
+char pthread_join ();
+int
+main (void)
+{
+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.beam \
+    conftest$ac_exeext conftest.$ac_ext
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+printf "%s\n" "$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 with a "," contain both
+# C compiler flags (before ",") and linker flags (after ","). Other items
+# starting with a "-" are C compiler flags, and remaining 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 |
+  $EGREP "AX_PTHREAD_ZOS_MISSING" >/dev/null 2>&1
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&5
+printf "%s\n" "$as_me: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&2;}
+fi
+rm -rf 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,-lpthread pthread $ax_pthread_flags"
+        ;;
+esac
+
+# Are we compiling with Clang?
+
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether $CC is Clang" >&5
+printf %s "checking whether $CC is Clang... " >&6; }
+if test ${ax_cv_PTHREAD_CLANG+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$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 |
+  $EGREP "AX_PTHREAD_CC_IS_CLANG" >/dev/null 2>&1
+then :
+  ax_cv_PTHREAD_CLANG=yes
+fi
+rm -rf conftest*
+
+     fi
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG" >&5
+printf "%s\n" "$ax_cv_PTHREAD_CLANG" >&6; }
+ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+# Note that for GCC and Clang -pthread generally implies -lpthread,
+# except when -nostdlib is passed.
+# This is problematic using libtool to build C++ shared libraries with pthread:
+# [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460
+# [2] https://bugzilla.redhat.com/show_bug.cgi?id=661333
+# [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=468555
+# To solve this, first try -pthread together with -lpthread for GCC
+
+if test "x$GCC" = "xyes"
+then :
+  ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"
+fi
+
+# Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first
+
+if test "x$ax_pthread_clang" = "xyes"
+then :
+  ax_pthread_flags="-pthread,-lpthread -pthread"
+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 $as_nop
+  ax_pthread_check_cond="!defined($ax_pthread_check_macro)"
+fi
+
+
+if test "x$ax_pthread_ok" = "xno"; then
+for ax_pthread_try_flag in $ax_pthread_flags; do
+
+        case $ax_pthread_try_flag in
+                none)
+                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether pthreads work without any flags" >&5
+printf %s "checking whether pthreads work without any flags... " >&6; }
+                ;;
+
+                *,*)
+                PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"`
+                PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"`
+                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with \"$PTHREAD_CFLAGS\" and \"$PTHREAD_LIBS\"" >&5
+printf %s "checking whether pthreads work with \"$PTHREAD_CFLAGS\" and \"$PTHREAD_LIBS\"... " >&6; }
+                ;;
+
+                -*)
+                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with $ax_pthread_try_flag" >&5
+printf %s "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=$2
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+printf %s "checking for $ac_word... " >&6; }
+if test ${ac_cv_prog_ax_pthread_config+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  if test -n "$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
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ax_pthread_config="yes"
+    printf "%s\n" "$as_me:${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 "$ax_pthread_config"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_config" >&5
+printf "%s\n" "$ax_pthread_config" >&6; }
+else
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+fi
+
+
+                if test "x$ax_pthread_config" = "xno"
+then :
+  continue
+fi
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for the pthreads library -l$ax_pthread_try_flag" >&5
+printf %s "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 *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 (void)
+{
+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.beam \
+    conftest$ac_exeext conftest.$ac_ext
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+printf "%s\n" "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xyes"
+then :
+  break
+fi
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+
+# Clang needs special handling, because older versions handle the -pthread
+# option in a rather... idiosyncratic way
+
+if test "x$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.
+
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread" >&5
+printf %s "checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread... " >&6; }
+if test ${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  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.$ac_objext/g'
+             ax_pthread_link_step=`printf "%s\n" "$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.beam \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam \
+    conftest$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="$ax_pthread_try"
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&5
+printf "%s\n" "$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="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for joinable pthread attribute" >&5
+printf %s "checking for joinable pthread attribute... " >&6; }
+if test ${ax_cv_PTHREAD_JOINABLE_ATTR+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main (void)
+{
+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.beam \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_JOINABLE_ATTR" >&5
+printf "%s\n" "$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 :
+
+printf "%s\n" "#define PTHREAD_CREATE_JOINABLE $ax_cv_PTHREAD_JOINABLE_ATTR" >>confdefs.h
+
+               ax_pthread_joinable_attr_defined=yes
+
+fi
+
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether more special flags are required for pthreads" >&5
+printf %s "checking whether more special flags are required for pthreads... " >&6; }
+if test ${ax_cv_PTHREAD_SPECIAL_FLAGS+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_SPECIAL_FLAGS" >&5
+printf "%s\n" "$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 $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes
+fi
+
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for PTHREAD_PRIO_INHERIT" >&5
+printf %s "checking for PTHREAD_PRIO_INHERIT... " >&6; }
+if test ${ax_cv_PTHREAD_PRIO_INHERIT+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main (void)
+{
+int i = PTHREAD_PRIO_INHERIT;
+                                               return i;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"
+then :
+  ax_cv_PTHREAD_PRIO_INHERIT=yes
+else $as_nop
+  ax_cv_PTHREAD_PRIO_INHERIT=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_PRIO_INHERIT" >&5
+printf "%s\n" "$ax_cv_PTHREAD_PRIO_INHERIT" >&6; }
+        if test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"
+then :
+
+printf "%s\n" "#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 as_fn_executable_p ${CC}_r
+then :
+  PTHREAD_CC="${CC}_r"
+fi
+			   if test "x${CXX}" != "x"
+then :
+  if as_fn_executable_p ${CXX}_r
+then :
+  PTHREAD_CXX="${CXX}_r"
+fi
+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=$2
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+printf %s "checking for $ac_word... " >&6; }
+if test ${ac_cv_prog_PTHREAD_CC+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  if test -n "$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
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
+    ac_cv_prog_PTHREAD_CC="$ac_prog"
+    printf "%s\n" "$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
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $PTHREAD_CC" >&5
+printf "%s\n" "$PTHREAD_CC" >&6; }
+else
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+fi
+
+
+  test -n "$PTHREAD_CC" && break
+done
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+
+			   if test "x${CXX}" != "x"
+then :
+  for ac_prog in ${CXX}_r
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+printf %s "checking for $ac_word... " >&6; }
+if test ${ac_cv_prog_PTHREAD_CXX+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  if test -n "$PTHREAD_CXX"; then
+  ac_cv_prog_PTHREAD_CXX="$PTHREAD_CXX" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
+    ac_cv_prog_PTHREAD_CXX="$ac_prog"
+    printf "%s\n" "$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_CXX=$ac_cv_prog_PTHREAD_CXX
+if test -n "$PTHREAD_CXX"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $PTHREAD_CXX" >&5
+printf "%s\n" "$PTHREAD_CXX" >&6; }
+else
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+fi
+
+
+  test -n "$PTHREAD_CXX" && break
+done
+test -n "$PTHREAD_CXX" || PTHREAD_CXX="$CXX"
+
+fi
+
+                      ;;
+esac
+                     ;; #(
+  *) :
+     ;;
+esac
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+test -n "$PTHREAD_CXX" || PTHREAD_CXX="$CXX"
+
+
+
+
+
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+
+printf "%s\n" "#define HAVE_PTHREAD 1" >>confdefs.h
+
+LIBS="$PTHREAD_LIBS $LIBS"
+CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS"
+CC="$PTHREAD_CC"
+CXX="$PTHREAD_CXX"
+
+        :
+else
+        ax_pthread_ok=no
+
+fi
+ac_ext=c
+ac_cpp='$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
+
+
+
+# Atomics
+ac_fn_c_check_header_compile "$LINENO" "stdatomic.h" "ac_cv_header_stdatomic_h" "$ac_includes_default"
+if test "x$ac_cv_header_stdatomic_h" = xyes
+then :
+  printf "%s\n" "#define HAVE_STDATOMIC_H 1" >>confdefs.h
+
+fi
+
+
+# Check for poll.h (it's in POSIX so everyone should have it?)
+ac_fn_c_check_header_compile "$LINENO" "poll.h" "ac_cv_header_poll_h" "$ac_includes_default"
+if test "x$ac_cv_header_poll_h" = xyes
+then :
+  printf "%s\n" "#define HAVE_POLL_H 1" >>confdefs.h
+
+fi
+
+
+# SCTP.  Allow user to disable SCTP support with --without-sctp.
+# Otherwise we try to find whatever support is required.
+try_sctp=true
+
+# Check whether --with-sctp was given.
+if test ${with_sctp+y}
+then :
+  withval=$with_sctp;
+        case "$withval" in
+	y | ye | yes)
+	  ;;
+	n | no)
+	try_sctp=false
+	  ;;
+	*)
+	as_fn_error $? "Invalid --with-sctp value" "$LINENO" 5
+	  ;;
+	esac
+
+else $as_nop
+
+        try_sctp=true
+
+
+fi
+
+
+ac_fn_c_check_header_compile "$LINENO" "linux/tcp.h" "ac_cv_header_linux_tcp_h" "$ac_includes_default"
+if test "x$ac_cv_header_linux_tcp_h" = xyes
+then :
+  printf "%s\n" "#define HAVE_LINUX_TCP_H 1" >>confdefs.h
+
+fi
+
+
+# Check for SCTP support
+if $try_sctp; then
+ac_fn_c_check_header_compile "$LINENO" "sys/socket.h" "ac_cv_header_sys_socket_h" "$ac_includes_default"
+if test "x$ac_cv_header_sys_socket_h" = xyes
+then :
+  printf "%s\n" "#define HAVE_SYS_SOCKET_H 1" >>confdefs.h
+
+fi
+
+       for ac_header in netinet/sctp.h
 do :
   ac_fn_c_check_header_compile "$LINENO" "netinet/sctp.h" "ac_cv_header_netinet_sctp_h" "#ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
@@ -14351,7 +15319,7 @@ if test "x$with_openssl" = "xno"; then
 printf "%s\n" "$as_me: WARNING: Building without OpenSSL; disabling iperf_auth functionality. " >&2;}
 else
     # Check for OPENSSL support
-    havs_ssl=false
+    have_ssl=false
 
     found=false
 
@@ -17350,4 +18318,3 @@ printf "%s\n" "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2
 fi
 
 
-
diff --git a/examples/Makefile.in b/examples/Makefile.in
index 93898c070..6e1365b57 100644
--- a/examples/Makefile.in
+++ b/examples/Makefile.in
@@ -92,6 +92,7 @@ noinst_PROGRAMS = mic$(EXEEXT) mis$(EXEEXT)
 subdir = examples
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps = $(top_srcdir)/config/ax_check_openssl.m4 \
+	$(top_srcdir)/config/ax_pthread.m4 \
 	$(top_srcdir)/config/iperf_config_static_bin.m4 \
 	$(top_srcdir)/configure.ac
 am__configure_deps = $(am__aclocal_m4_deps) $(CONFIGURE_DEPENDENCIES) \
@@ -191,6 +192,7 @@ AWK = @AWK@
 CC = @CC@
 CCDEPMODE = @CCDEPMODE@
 CFLAGS = @CFLAGS@
+CPP = @CPP@
 CPPFLAGS = @CPPFLAGS@
 CSCOPE = @CSCOPE@
 CTAGS = @CTAGS@
@@ -245,6 +247,10 @@ PACKAGE_URL = @PACKAGE_URL@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 PATH_SEPARATOR = @PATH_SEPARATOR@
 PKG_CONFIG = @PKG_CONFIG@
+PTHREAD_CC = @PTHREAD_CC@
+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_CXX = @PTHREAD_CXX@
+PTHREAD_LIBS = @PTHREAD_LIBS@
 RANLIB = @RANLIB@
 SED = @SED@
 SET_MAKE = @SET_MAKE@
@@ -263,6 +269,7 @@ am__leading_dot = @am__leading_dot@
 am__quote = @am__quote@
 am__tar = @am__tar@
 am__untar = @am__untar@
+ax_pthread_config = @ax_pthread_config@
 bindir = @bindir@
 build = @build@
 build_alias = @build_alias@
diff --git a/src/Makefile.in b/src/Makefile.in
index 91c9b156e..e13e4edc5 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -103,6 +103,7 @@ TESTS = t_timer$(EXEEXT) t_units$(EXEEXT) t_uuid$(EXEEXT) \
 subdir = src
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps = $(top_srcdir)/config/ax_check_openssl.m4 \
+	$(top_srcdir)/config/ax_pthread.m4 \
 	$(top_srcdir)/config/iperf_config_static_bin.m4 \
 	$(top_srcdir)/configure.ac
 am__configure_deps = $(am__aclocal_m4_deps) $(CONFIGURE_DEPENDENCIES) \
@@ -517,6 +518,7 @@ AWK = @AWK@
 CC = @CC@
 CCDEPMODE = @CCDEPMODE@
 CFLAGS = @CFLAGS@
+CPP = @CPP@
 CPPFLAGS = @CPPFLAGS@
 CSCOPE = @CSCOPE@
 CTAGS = @CTAGS@
@@ -571,6 +573,10 @@ PACKAGE_URL = @PACKAGE_URL@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 PATH_SEPARATOR = @PATH_SEPARATOR@
 PKG_CONFIG = @PKG_CONFIG@
+PTHREAD_CC = @PTHREAD_CC@
+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_CXX = @PTHREAD_CXX@
+PTHREAD_LIBS = @PTHREAD_LIBS@
 RANLIB = @RANLIB@
 SED = @SED@
 SET_MAKE = @SET_MAKE@
@@ -589,6 +595,7 @@ 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@
diff --git a/src/iperf_config.h.in b/src/iperf_config.h.in
index 883107901..bb8853ff4 100644
--- a/src/iperf_config.h.in
+++ b/src/iperf_config.h.in
@@ -48,6 +48,12 @@
 /* Define to 1 if you have the <poll.h> header file. */
 #undef HAVE_POLL_H
 
+/* Define if you have POSIX threads libraries and header files. */
+#undef HAVE_PTHREAD
+
+/* Have PTHREAD_PRIO_INHERIT. */
+#undef HAVE_PTHREAD_PRIO_INHERIT
+
 /* Define to 1 if you have the `sched_setaffinity' function. */
 #undef HAVE_SCHED_SETAFFINITY
 
@@ -69,6 +75,9 @@
 /* OpenSSL Is Available */
 #undef HAVE_SSL
 
+/* Define to 1 if you have the <stdatomic.h> header file. */
+#undef HAVE_STDATOMIC_H
+
 /* Define to 1 if you have the <stdint.h> header file. */
 #undef HAVE_STDINT_H
 
@@ -135,6 +144,10 @@
 /* Define to the version of this package. */
 #undef PACKAGE_VERSION
 
+/* Define to necessary symbol if this constant uses a non-standard name on
+   your system. */
+#undef PTHREAD_CREATE_JOINABLE
+
 /* Define to 1 if all of the C90 standard headers exist (not just the ones
    required in a freestanding environment). This macro is provided for
    backward compatibility; new code need not use it. */