diff --git a/configure.ac b/configure.ac
index 46e45b21..d468de92 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,9 +23,11 @@ xxx_ar_flags=$((ar --help) 2>&1)
 AS_CASE([$xxx_ar_flags],[*'use actual timestamps and uids/gids'*],[: ${AR_FLAGS="Ucru"}])
 
 AC_CANONICAL_HOST
+AC_CANONICAL_TARGET
 
 AM_INIT_AUTOMAKE([1.11 -Wall -Werror -Wno-portability foreign tar-ustar subdir-objects no-define color-tests])
 
+AC_PROG_INSTALL
 AC_ARG_PROGRAM
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_HEADERS([wolfpkcs11/config.h])
@@ -60,10 +62,8 @@ m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 # Checks for programs.
 AC_PROG_CC
 AM_PROG_CC_C_O
-AC_PROG_INSTALL
 
 # Checks for header files.
-AC_HEADER_STDC
 AC_CHECK_SIZEOF([long long], 8)
 AC_CHECK_SIZEOF([long], 4)
 
diff --git a/m4/ax_create_generic_config.m4 b/m4/ax_create_generic_config.m4
index 535838f4..59aeee61 100644
--- a/m4/ax_create_generic_config.m4
+++ b/m4/ax_create_generic_config.m4
@@ -9,7 +9,7 @@
 # DESCRIPTION
 #
 #   Creates a generic PACKAGE-config file that has all the things that you
-#   want, hmm, well, atleast it has --cflags, --version, --libs. Ahhm, did
+#   want, hmm, well, at least it has --cflags, --version, --libs. Ahhm, did
 #   you see ax_path_generic in the autoconf-archive? ;-)
 #
 #   this macros saves you all the typing for a pkg-config.in script, you
@@ -78,7 +78,7 @@ echo 'package="'$P'"' >>$F
 echo 'version="'$V'"' >>$F
 echo 'libs="'$L'"' >>$F
 echo ' ' >>$F
-# in the order of occurence a standard automake Makefile
+# in the order of occurrence a standard automake Makefile
 echo 'prefix="'$prefix'"' >>$F
 echo 'exec_prefix="'$exec_prefix'"' >>$F
 echo 'bindir="'$bindir'"' >>$F
diff --git a/m4/ax_harden_compiler_flags.m4 b/m4/ax_harden_compiler_flags.m4
index 90885562..d9ae175c 100644
--- a/m4/ax_harden_compiler_flags.m4
+++ b/m4/ax_harden_compiler_flags.m4
@@ -119,7 +119,6 @@
       AX_APPEND_COMPILE_FLAGS([-Wno-pragmas],,[$ax_append_compile_cflags_extra])
 
       AX_APPEND_COMPILE_FLAGS([-Wall],,[$ax_append_compile_cflags_extra])
-      AX_APPEND_COMPILE_FLAGS([-Wno-strict-aliasing],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wextra],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wunknown-pragmas],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wthis-test-should-fail],,[$ax_append_compile_cflags_extra])
@@ -145,7 +144,7 @@
       AX_APPEND_COMPILE_FLAGS([-Woverride-init],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wpointer-arith],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wpointer-sign],,[$ax_append_compile_cflags_extra])
-      AX_APPEND_COMPILE_FLAGS([-Wredundant-decls],,[$ax_append_compile_cflags_extra])
+dnl      AX_APPEND_COMPILE_FLAGS([-Wredundant-decls],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wshadow],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wshorten-64-to-32],,[$ax_append_compile_cflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wsign-compare],,[$ax_append_compile_cflags_extra])
@@ -188,7 +187,6 @@
         ])
 
       AX_APPEND_COMPILE_FLAGS([-Wall],,[$ax_append_compile_cxxflags_extra])
-      AX_APPEND_COMPILE_FLAGS([-Wno-strict-aliasing],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wextra],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wunknown-pragmas],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wthis-test-should-fail],,[$ax_append_compile_cxxflags_extra])
@@ -208,7 +206,7 @@
       AX_APPEND_COMPILE_FLAGS([-Wnormalized=id],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Woverloaded-virtual],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wpointer-arith],,[$ax_append_compile_cxxflags_extra])
-      AX_APPEND_COMPILE_FLAGS([-Wredundant-decls],,[$ax_append_compile_cxxflags_extra])
+dnl      AX_APPEND_COMPILE_FLAGS([-Wredundant-decls],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wshadow],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wshorten-64-to-32],,[$ax_append_compile_cxxflags_extra])
       AX_APPEND_COMPILE_FLAGS([-Wsign-compare],,[$ax_append_compile_cxxflags_extra])
diff --git a/m4/ax_pthread.m4 b/m4/ax_pthread.m4
index ada7071f..e5858e50 100644
--- a/m4/ax_pthread.m4
+++ b/m4/ax_pthread.m4
@@ -14,20 +14,24 @@
 #   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.)
+#   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
@@ -55,6 +59,7 @@
 #
 #   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
@@ -82,11 +87,11 @@
 #   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 30
 
 AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
 AC_DEFUN([AX_PTHREAD], [
-AC_REQUIRE([AC_CANONICAL_HOST])
+AC_REQUIRE([AC_CANONICAL_TARGET])
 AC_REQUIRE([AC_PROG_CC])
 AC_REQUIRE([AC_PROG_SED])
 AC_LANG_PUSH([C])
@@ -104,6 +109,7 @@ if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
         ax_pthread_save_CFLAGS="$CFLAGS"
         ax_pthread_save_LIBS="$LIBS"
         AS_IF([test "x$PTHREAD_CC" != "x"], [CC="$PTHREAD_CC"])
+        AS_IF([test "x$PTHREAD_CXX" != "x"], [CXX="$PTHREAD_CXX"])
         CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
         LIBS="$PTHREAD_LIBS $LIBS"
         AC_MSG_CHECKING([for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS])
@@ -123,10 +129,12 @@ 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
-# 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.
+# 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"
 
@@ -150,7 +158,7 @@ ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --
 # --thread-safe: KAI C++
 # pthread-config: use pthread-config program (for GNU Pth library)
 
-case $host_os in
+case $target_os in
 
         freebsd*)
 
@@ -194,36 +202,10 @@ 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
 
-# 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],
@@ -242,83 +224,47 @@ AC_CACHE_CHECK([whether $CC is Clang],
     ])
 ax_pthread_clang="$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
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
 
-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
+AS_IF([test "x$GCC" = "xyes"],
+      [ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"])
 
-        # (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.)
+# Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first
 
-        # (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.)
+AS_IF([test "x$ax_pthread_clang" = "xyes"],
+      [ax_pthread_flags="-pthread,-lpthread -pthread"])
 
-        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
-        # 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.
+case $target_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
 
-        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"
-            ])
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
 
-        case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
-                no | unknown) ;;
-                *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
-        esac
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+AS_IF([test "x$ax_pthread_check_macro" = "x--"],
+      [ax_pthread_check_cond=0],
+      [ax_pthread_check_cond="!defined($ax_pthread_check_macro)"])
 
-fi # $ax_pthread_clang = yes
 
 if test "x$ax_pthread_ok" = "xno"; then
 for ax_pthread_try_flag in $ax_pthread_flags; do
@@ -328,10 +274,10 @@ for ax_pthread_try_flag in $ax_pthread_flags; do
                 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"
+                *,*)
+                PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"`
+                PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"`
+                AC_MSG_CHECKING([whether pthreads work with "$PTHREAD_CFLAGS" and "$PTHREAD_LIBS"])
                 ;;
 
                 -*)
@@ -368,10 +314,16 @@ for ax_pthread_try_flag in $ax_pthread_flags; do
         # We try pthread_create on general principles.
 
         AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>
-dnl#                       if $ax_pthread_check_cond
-dnl#                        error "$ax_pthread_check_macro must be defined"
-dnl#                       endif
-                        static void routine(void *a) { a = 0; }
+#                       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);
@@ -393,6 +345,80 @@ dnl#                       endif
 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.
+
+        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 # $ax_pthread_clang = yes
+
+
+
 # Various other checks:
 if test "x$ax_pthread_ok" = "xyes"; then
         ax_pthread_save_CFLAGS="$CFLAGS"
@@ -424,7 +450,7 @@ if test "x$ax_pthread_ok" = "xyes"; then
         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
+             case $target_os in
              solaris*)
              ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
              ;;
@@ -438,7 +464,8 @@ if test "x$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])
             ])
@@ -453,25 +480,35 @@ if test "x$ax_pthread_ok" = "xyes"; then
 
         # More AIX lossage: compile with *_r variant
         if test "x$GCC" != "xyes"; then
-            case $host_os in
+            case $target_os in
                 aix*)
                 AS_CASE(["x/$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],[$CC])])])
+                         [
+			   AS_IF([AS_EXECUTABLE_P([${CC}_r])],[PTHREAD_CC="${CC}_r"])
+			   AS_IF([test "x${CXX}" != "x"], [AS_IF([AS_EXECUTABLE_P([${CXX}_r])],[PTHREAD_CXX="${CXX}_r"])])
+			 ],
+                         [
+			   AC_CHECK_PROGS([PTHREAD_CC],[${CC}_r],[$CC])
+			   AS_IF([test "x${CXX}" != "x"], [AC_CHECK_PROGS([PTHREAD_CXX],[${CXX}_r],[$CXX])])
+			 ]
+                     )
+                    ])
                 ;;
             esac
         fi
 fi
 
 test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+test -n "$PTHREAD_CXX" || PTHREAD_CXX="$CXX"
 
 AC_SUBST([PTHREAD_LIBS])
 AC_SUBST([PTHREAD_CFLAGS])
 AC_SUBST([PTHREAD_CC])
+AC_SUBST([PTHREAD_CXX])
 
 # Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
 if test "x$ax_pthread_ok" = "xyes"; then
diff --git a/m4/ax_tls.m4 b/m4/ax_tls.m4
index 3f6b5e10..deba1feb 100644
--- a/m4/ax_tls.m4
+++ b/m4/ax_tls.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#          http://www.gnu.org/software/autoconf-archive/ax_tls.html
+#          https://www.gnu.org/software/autoconf-archive/ax_tls.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -9,9 +9,9 @@
 # DESCRIPTION
 #
 #   Provides a test for the compiler support of thread local storage (TLS)
-#   extensions. Defines TLS if it is found. Currently knows about GCC/ICC
-#   and MSVC. I think SunPro uses the same as GCC, and Borland apparently
-#   supports either.
+#   extensions. Defines TLS if it is found. Currently knows about C++11,
+#   GCC/ICC, and MSVC. I think SunPro uses the same as GCC, and Borland
+#   apparently supports either.
 #
 # LICENSE
 #
@@ -29,7 +29,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   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
@@ -44,7 +44,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 11
+#serial 15
 
 #   Define m4_ifblank and m4_ifnblank macros from introduced in
 #   autotools 2.64 m4sugar.m4 if using an earlier autotools.
@@ -55,7 +55,6 @@ ifdef([m4_ifblank], [], [
 ]), [], [$2], [$3])])
     ])
 
-
 ifdef([m4_ifnblank], [], [
     m4_define([m4_ifnblank],
     [m4_if(m4_translit([[$1]], [ ][	][
@@ -63,30 +62,25 @@ ifdef([m4_ifnblank], [], [
     ])
 
 AC_DEFUN([AX_TLS], [
-  AC_MSG_CHECKING(for thread local storage (TLS) class)
-  AC_CACHE_VAL(ac_cv_tls, [
-    ax_tls_keywords="__thread __declspec(thread) none"
-    for ax_tls_keyword in $ax_tls_keywords; do
+  AC_MSG_CHECKING([for thread local storage (TLS) class])
+  AC_CACHE_VAL([ac_cv_tls],
+   [for ax_tls_keyword in thread_local _Thread_local __thread '__declspec(thread)' none; do
        AS_CASE([$ax_tls_keyword],
           [none], [ac_cv_tls=none ; break],
-          [AC_TRY_COMPILE(
-              [#include <stdlib.h>
-               static void
-               foo(void) {
-               static ] $ax_tls_keyword [ int bar;
-               exit(1);
-               }],
-               [],
-               [ac_cv_tls=$ax_tls_keyword ; break],
-               ac_cv_tls=none
-           )])
-    done
-  ])
-  AC_MSG_RESULT($ac_cv_tls)
+          [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+              [#include <stdlib.h>],
+              [static  $ax_tls_keyword  int bar;]
+            )],
+            [ac_cv_tls=$ax_tls_keyword ; break],
+            [ac_cv_tls=none]
+          )]
+        )
+    done ]
+  )
+  AC_MSG_RESULT([$ac_cv_tls])
 
   AS_IF([test "$ac_cv_tls" != "none"],
-    AC_DEFINE_UNQUOTED([TLS], $ac_cv_tls, [If the compiler supports a TLS storage class define it to that here])
-      m4_ifnblank([$1], [$1]),
-    m4_ifnblank([$2], [$2])
-  )
+    [AC_DEFINE_UNQUOTED([TLS],[$ac_cv_tls],[If the compiler supports a TLS storage class, define it to that here])
+     m4_ifnblank([$1],[$1],[[:]])],
+    [m4_ifnblank([$2],[$2],[[:]])])
 ])