diff --git a/Misc/NEWS b/Misc/NEWS
index 0f9e825c220..dd26444bd95 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -658,6 +658,8 @@ Tests
 Build
 -----
 
+- Issue #16836: Enable IPv6 support even if IPv6 is disabled on the build host.
+
 - Issue #15923: fix a mistake in asdl_c.py that resulted in a TypeError after
   2801bf875a24 (see #15801).
 
diff --git a/configure b/configure
index ac2d86eb216..056f69ba296 100755
--- a/configure
+++ b/configure
@@ -1,14 +1,12 @@
 #! /bin/sh
 # From configure.ac Revision.
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.68 for python 2.7.
+# Generated by GNU Autoconf 2.69 for python 2.7.
 #
 # Report bugs to <http://bugs.python.org/>.
 #
 #
-# Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
-# 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software
-# Foundation, Inc.
+# Copyright (C) 1992-1996, 1998-2012 Free Software Foundation, Inc.
 #
 #
 # This configure script is free software; the Free Software Foundation
@@ -137,6 +135,31 @@ export LANGUAGE
 # CDPATH.
 (unset CDPATH) >/dev/null 2>&1 && unset CDPATH
 
+# Use a proper internal environment variable to ensure we don't fall
+  # into an infinite loop, continuously re-executing ourselves.
+  if test x"${_as_can_reexec}" != xno && test "x$CONFIG_SHELL" != x; then
+    _as_can_reexec=no; export _as_can_reexec;
+    # We cannot yet assume a decent shell, so we have to provide a
+# neutralization value for shells without unset; and this also
+# works around shells that cannot unset nonexistent variables.
+# Preserve -v and -x to the replacement shell.
+BASH_ENV=/dev/null
+ENV=/dev/null
+(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
+case $- in # ((((
+  *v*x* | *x*v* ) as_opts=-vx ;;
+  *v* ) as_opts=-v ;;
+  *x* ) as_opts=-x ;;
+  * ) as_opts= ;;
+esac
+exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
+# Admittedly, this is quite paranoid, since all the known shells bail
+# out after a failed `exec'.
+$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
+as_fn_exit 255
+  fi
+  # We don't want this to propagate to other subprocesses.
+          { _as_can_reexec=; unset _as_can_reexec;}
 if test "x$CONFIG_SHELL" = x; then
   as_bourne_compatible="if test -n \"\${ZSH_VERSION+set}\" && (emulate sh) >/dev/null 2>&1; then :
   emulate sh
@@ -170,7 +193,8 @@ if ( set x; as_fn_ret_success y && test x = \"\$1\" ); then :
 else
   exitcode=1; echo positional parameters were not saved.
 fi
-test x\$exitcode = x0 || exit 1"
+test x\$exitcode = x0 || exit 1
+test -x / || exit 1"
   as_suggested="  as_lineno_1=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_1a=\$LINENO
   as_lineno_2=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_2a=\$LINENO
   eval 'test \"x\$as_lineno_1'\$as_run'\" != \"x\$as_lineno_2'\$as_run'\" &&
@@ -215,21 +239,25 @@ IFS=$as_save_IFS
 
 
       if test "x$CONFIG_SHELL" != x; then :
-  # We cannot yet assume a decent shell, so we have to provide a
-	# neutralization value for shells without unset; and this also
-	# works around shells that cannot unset nonexistent variables.
-	# Preserve -v and -x to the replacement shell.
-	BASH_ENV=/dev/null
-	ENV=/dev/null
-	(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
-	export CONFIG_SHELL
-	case $- in # ((((
-	  *v*x* | *x*v* ) as_opts=-vx ;;
-	  *v* ) as_opts=-v ;;
-	  *x* ) as_opts=-x ;;
-	  * ) as_opts= ;;
-	esac
-	exec "$CONFIG_SHELL" $as_opts "$as_myself" ${1+"$@"}
+  export CONFIG_SHELL
+             # We cannot yet assume a decent shell, so we have to provide a
+# neutralization value for shells without unset; and this also
+# works around shells that cannot unset nonexistent variables.
+# Preserve -v and -x to the replacement shell.
+BASH_ENV=/dev/null
+ENV=/dev/null
+(unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
+case $- in # ((((
+  *v*x* | *x*v* ) as_opts=-vx ;;
+  *v* ) as_opts=-v ;;
+  *x* ) as_opts=-x ;;
+  * ) as_opts= ;;
+esac
+exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
+# Admittedly, this is quite paranoid, since all the known shells bail
+# out after a failed `exec'.
+$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
+exit 255
 fi
 
     if test x$as_have_required = xno; then :
@@ -332,6 +360,14 @@ $as_echo X"$as_dir" |
 
 
 } # as_fn_mkdir_p
+
+# as_fn_executable_p FILE
+# -----------------------
+# Test if FILE is an executable regular file.
+as_fn_executable_p ()
+{
+  test -f "$1" && test -x "$1"
+} # as_fn_executable_p
 # as_fn_append VAR VALUE
 # ----------------------
 # Append the text in VALUE to the end of the definition contained in VAR. Take
@@ -453,6 +489,10 @@ as_cr_alnum=$as_cr_Letters$as_cr_digits
   chmod +x "$as_me.lineno" ||
     { $as_echo "$as_me: error: cannot create $as_me.lineno; rerun with a POSIX shell" >&2; as_fn_exit 1; }
 
+  # If we had to re-execute with $CONFIG_SHELL, we're ensured to have
+  # already done that, so ensure we don't try to do so again and fall
+  # in an infinite loop.  This has already happened in practice.
+  _as_can_reexec=no; export _as_can_reexec
   # Don't try to exec as it changes $[0], causing all sort of problems
   # (the dirname of $[0] is not the place where we might find the
   # original and so on.  Autoconf is especially sensitive to this).
@@ -487,16 +527,16 @@ if (echo >conf$$.file) 2>/dev/null; then
     # ... but there are two gotchas:
     # 1) On MSYS, both `ln -s file dir' and `ln file dir' fail.
     # 2) DJGPP < 2.04 has no symlinks; `ln -s' creates a wrapper executable.
-    # In both cases, we have to default to `cp -p'.
+    # In both cases, we have to default to `cp -pR'.
     ln -s conf$$.file conf$$.dir 2>/dev/null && test ! -f conf$$.exe ||
-      as_ln_s='cp -p'
+      as_ln_s='cp -pR'
   elif ln conf$$.file conf$$ 2>/dev/null; then
     as_ln_s=ln
   else
-    as_ln_s='cp -p'
+    as_ln_s='cp -pR'
   fi
 else
-  as_ln_s='cp -p'
+  as_ln_s='cp -pR'
 fi
 rm -f conf$$ conf$$.exe conf$$.dir/conf$$.file conf$$.file
 rmdir conf$$.dir 2>/dev/null
@@ -508,28 +548,8 @@ else
   as_mkdir_p=false
 fi
 
-if test -x / >/dev/null 2>&1; then
-  as_test_x='test -x'
-else
-  if ls -dL / >/dev/null 2>&1; then
-    as_ls_L_option=L
-  else
-    as_ls_L_option=
-  fi
-  as_test_x='
-    eval sh -c '\''
-      if test -d "$1"; then
-	test -d "$1/.";
-      else
-	case $1 in #(
-	-*)set "./$1";;
-	esac;
-	case `ls -ld'$as_ls_L_option' "$1" 2>/dev/null` in #((
-	???[sx]*):;;*)false;;esac;fi
-    '\'' sh
-  '
-fi
-as_executable_p=$as_test_x
+as_test_x='test -x'
+as_executable_p=as_fn_executable_p
 
 # Sed expression to map a string onto a valid CPP name.
 as_tr_cpp="eval sed 'y%*$as_cr_letters%P$as_cr_LETTERS%;s%[^_$as_cr_alnum]%_%g'"
@@ -1235,8 +1255,6 @@ target=$target_alias
 if test "x$host_alias" != x; then
   if test "x$build_alias" = x; then
     cross_compiling=maybe
-    $as_echo "$as_me: WARNING: if you wanted to set the --build type, don't use --host.
-    If a cross compiler is detected then cross compile mode will be used" >&2
   elif test "x$build_alias" != "x$host_alias"; then
     cross_compiling=yes
   fi
@@ -1521,9 +1539,9 @@ test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
 python configure 2.7
-generated by GNU Autoconf 2.68
+generated by GNU Autoconf 2.69
 
-Copyright (C) 2010 Free Software Foundation, Inc.
+Copyright (C) 2012 Free Software Foundation, Inc.
 This configure script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it.
 _ACEOF
@@ -1800,7 +1818,7 @@ $as_echo "$ac_try_echo"; } >&5
 	 test ! -s conftest.err
        } && test -s conftest$ac_exeext && {
 	 test "$cross_compiling" = yes ||
-	 $as_test_x conftest$ac_exeext
+	 test -x conftest$ac_exeext
        }; then :
   ac_retval=0
 else
@@ -1897,7 +1915,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !((($ac_type) -1 >> ($2 / 2 - 1)) >> ($2 / 2 - 1) == 3)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -1951,7 +1970,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !(0 < ($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1))];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -1967,7 +1987,8 @@ main ()
 {
 static int test_array [1 - 2 * !(($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 1)
 		 < ($ac_type) ((((($ac_type) 1 << N) << N) - 1) * 2 + 2))];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2017,7 +2038,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !(($2) >= 0)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2033,7 +2055,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !(($2) <= $ac_mid)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2059,7 +2082,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !(($2) < 0)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2075,7 +2099,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !(($2) >= $ac_mid)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2109,7 +2134,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !(($2) <= $ac_mid)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -2352,7 +2378,7 @@ This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
 It was created by python $as_me 2.7, which was
-generated by GNU Autoconf 2.68.  Invocation command line was
+generated by GNU Autoconf 2.69.  Invocation command line was
 
   $ $0 $@
 
@@ -3296,7 +3322,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CC="${ac_tool_prefix}gcc"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3336,7 +3362,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_ac_ct_CC="gcc"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3389,7 +3415,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CC="${ac_tool_prefix}cc"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3430,7 +3456,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     if test "$as_dir/$ac_word$ac_exec_ext" = "/usr/ucb/cc"; then
        ac_prog_rejected=yes
        continue
@@ -3488,7 +3514,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CC="$ac_tool_prefix$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3532,7 +3558,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_ac_ct_CC="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -3978,8 +4004,7 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 #include <stdarg.h>
 #include <stdio.h>
-#include <sys/types.h>
-#include <sys/stat.h>
+struct stat;
 /* Most of the following tests are stolen from RCS 5.7's src/conf.sh.  */
 struct buf { int x; };
 FILE * (*rcsopen) (struct buf *, struct stat *, int);
@@ -4122,7 +4147,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_CXX="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -4163,7 +4188,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_CXX="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -4212,7 +4237,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_CXX="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -4413,7 +4438,7 @@ do
     for ac_prog in grep ggrep; do
     for ac_exec_ext in '' $ac_executable_extensions; do
       ac_path_GREP="$as_dir/$ac_prog$ac_exec_ext"
-      { test -f "$ac_path_GREP" && $as_test_x "$ac_path_GREP"; } || continue
+      as_fn_executable_p "$ac_path_GREP" || continue
 # Check for GNU ac_path_GREP and select it if it is found.
   # Check for GNU $ac_path_GREP
 case `"$ac_path_GREP" --version 2>&1` in
@@ -4479,7 +4504,7 @@ do
     for ac_prog in egrep; do
     for ac_exec_ext in '' $ac_executable_extensions; do
       ac_path_EGREP="$as_dir/$ac_prog$ac_exec_ext"
-      { test -f "$ac_path_EGREP" && $as_test_x "$ac_path_EGREP"; } || continue
+      as_fn_executable_p "$ac_path_EGREP" || continue
 # Check for GNU ac_path_EGREP and select it if it is found.
   # Check for GNU $ac_path_EGREP
 case `"$ac_path_EGREP" --version 2>&1` in
@@ -4686,8 +4711,8 @@ else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
-#	  define __EXTENSIONS__ 1
-	  $ac_includes_default
+#         define __EXTENSIONS__ 1
+          $ac_includes_default
 int
 main ()
 {
@@ -5036,7 +5061,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_RANLIB="${ac_tool_prefix}ranlib"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5076,7 +5101,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_ac_ct_RANLIB="ranlib"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5130,7 +5155,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_AR="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5180,7 +5205,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_SVNVERSION="found"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5242,7 +5267,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_HAS_HG="found"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -5349,7 +5374,7 @@ case $as_dir/ in #((
     # by default.
     for ac_prog in ginstall scoinst install; do
       for ac_exec_ext in '' $ac_executable_extensions; do
-	if { test -f "$as_dir/$ac_prog$ac_exec_ext" && $as_test_x "$as_dir/$ac_prog$ac_exec_ext"; }; then
+	if as_fn_executable_p "$as_dir/$ac_prog$ac_exec_ext"; then
 	  if test $ac_prog = install &&
 	    grep dspmsg "$as_dir/$ac_prog$ac_exec_ext" >/dev/null 2>&1; then
 	    # AIX install.  It has an incompatible calling convention.
@@ -5418,7 +5443,7 @@ do
   test -z "$as_dir" && as_dir=.
     for ac_prog in mkdir gmkdir; do
 	 for ac_exec_ext in '' $ac_executable_extensions; do
-	   { test -f "$as_dir/$ac_prog$ac_exec_ext" && $as_test_x "$as_dir/$ac_prog$ac_exec_ext"; } || continue
+	   as_fn_executable_p "$as_dir/$ac_prog$ac_exec_ext" || continue
 	   case `"$as_dir/$ac_prog$ac_exec_ext" --version 2>&1` in #(
 	     'mkdir (GNU coreutils) '* | \
 	     'mkdir (coreutils) '* | \
@@ -8426,7 +8451,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -8469,7 +8494,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_path_ac_pt_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -9243,28 +9268,20 @@ $as_echo "yes" >&6; }
   esac
 else
 
-  if test "$cross_compiling" = yes; then :
-
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-  ipv6=no
-
-else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
  /* AF_INET6 available check */
 #include <sys/types.h>
 #include <sys/socket.h>
-main()
+int
+main ()
 {
- if (socket(AF_INET6, SOCK_STREAM, 0) < 0)
-   exit(1);
- else
-   exit(0);
+int domain = AF_INET6;
+  ;
+  return 0;
 }
-
 _ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
+if ac_fn_c_try_compile "$LINENO"; then :
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
@@ -9277,10 +9294,7 @@ $as_echo "no" >&6; }
   ipv6=no
 
 fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
-  conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
 if test "$ipv6" = "yes"; then
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if RFC2553 API is available" >&5
@@ -10130,7 +10144,7 @@ do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
     ac_cv_prog_TRUE="$ac_prog"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
@@ -11444,7 +11458,8 @@ int
 main ()
 {
 static int test_array [1 - 2 * !(((char) -1) < 0)];
-test_array [0] = 0
+test_array [0] = 0;
+return test_array [0];
 
   ;
   return 0;
@@ -11475,11 +11490,11 @@ else
 int
 main ()
 {
-/* FIXME: Include the comments suggested by Paul. */
+
 #ifndef __cplusplus
-  /* Ultrix mips cc rejects this.  */
+  /* Ultrix mips cc rejects this sort of thing.  */
   typedef int charset[2];
-  const charset cs;
+  const charset cs = { 0, 0 };
   /* SunOS 4.1.1 cc rejects this.  */
   char const *const *pcpcc;
   char **ppc;
@@ -11496,8 +11511,9 @@ main ()
   ++pcpcc;
   ppc = (char**) pcpcc;
   pcpcc = (char const *const *) ppc;
-  { /* SCO 3.2v4 cc rejects this.  */
-    char *t;
+  { /* SCO 3.2v4 cc rejects this sort of thing.  */
+    char tx;
+    char *t = &tx;
     char const *s = 0 ? (char *) 0 : (char const *) 0;
 
     *t++ = 0;
@@ -11513,10 +11529,10 @@ main ()
     iptr p = 0;
     ++p;
   }
-  { /* AIX XL C 1.02.0.0 rejects this saying
+  { /* AIX XL C 1.02.0.0 rejects this sort of thing, saying
        "k.c", line 2.27: 1506-025 (S) Operand must be a modifiable lvalue. */
-    struct s { int j; const int *ap[3]; };
-    struct s *b; b->j = 5;
+    struct s { int j; const int *ap[3]; } bx;
+    struct s *b = &bx; b->j = 5;
   }
   { /* ULTRIX-32 V3.1 (Rev 9) vcc rejects this */
     const int foo = 10;
@@ -14447,16 +14463,16 @@ if (echo >conf$$.file) 2>/dev/null; then
     # ... but there are two gotchas:
     # 1) On MSYS, both `ln -s file dir' and `ln file dir' fail.
     # 2) DJGPP < 2.04 has no symlinks; `ln -s' creates a wrapper executable.
-    # In both cases, we have to default to `cp -p'.
+    # In both cases, we have to default to `cp -pR'.
     ln -s conf$$.file conf$$.dir 2>/dev/null && test ! -f conf$$.exe ||
-      as_ln_s='cp -p'
+      as_ln_s='cp -pR'
   elif ln conf$$.file conf$$ 2>/dev/null; then
     as_ln_s=ln
   else
-    as_ln_s='cp -p'
+    as_ln_s='cp -pR'
   fi
 else
-  as_ln_s='cp -p'
+  as_ln_s='cp -pR'
 fi
 rm -f conf$$ conf$$.exe conf$$.dir/conf$$.file conf$$.file
 rmdir conf$$.dir 2>/dev/null
@@ -14516,28 +14532,16 @@ else
   as_mkdir_p=false
 fi
 
-if test -x / >/dev/null 2>&1; then
-  as_test_x='test -x'
-else
-  if ls -dL / >/dev/null 2>&1; then
-    as_ls_L_option=L
-  else
-    as_ls_L_option=
-  fi
-  as_test_x='
-    eval sh -c '\''
-      if test -d "$1"; then
-	test -d "$1/.";
-      else
-	case $1 in #(
-	-*)set "./$1";;
-	esac;
-	case `ls -ld'$as_ls_L_option' "$1" 2>/dev/null` in #((
-	???[sx]*):;;*)false;;esac;fi
-    '\'' sh
-  '
-fi
-as_executable_p=$as_test_x
+
+# as_fn_executable_p FILE
+# -----------------------
+# Test if FILE is an executable regular file.
+as_fn_executable_p ()
+{
+  test -f "$1" && test -x "$1"
+} # as_fn_executable_p
+as_test_x='test -x'
+as_executable_p=as_fn_executable_p
 
 # Sed expression to map a string onto a valid CPP name.
 as_tr_cpp="eval sed 'y%*$as_cr_letters%P$as_cr_LETTERS%;s%[^_$as_cr_alnum]%_%g'"
@@ -14559,7 +14563,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # values after options handling.
 ac_log="
 This file was extended by python $as_me 2.7, which was
-generated by GNU Autoconf 2.68.  Invocation command line was
+generated by GNU Autoconf 2.69.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
   CONFIG_HEADERS  = $CONFIG_HEADERS
@@ -14621,10 +14625,10 @@ cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
 python config.status 2.7
-configured by $0, generated by GNU Autoconf 2.68,
+configured by $0, generated by GNU Autoconf 2.69,
   with options \\"\$ac_cs_config\\"
 
-Copyright (C) 2010 Free Software Foundation, Inc.
+Copyright (C) 2012 Free Software Foundation, Inc.
 This config.status script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it."
 
@@ -14714,7 +14718,7 @@ fi
 _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 if \$ac_cs_recheck; then
-  set X '$SHELL' '$0' $ac_configure_args \$ac_configure_extra_args --no-create --no-recursion
+  set X $SHELL '$0' $ac_configure_args \$ac_configure_extra_args --no-create --no-recursion
   shift
   \$as_echo "running CONFIG_SHELL=$SHELL \$*" >&6
   CONFIG_SHELL='$SHELL'
diff --git a/configure.ac b/configure.ac
index d7399ebc61e..db6b0b26c5e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2517,25 +2517,15 @@ AC_ARG_ENABLE(ipv6,
 
 [
 dnl the check does not work on cross compilation case...
-  AC_RUN_IFELSE([AC_LANG_SOURCE([[ /* AF_INET6 available check */
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ /* AF_INET6 available check */
 #include <sys/types.h>
-#include <sys/socket.h>
-main()
-{
- if (socket(AF_INET6, SOCK_STREAM, 0) < 0)
-   exit(1);
- else
-   exit(0);
-}
-]])],[
+#include <sys/socket.h>]],
+[[int domain = AF_INET6;]])],[
   AC_MSG_RESULT(yes)
   ipv6=yes
 ],[
   AC_MSG_RESULT(no)
   ipv6=no
-],[
-  AC_MSG_RESULT(no)
-  ipv6=no
 ])
 
 if test "$ipv6" = "yes"; then