diff --git a/aclocal.m4 b/aclocal.m4
index 09ae5d1aa8a..832aec19f48 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -150,6 +150,80 @@ AS_VAR_IF(CACHEVAR,yes,
 AS_VAR_POPDEF([CACHEVAR])dnl
 ])dnl AX_CHECK_COMPILE_FLAGS
 
+# ===========================================================================
+#     https://www.gnu.org/software/autoconf-archive/ax_check_define.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AC_CHECK_DEFINE([symbol], [ACTION-IF-FOUND], [ACTION-IF-NOT])
+#   AX_CHECK_DEFINE([includes],[symbol], [ACTION-IF-FOUND], [ACTION-IF-NOT])
+#
+# DESCRIPTION
+#
+#   Complements AC_CHECK_FUNC but it does not check for a function but for a
+#   define to exist. Consider a usage like:
+#
+#    AC_CHECK_DEFINE(__STRICT_ANSI__, CFLAGS="$CFLAGS -D_XOPEN_SOURCE=500")
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 11
+
+AU_ALIAS([AC_CHECK_DEFINED], [AC_CHECK_DEFINE])
+AC_DEFUN([AC_CHECK_DEFINE],[
+AS_VAR_PUSHDEF([ac_var],[ac_cv_defined_$1])dnl
+AC_CACHE_CHECK([for $1 defined], ac_var,
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[
+  #ifdef $1
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+]])],[AS_VAR_SET(ac_var, yes)],[AS_VAR_SET(ac_var, no)]))
+AS_IF([test AS_VAR_GET(ac_var) != "no"], [$2], [$3])dnl
+AS_VAR_POPDEF([ac_var])dnl
+])
+
+AU_ALIAS([AX_CHECK_DEFINED], [AX_CHECK_DEFINE])
+AC_DEFUN([AX_CHECK_DEFINE],[
+AS_VAR_PUSHDEF([ac_var],[ac_cv_defined_$2_$1])dnl
+AC_CACHE_CHECK([for $2 defined in $1], ac_var,
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <$1>]], [[
+  #ifdef $2
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+]])],[AS_VAR_SET(ac_var, yes)],[AS_VAR_SET(ac_var, no)]))
+AS_IF([test AS_VAR_GET(ac_var) != "no"], [$3], [$4])dnl
+AS_VAR_POPDEF([ac_var])dnl
+])
+
+AC_DEFUN([AX_CHECK_FUNC],
+[AS_VAR_PUSHDEF([ac_var], [ac_cv_func_$2])dnl
+AC_CACHE_CHECK([for $2], ac_var,
+dnl AC_LANG_FUNC_LINK_TRY
+[AC_LINK_IFELSE([AC_LANG_PROGRAM([$1
+                #undef $2
+                char $2 ();],[
+                char (*f) () = $2;
+                return f != $2; ])],
+                [AS_VAR_SET(ac_var, yes)],
+                [AS_VAR_SET(ac_var, no)])])
+AS_IF([test AS_VAR_GET(ac_var) = yes], [$3], [$4])dnl
+AS_VAR_POPDEF([ac_var])dnl
+])# AC_CHECK_FUNC
+
 # ===========================================================================
 #     https://www.gnu.org/software/autoconf-archive/ax_check_openssl.html
 # ===========================================================================
diff --git a/configure b/configure
index c204c9eb499..f431c5dd15e 100755
--- a/configure
+++ b/configure
@@ -11297,42 +11297,22 @@ then :
 fi
 
 
-# checks for typedefs
-
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for clock_t in time.h" >&5
-printf %s "checking for clock_t in time.h... " >&6; }
-if test ${ac_cv_clock_t_time_h+y}
+# Check for clock_t in time.h.
+ac_fn_c_check_type "$LINENO" "clock_t" "ac_cv_type_clock_t" "#include <time.h>
+"
+if test "x$ac_cv_type_clock_t" = xyes
 then :
-  printf %s "(cached) " >&6
+
+printf "%s\n" "#define HAVE_CLOCK_T 1" >>confdefs.h
+
+
 else $as_nop
 
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <time.h>
-
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "clock_t" >/dev/null 2>&1
-then :
-  ac_cv_clock_t_time_h=yes
-else $as_nop
-  ac_cv_clock_t_time_h=no
-fi
-rm -rf conftest*
-
-
-fi
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_clock_t_time_h" >&5
-printf "%s\n" "$ac_cv_clock_t_time_h" >&6; }
-if test "x$ac_cv_clock_t_time_h" = xno
-then :
-
-
 printf "%s\n" "#define clock_t long" >>confdefs.h
 
-
 fi
 
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for makedev" >&5
 printf %s "checking for makedev... " >&6; }
 if test ${ac_cv_func_makedev+y}
@@ -11534,6 +11514,7 @@ printf "%s\n" "#define size_t unsigned int" >>confdefs.h
 
 fi
 
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for uid_t in sys/types.h" >&5
 printf %s "checking for uid_t in sys/types.h... " >&6; }
 if test ${ac_cv_type_uid_t+y}
@@ -16184,24 +16165,47 @@ else
     # (e.g. gnu pth with pthread emulation)
     { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for _POSIX_THREADS in unistd.h" >&5
 printf %s "checking for _POSIX_THREADS in unistd.h... " >&6; }
-    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for _POSIX_THREADS defined in unistd.h" >&5
+printf %s "checking for _POSIX_THREADS defined in unistd.h... " >&6; }
+if test ${ac_cv_defined__POSIX_THREADS_unistd_h+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
-
 #include <unistd.h>
-#ifdef _POSIX_THREADS
-yes
-#endif
+int
+main (void)
+{
 
+  #ifdef _POSIX_THREADS
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+
+  ;
+  return 0;
+}
 _ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "yes" >/dev/null 2>&1
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_defined__POSIX_THREADS_unistd_h=yes
+else $as_nop
+  ac_cv_defined__POSIX_THREADS_unistd_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_defined__POSIX_THREADS_unistd_h" >&5
+printf "%s\n" "$ac_cv_defined__POSIX_THREADS_unistd_h" >&6; }
+if test $ac_cv_defined__POSIX_THREADS_unistd_h != "no"
 then :
   unistd_defines_pthreads=yes
 else $as_nop
   unistd_defines_pthreads=no
 fi
-rm -rf conftest*
-
     { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $unistd_defines_pthreads" >&5
 printf "%s\n" "$unistd_defines_pthreads" >&6; }
 
@@ -16708,59 +16712,131 @@ printf %s "checking ipv6 stack type... " >&6; }
 	do
 		case $i in
 		inria)
-						cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
 
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for IPV6_INRIA_VERSION defined in netinet/in.h" >&5
+printf %s "checking for IPV6_INRIA_VERSION defined in netinet/in.h... " >&6; }
+if test ${ac_cv_defined_IPV6_INRIA_VERSION_netinet_in_h+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
 #include <netinet/in.h>
-#ifdef IPV6_INRIA_VERSION
-yes
-#endif
+int
+main (void)
+{
+
+  #ifdef IPV6_INRIA_VERSION
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+
+  ;
+  return 0;
+}
 _ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "yes" >/dev/null 2>&1
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_defined_IPV6_INRIA_VERSION_netinet_in_h=yes
+else $as_nop
+  ac_cv_defined_IPV6_INRIA_VERSION_netinet_in_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_defined_IPV6_INRIA_VERSION_netinet_in_h" >&5
+printf "%s\n" "$ac_cv_defined_IPV6_INRIA_VERSION_netinet_in_h" >&6; }
+if test $ac_cv_defined_IPV6_INRIA_VERSION_netinet_in_h != "no"
 then :
   ipv6type=$i
 fi
-rm -rf conftest*
-
 			;;
 		kame)
-						cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
 
-#include <netinet/in.h>
-#ifdef __KAME__
-yes
-#endif
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "yes" >/dev/null 2>&1
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for __KAME__ defined in netinet/in.h" >&5
+printf %s "checking for __KAME__ defined in netinet/in.h... " >&6; }
+if test ${ac_cv_defined___KAME___netinet_in_h+y}
 then :
-  ipv6type=$i;
-				ipv6lib=inet6
-				ipv6libdir=/usr/local/v6/lib
-				ipv6trylibc=yes
-fi
-rm -rf conftest*
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <netinet/in.h>
+int
+main (void)
+{
 
+  #ifdef __KAME__
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_defined___KAME___netinet_in_h=yes
+else $as_nop
+  ac_cv_defined___KAME___netinet_in_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_defined___KAME___netinet_in_h" >&5
+printf "%s\n" "$ac_cv_defined___KAME___netinet_in_h" >&6; }
+if test $ac_cv_defined___KAME___netinet_in_h != "no"
+then :
+  ipv6type=$i
+                             ipv6lib=inet6
+                             ipv6libdir=/usr/local/v6/lib
+                             ipv6trylibc=yes
+fi
 			;;
 		linux-glibc)
-						cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
 
-#include <features.h>
-#if defined(__GLIBC__) && ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1) || (__GLIBC__ > 2))
-yes
-#endif
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "yes" >/dev/null 2>&1
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for __GLIBC__ defined in features.h" >&5
+printf %s "checking for __GLIBC__ defined in features.h... " >&6; }
+if test ${ac_cv_defined___GLIBC___features_h+y}
 then :
-  ipv6type=$i;
-				ipv6trylibc=yes
-fi
-rm -rf conftest*
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <features.h>
+int
+main (void)
+{
 
+  #ifdef __GLIBC__
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_defined___GLIBC___features_h=yes
+else $as_nop
+  ac_cv_defined___GLIBC___features_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_defined___GLIBC___features_h" >&5
+printf "%s\n" "$ac_cv_defined___GLIBC___features_h" >&6; }
+if test $ac_cv_defined___GLIBC___features_h != "no"
+then :
+  ipv6type=$i
+                             ipv6trylibc=yes
+fi
 			;;
 		linux-inet6)
 						if test -d /usr/inet6; then
@@ -16779,62 +16855,134 @@ rm -rf conftest*
                         fi
 			;;
 		toshiba)
-			cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
 
-#include <sys/param.h>
-#ifdef _TOSHIBA_INET6
-yes
-#endif
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "yes" >/dev/null 2>&1
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for _TOSHIBA_INET6 defined in sys/param.h" >&5
+printf %s "checking for _TOSHIBA_INET6 defined in sys/param.h... " >&6; }
+if test ${ac_cv_defined__TOSHIBA_INET6_sys_param_h+y}
 then :
-  ipv6type=$i;
-				ipv6lib=inet6;
-				ipv6libdir=/usr/local/v6/lib
-fi
-rm -rf conftest*
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <sys/param.h>
+int
+main (void)
+{
 
+  #ifdef _TOSHIBA_INET6
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_defined__TOSHIBA_INET6_sys_param_h=yes
+else $as_nop
+  ac_cv_defined__TOSHIBA_INET6_sys_param_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_defined__TOSHIBA_INET6_sys_param_h" >&5
+printf "%s\n" "$ac_cv_defined__TOSHIBA_INET6_sys_param_h" >&6; }
+if test $ac_cv_defined__TOSHIBA_INET6_sys_param_h != "no"
+then :
+  ipv6type=$i
+                             ipv6lib=inet6
+                             ipv6libdir=/usr/local/v6/lib
+fi
 			;;
 		v6d)
-			cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
 
-#include </usr/local/v6/include/sys/v6config.h>
-#ifdef __V6D__
-yes
-#endif
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "yes" >/dev/null 2>&1
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for __V6D__ defined in /usr/local/v6/include/sys/v6config.h" >&5
+printf %s "checking for __V6D__ defined in /usr/local/v6/include/sys/v6config.h... " >&6; }
+if test ${ac_cv_defined___V6D____usr_local_v6_include_sys_v6config_h+y}
 then :
-  ipv6type=$i;
-				ipv6lib=v6;
-				ipv6libdir=/usr/local/v6/lib;
-				BASECFLAGS="-I/usr/local/v6/include $BASECFLAGS"
-fi
-rm -rf conftest*
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include </usr/local/v6/include/sys/v6config.h>
+int
+main (void)
+{
 
+  #ifdef __V6D__
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_defined___V6D____usr_local_v6_include_sys_v6config_h=yes
+else $as_nop
+  ac_cv_defined___V6D____usr_local_v6_include_sys_v6config_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_defined___V6D____usr_local_v6_include_sys_v6config_h" >&5
+printf "%s\n" "$ac_cv_defined___V6D____usr_local_v6_include_sys_v6config_h" >&6; }
+if test $ac_cv_defined___V6D____usr_local_v6_include_sys_v6config_h != "no"
+then :
+  ipv6type=$i
+                             ipv6lib=v6
+                             ipv6libdir=/usr/local/v6/lib
+                             BASECFLAGS="-I/usr/local/v6/include $BASECFLAGS"
+fi
 			;;
 		zeta)
-			cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
 
-#include <sys/param.h>
-#ifdef _ZETA_MINAMI_INET6
-yes
-#endif
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "yes" >/dev/null 2>&1
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for _ZETA_MINAMI_INET6 defined in sys/param.h" >&5
+printf %s "checking for _ZETA_MINAMI_INET6 defined in sys/param.h... " >&6; }
+if test ${ac_cv_defined__ZETA_MINAMI_INET6_sys_param_h+y}
 then :
-  ipv6type=$i;
-				ipv6lib=inet6;
-				ipv6libdir=/usr/local/v6/lib
-fi
-rm -rf conftest*
+  printf %s "(cached) " >&6
+else $as_nop
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <sys/param.h>
+int
+main (void)
+{
 
+  #ifdef _ZETA_MINAMI_INET6
+  int ok;
+  (void)ok;
+  #else
+  choke me
+  #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_defined__ZETA_MINAMI_INET6_sys_param_h=yes
+else $as_nop
+  ac_cv_defined__ZETA_MINAMI_INET6_sys_param_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_defined__ZETA_MINAMI_INET6_sys_param_h" >&5
+printf "%s\n" "$ac_cv_defined__ZETA_MINAMI_INET6_sys_param_h" >&6; }
+if test $ac_cv_defined__ZETA_MINAMI_INET6_sys_param_h != "no"
+then :
+  ipv6type=$i
+                             ipv6lib=inet6
+                             ipv6libdir=/usr/local/v6/lib
+fi
 			;;
 		esac
 		if test "$ipv6type" != "unknown"; then
diff --git a/configure.ac b/configure.ac
index 702e5883577..a5abb06a829 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2895,15 +2895,11 @@ AC_CHECK_HEADERS(
 #endif
 ])
 
-# checks for typedefs
-AC_CACHE_CHECK([for clock_t in time.h], [ac_cv_clock_t_time_h], [
-  AC_EGREP_HEADER([clock_t], [time.h], [ac_cv_clock_t_time_h=yes], [ac_cv_clock_t_time_h=no])
-])
-dnl checks for "no"
-AS_VAR_IF([ac_cv_clock_t_time_h], [no], [
-  AC_DEFINE([clock_t], [long],
-            [Define to 'long' if <time.h> doesn't define.])
-])
+# Check for clock_t in time.h.
+AC_CHECK_TYPES([clock_t], [],
+               [AC_DEFINE([clock_t], [long],
+                          [Define to 'long' if <time.h> does not define clock_t.])],
+               [@%:@include <time.h>])
 
 AC_CACHE_CHECK([for makedev], [ac_cv_func_makedev], [
 AC_LINK_IFELSE([AC_LANG_PROGRAM([[
@@ -4331,13 +4327,9 @@ else
     # define _POSIX_THREADS in unistd.h. Some apparently don't
     # (e.g. gnu pth with pthread emulation)
     AC_MSG_CHECKING([for _POSIX_THREADS in unistd.h])
-    AC_EGREP_CPP([yes],
-    [
-#include <unistd.h>
-#ifdef _POSIX_THREADS
-yes
-#endif
-    ], unistd_defines_pthreads=yes, unistd_defines_pthreads=no)
+    AX_CHECK_DEFINE([unistd.h], [_POSIX_THREADS],
+                    [unistd_defines_pthreads=yes],
+                    [unistd_defines_pthreads=no])
     AC_MSG_RESULT([$unistd_defines_pthreads])
 
     AC_DEFINE([_REENTRANT])
@@ -4517,34 +4509,21 @@ if test "$ipv6" = yes -a "$cross_compiling" = no; then
 		case $i in
 		inria)
 			dnl http://www.kame.net/
-			AC_EGREP_CPP([yes], [
-#include <netinet/in.h>
-#ifdef IPV6_INRIA_VERSION
-yes
-@%:@endif],
-				[ipv6type=$i])
+			AX_CHECK_DEFINE([netinet/in.h], [IPV6_INRIA_VERSION], [ipv6type=$i])
 			;;
 		kame)
 			dnl http://www.kame.net/
-			AC_EGREP_CPP([yes], [
-#include <netinet/in.h>
-#ifdef __KAME__
-yes
-@%:@endif],
-				[ipv6type=$i;
-				ipv6lib=inet6
-				ipv6libdir=/usr/local/v6/lib
-				ipv6trylibc=yes])
+			AX_CHECK_DEFINE([netinet/in.h], [__KAME__],
+                            [ipv6type=$i
+                             ipv6lib=inet6
+                             ipv6libdir=/usr/local/v6/lib
+                             ipv6trylibc=yes])
 			;;
 		linux-glibc)
-			dnl http://www.v6.linux.or.jp/
-			AC_EGREP_CPP([yes], [
-#include <features.h>
-#if defined(__GLIBC__) && ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1) || (__GLIBC__ > 2))
-yes
-@%:@endif],
-				[ipv6type=$i;
-				ipv6trylibc=yes])
+			dnl Advanced IPv6 support was added to glibc 2.1 in 1999.
+			AX_CHECK_DEFINE([features.h], [__GLIBC__],
+                            [ipv6type=$i
+                             ipv6trylibc=yes])
 			;;
 		linux-inet6)
 			dnl http://www.v6.linux.or.jp/
@@ -4564,35 +4543,23 @@ yes
                         fi
 			;;
 		toshiba)
-			AC_EGREP_CPP([yes], [
-#include <sys/param.h>
-#ifdef _TOSHIBA_INET6
-yes
-@%:@endif],
-				[ipv6type=$i;
-				ipv6lib=inet6;
-				ipv6libdir=/usr/local/v6/lib])
+			AX_CHECK_DEFINE([sys/param.h], [_TOSHIBA_INET6],
+                            [ipv6type=$i
+                             ipv6lib=inet6
+                             ipv6libdir=/usr/local/v6/lib])
 			;;
 		v6d)
-			AC_EGREP_CPP([yes], [
-#include </usr/local/v6/include/sys/v6config.h>
-#ifdef __V6D__
-yes
-@%:@endif],
-				[ipv6type=$i;
-				ipv6lib=v6;
-				ipv6libdir=/usr/local/v6/lib;
-				BASECFLAGS="-I/usr/local/v6/include $BASECFLAGS"])
+			AX_CHECK_DEFINE([/usr/local/v6/include/sys/v6config.h], [__V6D__],
+                            [ipv6type=$i
+                             ipv6lib=v6
+                             ipv6libdir=/usr/local/v6/lib
+                             BASECFLAGS="-I/usr/local/v6/include $BASECFLAGS"])
 			;;
 		zeta)
-			AC_EGREP_CPP([yes], [
-#include <sys/param.h>
-#ifdef _ZETA_MINAMI_INET6
-yes
-@%:@endif],
-				[ipv6type=$i;
-				ipv6lib=inet6;
-				ipv6libdir=/usr/local/v6/lib])
+			AX_CHECK_DEFINE([sys/param.h], [_ZETA_MINAMI_INET6],
+                            [ipv6type=$i
+                             ipv6lib=inet6
+                             ipv6libdir=/usr/local/v6/lib])
 			;;
 		esac
 		if test "$ipv6type" != "unknown"; then
diff --git a/pyconfig.h.in b/pyconfig.h.in
index b93cac9d23c..e28baef51d5 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -157,6 +157,9 @@
 /* Define to 1 if you have the `clock_settime' function. */
 #undef HAVE_CLOCK_SETTIME
 
+/* Define to 1 if the system has the type `clock_t'. */
+#undef HAVE_CLOCK_T
+
 /* Define to 1 if you have the `closefrom' function. */
 #undef HAVE_CLOSEFROM
 
@@ -1941,7 +1944,7 @@
 /* Define on FreeBSD to activate all library features */
 #undef __BSD_VISIBLE
 
-/* Define to 'long' if <time.h> doesn't define. */
+/* Define to 'long' if <time.h> does not define clock_t. */
 #undef clock_t
 
 /* Define to empty if `const' does not conform to ANSI C. */