diff --git a/configure b/configure
index 3e7e901716e..35071dc0cea 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 1.357 .
+# From configure.in Revision: 1.358 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.53.
 #
@@ -901,7 +901,7 @@ esac
 # Don't blindly perform a `cd "$ac_dir"/$ac_foo && pwd` since $ac_foo can be
 # absolute.
 ac_abs_builddir=`cd "$ac_dir" && cd $ac_builddir && pwd`
-ac_abs_top_builddir=`cd "$ac_dir" && cd ${ac_top_builddir}. && pwd`
+ac_abs_top_builddir=`cd "$ac_dir" && cd $ac_top_builddir && pwd`
 ac_abs_srcdir=`cd "$ac_dir" && cd $ac_srcdir && pwd`
 ac_abs_top_srcdir=`cd "$ac_dir" && cd $ac_top_srcdir && pwd`
 
@@ -1242,6 +1242,21 @@ cat >>confdefs.h <<\_ACEOF
 _ACEOF
 
 
+# On Tru64 Unix 4.0F, defining _XOPEN_SOURCE also requires definition
+# of _XOPEN_SOURCE_EXTENDED and _POSIX_C_SOURCE, or else several APIs
+# are not declared. Since this is also needed in some cases for HP-UX,
+# we define it globally.
+
+cat >>confdefs.h <<\_ACEOF
+#define _XOPEN_SOURCE_EXTENDED 1
+_ACEOF
+
+
+cat >>confdefs.h <<\_ACEOF
+#define _POSIX_C_SOURCE 199506L
+_ACEOF
+
+
 # Arguments passed to configure.
 
 CONFIG_ARGS="$ac_configure_args"
@@ -17160,7 +17175,7 @@ esac
 # Don't blindly perform a `cd "$ac_dir"/$ac_foo && pwd` since $ac_foo can be
 # absolute.
 ac_abs_builddir=`cd "$ac_dir" && cd $ac_builddir && pwd`
-ac_abs_top_builddir=`cd "$ac_dir" && cd ${ac_top_builddir}. && pwd`
+ac_abs_top_builddir=`cd "$ac_dir" && cd $ac_top_builddir && pwd`
 ac_abs_srcdir=`cd "$ac_dir" && cd $ac_srcdir && pwd`
 ac_abs_top_srcdir=`cd "$ac_dir" && cd $ac_top_srcdir && pwd`
 
diff --git a/configure.in b/configure.in
index 002666d5d17..a3b726c8cab 100644
--- a/configure.in
+++ b/configure.in
@@ -33,6 +33,13 @@ AH_VERBATIM([_XOPEN_SOURCE],
 #endif])
 AC_DEFINE(_XOPEN_SOURCE, 500)
 
+# On Tru64 Unix 4.0F, defining _XOPEN_SOURCE also requires definition
+# of _XOPEN_SOURCE_EXTENDED and _POSIX_C_SOURCE, or else several APIs
+# are not declared. Since this is also needed in some cases for HP-UX,
+# we define it globally.
+AC_DEFINE(_XOPEN_SOURCE_EXTENDED, 1, Define to activate Unix95-and-earlier features)
+AC_DEFINE(_POSIX_C_SOURCE, 199506L, Define to activate features from IEEE Stds 1003.{123}-1995)
+
 # Arguments passed to configure.
 AC_SUBST(CONFIG_ARGS)
 CONFIG_ARGS="$ac_configure_args"
diff --git a/pyconfig.h.in b/pyconfig.h.in
index c6713de7699..ce17133719b 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -785,6 +785,9 @@
    this defined. */
 #undef _POSIX_1_SOURCE
 
+/* Define to activate features from IEEE Stds 1003.{123}-1995 */
+#undef _POSIX_C_SOURCE
+
 /* Define to 1 if you need to in order for `stat' and other things to work. */
 #undef _POSIX_SOURCE
 
@@ -799,6 +802,9 @@
 # define _XOPEN_SOURCE 500
 #endif
 
+/* Define to activate Unix95-and-earlier features */
+#undef _XOPEN_SOURCE_EXTENDED
+
 /* Define to 1 if type `char' is unsigned and you are not using gcc.  */
 #ifndef __CHAR_UNSIGNED__
 # undef __CHAR_UNSIGNED__