diff -Nur autoconf-2.61.orig/doc/autoconf.texi autoconf-2.61/doc/autoconf.texi
--- autoconf-2.61.orig/doc/autoconf.texi	Fri Nov 17 01:16:27 2006
+++ autoconf-2.61/doc/autoconf.texi	Wed Aug 29 14:39:58 2007
@@ -7297,6 +7297,13 @@
 functions.  Should be called before any macros that run the C compiler.
 @end defmac
 
address@hidden AC_INTERIX
address@hidden
address@hidden _ALL_SOURCE
+If on @acronym{Interix} and using @acronym{GCC}, define @code{_ALL_SOURCE}.
+Should be called before any macros that run the C compiler.
address@hidden defmac
+
 @defmac AC_GNU_SOURCE
 @acindex{GNU_SOURCE}
 @cvindex _GNU_SOURCE
@@ -7344,7 +7351,7 @@
 @code{_POSIX_PTHREAD_SEMANTICS}, which are macros used by Solaris.
 It also defines @code{_TANDEM_SOURCE} for the @acronym{HP} NonStop platform.
 This macro also has the combined effects of @code{AC_GNU_SOURCE},
address@hidden, and @code{AC_MINIX}.
address@hidden, @code{AC_INTERIX}, and @code{AC_MINIX}.
 @end defmac
 
 
diff -Nur autoconf-2.61.orig/lib/autoconf/specific.m4 autoconf-2.61/lib/autoconf/specific.m4
--- autoconf-2.61.orig/lib/autoconf/specific.m4	Tue Oct 24 21:34:09 2006
+++ autoconf-2.61/lib/autoconf/specific.m4	Wed Aug 29 14:36:18 2007
@@ -393,6 +393,7 @@
 
   AC_REQUIRE([AC_GNU_SOURCE])
   AC_REQUIRE([AC_AIX])
+  AC_REQUIRE([AC_INTERIX])
   AC_REQUIRE([AC_MINIX])
 
   AH_VERBATIM([__EXTENSIONS__],
@@ -453,6 +454,30 @@
 AC_DEFINE(_ALL_SOURCE)],
 [AC_MSG_RESULT([no])])
 ])# AC_AIX
+
+
+# AC_INTERIX
+# ----------
+AC_DEFUN([AC_INTERIX],
+[AH_VERBATIM([_ALL_SOURCE],
+[/* Define to 1 if on Interix.
+   System headers sometimes define this.
+   We just want to avoid a redefinition error message.  */
address@hidden:@ifndef _ALL_SOURCE
address@hidden:@ undef _ALL_SOURCE
address@hidden:@endif])dnl
+AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
+AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
+AC_MSG_CHECKING([for Interix])
+AC_EGREP_CPP(yes,
+[#ifdef __INTERIX
+  yes
+#endif
+],
+[AC_MSG_RESULT([yes])
+AC_DEFINE(_ALL_SOURCE)],
+[AC_MSG_RESULT([no])])
+])# AC_INTERIX
 
 
 # AC_MINIX