--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2008-01-09  Paul Eggert  <eggert@cs.ucla.edu>
+
+	gl_FUNC_ALLOCA no longer defines HAVE_ALLOCA_H unconditionally.
+	See <http://lists.gnu.org/archive/html/bug-gnulib/2007-12/msg00149.html>.
+	* NEWS: announce this.
+	* m4/alloca.m4 (gl_FUNC_ALLOCA): Don't define HAVE_ALLOCA_H.
+
 2008-01-09  Simon Josefsson  <simon@josefsson.org>
 	and Eric Blake  <ebb9@byu.net>
 

--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,12 @@
 
 Date        Modules         Changes
 
+2008-01-09  alloca-opt      Now defines HAVE_ALLOCA_H only when the system
+                            supplies an <alloca.h>.  Gnulib-using code is now
+                            expected to include <alloca.h> unconditionally.
+                            Non-gnulib-using code can continue to include
+                            <alloca.h> only if HAVE_ALLOCA_H is defined.
+
 2008-01-08  memmem          This module now replaces worst-case inefficient
                             implementations; clients that use controlled
                             needles and thus do not care about worst-case

--- a/m4/alloca.m4
+++ b/m4/alloca.m4
@@ -1,5 +1,5 @@
-# alloca.m4 serial 7
-dnl Copyright (C) 2002-2004, 2006 Free Software Foundation, Inc.
+# alloca.m4 serial 8
+dnl Copyright (C) 2002-2004, 2006, 2007 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -39,10 +39,6 @@
     ALLOCA_H=alloca.h
   fi
   AC_SUBST([ALLOCA_H])
-
-  AC_DEFINE(HAVE_ALLOCA_H, 1,
-    [Define HAVE_ALLOCA_H for backward compatibility with older code
-     that includes <alloca.h> only if HAVE_ALLOCA_H is defined.])
 ])
 
 # Prerequisites of lib/alloca.c.