--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2014-11-03  Paul Eggert  <eggert@cs.ucla.edu>
 
+	obstack: do not assume system-supplied obstack is size_t safe
+	* m4/obstack.m4: New file.
+	* modules/obstack (Files): Add it.
+
 	obstack: port to platforms that #define __alignof__
 	* lib/obstack.c: Include <alignof.h> if !defined __alignof__,
 	not if !_LIBC.  We don't know of any platforms that #define

new file mode 100644
--- /dev/null
+++ b/m4/obstack.m4
@@ -0,0 +1,35 @@
+# See if we need to provide obstacks.
+
+dnl Copyright 1996-2014 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.
+
+dnl This replaces Autoconf's AC_FUNC_OBSTACK.
+dnl The Autoconf version should be marked obsolete at some point.
+
+AC_DEFUN([AC_FUNC_OBSTACK],
+  [AC_LIBSOURCES([obstack.h, obstack.c])dnl
+   AC_CACHE_CHECK([for obstacks that work with any size object],
+     [ac_cv_func_obstack],
+     [AC_LINK_IFELSE(
+        [AC_LANG_PROGRAM(
+           [[#include "obstack.h"
+             void *obstack_chunk_alloc (size_t n) { return 0; }
+             void obstack_chunk_free (void *p) { }
+             /* Check that an internal function returns size_t, not int.  */
+             size_t _obstack_memory_used (struct obstack *);
+            ]],
+           [[struct obstack mem;
+             obstack_init (&mem);
+             obstack_free (&mem, 0);
+           ]])],
+        [ac_cv_func_obstack=yes],
+        [ac_cv_func_obstack=no])])
+   if test "$ac_cv_func_obstack" = yes; then
+     AC_DEFINE([HAVE_OBSTACK], 1,
+       [Define to 1 if the system has obstacks that work with any size object.])
+   else
+     AC_LIBOBJ([obstack])
+   fi
+])

--- a/modules/obstack
+++ b/modules/obstack
@@ -4,6 +4,7 @@
 Files:
 lib/obstack.h
 lib/obstack.c
+m4/obstack.m4
 
 Depends-on:
 alignof