diff --git a/include/ChangeLog b/include/ChangeLog
index ac8f2848a..fe6887463 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,8 @@
+2009-03-18  Alan Modra  <amodra@bigpond.net.au>
+
+	* alloca-conf.h: Revise based on autoconf-2.61, autoconf-2.13
+	documentation.
+
 2009-03-17  Jason Merrill  <jason@redhat.com>
 
 	* demangle.h (enum demangle_component_type): Add
diff --git a/include/alloca-conf.h b/include/alloca-conf.h
index 9c3eea396..9ba77953d 100644
--- a/include/alloca-conf.h
+++ b/include/alloca-conf.h
@@ -1,24 +1,44 @@
 #include "config.h"
 
-#if defined(__GNUC__) && !defined(C_ALLOCA)
-# ifndef alloca
-#  define alloca __builtin_alloca
-# endif
-#else /* ! defined (__GNUC__) */
-#  ifdef _AIX
- #pragma alloca
-#  else
-#  if defined(HAVE_ALLOCA_H) && !defined(C_ALLOCA)
-#   include <alloca.h>
-#  else /* ! defined (HAVE_ALLOCA_H) */
-#   ifdef __STDC__
-extern PTR alloca (size_t);
-#   else /* ! defined (__STDC__) */
-extern PTR alloca ();
-#   endif /* ! defined (__STDC__) */
-#  endif /* ! defined (HAVE_ALLOCA_H) */
-#  ifdef _WIN32
-#   include <malloc.h>
+/* This is a merge of code recommended in the autoconf-2.61 documentation
+   with that recommended in the autoconf-2.13 documentation, with added
+   tweaks to heed C_ALLOCA.  */
+
+#if defined HAVE_ALLOCA_H && !defined C_ALLOCA
+# include <alloca.h>
+#else
+# if defined __GNUC__ && !defined C_ALLOCA
+#  if !defined alloca
+#   define alloca __builtin_alloca
 #  endif
-# endif /* ! defined (_AIX) */
-#endif /* ! defined (__GNUC__) */
+# else
+#  if defined _AIX
+/* Indented so that pre-ansi C compilers will ignore it, rather than
+   choke on it.  Some versions of AIX require this to be the first
+   thing in the file except for comments and preprocessor directives.  */
+    #pragma alloca
+#  else
+#   if defined _MSC_VER && !defined C_ALLOCA
+#    include <malloc.h>
+#    define alloca _alloca
+#   else
+#    if !defined alloca
+#     if defined __STDC__ || defined __hpux
+#      if defined HAVE_STDDEF_H
+#       include <stddef.h>
+#       if defined  __cplusplus
+extern "C" void *alloca (size_t);
+#       else
+extern void *alloca (size_t);
+#       endif
+#      else
+extern void *alloca ();
+#      endif
+#     else
+extern char *alloca ();
+#     endif
+#    endif
+#   endif
+#  endif
+# endif
+#endif