md5, sha1, sha256, sha512: support older autoconf

[gnulib.git] / m4 / 00gnulib.m4

diff --git a/m4/00gnulib.m4 b/m4/00gnulib.m4
index b494772..8eca551 100644 (file)
--- a/m4/00gnulib.m4
+++ b/m4/00gnulib.m4
@@ -1,4 +1,4 @@
-# 00gnulib.m4 serial 2
+# 00gnulib.m4 serial 3
 dnl Copyright (C) 2009-2014 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,7 +6,23 @@ dnl with or without modifications, as long as this notice is preserved.
 
 dnl This file must be named something that sorts before all other
 dnl gnulib-provided .m4 files.  It is needed until such time as we can
-dnl assume Autoconf 2.64, with its improved AC_DEFUN_ONCE semantics.
+dnl assume Autoconf 2.64, with its improved AC_DEFUN_ONCE and
+dnl m4_divert semantics.
+
+# Until autoconf 2.63, handling of the diversion stack required m4_init
+# to be called first; but this does not happen with aclocal.  Wrapping
+# the entire execution in another layer of the diversion stack fixes this.
+# Worse, prior to autoconf 2.62, m4_wrap depended on the underlying m4
+# for whether it was FIFO or LIFO; in order to properly balance with
+# m4_init, we need to undo our push just before anything wrapped within
+# the m4_init body.  The way to ensure this is to wrap both sides of
+# m4_init with a one-shot macro that does the pop at the right time.
+m4_ifndef([_m4_divert_diversion],
+[m4_divert_push([KILL])
+m4_define([gl_divert_fixup], [m4_divert_pop()m4_define([$0])])
+m4_define([m4_init],
+  [gl_divert_fixup()]m4_defn([m4_init])[gl_divert_fixup()])])
+
 
 # AC_DEFUN_ONCE([NAME], VALUE)
 # ----------------------------