--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2010-06-03  Bruno Haible  <bruno@clisp.org>
+
+	Choose among AC_DEFUN_ONCE, AC_DEFUN in a way that aclocal understands.
+	* m4/iconv.m4 (gl_iconv_AC_DEFUN): New macro.
+	(AM_ICONV): Define it through gl_iconv_AC_DEFUN.
+	* m4/libunistring.m4 (gl_libunistring_AC_DEFUN): New macro.
+	(gl_LIBUNISTRING): Define it through gl_libunistring_AC_DEFUN.
+	Reported by Ludovic Courtès <ludo@gnu.org>.
+
 2010-06-02  Eric Blake  <eblake@redhat.com>
 
 	time: work with mingw + pthreads-win32 library

--- a/m4/iconv.m4
+++ b/m4/iconv.m4
@@ -1,4 +1,4 @@
-# iconv.m4 serial 10 (gettext-0.18.1)
+# iconv.m4 serial 11 (gettext-0.18.1)
 dnl Copyright (C) 2000-2002, 2007-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -173,7 +173,19 @@
 dnl Define AM_ICONV using AC_DEFUN_ONCE for Autoconf >= 2.64, in order to
 dnl avoid warnings like
 dnl "warning: AC_REQUIRE: `AM_ICONV' was expanded before it was required".
-m4_version_prereq([2.64],[AC_DEFUN_ONCE],[AC_DEFUN])([AM_ICONV],
+dnl This is tricky because of the way 'aclocal' is implemented:
+dnl - It requires defining an auxiliary macro whose name ends in AC_DEFUN.
+dnl   Otherwise aclocal's initial scan pass would miss the macro definition.
+dnl - It requires a line break inside the AC_DEFUN_ONCE and AC_DEFUN expansions.
+dnl   Otherwise aclocal would emit many "Use of uninitialized value $1"
+dnl   warnings.
+m4_define([gl_iconv_AC_DEFUN],
+  m4_version_prereq([2.64],
+    [[AC_DEFUN_ONCE(
+        [$1], [$2])]],
+    [[AC_DEFUN(
+        [$1], [$2])]]))
+gl_iconv_AC_DEFUN([AM_ICONV],
 [
   AM_ICONV_LINK
   if test "$am_cv_func_iconv" = yes; then

--- a/m4/libunistring.m4
+++ b/m4/libunistring.m4
@@ -1,4 +1,4 @@
-# libunistring.m4 serial 7
+# libunistring.m4 serial 8
 dnl Copyright (C) 2009-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -15,7 +15,19 @@
 dnl Define gl_LIBUNISTRING using AC_DEFUN_ONCE for Autoconf >= 2.64, in order
 dnl to avoid warnings like
 dnl "warning: AC_REQUIRE: `gl_LIBUNISTRING' was expanded before it was required".
-m4_version_prereq([2.64],[AC_DEFUN_ONCE],[AC_DEFUN])([gl_LIBUNISTRING],
+dnl This is tricky because of the way 'aclocal' is implemented:
+dnl - It requires defining an auxiliary macro whose name ends in AC_DEFUN.
+dnl   Otherwise aclocal's initial scan pass would miss the macro definition.
+dnl - It requires a line break inside the AC_DEFUN_ONCE and AC_DEFUN expansions.
+dnl   Otherwise aclocal would emit many "Use of uninitialized value $1"
+dnl   warnings.
+m4_define([gl_libunistring_AC_DEFUN],
+  m4_version_prereq([2.64],
+    [[AC_DEFUN_ONCE(
+        [$1], [$2])]],
+    [[AC_DEFUN(
+        [$1], [$2])]]))
+gl_libunistring_AC_DEFUN([gl_LIBUNISTRING],
 [
   AC_BEFORE([$0], [gl_LIBUNISTRING_LIBSOURCE])
   AC_BEFORE([$0], [gl_LIBUNISTRING_LIBHEADER])