aclocal: AC_CONFIG_MACRO_DIRS: work around autom4te option parsing bugs

The autom4te program coming with autoconf 2.68 and earlier had a bug
which caused the "-" command line argument (with which we tell it to
read some input from from standard input) to aways be pushed at the
*end* of the command line, regardless of where the user specified it
(that bug was fixed by autoconf commit 'v2.68-120-gf4be358', "getopt:
new Autom4te::Getopt module").

This broken semantics conflict with our usage in aclocal, where we
need to pass some input to the invoked autom4te program early, and
have so far been using the stdin to do so.  Now we start using an
external file instead.

* m4/internal/ac-config-macro-dirs.m4: New file, contain a fallback
definition of the AC_CONFIG_MACRO_DIRS macro for older autoconf
releases.
* aclocal.in (trace_used_macros): When invoking autom4te, use that
file instead of "abusing" standard input.
* Makefile.am (dist_automake_ac_DATA): Rename ...
(nobase_dist_automake_ac_DATA): ... like this.
Add 'm4/internal/ac-config-macro-dirs.m4' to it.
* t/aclocal-acdir.sh: Adjust to avoid spurious failures.

Helped-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

4 files changed, 35 insertions, 12 deletions

diff --git a/Makefile.am b/Makefile.am
index 065500f90..34abc5a49 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -255,7 +255,8 @@ dist_am_DATA = \
 ##  Automake-provided m4 macros.  ##
 ## ------------------------------ ##
 
-dist_automake_ac_DATA = \
+nobase_dist_automake_ac_DATA = \
+  m4/internal/ac-config-macro-dirs.m4 \
   m4/amversion.m4 \
   m4/ar-lib.m4 \
   m4/as.m4 \
diff --git a/aclocal.in b/aclocal.in
index 1e56649b6..76b556a6b 100644
--- a/aclocal.in
+++ b/aclocal.in
@@ -48,12 +48,12 @@ use File::Path ();
 # Support AC_CONFIG_MACRO_DIRS also with older autoconf.
 # FIXME: To be removed in Automake 1.14, once we can assume autoconf
 #        2.70 or later.
-# NOTE: This variable deliberately contain no newlines.
+# FIXME: keep in sync with 'internal/ac-config-macro-dirs.m4'.
 my $ac_config_macro_dirs_fallback =
-  "m4_ifndef([AC_CONFIG_MACRO_DIRS], [" .
-    "m4_defun([_AM_CONFIG_MACRO_DIRS], [])" .
-    "m4_defun([AC_CONFIG_MACRO_DIRS], [_AM_CONFIG_MACRO_DIRS(\$@)])" .
-  "])";
+  'm4_ifndef([AC_CONFIG_MACRO_DIRS], [' .
+    'm4_defun([_AM_CONFIG_MACRO_DIRS], [])' .
+    'm4_defun([AC_CONFIG_MACRO_DIRS], [_AM_CONFIG_MACRO_DIRS($@)])' .
+  '])';
 
 # We do not operate in threaded mode.
 $perl_threads = 0;
@@ -726,23 +726,27 @@ sub trace_used_macros ()
   my %files = map { $map{$_} => 1 } keys %macro_seen;
   %files = strip_redundant_includes %files;
 
-  my $early_m4_code = "";
   # When AC_CONFIG_MACRO_DIRS is used, avoid possible spurious warnings
   # from autom4te about macros being "m4_require'd but not m4_defun'd";
   # for more background, see:
   # http://lists.gnu.org/archive/html/autoconf-patches/2012-11/msg00004.html
   # as well as autoconf commit 'v2.69-44-g1ed0548', "warn: allow aclocal
   # to silence m4_require warnings".
-  $early_m4_code .= "m4_define([m4_require_silent_probe], [-])";
-  # Support AC_CONFIG_MACRO_DIRS also with older autoconf.
-  # FIXME: To be removed in Automake 1.14, once we can assume autoconf
-  #        2.70 or later.
-  $early_m4_code .= $ac_config_macro_dirs_fallback;
+  my $early_m4_code .= "m4_define([m4_require_silent_probe], [-])";
 
   my $traces = ($ENV{AUTOM4TE} || '@am_AUTOM4TE@');
   $traces .= " --language Autoconf-without-aclocal-m4 ";
   $traces = "echo '$early_m4_code' | $traces - ";
 
+  # Support AC_CONFIG_MACRO_DIRS also with older autoconf.
+  # Note that we can't use '$ac_config_macro_dirs_fallback' here, because
+  # a bug in option parsing code of autom4te 2.68 and earlier will cause
+  # it to read standard input last, even if the "-" argument is specified
+  # early.
+  # FIXME: To be removed in Automake 1.14, once we can assume autoconf
+  #        2.70 or later.
+  $traces .= "$automake_includes[0]/internal/ac-config-macro-dirs.m4 ";
+
   # All candidate files.
   $traces .= join (' ',
 		   (map { "'$_'" }
diff --git a/m4/internal/ac-config-macro-dirs.m4 b/m4/internal/ac-config-macro-dirs.m4
new file mode 100644
index 000000000..530e655c3
--- /dev/null
+++ b/m4/internal/ac-config-macro-dirs.m4
@@ -0,0 +1,15 @@
+# Support AC_CONFIG_MACRO_DIRS with older autoconf.     -*- Autoconf -*-
+# FIXME: To be removed in Automake 1.14, once we can assume autoconf
+#        2.70 or later.
+# FIXME: keep in sync with the contents of the variable
+#        '$ac_config_macro_dirs_fallback' in aclocal.in.
+
+# Copyright (C) 2012 Free Software Foundation, Inc.
+#
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+m4_ifndef([AC_CONFIG_MACRO_DIRS],
+[m4_defun([_AM_CONFIG_MACRO_DIRS],[])]dnl
+[m4_defun([AC_CONFIG_MACRO_DIRS],[_AM_CONFIG_MACRO_DIRS($@)])])
diff --git a/t/aclocal-acdir.sh b/t/aclocal-acdir.sh
index 59182bbf5..944604b44 100755
--- a/t/aclocal-acdir.sh
+++ b/t/aclocal-acdir.sh
@@ -21,6 +21,9 @@
 . test-init.sh
 
 mkdir am sys
+# FIXME: remove in Automake 1.14.
+mkdir am/internal
+: > am/internal/ac-config-macro-dirs.m4
 
 cat >> configure.ac <<'END'
 MY_MACRO