[PATCH] automake: do not require ltmain.sh for out-of-tree libtool

If Automake does not see LT_SUPPORTED_TAG, it assumes an old libtool
that does not know about AC_REQUIRE_AUX_FILE.  However, if the program
does not use Libtool's configure.ac macros this check gets a
false positive.  Do not require ltmain.sh if no Libtool macro is
found in configure.ac.

Libtools that are not stone-age are already covered by LT_SUPPORTED_TAG
and _LT_AC_TAGCONFIG, but add AC_PROG_LIBTOOL just in case for Libtool
up to 1.4.

2016-10-31  Paolo Bonzini  <[email protected]>

	* bin/automake.in ($libtool_bundled): New.
	(handle_libtool): Do not require libtool files if libtool is
	not being bundled.
	(scan_autoconf_traces): Set $libtool_bundled.  Trace
	AC_PROG_LIBTOOL too.

Signed-off-by: Paolo Bonzini <[email protected]>
---
	If the patch is accepted I will send an Autoconf patch to
	preselect AC_PROG_LIBTOOL.

	Since this is a bug, it would be nice to add it at least to
	the 1.16 branch.

 bin/automake.in | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/bin/automake.in b/bin/automake.in
index 3abee49..cb2a480 100644
--- a/bin/automake.in
+++ b/bin/automake.in
@@ -274,6 +274,8 @@ my @extra_recursive_targets = ();
 
 # Lists of tags supported by Libtool.
 my %libtool_tags = ();
+# 1 if Libtool is being bundled, so ltmain.sh is required.
+my $libtool_bundled = 0;
 # 1 if Libtool uses LT_SUPPORTED_TAG.  If it does, then it also
 # uses AC_REQUIRE_AUX_FILE.
 my $libtool_new_api = 0;
@@ -2304,7 +2306,7 @@ sub handle_libtool ()
   # (Starting with Libtool 2.0 we do not have to bother.  These
   # requirements are done with AC_REQUIRE_AUX_FILE.)
   require_conf_file_with_macro (TRUE, 'LIBTOOL', FOREIGN, @libtool_files)
-    if $relative_dir eq '.' && ! $libtool_new_api;
+    if $relative_dir eq '.' && $libtool_bundled && ! $libtool_new_api;
 
   my @libtool_rms;
   foreach my $item (sort keys %libtool_clean_directories)
@@ -4952,6 +4954,7 @@ sub scan_autoconf_traces
 		_AM_COND_IF => 1,
 		_AM_COND_ELSE => 1,
 		_AM_COND_ENDIF => 1,
+		AC_PROG_LIBTOOL => 0,
 		LT_SUPPORTED_TAG => 1,
 		_LT_AC_TAGCONFIG => 0,
 		m4_include => 1,
@@ -5185,10 +5188,16 @@ sub scan_autoconf_traces
 		if $mtime > $configure_deps_greatest_timestamp;
 	    }
 	}
+      elsif ($macro eq 'AC_PROG_LIBTOOL')
+	{
+	  # Detect bundling of really old Libtool that does not support tags.
+	  $libtool_bundled = 1;
+	}
       elsif ($macro eq 'LT_SUPPORTED_TAG')
 	{
 	  $libtool_tags{$args[1]} = 1;
 	  $libtool_new_api = 1;
+	  $libtool_bundled = 1;
 	}
       elsif ($macro eq '_LT_AC_TAGCONFIG')
 	{
@@ -5201,6 +5210,7 @@ sub scan_autoconf_traces
 	      # Hardcode the tags supported by Libtool 1.5.
 	      %libtool_tags = (CC => 1, CXX => 1, GCJ => 1, F77 => 1);
 	    }
+	  $libtool_bundled = 1;
 	}
     }
 
-- 
2.7.4