diff --git a/automake.in b/automake.in
index c0c5289..25c3467 100644
--- a/automake.in
+++ b/automake.in
@@ -107,7 +107,14 @@ struct (# Short name of the language (c, f77...).
 
 	# If TRUE, nodist_ sources will be compiled using specific rules
 	# (i.e. not inference rules).  The default is FALSE.
-	'nodist_specific' => "\$");
+	'nodist_specific' => "\$",
+
+        # This subroutine follows a simple formula: Return value is
+        # LANG_SUBDIR if the resulting object file should be in a
+        # subdir if the source file is, LANG_PROCESS if file is to
+        # be dealt with, LANG_IGNORE otherwise.
+	# Arguments are ($DIRECTORY, $BASE, $EXT)
+        'rewrite' => "\$");
 
 
 sub finish ($)
@@ -298,6 +305,9 @@ use constant QUEUE_STRING    => "string";
 ## Variables related to the options.  ##
 ## ---------------------------------- ##
 
+# Contains directories where library files are.
+my @userlibdir = ();
+
 # TRUE if we should always generate Makefile.in.
 my $force_generation = 1;
 
@@ -744,7 +754,8 @@ register_language ('name' => 'c',
 		   'compile_flag' => '-c',
 		   'libtool_tag' => 'CC',
 		   'extensions' => ['.c'],
-		   '_finish' => \&lang_c_finish);
+		   '_finish' => \&lang_c_finish,
+                   'rewrite' => \&lang_c_rewrite);
 
 # C++.
 register_language ('name' => 'cxx',
@@ -809,7 +820,8 @@ register_language ('name' => 'header',
 		   # No output.
 		   'output_extensions' => sub { return () },
 		   # Nothing to do.
-		   '_finish' => sub { });
+		   '_finish' => sub { },
+                   'rewrite' => sub { return LANG_IGNORE; });
 
 # Vala
 register_language ('name' => 'vala',
@@ -1045,7 +1057,8 @@ register_language ('name' => 'java',
 		   'lder' => 'GCJLD',
 		   'ld' => '$(GCJ)',
 		   'pure' => 1,
-		   'extensions' => ['.java', '.class', '.zip', '.jar']);
+		   'extensions' => ['.java', '.class', '.zip', '.jar'],
+                   'rewrite' => sub { return LANG_SUBDIR; });
 
 ################################################################
 
@@ -1858,17 +1871,15 @@ sub handle_single_transform ($$$$$%)
 		  }
 	      }
 
-	    # Note: computed subr call.  The language rewrite function
-	    # should return one of the LANG_* constants.  It could
-	    # also return a list whose first value is such a constant
-	    # and whose second value is a new source extension which
-	    # should be applied.  This means this particular language
-	    # generates another source file which we must then process
-	    # further.
-	    my $subr = \&{'lang_' . $lang->name . '_rewrite'};
-	    my ($r, $source_extension)
-		= &$subr ($directory, $base, $extension,
+	    # The language rewrite function should return one of the
+            # LANG_* constants.
+	    my $r
+		= &{$lang->rewrite} ($directory, $base, $extension,
 			  $nonansi_obj, $have_per_exec_flags, $var);
+
+	    my $output_extension
+	        = (&{$lang->output_extensions} ($extension))[0];
+
 	    # Skip this entry if we were asked not to process it.
 	    next if $r == LANG_IGNORE;
 
@@ -1876,9 +1887,9 @@ sub handle_single_transform ($$$$$%)
 	    $linker = $lang->linker;
 
 	    my $this_obj_ext;
-	    if (defined $source_extension)
+	    if ($output_extension ne '.$(OBJEXT)')
 	    {
-		$this_obj_ext = $source_extension;
+		$this_obj_ext = $output_extension;
 		$derived_source = 1;
 	    }
 	    elsif ($lang->ansi)
@@ -2056,10 +2067,19 @@ sub handle_single_transform ($$$$$%)
 	    $lang->target_hook ($aggregate, $object, $full, %transform);
 	}
 
+	# Transform .o or $o file into .P file (for automatic
+	# dependency code).
+	if ($lang && $lang->autodep ne 'no')
+	{
+	    my $depfile = $object;
+	    $depfile =~ s/\.([^.]*)$/.P$1/;
+	    $depfile =~ s/\$\(OBJEXT\)$/o/;
+	    $dep_files{dirname ($depfile) . '/$(DEPDIR)/'
+			 . basename ($depfile)} = 1;
+	}
+
 	if ($derived_source)
 	  {
-	    prog_error ($lang->name . " has automatic dependency tracking")
-	      if $lang->autodep ne 'no';
 	    # Make sure this new source file is handled next.  That will
 	    # make it appear to be at the right place in the list.
 	    unshift (@files, $object);
@@ -2120,16 +2140,6 @@ sub handle_single_transform ($$$$$%)
 		if scalar @dep_list > 0;
 	}
 
-	# Transform .o or $o file into .P file (for automatic
-	# dependency code).
-	if ($lang && $lang->autodep ne 'no')
-	{
-	    my $depfile = $object;
-	    $depfile =~ s/\.([^.]*)$/.P$1/;
-	    $depfile =~ s/\$\(OBJEXT\)$/o/;
-	    $dep_files{dirname ($depfile) . '/$(DEPDIR)/'
-			 . basename ($depfile)} = 1;
-	}
     }
 
     return @result;
@@ -2555,7 +2565,7 @@ sub handle_compile ()
     }
 
     my ($coms, $vars, $rules) =
-      &file_contents_internal (1, "$libdir/am/compile.am",
+      &file_contents_internal (1, libfile ("am/compile.am"),
 			       new Automake::Location,
 			       ('DEFAULT_INCLUDES' => $default_includes,
 				'MOSTLYRMS' => join ("\n", @mostly_rms),
@@ -5726,16 +5736,9 @@ sub check_gnits_standards
 #
 # Functions to handle files of each language.
 
-# Each `lang_X_rewrite($DIRECTORY, $BASE, $EXT)' function follows a
-# simple formula: Return value is LANG_SUBDIR if the resulting object
-# file should be in a subdir if the source file is, LANG_PROCESS if
-# file is to be dealt with, LANG_IGNORE otherwise.
-
 # Much of the actual processing is handled in
 # handle_single_transform.  These functions exist so that
 # auxiliary information can be recorded for a later cleanup pass.
-# Note that the calls to these functions are computed, so don't bother
-# searching for their precise names in the source.
 
 # This is just a convenience function that can be used to determine
 # when a subdir object should be used.
@@ -5799,128 +5802,6 @@ sub lang_c_rewrite
     return $r;
 }
 
-# Rewrite a single C++ source file.
-sub lang_cxx_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single header file.
-sub lang_header_rewrite
-{
-    # Header files are simply ignored.
-    return LANG_IGNORE;
-}
-
-# Rewrite a single Vala source file.
-sub lang_vala_rewrite
-{
-    my ($directory, $base, $ext) = @_;
-
-    (my $newext = $ext) =~ s/vala$/c/;
-    return (LANG_SUBDIR, $newext);
-}
-
-# Rewrite a single yacc file.
-sub lang_yacc_rewrite
-{
-    my ($directory, $base, $ext) = @_;
-
-    my $r = &lang_sub_obj;
-    (my $newext = $ext) =~ tr/y/c/;
-    return ($r, $newext);
-}
-
-# Rewrite a single yacc++ file.
-sub lang_yaccxx_rewrite
-{
-    my ($directory, $base, $ext) = @_;
-
-    my $r = &lang_sub_obj;
-    (my $newext = $ext) =~ tr/y/c/;
-    return ($r, $newext);
-}
-
-# Rewrite a single lex file.
-sub lang_lex_rewrite
-{
-    my ($directory, $base, $ext) = @_;
-
-    my $r = &lang_sub_obj;
-    (my $newext = $ext) =~ tr/l/c/;
-    return ($r, $newext);
-}
-
-# Rewrite a single lex++ file.
-sub lang_lexxx_rewrite
-{
-    my ($directory, $base, $ext) = @_;
-
-    my $r = &lang_sub_obj;
-    (my $newext = $ext) =~ tr/l/c/;
-    return ($r, $newext);
-}
-
-# Rewrite a single assembly file.
-sub lang_asm_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single preprocessed assembly file.
-sub lang_cppasm_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single Fortran 77 file.
-sub lang_f77_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single Fortran file.
-sub lang_fc_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single preprocessed Fortran file.
-sub lang_ppfc_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single preprocessed Fortran 77 file.
-sub lang_ppf77_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single ratfor file.
-sub lang_ratfor_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single Objective C file.
-sub lang_objc_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single Unified Parallel C file.
-sub lang_upc_rewrite
-{
-    return &lang_sub_obj;
-}
-
-# Rewrite a single Java file.
-sub lang_java_rewrite
-{
-    return LANG_SUBDIR;
-}
-
 # The lang_X_finish functions are called after all source file
 # processing is done.  Each should handle defining rules for the
 # language, etc.  A finish function is only called if a source file of
@@ -6288,6 +6169,8 @@ sub register_language (%)
     unless defined $option{'output_extensions'};
   $option{'nodist_specific'} = 0
     unless defined $option{'nodist_specific'};
+  $option{'rewrite'} = \&lang_sub_obj
+    unless defined $option{'rewrite'};
 
   my $lang = new Language (%option);
 
@@ -6969,7 +6852,7 @@ sub define_standard_variables
 {
   my $saved_output_vars = $output_vars;
   my ($comments, undef, $rules) =
-    file_contents_internal (1, "$libdir/am/header-vars.am",
+    file_contents_internal (1, libfile ("am/header-vars.am"),
 			    new Automake::Location);
 
   foreach my $var (sort keys %configure_vars)
@@ -7187,7 +7070,20 @@ sub make_paragraphs ($%)
   return @res;
 }
 
-
+# libfile ($FILE)
+# ---------------
+# Look for $FILE in the library directories. Returns the first path
+# found. If not found, returns a path from the library directory with
+# highest priority.
+sub libfile ($)
+{
+  my ($f) = @_;
+  foreach (@userlibdir) {
+    return "$_/$f"
+      if -r "$_/$f";
+  }
+  return $userlibdir[0] . "/" . $f;
+}
 
 # ($COMMENT, $VARIABLES, $RULES)
 # &file_contents_internal ($IS_AM, $FILE, $WHERE, [%TRANSFORM])
@@ -7246,7 +7142,7 @@ sub file_contents_internal ($$$%)
 	{
 	    if ($cond != FALSE)
 	      {
-		my $file = ($is_am ? "$libdir/am/" : '') . $1;
+		my $file = ($is_am ? libfile ("am/".$1) : $1);
 		$where->push_context ("`$file' included from here");
 		# N-ary `.=' fails.
 		my ($com, $vars, $rules)
@@ -7391,7 +7287,7 @@ sub file_contents ($$%)
 {
     my ($basename, $where, %transform) = @_;
     my ($comments, $variables, $rules) =
-      file_contents_internal (1, "$libdir/am/$basename.am", $where,
+      file_contents_internal (1, libfile ("am/$basename.am"), $where,
 			      %transform);
     return "$comments$variables$rules";
 }
@@ -7864,7 +7760,7 @@ sub require_file_internal ($$$@)
 	      my $message = "required file `$fullfile' not found";
 	      if ($add_missing)
 		{
-		  if (-f "$libdir/$file")
+		  if (-f libfile ("$file") )
 		    {
 		      $suppress = 1;
 
@@ -7888,14 +7784,14 @@ sub require_file_internal ($$$@)
 		      unlink ($fullfile) if -f $fullfile;
 		      if ($symlink_exists && ! $copy_missing)
 			{
-			  if (! symlink ("$libdir/$file", $fullfile)
+			  if (! symlink (libfile ("$file"), $fullfile)
 			      || ! -e $fullfile)
 			    {
 			      $suppress = 0;
 			      $trailer = "; error while making link: $!";
 			    }
 			}
-		      elsif (system ('cp', "$libdir/$file", $fullfile))
+		      elsif (system ('cp', libfile ("$file"), $fullfile))
 			{
 			  $suppress = 0;
 			  $trailer = "\n    error while copying";
@@ -7923,7 +7819,7 @@ sub require_file_internal ($$$@)
 	      else
 		{
 		  $trailer = "\n  `automake --add-missing' can install `$file'"
-		    if -f "$libdir/$file";
+		    if -f libfile ("$file");
 		}
 
 	      # If --force-missing was specified, and we have
@@ -8458,7 +8354,9 @@ sub parse_arguments ()
   my $cli_where = new Automake::Location;
   my %cli_options =
     (
-     'libdir=s'	=> \$libdir,
+     'libdir=s'	=> sub { push @userlibdir,
+			       (map { ($_ eq '') ? "$libdir" : $_ }
+                                    split (':', $_[1])); },
      'gnu'		=> sub { set_strictness ('gnu'); },
      'gnits'		=> sub { set_strictness ('gnits'); },
      'cygnus'	        => sub { set_global_option ('cygnus', $cli_where); },
@@ -8724,6 +8622,25 @@ sub handle_makefiles_threaded ($)
     }
 }
 
+# load_languages ()
+# -----------------
+# Load Perl files for each .pm files in all libdir/lang.
+sub load_languages
+{
+  foreach (@userlibdir) {
+    my $dir = $_;
+    if (-d "$dir/lang") {
+      opendir(LANG_DIR, "$dir/lang") || next;
+      my @files=readdir(LANG_DIR);
+      foreach (@files) {
+	do "$dir/lang/$_"
+	  if (-r "$dir/lang/$_" && $_ =~ /\.pm$/);
+      }
+      closedir(LANG_DIR);
+    }
+  }
+}
+
 ################################################################
 
 # Parse the WARNINGS environment variable.
@@ -8732,6 +8649,8 @@ parse_WARNINGS;
 # Parse command line.
 parse_arguments;
 
+load_languages;
+
 $configure_ac = require_configure_ac;
 
 # Do configure.ac scan only once.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index d86b03b..23903a0 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -774,6 +774,7 @@ unused.test \
 upc.test \
 upc2.test \
 upc3.test \
+user_def_language.test \
 vala.test \
 vala1.test \
 vala2.test \
diff --git a/tests/Makefile.in b/tests/Makefile.in
index 77ec888..bf22206 100644
--- a/tests/Makefile.in
+++ b/tests/Makefile.in
@@ -985,6 +985,7 @@ unused.test \
 upc.test \
 upc2.test \
 upc3.test \
+user_def_lang.test \
 vala.test \
 vala1.test \
 vala2.test \
diff --git a/tests/user_def_lang.test b/tests/user_def_lang.test
new file mode 100755
index 0000000..9b015da
--- /dev/null
+++ b/tests/user_def_lang.test
@@ -0,0 +1,80 @@
+. ./defs || Exit 1
+
+set -e
+
+cat > configure.in << 'END'
+AC_INIT
+AM_INIT_AUTOMAKE(nonesuch, nonesuch)
+AC_PROG_CC
+AC_SUBST([FOO], "foo")
+AC_OUTPUT(Makefile)
+END
+
+cat > Makefile.am <<'END'
+bin_PROGRAMS = bar
+bar_SOURCES = bar.foo
+END
+
+mkdir -p lib/am
+cat > lib/am/foo.am <<'END'
+?GENERIC?%EXT%%DERIVED-EXT%:
+?!GENERIC?%OBJ%: %SOURCE%
+?GENERIC?	%VERBOSE%%COMPILE% <%SOURCE% >%OBJ%
+?GENERIC?	%SILENT%echo %OBJ%: somefile >%DEPBASE%.Po
+?!GENERIC?	%VERBOSE%%COMPILE% <`test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE% >%OBJ%
+?!GENERIC??SUBDIROBJ?	%SILENT%depbase=`echo %OBJ% | sed 's|[^/]*$$|$(DEPDIR)/&|;s|\.o$$||'`;\
+?!GENERIC??SUBDIROBJ?	echo %OBJ%: somefile >%DEPBASE%.Po
+?!GENERIC??!SUBDIROBJ?	%SILENT%echo %OBJ%: somefile >%DEPBASE%.Po
+END
+
+mkdir -p lib/lang
+cat > lib/lang/foo.pm <<'END'
+register_language (# Short name of the language (c, f77...).
+		   'name' => "foo",
+		   # Nice name of the language (C, Fortran 77...).
+		   'Name' => "Foo",
+		   # List of configure variables which must be defined.
+		   'config_vars' => ['FOO'],
+		   'autodep' => 'FOO',
+
+		   # Name of the compiling variable (COMPILE).
+		   'compiler'  => "FOOCOMPILE",
+		   # Content of the compiling variable.
+		   'compile'  => '$(FOO) $(FOOFLAGS)',
+		   # Flag to require compilation without linking (-c).
+		   'extensions' => ['.foo'],
+		   # A subroutine to compute a list of possible extensions of
+		   # the product given the input extensions.
+		   # (defaults to a subroutine which returns ('.$(OBJEXT)', '.lo'))
+		   'output_extensions' => sub { return ('.c',); },
+		   # A list of flag variables used in 'compile'.
+		   # (defaults to [])
+		   'flags' => ["FOOFLAGS"],
+
+		   # The file to use when generating rules for this language.
+		   # The default is 'depend2'.
+		   'rule_file' => "foo",
+
+		   # Name of the compiler variable (CC).
+		   'ccer' => "FOO",
+
+		   '_finish' => sub {},
+
+		   # This is a subroutine which is called whenever we finally
+		   # determine the context in which a source file will be
+		   # compiled.
+
+		   '_target_hook' => sub {
+		     my ($self, $aggregate, $output, $input, %transform) = @_;
+		     $clean_files{$output} = MAINTAINER_CLEAN;
+		   },
+
+		   # If TRUE, nodist_ sources will be compiled using specific rules
+		   # (i.e. not inference rules).  The default is FALSE.
+		   'nodist_specific' => 1);
+END
+
+$ACLOCAL
+$AUTOMAKE -a --libdir=:`pwd`/lib
+
+grep 'bar.c' Makefile.in