diff --git a/NEWS b/NEWS

index ef594b4..5a23a3b 100644

--- a/NEWS

+++ b/NEWS

@@ -55,6 +55,13 @@ New in 1.13.1:

     causes a clear and helpful error message, instead of obscure ones

     (issue introduced in Automake 1.13).

+  - Aclocal no longer error out if the first local m4 directory (as

+    specified by the '-I' option or the 'AC_CONFIG_MACRO_DIRS' or

+    'AC_CONFIG_MACRO_DIR' macros) doesn't exist; it merely report a

+    warning in the 'unsupported' category.  This is done to support

+    some pre-existing real-world usages; refer to automake bug#13514

+    for more details.

+

 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 New in 1.13:

diff --git a/THANKS b/THANKS

index 5fa307d..0c143c4 100644

--- a/THANKS

+++ b/THANKS

@@ -295,6 +295,7 @@ Paul Jarc                       prj@po.cwru.edu

 Paul Lunau                      temp@lunau.me.uk

 Paul Martinolich                martinol@datasync.com

 Paul Thomas                     PTHOMAS@novell.com

+Pavel Raiskup                   praiskup@redhat.com

 Pavel Roskin                    pavel_roskin@geocities.com

 Pavel Sanda                     ps@twin.jikos.cz

 Per Bothner                     bothner@cygnus.com

diff --git a/aclocal.in b/aclocal.in

index b51c09d..d68ea33 100644

--- a/aclocal.in

+++ b/aclocal.in

@@ -165,6 +165,11 @@ my @ac_config_macro_dirs;

 # If set, names a temporary file that must be erased on abnormal exit.

 my $erase_me;

+# Constants for the $ERR_LEVEL parameter of the 'scan_m4_dirs' function.

+use constant SCAN_M4_DIRS_SILENT => 0;

+use constant SCAN_M4_DIRS_WARN => 1;

+use constant SCAN_M4_DIRS_ERROR => 2;

+

 ################################################################

 # Prototypes for all subroutines.

@@ -355,21 +360,42 @@ sub list_compare (\@\@)

 ################################################################

-# scan_m4_dirs($TYPE, $ERR_ON_NONEXISTING, @DIRS)

+# scan_m4_dirs($TYPE, $ERR_LEVEL, @DIRS)

 # -----------------------------------------------

 # Scan all M4 files installed in @DIRS for new macro definitions.

 # Register each file as of type $TYPE (one of the FT_* constants).

+# If a directory in @DIRS cannot be read:

+#  - fail hard                if $ERR_LEVEL == SCAN_M4_DIRS_ERROR

+#  - just print a warning     if $ERR_LEVEL == SCAN_M4_DIRS_WA

+#  - continue silently        if $ERR_LEVEL == SCAN_M4_DIRS_SILENT

 sub scan_m4_dirs ($$@)

 {

-  my ($type, $err_on_nonexisting, @dirlist) = @_;

+  my ($type, $err_level, @dirlist) = @_;

   foreach my $m4dir (@dirlist)

     {

       if (! opendir (DIR, $m4dir))

 	{

 	  # TODO: maybe avoid complaining only if errno == ENONENT?

-	  next unless $err_on_nonexisting;

-	  fatal "couldn't open directory '$m4dir': $!";

+          my $message = "couldn't open directory '$m4dir': $!";

+

+          if ($err_level == SCAN_M4_DIRS_ERROR)

+            {

+              fatal $message;

+            }

+          elsif ($err_level == SCAN_M4_DIRS_WARN)

+            {

+              msg ('unsupported', $message);

+              next;

+            }

+          elsif ($err_level == SCAN_M4_DIRS_SILENT)

+            {

+              next; # Silently ignore.

+            }

+          else

+            {

+               prog_error "invalid \$err_level value '$err_level'";

+            }

 	}

       # We reverse the directory contents so that foo2.m4 gets

@@ -406,13 +432,27 @@ sub scan_m4_files ()

   if (@user_includes)

     {

+      # Don't explore the same directory multiple times.  This is here not

+      # only for speedup purposes.  We need this when the user has e.g.

+      # specified 'ACLOCAL_AMFLAGS = -I m4' and has also set

+      # AC_CONFIG_MACRO_DIR[S]([m4]) in configure.ac.  This makes the 'm4'

+      # directory to occur twice here and fail on the second call to

+      # scan_m4_dirs([m4]) when the 'm4' directory doesn't exist.

+      # TODO: Shouldn't there be rather a check in scan_m4_dirs for

+      #       @user_includes[0]?

+      @user_includes = uniq @user_includes;

+

       # Don't complain if the first user directory doesn't exist, in case

       # we need to create it later (can happen if '--install' was given).

-      scan_m4_dirs (FT_USER, !$install, $user_includes[0]);

-      scan_m4_dirs (FT_USER, 1, @user_includes[1..$#user_includes]);

+      scan_m4_dirs (FT_USER,

+                    $install ? SCAN_M4_DIRS_SILENT : SCAN_M4_DIRS_WARN,

+                    $user_includes[0]);

+      scan_m4_dirs (FT_USER,

+                    SCAN_M4_DIRS_ERROR,

+		    @user_includes[1..$#user_includes]);

     }

-  scan_m4_dirs (FT_AUTOMAKE, 1, @automake_includes);

-  scan_m4_dirs (FT_SYSTEM,   1, @system_includes);

+  scan_m4_dirs (FT_AUTOMAKE, SCAN_M4_DIRS_ERROR, @automake_includes);

+  scan_m4_dirs (FT_SYSTEM, SCAN_M4_DIRS_ERROR, @system_includes);

   # Construct a new function that does the searching.  We use a

   # function (instead of just evaluating $search in the loop) so that

diff --git a/t/aclocal-macrodir.tap b/t/aclocal-macrodir.tap

index 3c66e53..051fdb5 100755

--- a/t/aclocal-macrodir.tap

+++ b/t/aclocal-macrodir.tap

@@ -20,7 +20,7 @@

 am_create_testdir=empty

 . test-init.sh

-plan_ 6

+plan_ 7

 ocwd=$(pwd) || fatal_ "getting current working directory"

 ACLOCAL_PATH=; unset ACLOCAL_PATH

@@ -157,16 +157,44 @@ test_end

 #---------------------------------------------------------------------------

-test_begin "AC_CONFIG_MACRO_DIR([non-existent]) errors out (1)"

+test_begin "AC_CONFIG_MACRO_DIR([non-existent]) warns with -Wunsupported"

 cat > configure.ac << 'END'

 AC_INIT([oops], [1.0])

 AC_CONFIG_MACRO_DIR([non-existent])

+AM_INIT_AUTOMAKE

 END

-not $ACLOCAL -Wnone 2>stderr \

+$ACLOCAL -Wno-error 2>stderr \

   && cat stderr >&2 \

   && grep "couldn't open directory 'non-existent'" stderr \

+  && test -f aclocal.m4 \

+  || r='not ok'

+

+rm -rf aclocal.m4 autom4te*.cache

+

+$ACLOCAL -Werror -Wno-unsupported \

+  && test -f aclocal.m4 \

+  || r='not ok'

+

+test_end

+

+#---------------------------------------------------------------------------

+

+test_begin "AC_CONFIG_MACRO_DIR([not-exist]) and ACLOCAL_AMFLAGS = -I not-exist"

+

+cat > configure.ac << 'END'

+AC_INIT([oops], [1.0])

+AC_CONFIG_MACRO_DIR([not-exist])

+END

+

+cat > Makefile.am << 'END'

+ACLOCAL_AMFLAGS = -I not-exist

+END

+

+$ACLOCAL -Wno-error 2>stderr \

+  && cat stderr >&2 \

+  && test $(grep -c "couldn't open directory 'not-exist'" stderr) -eq 1 \

   || r='not ok'

 test_end

diff --git a/t/aclocal-macrodirs.tap b/t/aclocal-macrodirs.tap

index 89e424d..0deae72 100755

--- a/t/aclocal-macrodirs.tap

+++ b/t/aclocal-macrodirs.tap

@@ -20,7 +20,7 @@

 am_create_testdir=empty

 . test-init.sh

-plan_ 14

+plan_ 15

 ocwd=$(pwd) || fatal_ "getting current working directory"

 ACLOCAL_PATH=; unset ACLOCAL_PATH

@@ -317,23 +317,31 @@ test_end

 #---------------------------------------------------------------------------

-test_begin "AC_CONFIG_MACRO_DIRS([non-existent]) errors out (1)"

+test_begin "AC_CONFIG_MACRO_DIRS([non-existent]) warns (1)"

 cat > configure.ac << 'END'

 AC_INIT([oops], [1.0])

 AC_CONFIG_MACRO_DIRS([non-existent])

+AM_INIT_AUTOMAKE

 END

-not $ACLOCAL 2>stderr \

+$ACLOCAL -Wno-error 2>stderr \

   && cat stderr >&2 \

   && grep "couldn't open directory 'non-existent'" stderr \

+  && test -f aclocal.m4 \

+  || r='not ok'

+

+rm -rf aclocal.m4 autom4te*.cache

+

+$ACLOCAL -Werror -Wno-unsupported \

+  && test -f aclocal.m4 \

   || r='not ok'

 test_end

 #---------------------------------------------------------------------------

-test_begin "AC_CONFIG_MACRO_DIRS([non-existent]) errors out (2)"

+test_begin "AC_CONFIG_MACRO_DIRS([non-existent]) warns (2)"

 cat > configure.ac << 'END'

 AC_INIT([oops], [1.0])

@@ -346,13 +354,14 @@ not $ACLOCAL 2>stderr \

   && cat stderr >&2 \

   && grep "couldn't open directory 'dir-ko'" stderr \

   && not grep "dir-ok" stderr \

+  && test ! -e aclocal.m4 \

   || r='not ok'

 test_end

 #---------------------------------------------------------------------------

-test_begin "AC_CONFIG_MACRO_DIRS([non-existent]) errors out (tricky setup)"

+test_begin "AC_CONFIG_MACRO_DIRS([existent non-existent]) errors out"

 cat > configure.ac << 'END'

 AC_INIT([oops], [1.0])

@@ -372,6 +381,26 @@ test_end

 #---------------------------------------------------------------------------

+test_begin "AC_CONFIG_MACRO_DIRS([not-exist]) and ACLOCAL_AMFLAGS = -I not-exist"

+

+cat > configure.ac << 'END'

+AC_INIT([oops], [1.0])

+AC_CONFIG_MACRO_DIRS([not-exist])

+END

+

+cat > Makefile.am << 'END'

+ACLOCAL_AMFLAGS = -I not-exist

+END

+

+$ACLOCAL -Wno-error 2>stderr \

+  && cat stderr >&2 \

+  && test $(grep -c "couldn't open directory 'not-exist'" stderr) -eq 1 \

+  || r='not ok'

+

+test_end

+

+#---------------------------------------------------------------------------

+

 # Avoid spurious failures with pre-2.70 autoconf.

 # FIXME: remove this in automake 1.14, once we require Autoconf 2.70.

 if echo 'AC_INIT AC_CONFIG_MACRO_DIRS' | $AUTOCONF -o/dev/null -; then