diff --git a/config/config.mk b/config/config.mk
index a830bfe969b..516b1c1790e 100644
--- a/config/config.mk
+++ b/config/config.mk
@@ -783,7 +783,7 @@ OPTIMIZE_JARS_CMD = $(PYTHON) $(call core_abspath,$(topsrcdir)/config/optimizeja
 
 CREATE_PRECOMPLETE_CMD = $(PYTHON) $(call core_abspath,$(topsrcdir)/config/createprecomplete.py)
 
-EXPAND_LIBS = $(PYTHON) -I$(DEPTH)/config $(topsrcdir)/config/expandlibs.py
+EXPAND_LIBS_DEPS = $(PYTHON) $(topsrcdir)/config/pythonpath.py -I$(DEPTH)/config $(topsrcdir)/config/expandlibs_deps.py
 EXPAND_LIBS_EXEC = $(PYTHON) $(topsrcdir)/config/pythonpath.py -I$(DEPTH)/config $(topsrcdir)/config/expandlibs_exec.py
 EXPAND_LIBS_GEN = $(PYTHON) $(topsrcdir)/config/pythonpath.py -I$(DEPTH)/config $(topsrcdir)/config/expandlibs_gen.py
 EXPAND_AR = $(EXPAND_LIBS_EXEC) --extract -- $(AR)
diff --git a/config/expandlibs_deps.py b/config/expandlibs_deps.py
new file mode 100644
index 00000000000..022b6e23524
--- /dev/null
+++ b/config/expandlibs_deps.py
@@ -0,0 +1,83 @@
+# ***** BEGIN LICENSE BLOCK *****
+# Version: MPL 1.1/GPL 2.0/LGPL 2.1
+#
+# The contents of this file are subject to the Mozilla Public License Version
+# 1.1 (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+# http://www.mozilla.org/MPL/
+#
+# Software distributed under the License is distributed on an "AS IS" basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+# for the specific language governing rights and limitations under the
+# License.
+#
+# The Original Code is a build helper for libraries
+#
+# The Initial Developer of the Original Code is
+# the Mozilla Foundation
+# Portions created by the Initial Developer are Copyright (C) 2011
+# the Initial Developer. All Rights Reserved.
+#
+# Contributor(s):
+# Mike Hommey <mh@glandium.org>
+#
+# Alternatively, the contents of this file may be used under the terms of
+# either the GNU General Public License Version 2 or later (the "GPL"), or
+# the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+# in which case the provisions of the GPL or the LGPL are applicable instead
+# of those above. If you wish to allow use of your version of this file only
+# under the terms of either the GPL or the LGPL, and not to allow others to
+# use your version of this file under the terms of the MPL, indicate your
+# decision by deleting the provisions above and replace them with the notice
+# and other provisions required by the GPL or the LGPL. If you do not delete
+# the provisions above, a recipient may use your version of this file under
+# the terms of any one of the MPL, the GPL or the LGPL.
+#
+# ***** END LICENSE BLOCK *****
+
+'''expandlibs_deps.py takes a list of key/value pairs and prints, for each
+key, a list of all dependencies corresponding to the corresponding value.
+Libraries are thus expanded, and their descriptor is also made part of this
+list.
+The list of key/value is passed on the command line in the form
+"var1 = value , var2 = value ..."
+'''
+import sys
+import os
+from expandlibs import ExpandArgs, relativize
+import expandlibs_config as conf
+
+class ExpandLibsDeps(ExpandArgs):
+    def _expand_desc(self, arg):
+        objs = super(ExpandLibsDeps, self)._expand_desc(arg)
+        if os.path.exists(arg + conf.LIBS_DESC_SUFFIX):
+            objs += [relativize(arg + conf.LIBS_DESC_SUFFIX)]
+        return objs
+
+def split_args(args):
+    '''Transforms a list in the form
+    ['var1', '=', 'value', ',', 'var2', '=', 'other', 'value', ',' ...]
+    into a corresponding dict 
+    { 'var1': ['value'],
+      'var2': ['other', 'value'], ... }'''
+
+    result = {}
+    while args:
+        try:
+            i = args.index(',')
+            l = args[:i]
+            args[:i + 1] = []
+        except:
+            l = args
+            args = []
+        if l[1] != '=':
+            raise RuntimeError('Expected "var = value" format')
+        result[l[0]] = l[2:]
+    return result
+
+if __name__ == '__main__':
+    for key, value in split_args(sys.argv[1:]).iteritems():
+        expanded = ExpandLibsDeps(value)
+        if os.sep == '\\':
+            expanded = [o.replace(os.sep, '/') for o in expanded]
+        print "%s = %s" % (key, " ".join(expanded))
diff --git a/config/rules.mk b/config/rules.mk
index e6353e18f9c..254f2aa474e 100644
--- a/config/rules.mk
+++ b/config/rules.mk
@@ -778,11 +778,23 @@ $(error SHARED_LIBRARY_LIBS must contain .$(LIB_SUFFIX) files only)
 endif
 
 # Create dependencies on static (and shared EXTRA_DSO_LIBS) libraries
-DO_EXPAND_LIBS = $(foreach f,$(1),$(if $(filter %.$(LIB_SUFFIX),$(f)),$(if $(wildcard $(f).$(LIBS_DESC_SUFFIX)),$(f).$(LIBS_DESC_SUFFIX),$(if $(wildcard $(f)),$(f)))))
-LIBS_DEPS = $(call DO_EXPAND_LIBS,$(filter %.$(LIB_SUFFIX),$(LIBS) $(if $(PROGRAM)$(SIMPLE_PROGRAMS),$(MOZ_GLUE_PROGRAM_LDFLAGS))))
-SHARED_LIBRARY_LIBS_DEPS = $(call DO_EXPAND_LIBS,$(SHARED_LIBRARY_LIBS))
+ifneq (,$(strip $(filter %.$(LIB_SUFFIX),$(LIBS) $(EXTRA_DSO_LDOPTS)) $(SHARED_LIBRARY_LIBS) $(EXTRA_DSO_LIBS)))
+$(MDDEPDIR)/libs: Makefile.in
+	@mkdir -p $(MDDEPDIR)
+	@$(EXPAND_LIBS_DEPS) LIBS_DEPS = $(filter %.$(LIB_SUFFIX),$(LIBS)) , \
+	                     SHARED_LIBRARY_LIBS_DEPS = $(SHARED_LIBRARY_LIBS) , \
+	                     DSO_LDOPTS_DEPS = $(EXTRA_DSO_LIBS) $(filter %.$(LIB_SUFFIX), $(EXTRA_DSO_LDOPTS)) > $@
+
+ifneq (,$(wildcard $(MDDEPDIR)/libs))
+include $(MDDEPDIR)/libs
+endif
+
+$(MDDEPDIR)/libs: $(wildcard $(filter %.$(LIBS_DESC_SUFFIX),$(LIBS_DEPS) $(SHARED_LIBRARY_LIBS_DEPS) $(DSO_LDOPTS_DEPS)))
+
+EXTRA_DEPS += $(MDDEPDIR)/libs
+endif
+
 HOST_LIBS_DEPS = $(filter %.$(LIB_SUFFIX),$(HOST_LIBS))
-DSO_LDOPTS_DEPS = $(call DO_EXPAND_LIBS,$(EXTRA_DSO_LIBS) $(filter %.$(LIB_SUFFIX), $(EXTRA_DSO_LDOPTS)))
 
 # Dependencies which, if modified, should cause everything to rebuild
 GLOBAL_DEPS += Makefile Makefile.in $(DEPTH)/config/autoconf.mk $(topsrcdir)/config/config.mk
diff --git a/config/tests/unit-expandlibs.py b/config/tests/unit-expandlibs.py
index 491c95448b1..20c08eadab8 100644
--- a/config/tests/unit-expandlibs.py
+++ b/config/tests/unit-expandlibs.py
@@ -37,6 +37,7 @@ config_unix = {
 config = sys.modules['expandlibs_config'] = imp.new_module('expandlibs_config')
 
 from expandlibs import LibDescriptor, ExpandArgs, relativize
+from expandlibs_deps import ExpandLibsDeps, split_args
 from expandlibs_gen import generate
 from expandlibs_exec import ExpandArgsMore, SectionFinder
 
@@ -191,6 +192,30 @@ class TestExpandArgs(TestExpandInit):
         args = ExpandArgs(['foo', '-bar'] + self.arg_files + [self.tmpfile('liby', Lib('y'))])
         self.assertRelEqual(args, ['foo', '-bar'] + self.files + [self.tmpfile('liby', Lib('y'))])
 
+class TestExpandLibsDeps(TestExpandInit):
+    def test_expandlibsdeps(self):
+        '''Test library expansion for dependencies'''
+        # Dependency list for a library with a descriptor is equivalent to
+        # the arguments expansion, to which we add each descriptor
+        args = self.arg_files + [self.tmpfile('liby', Lib('y'))]
+        self.assertRelEqual(ExpandLibsDeps(args), ExpandArgs(args) + [self.tmpfile('libx', Lib('x') + config.LIBS_DESC_SUFFIX), self.tmpfile('liby', Lib('y') + config.LIBS_DESC_SUFFIX)])
+
+        # When a library exists at the same time as a descriptor, the
+        # descriptor is not a dependency
+        self.touch([self.tmpfile('libx', Lib('x'))])
+        args = self.arg_files + [self.tmpfile('liby', Lib('y'))]
+        self.assertRelEqual(ExpandLibsDeps(args), ExpandArgs(args) + [self.tmpfile('liby', Lib('y') + config.LIBS_DESC_SUFFIX)])
+
+        self.touch([self.tmpfile('liby', Lib('y'))])
+        args = self.arg_files + [self.tmpfile('liby', Lib('y'))]
+        self.assertRelEqual(ExpandLibsDeps(args), ExpandArgs(args))
+
+class TestSplitArgs(unittest.TestCase):
+    def test_split_args(self):
+        self.assertEqual(split_args(['a', '=', 'b', 'c']), {'a': ['b', 'c']})
+        self.assertEqual(split_args(['a', '=', 'b', 'c', ',', 'd', '=', 'e', 'f', 'g', ',', 'h', '=', 'i']),
+                         {'a': ['b', 'c'], 'd': ['e', 'f', 'g'], 'h': ['i']})
+
 class TestExpandArgsMore(TestExpandInit):
     def test_makelist(self):
         '''Test grouping object files in lists'''
diff --git a/js/src/config/config.mk b/js/src/config/config.mk
index a830bfe969b..516b1c1790e 100644
--- a/js/src/config/config.mk
+++ b/js/src/config/config.mk
@@ -783,7 +783,7 @@ OPTIMIZE_JARS_CMD = $(PYTHON) $(call core_abspath,$(topsrcdir)/config/optimizeja
 
 CREATE_PRECOMPLETE_CMD = $(PYTHON) $(call core_abspath,$(topsrcdir)/config/createprecomplete.py)
 
-EXPAND_LIBS = $(PYTHON) -I$(DEPTH)/config $(topsrcdir)/config/expandlibs.py
+EXPAND_LIBS_DEPS = $(PYTHON) $(topsrcdir)/config/pythonpath.py -I$(DEPTH)/config $(topsrcdir)/config/expandlibs_deps.py
 EXPAND_LIBS_EXEC = $(PYTHON) $(topsrcdir)/config/pythonpath.py -I$(DEPTH)/config $(topsrcdir)/config/expandlibs_exec.py
 EXPAND_LIBS_GEN = $(PYTHON) $(topsrcdir)/config/pythonpath.py -I$(DEPTH)/config $(topsrcdir)/config/expandlibs_gen.py
 EXPAND_AR = $(EXPAND_LIBS_EXEC) --extract -- $(AR)
diff --git a/js/src/config/expandlibs_deps.py b/js/src/config/expandlibs_deps.py
new file mode 100644
index 00000000000..022b6e23524
--- /dev/null
+++ b/js/src/config/expandlibs_deps.py
@@ -0,0 +1,83 @@
+# ***** BEGIN LICENSE BLOCK *****
+# Version: MPL 1.1/GPL 2.0/LGPL 2.1
+#
+# The contents of this file are subject to the Mozilla Public License Version
+# 1.1 (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+# http://www.mozilla.org/MPL/
+#
+# Software distributed under the License is distributed on an "AS IS" basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+# for the specific language governing rights and limitations under the
+# License.
+#
+# The Original Code is a build helper for libraries
+#
+# The Initial Developer of the Original Code is
+# the Mozilla Foundation
+# Portions created by the Initial Developer are Copyright (C) 2011
+# the Initial Developer. All Rights Reserved.
+#
+# Contributor(s):
+# Mike Hommey <mh@glandium.org>
+#
+# Alternatively, the contents of this file may be used under the terms of
+# either the GNU General Public License Version 2 or later (the "GPL"), or
+# the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+# in which case the provisions of the GPL or the LGPL are applicable instead
+# of those above. If you wish to allow use of your version of this file only
+# under the terms of either the GPL or the LGPL, and not to allow others to
+# use your version of this file under the terms of the MPL, indicate your
+# decision by deleting the provisions above and replace them with the notice
+# and other provisions required by the GPL or the LGPL. If you do not delete
+# the provisions above, a recipient may use your version of this file under
+# the terms of any one of the MPL, the GPL or the LGPL.
+#
+# ***** END LICENSE BLOCK *****
+
+'''expandlibs_deps.py takes a list of key/value pairs and prints, for each
+key, a list of all dependencies corresponding to the corresponding value.
+Libraries are thus expanded, and their descriptor is also made part of this
+list.
+The list of key/value is passed on the command line in the form
+"var1 = value , var2 = value ..."
+'''
+import sys
+import os
+from expandlibs import ExpandArgs, relativize
+import expandlibs_config as conf
+
+class ExpandLibsDeps(ExpandArgs):
+    def _expand_desc(self, arg):
+        objs = super(ExpandLibsDeps, self)._expand_desc(arg)
+        if os.path.exists(arg + conf.LIBS_DESC_SUFFIX):
+            objs += [relativize(arg + conf.LIBS_DESC_SUFFIX)]
+        return objs
+
+def split_args(args):
+    '''Transforms a list in the form
+    ['var1', '=', 'value', ',', 'var2', '=', 'other', 'value', ',' ...]
+    into a corresponding dict 
+    { 'var1': ['value'],
+      'var2': ['other', 'value'], ... }'''
+
+    result = {}
+    while args:
+        try:
+            i = args.index(',')
+            l = args[:i]
+            args[:i + 1] = []
+        except:
+            l = args
+            args = []
+        if l[1] != '=':
+            raise RuntimeError('Expected "var = value" format')
+        result[l[0]] = l[2:]
+    return result
+
+if __name__ == '__main__':
+    for key, value in split_args(sys.argv[1:]).iteritems():
+        expanded = ExpandLibsDeps(value)
+        if os.sep == '\\':
+            expanded = [o.replace(os.sep, '/') for o in expanded]
+        print "%s = %s" % (key, " ".join(expanded))
diff --git a/js/src/config/rules.mk b/js/src/config/rules.mk
index e6353e18f9c..254f2aa474e 100644
--- a/js/src/config/rules.mk
+++ b/js/src/config/rules.mk
@@ -778,11 +778,23 @@ $(error SHARED_LIBRARY_LIBS must contain .$(LIB_SUFFIX) files only)
 endif
 
 # Create dependencies on static (and shared EXTRA_DSO_LIBS) libraries
-DO_EXPAND_LIBS = $(foreach f,$(1),$(if $(filter %.$(LIB_SUFFIX),$(f)),$(if $(wildcard $(f).$(LIBS_DESC_SUFFIX)),$(f).$(LIBS_DESC_SUFFIX),$(if $(wildcard $(f)),$(f)))))
-LIBS_DEPS = $(call DO_EXPAND_LIBS,$(filter %.$(LIB_SUFFIX),$(LIBS) $(if $(PROGRAM)$(SIMPLE_PROGRAMS),$(MOZ_GLUE_PROGRAM_LDFLAGS))))
-SHARED_LIBRARY_LIBS_DEPS = $(call DO_EXPAND_LIBS,$(SHARED_LIBRARY_LIBS))
+ifneq (,$(strip $(filter %.$(LIB_SUFFIX),$(LIBS) $(EXTRA_DSO_LDOPTS)) $(SHARED_LIBRARY_LIBS) $(EXTRA_DSO_LIBS)))
+$(MDDEPDIR)/libs: Makefile.in
+	@mkdir -p $(MDDEPDIR)
+	@$(EXPAND_LIBS_DEPS) LIBS_DEPS = $(filter %.$(LIB_SUFFIX),$(LIBS)) , \
+	                     SHARED_LIBRARY_LIBS_DEPS = $(SHARED_LIBRARY_LIBS) , \
+	                     DSO_LDOPTS_DEPS = $(EXTRA_DSO_LIBS) $(filter %.$(LIB_SUFFIX), $(EXTRA_DSO_LDOPTS)) > $@
+
+ifneq (,$(wildcard $(MDDEPDIR)/libs))
+include $(MDDEPDIR)/libs
+endif
+
+$(MDDEPDIR)/libs: $(wildcard $(filter %.$(LIBS_DESC_SUFFIX),$(LIBS_DEPS) $(SHARED_LIBRARY_LIBS_DEPS) $(DSO_LDOPTS_DEPS)))
+
+EXTRA_DEPS += $(MDDEPDIR)/libs
+endif
+
 HOST_LIBS_DEPS = $(filter %.$(LIB_SUFFIX),$(HOST_LIBS))
-DSO_LDOPTS_DEPS = $(call DO_EXPAND_LIBS,$(EXTRA_DSO_LIBS) $(filter %.$(LIB_SUFFIX), $(EXTRA_DSO_LDOPTS)))
 
 # Dependencies which, if modified, should cause everything to rebuild
 GLOBAL_DEPS += Makefile Makefile.in $(DEPTH)/config/autoconf.mk $(topsrcdir)/config/config.mk