diff -r 000000000000 -r 6474c204b198 js/src/gdb/mozilla/JSObject.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/gdb/mozilla/JSObject.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+# Pretty-printers for SpiderMonkey JSObjects.
+
+import gdb
+import mozilla.JSString
+import mozilla.prettyprinters as prettyprinters
+from mozilla.prettyprinters import ptr_pretty_printer, ref_pretty_printer
+from mozilla.Root import deref
+
+prettyprinters.clear_module_printers(__name__)
+
+class JSObjectTypeCache(object):
+    def __init__(self, value, cache):
+        # In GDB 7.4.50, with some programs, this first dummy gdb.lookup_type
+        # call is required to make the second lookup_type call succeed. A GDB
+        # built from the public sources as of 2012-12-12 did not require the
+        # dummy lookup.
+        gdb.lookup_type('js::BaseShape')
+        baseshape_flags = gdb.lookup_type('js::BaseShape::Flag')
+        self.flag_DELEGATE = prettyprinters.enum_value(baseshape_flags, 'js::BaseShape::DELEGATE')
+        self.func_ptr_type = gdb.lookup_type('JSFunction').pointer()
+
+# There should be no need to register this for JSFunction as well, since we
+# search for pretty-printers under the names of base classes, and
+# JSFunction has JSObject as a base class.
+
+@ptr_pretty_printer('JSObject')
+class JSObjectPtrOrRef(prettyprinters.Pointer):
+    def __init__(self, value, cache):
+        super(JSObjectPtrOrRef, self).__init__(value, cache)
+        if not cache.mod_JSObject:
+            cache.mod_JSObject = JSObjectTypeCache(value, cache)
+        self.otc = cache.mod_JSObject
+
+    def summary(self):
+        shape = deref(self.value['shape_'])
+        baseshape = deref(shape['base_'])
+        otype = deref(self.value['type_'])
+        class_name = otype['clasp_']['name'].string()
+        flags = baseshape['flags']
+        is_delegate = bool(flags & self.otc.flag_DELEGATE)
+        name = None
+        if class_name == 'Function':
+            function = self.value
+            concrete_type = function.type.strip_typedefs()
+            if concrete_type.code == gdb.TYPE_CODE_REF:
+                function = function.address
+            function = function.cast(self.otc.func_ptr_type)
+            atom = deref(function['atom_'])
+            name = str(atom) if atom else '<unnamed>'
+        return '[object %s%s]%s' % (class_name,
+                                    ' ' + name if name else '',
+                                    ' delegate' if is_delegate else '')
+
+@ref_pretty_printer('JSObject')
+def JSObjectRef(value, cache): return JSObjectPtrOrRef(value, cache)