Index: includes/module.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/module.inc,v
retrieving revision 1.68
diff -u -r1.68 module.inc
--- includes/module.inc	29 Jul 2005 07:09:30 -0000	1.68
+++ includes/module.inc	22 Aug 2005 22:37:21 -0000
@@ -162,10 +162,28 @@
   $module = array_shift($args);
   $hook = array_shift($args);
   $function = $module .'_'. $hook;
-  if (module_hook($module, $hook)) {
-    return call_user_func_array($function, $args);
+  $override = FALSE;
+  // Determine if an override function has been defined, and if so execute it.
+  foreach (module_list() as $override_module) {
+    if (module_hook($override_module, $function . '_override')) {
+      $return = call_user_func_array($override_module . '_' . $function . '_override', $args);
+      $override = TRUE;
+      break;
+    }
+  }
+  // If not overridden, execute the requested module hook.
+  if (!$override && module_hook($module, $hook)) {
+    $return = call_user_func_array($function, $args);
+  }
+  // Execute any registered hook extensions.
+  foreach (module_list() as $extension_module) {
+    if (module_hook($extension_module, $function . '_extension')) {
+      call_user_func_array($extension_module . '_' . $function . '_extension', $args);
+    }
   }
+  return $return;
 }
+
 /**
  * Invoke a hook in all enabled modules that implement it.
  *