Change the representation of catch contexts.

src/runtime.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 596 matching lines @@
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_GetHandler) {
   ASSERT(args.length() == 1);
   CONVERT_CHECKED(JSProxy, proxy, args[0]);
   return proxy->handler();
 }
 
 
-RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateCatchExtensionObject) {
-  ASSERT(args.length() == 2);
-  CONVERT_CHECKED(String, key, args[0]);
-  Object* value = args[1];
-  ASSERT(!value->IsFailure());
-  // Create a catch context extension object.
-  JSFunction* constructor =
-      isolate->context()->global_context()->
-          context_extension_function();
-  Object* object;
-  { MaybeObject* maybe_object = isolate->heap()->AllocateJSObject(constructor);
-    if (!maybe_object->ToObject(&object)) return maybe_object;
-  }
-  // Assign the exception value to the catch variable and make sure
-  // that the catch variable is DontDelete.
-  { MaybeObject* maybe_value =
-        // Passing non-strict per ECMA-262 5th Ed. 12.14. Catch, bullet #4.
-        JSObject::cast(object)->SetProperty(
-            key, value, DONT_DELETE, kNonStrictMode);
-    if (!maybe_value->ToObject(&value)) return maybe_value;
-  }
-  return object;
-}
-
-
 RUNTIME_FUNCTION(MaybeObject*, Runtime_ClassOf) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);
   Object* obj = args[0];
   if (!obj->IsJSObject()) return isolate->heap()->null_value();
   return JSObject::cast(obj)->class_name();
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_GetPrototype) {
@@ skipping 651 matching lines @@
       }
     }
 
   } else {
     // The property is not in the function context. It needs to be
     // "declared" in the function context's extension context, or in the
     // global context.
     Handle<JSObject> context_ext;
     if (context->has_extension()) {
       // The function context's extension context exists - use it.
-      context_ext = Handle<JSObject>(context->extension());
+      context_ext = Handle<JSObject>(JSObject::cast(context->extension()));
     } else {
       // The function context's extension context does not exists - allocate
       // it.
       context_ext = isolate->factory()->NewJSObject(
           isolate->context_extension_function());
       // And store it in the extension slot.
       context->set_extension(*context_ext);
     }
     ASSERT(*context_ext != NULL);
 
@@ skipping 6611 matching lines @@
       isolate->heap()->AllocateWithContext(isolate->context(),
                                            extension_object);
   if (!maybe_context->To(&context)) return maybe_context;
   isolate->set_context(context);
   return context;
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_PushCatchContext) {
   NoHandleAllocation ha;
-  ASSERT(args.length() == 1);
-  JSObject* extension_object = JSObject::cast(args[0]);
+  ASSERT(args.length() == 2);
+  String* name = String::cast(args[0]);
+  Object* thrown_object = args[1];
   Context* context;
   MaybeObject* maybe_context =
       isolate->heap()->AllocateCatchContext(isolate->context(),
-                                            extension_object);
+                                            name,
+                                            thrown_object);
   if (!maybe_context->To(&context)) return maybe_context;
   isolate->set_context(context);
   return context;
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_DeleteContextSlot) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 2);
 
@@ skipping 2232 matching lines @@
                       NONE,
                       kNonStrictMode),
           Handle<JSObject>());
     }
   }
 
   return closure_scope;
 }
 
 
+// Create a plain JSObject which materializes the scope for the specified
+// catch context.
+static Handle<JSObject> MaterializeCatchScope(Isolate* isolate,
+                                              Handle<Context> context) {
+  ASSERT(context->IsCatchContext());
+  Handle<String> name(String::cast(context->extension()));
+  Handle<Object> thrown_object(context->get(Context::THROWN_OBJECT_INDEX));
+  Handle<JSObject> catch_scope =
+      isolate->factory()->NewJSObject(isolate->object_function());

[Mads Ager (chromium), 2011/06/14 11:54:17]

Do we really want this to be a plain JSObject. Don't we need this to be a
context extension object so we do not start looking up the prototype chain? I
guess this case is handled specifically in contexts.cc so it will be OK?

[Kevin Millikin (Chromium), 2011/06/14 12:06:35]

I'm pretty sure this is what we want.  This is an object that's put on an
indexed property of a "scope details" mirror object used by the debugger.  I'll
run it by Søren.

[Søren Thygesen Gjesse, 2011/06/14 12:18:32]

It looks fine. The objects representing the different scopes are just plain
read-only JSObjects created on demand.

+  RETURN_IF_EMPTY_HANDLE_VALUE(
+      isolate,
+      SetProperty(catch_scope, name, thrown_object, NONE, kNonStrictMode),
+      Handle<JSObject>());
+  return catch_scope;
+}
+
+
 // Iterate over the actual scopes visible from a stack frame. All scopes are
 // backed by an actual context except the local scope, which is inserted
 // "artifically" in the context chain.
 class ScopeIterator {
  public:
   enum ScopeType {
     ScopeTypeGlobal = 0,
     ScopeTypeLocal,
     ScopeTypeWith,
     ScopeTypeClosure,
-    // Every catch block contains an implicit with block (its parameter is
-    // a JSContextExtensionObject) that extends current scope with a variable
-    // holding exception object. Such with blocks are treated as scopes of their
-    // own type.
     ScopeTypeCatch
   };
 
   ScopeIterator(Isolate* isolate, JavaScriptFrame* frame)
     : isolate_(isolate),
       frame_(frame),
       function_(JSFunction::cast(frame->function())),
       context_(Context::cast(frame->context())),
       local_done_(false),
       at_local_(false) {
@@ skipping 57 matching lines @@
       return ScopeTypeLocal;
     }
     if (context_->IsGlobalContext()) {
       ASSERT(context_->global()->IsGlobalObject());
       return ScopeTypeGlobal;
     }
     if (context_->IsFunctionContext()) {
       return ScopeTypeClosure;
     }
     ASSERT(context_->has_extension());
-    // Current scope is either an explicit with statement or a with statement
-    // implicitely generated for a catch block.
-    // If the extension object here is a JSContextExtensionObject then
-    // current with statement is one frome a catch block otherwise it's a
-    // regular with statement.
-    if (context_->extension()->IsJSContextExtensionObject()) {
+    if (context_->IsCatchContext()) {
       return ScopeTypeCatch;
     }
     return ScopeTypeWith;
   }
 
   // Return the JavaScript object with the content of the current scope.
   Handle<JSObject> ScopeObject() {
     switch (Type()) {
       case ScopeIterator::ScopeTypeGlobal:
         return Handle<JSObject>(CurrentContext()->global());
-        break;
       case ScopeIterator::ScopeTypeLocal:
         // Materialize the content of the local scope into a JSObject.
         return MaterializeLocalScope(isolate_, frame_);
-        break;
       case ScopeIterator::ScopeTypeWith:
+        // Return the with object.
+        return Handle<JSObject>(JSObject::cast(CurrentContext()->extension()));
       case ScopeIterator::ScopeTypeCatch:
-        // Return the with object.
-        return Handle<JSObject>(CurrentContext()->extension());
-        break;
+        return MaterializeCatchScope(isolate_, CurrentContext());
       case ScopeIterator::ScopeTypeClosure:
         // Materialize the content of the closure scope into a JSObject.
         return MaterializeClosure(isolate_, CurrentContext());
-        break;
     }
     UNREACHABLE();
     return Handle<JSObject>();
   }
 
   // Return the context for this scope. For the local context there might not
   // be an actual context.
   Handle<Context> CurrentContext() {
     if (at_local_ && context_->closure() != *function_) {
       return Handle<Context>();
@@ skipping 10 matching lines @@
         CurrentContext()->Print();
         break;
 
       case ScopeIterator::ScopeTypeLocal: {
         PrintF("Local:\n");
         ScopeInfo<> scope_info(function_->shared()->scope_info());
         scope_info.Print();
         if (!CurrentContext().is_null()) {
           CurrentContext()->Print();
           if (CurrentContext()->has_extension()) {
-            Handle<JSObject> extension =
-                Handle<JSObject>(CurrentContext()->extension());
+            Handle<Object> extension(CurrentContext()->extension());
             if (extension->IsJSContextExtensionObject()) {
               extension->Print();
             }
           }
         }
         break;
       }
 
-      case ScopeIterator::ScopeTypeWith: {
+      case ScopeIterator::ScopeTypeWith:
         PrintF("With:\n");
-        Handle<JSObject> extension =
-            Handle<JSObject>(CurrentContext()->extension());
-        extension->Print();
+        CurrentContext()->extension()->Print();
         break;
-      }
 
-      case ScopeIterator::ScopeTypeCatch: {
+      case ScopeIterator::ScopeTypeCatch:
         PrintF("Catch:\n");
-        Handle<JSObject> extension =
-            Handle<JSObject>(CurrentContext()->extension());
-        extension->Print();
+        CurrentContext()->extension()->Print();
+        CurrentContext()->get(Context::THROWN_OBJECT_INDEX)->Print();
         break;
-      }
 
-      case ScopeIterator::ScopeTypeClosure: {
+      case ScopeIterator::ScopeTypeClosure:
         PrintF("Closure:\n");
         CurrentContext()->Print();
         if (CurrentContext()->has_extension()) {
-          Handle<JSObject> extension =
-              Handle<JSObject>(CurrentContext()->extension());
+          Handle<Object> extension(CurrentContext()->extension());
           if (extension->IsJSContextExtensionObject()) {
             extension->Print();
           }
         }
         break;
-      }
 
       default:
         UNREACHABLE();
     }
     PrintF("\n");
   }
 #endif
 
  private:
   Isolate* isolate_;
@@ skipping 458 matching lines @@
                                             Handle<Context> base) {
   // At the end of the chain. Return the base context to link to.
   if (current->IsFunctionContext() || current->IsGlobalContext()) {
     return base;
   }
 
   // Recursively copy the with and catch contexts.
   HandleScope scope(isolate);
   Handle<Context> previous(current->previous());
   Handle<Context> new_previous = CopyWithContextChain(isolate, previous, base);
-  Handle<JSObject> extension(JSObject::cast(current->extension()));
-  Handle<Context> new_current = current->IsCatchContext()
-      ? isolate->factory()->NewCatchContext(new_previous, extension)
-      : isolate->factory()->NewWithContext(new_previous, extension);
+  Handle<Context> new_current;
+  if (current->IsCatchContext()) {
+    Handle<String> name(String::cast(current->extension()));
+    Handle<Object> thrown_object(current->get(Context::THROWN_OBJECT_INDEX));
+    new_current =
+        isolate->factory()->NewCatchContext(new_previous, name, thrown_object);
+  } else {
+    Handle<JSObject> extension(JSObject::cast(current->extension()));
+    new_current =
+        isolate->factory()->NewWithContext(new_previous, extension);
+  }
   return scope.CloseAndEscape(new_current);
 }
 
 
 // Helper function to find or create the arguments object for
 // Runtime_DebugEvaluate.
 static Handle<Object> GetArgumentsObject(Isolate* isolate,
                                          JavaScriptFrame* frame,
                                          Handle<JSFunction> function,
                                          Handle<SerializedScopeInfo> scope_info,
@@ skipping 1475 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal