Changeset 153532 in webkit for trunk/Source/JavaScriptCore/runtime/JSCJSValueInlines.h

Timestamp:

Jul 31, 2013, 12:03:05 PM (12 years ago)

Author:

[email protected]

Message:

Some cleanup in JSValue::get
​https://bugs.webkit.org/show_bug.cgi?id=119343

Reviewed by Geoff Garen.

Source/JavaScriptCore:

JSValue::get is implemented to:

1) Check if the value is a cell – if not, synthesize a prototype to search,
2) call getOwnPropertySlot on the cell,
3) if this returns false, cast to JSObject to get the prototype, and walk the prototype chain.

By all rights this should crash when passed a string and accessing a property that does not exist, because
the string is a cell, getOwnPropertySlot should return false, and the cast to JSObject should be unsafe.
To work around this, JSString::getOwnPropertySlot actually implements 'get' functionality - searching the
prototype chain, and faking out a return value of undefined if no property is found.

This is a huge hazard, since fixing JSString::getOwnPropertySlot or calling getOwnPropertySlot on cells
from elsewhere would introduce bugs. Fortunately it is only ever called in this one place.

The fix here is to move getOwnPropertySlot onto JSObjecte and end this madness - cells don't have property
slots anyway.

Interesting changes are in JSCJSValueInlines.h, JSString.cpp - the rest is pretty much all JSCell -> JSObject.

Source/WebCore:

• WebCore.exp.in:
• bindings/js/JSDOMWindowCustom.cpp:

(WebCore::JSDOMWindow::getOwnPropertySlot):
(WebCore::JSDOMWindow::getOwnPropertySlotByIndex):

• bindings/scripts/CodeGeneratorJS.pm:

(GenerateHeader):
(GenerateImplementation):
(GenerateConstructorDeclaration):
(GenerateConstructorHelperMethods):

• bridge/objc/objc_runtime.h:
• bridge/objc/objc_runtime.mm:

(JSC::Bindings::ObjcFallbackObjectImp::getOwnPropertySlot):

• bridge/runtime_array.cpp:

(JSC::RuntimeArray::getOwnPropertySlot):
(JSC::RuntimeArray::getOwnPropertySlotByIndex):

• bridge/runtime_array.h:
• bridge/runtime_method.cpp:

(JSC::RuntimeMethod::getOwnPropertySlot):

• bridge/runtime_method.h:
• bridge/runtime_object.cpp:

(JSC::Bindings::RuntimeObject::getOwnPropertySlot):

• bridge/runtime_object.h:
  • getOwnPropertySlot, JSCell -> JSObject

Source/WebKit2:

• WebProcess/Plugins/Netscape/JSNPObject.cpp:

(WebKit::JSNPObject::getOwnPropertySlot):

• WebProcess/Plugins/Netscape/JSNPObject.h:
  • getOwnPropertySlot, JSCell -> JSObject

File:

• trunk/Source/JavaScriptCore/runtime/JSCJSValueInlines.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/runtime/JSCJSValueInlines.h

@@ -628 +628 @@
 inline JSValue JSValue::get(ExecState* exec, PropertyName propertyName, PropertySlot& slot) const
 {
-    if (UNLIKELY(!isCell())) {
-        JSObject* prototype = synthesizePrototype(exec);
-        if (!prototype->getPropertySlot(exec, propertyName, slot))
-            return jsUndefined();
+    // If this is a primitive, we'll need to synthesize the prototype -
+    // and if it's a string there are special properties to check first.
+    JSObject* object;
+    if (UNLIKELY(!isObject())) {
+        if (isCell() && asString(*this)->getStringPropertySlot(exec, propertyName, slot))
+            return slot.getValue(exec, propertyName);
+        object = synthesizePrototype(exec);
+    } else
+        object = asObject(asCell());
+    
+    if (object->getPropertySlot(exec, propertyName, slot))
         return slot.getValue(exec, propertyName);
-    }
-    JSCell* cell = asCell();
-    while (true) {
-        if (cell->fastGetOwnPropertySlot(exec, propertyName, slot))
-            return slot.getValue(exec, propertyName);
-        JSValue prototype = asObject(cell)->prototype();
-        if (!prototype.isObject())
-            return jsUndefined();
-        cell = asObject(prototype);
-    }
+    return jsUndefined();
 }
 
@@ -653 +651 @@
 inline JSValue JSValue::get(ExecState* exec, unsigned propertyName, PropertySlot& slot) const
 {
-    if (UNLIKELY(!isCell())) {
-        JSObject* prototype = synthesizePrototype(exec);
-        if (!prototype->getPropertySlot(exec, propertyName, slot))
-            return jsUndefined();
+    // If this is a primitive, we'll need to synthesize the prototype -
+    // and if it's a string there are special properties to check first.
+    JSObject* object;
+    if (UNLIKELY(!isObject())) {
+        if (isCell() && asString(*this)->getStringPropertySlot(exec, propertyName, slot))
+            return slot.getValue(exec, propertyName);
+        object = synthesizePrototype(exec);
+    } else
+        object = asObject(asCell());
+    
+    if (object->getPropertySlot(exec, propertyName, slot))
         return slot.getValue(exec, propertyName);
-    }
-    JSCell* cell = const_cast<JSCell*>(asCell());
-    while (true) {
-        if (cell->methodTable()->getOwnPropertySlotByIndex(cell, exec, propertyName, slot))
-            return slot.getValue(exec, propertyName);
-        JSValue prototype = asObject(cell)->prototype();
-        if (!prototype.isObject())
-            return jsUndefined();
-        cell = prototype.asCell();
-    }
+    return jsUndefined();
 }