During a GC mark the scope chain of QScriptContexts

It appears that simply being in the scope chain of an existant frame
isn't sufficient to be marked.  This can lead to a QScriptContext
scope chain that contains a JSObject that has been collected.

For example, this code:

QScriptContext *ctxt = engine->pushContext();
ctxt.pushScope(engine->newObject());
previouslyCreatedFunctionObject.call(); // causes a GC

can lead to the object added to the scope chain to have become
invalid.  This leads to hilarity later on.

Reviewed-by: Kent Hansen

1 files changed, 18 insertions, 0 deletions

diff --git a/src/script/api/qscriptengine.cpp b/src/script/api/qscriptengine.cpp
index 2b60a46..f41b4e2 100644
--- a/src/script/api/qscriptengine.cpp
+++ b/src/script/api/qscriptengine.cpp
@@ -1093,6 +1093,8 @@ void QScriptEnginePrivate::setContextFlags(JSC::ExecState *exec, uint flags)
 
 void QScriptEnginePrivate::mark(JSC::MarkStack& markStack)
 {
+    Q_Q(QScriptEngine);
+
     markStack.append(originalGlobalObject());
     markStack.append(globalObject());
     if (originalGlobalObjectProxy)
@@ -1130,6 +1132,22 @@ void QScriptEnginePrivate::mark(JSC::MarkStack& markStack)
                 markStack.append((*it)->prototype);
         }
     }
+
+    {
+        QScriptContext *context = q->currentContext();
+
+        while (context) {
+            JSC::ScopeChainNode *node = frameForContext(context)->scopeChain();
+            JSC::ScopeChainIterator it(node);
+            for (it = node->begin(); it != node->end(); ++it) {
+                JSC::JSObject *object = *it;
+                if (object)
+                    markStack.append(object);
+            }
+
+            context = context->parentContext();
+        }
+    }
 }
 
 bool QScriptEnginePrivate::isCollecting() const