QML: Make Heap::Object and all subclasses trivial

GCC6 might dead-store-eliminate out our secret write to Base::mmdata,
because it expects all memory content to be "undefined" before
constructor calls. Clang might take the same approach if the constructor
of Heap::Object is removed.

By making these structs trivial, it also makes them memcpy-able.

Change-Id: I055b2ad28311b997fbe059849ebda4d5894eaa9b
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/qml/jsruntime/qv4variantobject.cpp b/src/qml/jsruntime/qv4variantobject.cpp
index eff4db268c..b26dd27913 100644
--- a/src/qml/jsruntime/qv4variantobject.cpp
+++ b/src/qml/jsruntime/qv4variantobject.cpp
@@ -50,13 +50,15 @@ using namespace QV4;
 
 DEFINE_OBJECT_VTABLE(VariantObject);
 
-Heap::VariantObject::VariantObject()
+void Heap::VariantObject::init()
 {
+    Object::init();
     scarceData = new ExecutionEngine::ScarceResourceData;
 }
 
-Heap::VariantObject::VariantObject(const QVariant &value)
+void Heap::VariantObject::init(const QVariant &value)
 {
+    Object::init();
     scarceData = new ExecutionEngine::ScarceResourceData(value);
     if (isScarce())
         removeVmePropertyReference();