Avoid duplicate value type creation

We can actually produce an uninitialized but pre-allocated QVariant
using QVariant::Private. Using the new in-place construction support in
QMetaObject, we can minimize the amount of copying necessary for value
types.

Fixes: QTBUG-108789
Change-Id: I6b748794a6adbf6558e1e3086eab80fcfb3154a0
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 8 insertions, 7 deletions

diff --git a/src/qml/qml/qqmlproperty.cpp b/src/qml/qml/qqmlproperty.cpp
index 306f733e21..3c039ba55d 100644
--- a/src/qml/qml/qqmlproperty.cpp
+++ b/src/qml/qml/qqmlproperty.cpp
@@ -1423,14 +1423,15 @@ static ConvertAndAssignResult tryConvertAndAssign(
     }
     }
 
-    QVariant converted(propertyMetaType);
-    if (QQmlValueTypeProvider::createValueType(value, propertyMetaType, converted.data())
-            || QMetaType::convert(value.metaType(), value.constData(),
-                                  propertyMetaType, converted.data()))  {
-        return {true, property.writeProperty(object, converted.data(), flags)};
+    QVariant converted = QQmlValueTypeProvider::createValueType(value, propertyMetaType);
+    if (!converted.isValid()) {
+        converted = QVariant(propertyMetaType);
+        if (!QMetaType::convert(value.metaType(), value.constData(),
+                                propertyMetaType, converted.data()))  {
+            return {false, false};
+        }
     }
-
-    return {false, false};
+    return {true, property.writeProperty(object, converted.data(), flags)};
 };
 
 template<typename Op>