QmlProfiler: Reduce memory usage for file names and URLs

As the various file names are actually not kept as QStrings in the
respective objects being profiled, our saving them as QStrings in each
and every profiling event is not implicitly shared and causes a huge
memory overhead. Avoid that by saving each location only once, indexed
by a disguised pointer to the object it refers to.

Normally, objects could disappear during the profiling session, and new
objects could be allocated in their place, which would mess up our
indexing system. We prevent that by referencing the objects when we
index them, thus preventing them from getting auto-destructed.

Mind that those are not JavaScript objects but rather functions,
bindings, components and the like. So, this will only cause a memory
leak if you're compiling and dropping QML components over and over.

Task-number: QTBUG-52937
Change-Id: Ia4dfb09a71a5c9a2d6ce25c3811bbe2a1036c1c1
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

1 files changed, 8 insertions, 7 deletions

diff --git a/src/qml/qml/qqmlobjectcreator.cpp b/src/qml/qml/qqmlobjectcreator.cpp
index 29fff04325..cfe1c86eba 100644
--- a/src/qml/qml/qqmlobjectcreator.cpp
+++ b/src/qml/qml/qqmlobjectcreator.cpp
@@ -1037,8 +1037,8 @@ QObject *QQmlObjectCreator::createInstance(int index, QObject *parent, bool isCo
     if (compiledData->isComponent(index)) {
         isComponent = true;
         QQmlComponent *component = new QQmlComponent(engine, compiledData, index, parent);
-        Q_QML_OC_PROFILE(sharedState->profiler, profiler.update(QStringLiteral("<component>"),
-                context->url(), obj->location.line, obj->location.column));
+        Q_QML_OC_PROFILE(sharedState->profiler, profiler.update(
+                             compiledData, obj, QStringLiteral("<component>"), context->url()));
         QQmlComponentPrivate::get(component)->creationContext = context;
         instance = component;
         ddata = QQmlData::get(instance, /*create*/true);
@@ -1048,8 +1048,8 @@ QObject *QQmlObjectCreator::createInstance(int index, QObject *parent, bool isCo
         installPropertyCache = !typeRef->isFullyDynamicType;
         QQmlType *type = typeRef->type;
         if (type) {
-            Q_QML_OC_PROFILE(sharedState->profiler, profiler.update(type->qmlTypeName(),
-                    context->url(), obj->location.line, obj->location.column));
+            Q_QML_OC_PROFILE(sharedState->profiler, profiler.update(
+                                 compiledData, obj, type->qmlTypeName(), context->url()));
             instance = type->create();
             if (!instance) {
                 recordError(obj->location, tr("Unable to create object of type %1").arg(stringAt(obj->inheritedTypeNameIndex)));
@@ -1071,8 +1071,9 @@ QObject *QQmlObjectCreator::createInstance(int index, QObject *parent, bool isCo
             sharedState->allCreatedObjects.push(instance);
         } else {
             Q_ASSERT(typeRef->component);
-            Q_QML_OC_PROFILE(sharedState->profiler, profiler.update(typeRef->component->fileName(),
-                    context->url(), obj->location.line, obj->location.column));
+            Q_QML_OC_PROFILE(sharedState->profiler, profiler.update(
+                                 compiledData, obj, typeRef->component->fileName(),
+                                 context->url()));
             if (typeRef->component->compilationUnit->data->isSingleton())
             {
                 recordError(obj->location, tr("Composite Singleton Type %1 is not creatable").arg(stringAt(obj->inheritedTypeNameIndex)));
@@ -1115,7 +1116,7 @@ QObject *QQmlObjectCreator::createInstance(int index, QObject *parent, bool isCo
         parserStatus->classBegin();
         // push() the profiler state here, together with the parserStatus, as we'll pop() them
         // together, too.
-        Q_QML_OC_PROFILE(sharedState->profiler, sharedState->profiler.push(profiler));
+        Q_QML_OC_PROFILE(sharedState->profiler, sharedState->profiler.push(obj));
         sharedState->allParserStatusCallbacks.push(parserStatus);
         parserStatus->d = &sharedState->allParserStatusCallbacks.top();
     }