Long live incremental garbage collection in QML!

The design of the garbage collector is described in
src/qml/memory/design.md.

The gc and gcdone test helpers are adjusted to drive the gc to
completion, even when in incremental mode.

Parts of tst_qv4mm and tst_qqmlqt need to run with the incremental gc
disabled, as they call gc inside QML and assumes that the GC finishes
before returning.

Initial-patch-by: Rafal Chomentowski <rafal.chomentowski@ge.com>
Task-number: QTBUG-119274
Change-Id: I1d94f41bc7a434fad67de0fd46454b6db285f2eb
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/qml/jsruntime/qv4propertykey_p.h b/src/qml/jsruntime/qv4propertykey_p.h
index 0b8ad084d2..d6d15e402d 100644
--- a/src/qml/jsruntime/qv4propertykey_p.h
+++ b/src/qml/jsruntime/qv4propertykey_p.h
@@ -14,6 +14,7 @@
 // We mean it.
 //
 
+#include <private/qv4writebarrier_p.h>
 #include <private/qv4global_p.h>
 #include <private/qv4staticvalue_p.h>
 #include <QtCore/qhashfunctions.h>
@@ -70,11 +71,18 @@ public:
     // We cannot #include the declaration of Heap::StringOrSymbol here.
     // Therefore we do some gymnastics to enforce the type safety.
 
-    template<typename StringOrSymbol = Heap::StringOrSymbol>
-    static PropertyKey fromStringOrSymbol(StringOrSymbol *b)
+    template<typename StringOrSymbol = Heap::StringOrSymbol, typename Engine = QV4::EngineBase>
+    static PropertyKey fromStringOrSymbol(Engine *engine, StringOrSymbol *b)
     {
         static_assert(std::is_base_of_v<Heap::StringOrSymbol, StringOrSymbol>);
         PropertyKey key;
+        QV4::WriteBarrier::markCustom(engine, [&](QV4::MarkStack *stack) {
+            if constexpr (QV4::WriteBarrier::isInsertionBarrier) {
+                // treat this as an insertion - the StringOrSymbol becomes reachable
+                // via the propertykey, so we consequently need to mark it durnig gc
+                b->mark(stack);
+            }
+        });
         key.val.setM(b);
         Q_ASSERT(key.isManaged());
         return key;