Drain the markStack while collecting roots

This avoids overflows in the markStack for test cases where
we have a huge amount of compilation units with many runtime
strings that all want to get marked.

Task-number: QTBUG-63063
Change-Id: I7c1df0fdb9afada1830f8c218a0e52ebcd093850
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index caa6e8b7ac..8ca6b03950 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -982,10 +982,13 @@ void ExecutionEngine::markObjects(MarkStack *markStack)
     }
 
     classPool->markObjects(markStack);
+    markStack->drain();
 
     for (QSet<CompiledData::CompilationUnit*>::ConstIterator it = compilationUnits.constBegin(), end = compilationUnits.constEnd();
-         it != end; ++it)
+         it != end; ++it) {
         (*it)->markObjects(markStack);
+        markStack->drain();
+    }
 }
 
 ReturnedValue ExecutionEngine::throwError(const Value &value)