Fix some GC related tests to work with MSVC

Using alloca instead of memset we can convince even MSVC to allocate memory on the
stack, to overwrite any previous dead V4 pointers.

Change-Id: Ic01bebfc6368e9c3ce1f6155a0f0ea206b90764c
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

2 files changed, 37 insertions, 9 deletions

diff --git a/tests/auto/qml/qjsengine/tst_qjsengine.cpp b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
index ca3fa8bca4..1f43d21c51 100644
--- a/tests/auto/qml/qjsengine/tst_qjsengine.cpp
+++ b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
@@ -49,16 +49,28 @@
 #include <QtCore/qnumeric.h>
 #include <stdlib.h>
 
+#ifdef Q_CC_MSVC
+#define NO_INLINE __declspec(noinline)
+#else
+#define NO_INLINE __attribute__((noinline))
+#endif
+
+#if defined(Q_OS_WIN)
+#include <malloc.h>
+#else
+#include <alloca.h>
+#endif
+
 Q_DECLARE_METATYPE(QList<int>)
 Q_DECLARE_METATYPE(QObjectList)
 
 // The JavaScriptCore GC marks the C stack. To try to ensure that there is
 // no JSObject* left in stack memory by the compiler, we call this function
 // to zap some bytes of memory before calling collectGarbage().
-static void zapSomeStack()
+static void NO_INLINE zapSomeStack()
 {
-    char buf[4096];
-    memset(buf, 0, sizeof(buf));
+    char *buf = (char*)alloca(4096);
+    memset(buf, 0, 4096);
 }
 
 static void collectGarbage_helper(QJSEngine &eng)
diff --git a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
index 3574b58ba4..321aa47297 100644
--- a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
+++ b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
@@ -56,6 +56,18 @@
 #include <private/qv4functionobject_p.h>
 #include <private/qv4exception_p.h>
 
+#ifdef Q_CC_MSVC
+#define NO_INLINE __declspec(noinline)
+#else
+#define NO_INLINE __attribute__((noinline))
+#endif
+
+#if defined(Q_OS_WIN)
+#include <malloc.h>
+#else
+#include <alloca.h>
+#endif
+
 /*
 This test covers evaluation of ECMAScript expressions and bindings from within
 QML.  This does not include static QML language issues.
@@ -298,8 +310,18 @@ private:
     QQmlEngine engine;
 };
 
+// The JavaScriptCore GC marks the C stack. To try to ensure that there is
+// no JSObject* left in stack memory by the compiler, we call this function
+// to zap some bytes of memory before calling collectGarbage().
+static void NO_INLINE zapSomeStack()
+{
+    char *buf = (char*)alloca(4096);
+    memset(buf, 0, 4096);
+}
+
 static void gc(QQmlEngine &engine)
 {
+    zapSomeStack();
     engine.collectGarbage();
     QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
     QCoreApplication::processEvents();
@@ -4880,9 +4902,6 @@ void tst_qqmlecmascript::propertyVarCircular2()
     QCOMPARE(childObject->property("textCanary").toInt(), 10);
     QMetaObject::invokeMethod(object, "deassignCircular");
     gc(engine);
-#if defined(Q_CC_MSVC)
-    QSKIP("This test does not work reliably with MSVC.");
-#endif
     QVERIFY(rootObjectTracker.isNull());                           // should have been collected
     QVERIFY(childObjectTracker.isNull());                          // should have been collected
     delete object;
@@ -4976,9 +4995,6 @@ void tst_qqmlecmascript::propertyVarInheritance2()
     QMetaObject::invokeMethod(object, "deassignCircular");
     gc(engine);
     // an equivalent for pragma GCC optimize is still work-in-progress for CLang, so this test will fail.
-#if defined(Q_CC_MSVC)
-    QSKIP("This test does not work reliably with MSVC.");
-#endif
 #if !defined(Q_CC_CLANG)
     QVERIFY(childObjectVarArrayValueHandle.isEmpty()); // should have been collected now.
 #endif