Add garbage collector prologue callback to qv8engine

This commit provides a generic way to manage persistent handles
created by QML so that circular references don't cause leaks, by
utilising v8's garbage collector callbacks.

Change-Id: Ia898197fdf5d86b90915b835ce3e532f7d400de4
Reviewed-on: http://codereview.qt.nokia.com/3688
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>

4 files changed, 114 insertions, 0 deletions

diff --git a/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.handle.1.qml b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.handle.1.qml
new file mode 100644
index 0000000000..9c27653b34
--- /dev/null
+++ b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.handle.1.qml
@@ -0,0 +1,25 @@
+import QtQuick 2.0
+import Qt.test 1.0
+
+Item {
+    id: obj
+    objectName: "obj"
+    property CircularReferenceHandle first
+    property CircularReferenceHandle second
+
+    CircularReferenceHandle {
+        id: crh
+        objectName: "crh"
+    }
+
+    function createReference() {
+        first = crh.generate(crh);
+        second = crh.generate(crh);
+        // NOTE: manually add reference from first to second
+        // in unit test prior reparenting and gc.
+    }
+
+    function performGc() {
+        gc();
+    }
+}
diff --git a/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.handle.2.qml b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.handle.2.qml
new file mode 100644
index 0000000000..dc196263b4
--- /dev/null
+++ b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.handle.2.qml
@@ -0,0 +1,26 @@
+import QtQuick 2.0
+import Qt.test 1.0
+
+Item {
+    id: obj
+    objectName: "obj"
+    property CircularReferenceHandle first
+    property CircularReferenceHandle second
+
+    CircularReferenceHandle {
+        id: crh
+        objectName: "crh"
+    }
+
+    function circularReference() {
+        // generate the circularly referential pair
+        first = crh.generate(crh);
+        second = crh.generate(crh);
+        // note: must manually reparent in unit test
+        // after setting the handle references.
+    }
+
+    function performGc() {
+        gc();
+    }
+}
diff --git a/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.object.1.qml b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.object.1.qml
new file mode 100644
index 0000000000..4fd1311c29
--- /dev/null
+++ b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.object.1.qml
@@ -0,0 +1,31 @@
+import QtQuick 2.0
+import Qt.test 1.0
+
+Item {
+    id: obj
+    objectName: "obj"
+
+    property CircularReferenceObject first
+    property CircularReferenceObject second
+
+
+    CircularReferenceObject {
+        id: cro
+        objectName: "cro"
+    }
+
+    function createReference() {
+        // generate the objects
+        first = cro.generate(cro); // has parent, so won't be collected
+        second = cro.generate();   // no parent, but will be kept alive by first's reference
+        first.addReference(second);
+
+        // remove top level references
+        first = cro;
+        second = cro;
+    }
+
+    function performGc() {
+        gc();
+    }
+}
diff --git a/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.object.2.qml b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.object.2.qml
new file mode 100644
index 0000000000..3f8415ce0f
--- /dev/null
+++ b/tests/auto/declarative/qdeclarativeecmascript/data/handleReferenceManagement.object.2.qml
@@ -0,0 +1,32 @@
+import QtQuick 2.0
+import Qt.test 1.0
+
+Item {
+    id: obj
+    objectName: "obj"
+
+    property CircularReferenceObject first
+    property CircularReferenceObject second
+
+
+    CircularReferenceObject {
+        id: cro
+        objectName: "cro"
+    }
+
+    function circularReference() {
+        // generate the circularly referential pair - they should still be collected
+        first = cro.generate();  // no parent, so should be collected
+        second = cro.generate(); // no parent, so should be collected
+        first.addReference(second);
+        second.addReference(first);
+
+        // remove top level references
+        first = cro;
+        second = cro;
+    }
+
+    function performGc() {
+        gc();
+    }
+}