Prevent endless markDirtyAndNotifyObservers <-> notify loop

Before we had the option of eager evaluation, we were able to use the
dirty flag to detect whether we are recursing. However, eager properties
will lead to a evaluateIfDirtyAndReturnTrueIfValueChanged call, and that
in turn will clear the dirty flag.
Introduce a new member to detect that situation, and set the bindings
error state to BindingLoop if we detect that kind of loop.

Change-Id: If40b93221848bd9e9422502318d992fad95b0b74
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/corelib/kernel/qproperty.cpp b/src/corelib/kernel/qproperty.cpp
index 72f74ac1e8..81871587e8 100644
--- a/src/corelib/kernel/qproperty.cpp
+++ b/src/corelib/kernel/qproperty.cpp
@@ -41,6 +41,7 @@
 #include "qproperty_p.h"
 
 #include <qscopedvaluerollback.h>
+#include <QScopeGuard>
 
 QT_BEGIN_NAMESPACE
 
@@ -82,6 +83,13 @@ void QPropertyBindingPrivate::markDirtyAndNotifyObservers()
     if (dirty)
         return;
     dirty = true;
+    if (eagerlyUpdating) {
+        error = QPropertyBindingError(QPropertyBindingError::BindingLoop);
+        return;
+    }
+
+    eagerlyUpdating = true;
+    QScopeGuard guard([&](){eagerlyUpdating = false;});
     if (requiresEagerEvaluation()) {
         // these are compat properties that we will need to evaluate eagerly
         evaluateIfDirtyAndReturnTrueIfValueChanged(propertyDataPtr);