From 87409ce0007e92d43f8e502f44528858c84b85d4 Mon Sep 17 00:00:00 2001
From: Fabian Kosmale <fabian.kosmale@qt.io>
Date: Fri, 4 Dec 2020 09:11:50 +0100
Subject: [PATCH] QBindable: Disallow mutation if read-only

If a QBindable is created from a computed property, it is not possible
to actually set a value or a binding. If we try to do it anyway, we'd
get a crash. Thus we now check whether the function pointer is null
before invoking it.

Task-number: QTBUG-87153
Change-Id: I5bedb9080ccf79d9b8166b80d5733d095ed76f8d
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
(cherry picked from commit e236faa75f446aa3378fb013cce6598c9e076ccb)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/kernel/qproperty.h                        | 4 ++--
 tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index 946014dc6d4..a533f424e85 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -630,7 +630,7 @@ public:
     QPropertyBinding<T> setBinding(const QPropertyBinding<T> &binding)
     {
         Q_ASSERT(!iface || binding.isNull() || binding.valueMetaType() == iface->metaType());
-        return iface ? static_cast<QPropertyBinding<T> &&>(iface->setBinding(data, binding)) : QPropertyBinding<T>();
+        return (iface && iface->setBinding) ? static_cast<QPropertyBinding<T> &&>(iface->setBinding(data, binding)) : QPropertyBinding<T>();
     }
 #ifndef Q_CLANG_QDOC
     template <typename Functor>
@@ -657,7 +657,7 @@ public:
 
     void setValue(const T &value)
     {
-        if (iface)
+        if (iface && iface->setter)
             iface->setter(data, &value);
     }
 };
diff --git a/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp b/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
index 8145b066da3..3cc7bd6f9c0 100644
--- a/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
+++ b/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
@@ -1114,6 +1114,11 @@ void tst_QProperty::testNewStuff()
     object.readData.setValue(111);
     QCOMPARE(object.computed(), 111);
 
+    object.bindableComputed().setBinding(object.bindableBar().makeBinding());
+    QCOMPARE(object.computed(), 111);
+    object.bindableComputed().setValue(10);
+    QCOMPARE(object.computed(), 111);
+
     QCOMPARE(object.bindableFoo().value(), 111);
     object.bindableFoo().setValue(24);
     QCOMPARE(object.foo(), 24);