QInputDialog: prevent crash in static get*() functions when parent gets deleted

As explained in

   https://blogs.kde.org/2009/03/26/how-crash-almost-every-qtkde-application-and-how-fix-it-0

creating dialogs on the stack is a bad idea if the
application or the dialog's parent window can be closed
by means other than user interaction (such as a timer or
an IPC call). Since we cannot know whether Qt is used to
build such an application, we must assume it is, create
the dialog on the heap, and monitor its lifetime with a
QPointer.

Instead of using manual resource management, add a
minimal implementation of QAutoPointer, and use that in
all static get*() functions.

Task-number: QTBUG-54693
Change-Id: I6157dca18608e02be1ea2c2defbc31641defc9d1
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: David Faure <david.faure@kdab.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/widgets/dialogs/qdialog_p.h b/src/widgets/dialogs/qdialog_p.h
index 1c7c5f3c2a..ae9e3bcc93 100644
--- a/src/widgets/dialogs/qdialog_p.h
+++ b/src/widgets/dialogs/qdialog_p.h
@@ -119,6 +119,24 @@ private:
     mutable bool m_platformHelperCreated;
 };
 
+template <typename T>
+class QAutoPointer {
+    QPointer<T> o;
+    struct internal { void func() {} };
+    typedef void (internal::*RestrictedBool)();
+public:
+    explicit QAutoPointer(T *t) Q_DECL_NOTHROW : o(t) {}
+    ~QAutoPointer() { delete o; }
+
+    T *operator->() const Q_DECL_NOTHROW { return get(); }
+    T *get() const Q_DECL_NOTHROW { return o; }
+    T &operator*() const { return *get(); }
+    operator RestrictedBool() const Q_DECL_NOTHROW { return o ? &internal::func : Q_NULLPTR; }
+    bool operator!() const Q_DECL_NOTHROW { return !o; }
+private:
+    Q_DISABLE_COPY(QAutoPointer);
+};
+
 QT_END_NAMESPACE
 
 #endif // QDIALOG_P_H