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>

2 files changed, 72 insertions, 1 deletions

diff --git a/tests/auto/widgets/dialogs/qinputdialog/qinputdialog.pro b/tests/auto/widgets/dialogs/qinputdialog/qinputdialog.pro
index cc479812a8..9cb14c5350 100644
--- a/tests/auto/widgets/dialogs/qinputdialog/qinputdialog.pro
+++ b/tests/auto/widgets/dialogs/qinputdialog/qinputdialog.pro
@@ -1,4 +1,4 @@
 CONFIG += testcase
 TARGET = tst_qinputdialog
-QT += widgets testlib
+QT += widgets-private testlib
 SOURCES  += tst_qinputdialog.cpp
diff --git a/tests/auto/widgets/dialogs/qinputdialog/tst_qinputdialog.cpp b/tests/auto/widgets/dialogs/qinputdialog/tst_qinputdialog.cpp
index bbb6883238..0ea9e0259f 100644
--- a/tests/auto/widgets/dialogs/qinputdialog/tst_qinputdialog.cpp
+++ b/tests/auto/widgets/dialogs/qinputdialog/tst_qinputdialog.cpp
@@ -35,6 +35,7 @@
 #include <QComboBox>
 #include <QDialogButtonBox>
 #include <qinputdialog.h>
+#include <QtWidgets/private/qdialog_p.h>
 
 class tst_QInputDialog : public QObject
 {
@@ -52,6 +53,7 @@ private slots:
     void getInt();
     void getDouble_data();
     void getDouble();
+    void taskQTBUG_54693_crashWhenParentIsDeletedWhileDialogIsOpen();
     void task255502getDouble();
     void getText_data();
     void getText();
@@ -311,6 +313,75 @@ void tst_QInputDialog::getDouble()
     delete parent;
 }
 
+namespace {
+class SelfDestructParent : public QWidget
+{
+    Q_OBJECT
+public:
+    explicit SelfDestructParent(int delay = 100)
+        : QWidget(Q_NULLPTR)
+    {
+        QTimer::singleShot(delay, this, SLOT(deleteLater()));
+    }
+};
+}
+
+void tst_QInputDialog::taskQTBUG_54693_crashWhenParentIsDeletedWhileDialogIsOpen()
+{
+    // getText
+    {
+        QAutoPointer<SelfDestructParent> dialog(new SelfDestructParent);
+        bool ok = true;
+        const QString result = QInputDialog::getText(dialog.get(), "Title", "Label", QLineEdit::Normal, "Text", &ok);
+        QVERIFY(!dialog);
+        QVERIFY(!ok);
+        QVERIFY(result.isNull());
+    }
+
+    // getMultiLineText
+    {
+        QAutoPointer<SelfDestructParent> dialog(new SelfDestructParent);
+        bool ok = true;
+        const QString result = QInputDialog::getMultiLineText(dialog.get(), "Title", "Label", "Text", &ok);
+        QVERIFY(!dialog);
+        QVERIFY(!ok);
+        QVERIFY(result.isNull());
+    }
+
+    // getItem
+    for (int editable = false; editable <= true; ++editable) {
+        QAutoPointer<SelfDestructParent> dialog(new SelfDestructParent);
+        bool ok = true;
+        const QString result = QInputDialog::getItem(dialog.get(), "Title", "Label",
+                                                     QStringList() << "1" << "2", 1, editable, &ok);
+        QVERIFY(!dialog);
+        QVERIFY(!ok);
+        QCOMPARE(result, QLatin1String("2"));
+    }
+
+    // getInt
+    {
+        const int initial = 7;
+        QAutoPointer<SelfDestructParent> dialog(new SelfDestructParent);
+        bool ok = true;
+        const int result = QInputDialog::getInt(dialog.get(), "Title", "Label", initial, -10, +10, 1, &ok);
+        QVERIFY(!dialog);
+        QVERIFY(!ok);
+        QCOMPARE(result, initial);
+    }
+
+    // getDouble
+    {
+        const double initial = 7;
+        QAutoPointer<SelfDestructParent> dialog(new SelfDestructParent);
+        bool ok = true;
+        const double result = QInputDialog::getDouble(dialog.get(), "Title", "Label", initial, -10, +10, 2, &ok);
+        QVERIFY(!dialog);
+        QVERIFY(!ok);
+        QCOMPARE(result, initial);
+    }
+}
+
 void tst_QInputDialog::task255502getDouble()
 {
     parent = new QWidget;