From 0368b24a7f53c945b582097cc8ad22a053856d22 Mon Sep 17 00:00:00 2001
From: Friedemann Kleint <Friedemann.Kleint@digia.com>
Date: Thu, 9 Oct 2014 09:43:23 +0200
Subject: [PATCH] QSettings: Prevent assert when passing empty keys.
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[ChangeLog][Important behavior changes][QSettings]
QSettings::value() now returns an invalid QVariant
when passing an empty key. The code path ran into
an assert, which was only noticeable in debug
builds.

Task-number: QTBUG-41812
Change-Id: I5cc32be3aa267a132e9d6639ecd6cb0bbafc15b0
Reviewed-by: Stéphane Fabry, Cutesoft <stephane.fabry@gmail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/io/qsettings.cpp                      |  8 ++++++++
 tests/auto/corelib/io/qsettings/tst_qsettings.cpp | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/corelib/io/qsettings.cpp b/src/corelib/io/qsettings.cpp
index fd35ae33dcc..d896da176ae 100644
--- a/src/corelib/io/qsettings.cpp
+++ b/src/corelib/io/qsettings.cpp
@@ -3121,6 +3121,10 @@ bool QSettings::isWritable() const
 void QSettings::setValue(const QString &key, const QVariant &value)
 {
     Q_D(QSettings);
+    if (key.isEmpty()) {
+        qWarning("QSettings::setValue: Empty key passed");
+        return;
+    }
     QString k = d->actualKey(key);
     d->set(k, value);
     d->requestUpdate();
@@ -3253,6 +3257,10 @@ bool QSettings::event(QEvent *event)
 QVariant QSettings::value(const QString &key, const QVariant &defaultValue) const
 {
     Q_D(const QSettings);
+    if (key.isEmpty()) {
+        qWarning("QSettings::value: Empty key passed");
+        return QVariant();
+    }
     QVariant result = defaultValue;
     QString k = d->actualKey(key);
     d->get(k, &result);
diff --git a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
index 77a60997a62..3e68e4859fc 100644
--- a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
+++ b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
@@ -118,6 +118,7 @@ private slots:
     void testUpdateRequestEvent();
     void testThreadSafety();
     void testEmptyData();
+    void testEmptyKey();
     void testResourceFiles();
     void testRegistryShortRootNames();
     void trailingWhitespace();
@@ -2025,6 +2026,16 @@ void tst_QSettings::testEmptyData()
     QFile::remove(filename);
 }
 
+void tst_QSettings::testEmptyKey()
+{
+    QSettings settings;
+    QTest::ignoreMessage(QtWarningMsg, "QSettings::value: Empty key passed");
+    const QVariant value = settings.value(QString());
+    QCOMPARE(value, QVariant());
+    QTest::ignoreMessage(QtWarningMsg, "QSettings::setValue: Empty key passed");
+    settings.setValue(QString(), value);
+}
+
 void tst_QSettings::testResourceFiles()
 {
     QSettings settings(":/resourcefile.ini", QSettings::IniFormat);