Apple OS: Handle QSetting strings with embedded zero-bytes

Saving strings with embedded zero-bytes (\0) as CFStrings would
sometimes fail, and only write the part of the string leading
up to the first zero-byte, instead of all the way to the final
zero-terminator. This bug was revealed by the code-path that
falls back to storing e.g. QTime as strings, via the helper
method QSettingsPrivate::variantToString().

We now use the same approach as on platforms such as Windows
and WinRT, where the string produced by variantToString() is
checked for null-bytes, and if so, stored using a binary
representation instead of as a string. For our case that
means we fall back to CFData when detecting the null-byte.

To separate strings from regular byte arrays, new logic has
been added to variantToString() that wraps the null-byte
strings in @String(). That way we can implement a fast-path
when converting back from CFData, that doesn't go via the
slow and lossy conversion via UTF8, and the resulting QVariant
will be of type QVariant::ByteArray. The reason for using
UTF-8 as the binary representation of the string is that
in the case of storing a QByteArray("@foo") we need to
still be able to convert it back to the same byte array,
which doesn't work if the on-disk format is UTF-16.

Task-number: QTBUG-56124
Change-Id: Iab2f71cf96cf3225de48dc5e71870d74b6dde1e8
Cherry-picked: 764f5bf48cc87f4c72550b853ab93b815454cd48
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Jani Heikkinen <jani.heikkinen@qt.io>

1 files changed, 49 insertions, 1 deletions

diff --git a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
index 87a801c9dd..ed298bfafa 100644
--- a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
+++ b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
@@ -158,6 +158,8 @@ private slots:
     void testByteArray();
     void iniCodec();
     void bom();
+    void embeddedZeroByte_data();
+    void embeddedZeroByte();
 
 private:
     void cleanupTestFiles();
@@ -627,7 +629,6 @@ void tst_QSettings::testByteArray_data()
 #ifndef QT_NO_COMPRESS
     QTest::newRow("compressed") << qCompress(bytes);
 #endif
-    QTest::newRow("with \\0") << bytes + '\0' + bytes;
 }
 
 void tst_QSettings::testByteArray()
@@ -678,6 +679,53 @@ void tst_QSettings::bom()
     QVERIFY(allkeys.contains("section2/foo2"));
 }
 
+void tst_QSettings::embeddedZeroByte_data()
+{
+    QTest::addColumn<QVariant>("value");
+
+    QByteArray bytes("hello\0world", 11);
+
+    QTest::newRow("bytearray\\0") << QVariant(bytes);
+    QTest::newRow("string\\0") << QVariant(QString::fromLatin1(bytes.data(), bytes.size()));
+
+    bytes = QByteArray("@String(");
+
+    QTest::newRow("@bytearray") << QVariant(bytes);
+    QTest::newRow("@string") << QVariant(QString(bytes));
+
+    bytes = QByteArray("@String(\0test", 13);
+
+    QTest::newRow("@bytearray\\0") << QVariant(bytes);
+    QTest::newRow("@string\\0") << QVariant(QString::fromLatin1(bytes.data(), bytes.size()));
+}
+
+void tst_QSettings::embeddedZeroByte()
+{
+    QFETCH(QVariant, value);
+    {
+        QSettings settings("QtProject", "tst_qsettings");
+        settings.setValue(QTest::currentDataTag(), value);
+    }
+    {
+        QSettings settings("QtProject", "tst_qsettings");
+        QVariant outValue = settings.value(QTest::currentDataTag());
+
+        switch (value.type()) {
+        case QVariant::ByteArray:
+            QCOMPARE(outValue.toByteArray(), value.toByteArray());
+            break;
+        case QVariant::String:
+            QCOMPARE(outValue.toString(), value.toString());
+            break;
+        default:
+            Q_UNREACHABLE();
+        }
+
+        if (value.toByteArray().contains(QChar::Null))
+            QVERIFY(outValue.toByteArray().contains(QChar::Null));
+    }
+}
+
 void tst_QSettings::testErrorHandling_data()
 {
     QTest::addColumn<int>("filePerms"); // -1 means file should not exist