macOS: Don't mangle QByteArray settings with @ prefix by decoding as UTF-8

QSettings encodes QVariants as @Type(data) strings. If that data contains
a null-byte, we write the string as UTF-8 encoded CFData. When reading it
back we look for a @ prefix, and then pass it as UTF-8 through stringToVariant.

The problem arises then the user writes raw QByteArrays with a @ prefix.
We can detect this situation by checking the result of stringToVariant,
and if it's just a simple conversion of the string into a QVariant, we
know that stringToVariant hit its fallback path due to not finding any
embedded variants.

If that's the case, we return the raw bytes as a QByteArray.

Pick-to: 6.2 6.1 5.15 5.12
Change-Id: I4ac5c35d0a6890ebea983b9aca0a3a36b0143de2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
index 6186f5544b..9ae8fcf61f 100644
--- a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
+++ b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
@@ -711,6 +711,10 @@ void tst_QSettings::embeddedZeroByte_data()
 
     QTest::newRow("@bytearray\\0") << QVariant(bytes);
     QTest::newRow("@string\\0") << QVariant(QString::fromLatin1(bytes.data(), bytes.size()));
+
+    bytes = QByteArray("@\xdd\x7d", 3);
+    QTest::newRow("@-prefixed data") << QVariant(bytes);
+    QTest::newRow("@-prefixed data as string") << QVariant(QString::fromLatin1(bytes.data(), bytes.size()));
 }
 
 void tst_QSettings::embeddedZeroByte()