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, 9 insertions, 1 deletions

diff --git a/src/corelib/io/qsettings_mac.cpp b/src/corelib/io/qsettings_mac.cpp
index 29ea995f2d..59f0015b63 100644
--- a/src/corelib/io/qsettings_mac.cpp
+++ b/src/corelib/io/qsettings_mac.cpp
@@ -247,7 +247,15 @@ static QVariant qtValue(CFPropertyListRef cfvalue)
         }
 
         const QString str = QString::fromUtf8(byteArray.constData(), byteArray.size());
-        return QSettingsPrivate::stringToVariant(str);
+        QVariant variant = QSettingsPrivate::stringToVariant(str);
+        if (variant == QVariant(str)) {
+            // We did not find an encoded variant in the string,
+            // so return the raw byte array instead.
+            byteArray.detach();
+            return byteArray;
+        }
+
+        return variant;
     } else if (typeId == CFDictionaryGetTypeID()) {
         CFDictionaryRef cfdict = static_cast<CFDictionaryRef>(cfvalue);
         CFTypeID arrayTypeId = CFArrayGetTypeID();