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
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/corelib/io/qsettings_winrt.cpp b/src/corelib/io/qsettings_winrt.cpp
index 708287ce5e..209b56d920 100644
--- a/src/corelib/io/qsettings_winrt.cpp
+++ b/src/corelib/io/qsettings_winrt.cpp
@@ -402,7 +402,7 @@ void QWinRTSettingsPrivate::set(const QString &uKey, const QVariant &value)
         QStringList::const_iterator it = l.constBegin();
         bool containsNull = false;
         for (; it != l.constEnd(); ++it) {
-            if ((*it).length() == 0 || it->indexOf(QChar::Null) != -1) {
+            if ((*it).length() == 0 || it->contains(QChar::Null)) {
                 // We can only store as binary
                 containsNull = true;
                 break;
@@ -445,7 +445,7 @@ void QWinRTSettingsPrivate::set(const QString &uKey, const QVariant &value)
         break;
     default: {
         const QString s = variantToString(value);
-        if (s.indexOf(QChar::Null) != -1) {
+        if (s.contains(QChar::Null)) {
             hr = valueStatics->CreateUInt8Array(s.length() * 2, (BYTE*) s.utf16(), &val);
         } else {
             HStringReference ref((const wchar_t*)s.utf16(), s.size());