The old code assumed that a QByteArray's data() is always
NUL-terminated. Due to the conflation of owners and non-owners in
QByteArray (but also in case we ever get efficient substringing), this
is not always the case, e.g. QByteArray::fromRawData() does not ensure
NUL-termination.
From QString::utf16(), we learn that the condition to check for is
QArrayData::isMutable(). After working around the fact that
QByteArray::data_ptr() doesn't exist for const QBAs and that empty
QBAs always refer to QByteArray::empty_, which is !isMutable(), we can
detect this situation and re-allocate without introducing new API.
This is the fix for Qt ≤ 6.4. For Qt 6.5, we'll port the function to
QByteArrayView.
Pick-to: 6.4 6.3 6.2 5.15
Fixes: QTBUG-105302
Change-Id: I3416535ab09d601e0e87b2767f2c024ba1217e64
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
15422d191f