QByteArray(int size, Qt::Initialization) is not documented

It is often useful to allocate a QByteArray without explicitly initializing the content as it will immediately be filled out by some other means (eg reading from file)

The constructor QByteArray data(byteCount, Qt::Uninitialized) appears to do this, but it is not documented anywhere.

Note: In reality, many allocators do in fact null out allocated data for security reasons, so usually only the performance difference is visible unless you're using a debug or custom allocator.