They're ALWAYS const objects, though they also chock full of relocations
so they are never in read-only sections of memory (except maybe in final
executables that are position-dependent).
These are methods in a private sub-class of QVariant. No one outside of
QtCore (at least qtbase) should be using them directly. QVariant doesn't
have many friends (a bit anti-social); the one that matters is
qvariant_cast and that one does access QVariant::Private. This is not a
BC problem because QVariant::Private::type()'s signature is not
changing. In any case, QVariant's Q_CORE_EXPORT does not apply to
QVariant::Private anyway (see [1]).
[1] https://msvc.godbolt.org/z/r9cer8eWh
Pick-to: 6.3 6.4
Change-Id: I3859764fed084846bcb0fffd17035355f823dc8f
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>