There are two ways to register a type: using Q_DECLARE_METATYPE(T) and
using qRegisterMetaType<T>("T"). Doing one thing in one translation
unit and another thing in another TU constitutes an ODR violation,
because the value of QMetaTypeId<T>::Defined will differ in the two
TUs.
By adding the information whether a type was declared with
Q_DECLARE_METATYPE to the typeFlags(), such a use will trigger
the existing binary-incompatibility failure that checks for
equality of the incoming type flags with the stored ones (if any).
I had to encode the type as a defaulted function argument in order
to avoid the linker merging instantiations of the function templates
and therefore rendering the detection moot.
Change-Id: I82017caf300458b411cc8ac2f6653536fac64117
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
98b77f9faa