The patch that introduces the enforcing of signature types did so by passing the contained rather than the stored metatypes for the arguments. These types are used to populate the registers of the function with the arguments using the proper types by static_cast'ing the void* arguments to the actual types. However, for value types, the arguments were assumed to be QVariants and were thus casted to one even though they were actually passed as the actual argument type. This seems to have been mostly fine by accident because of the inline storage of QVariant that lays at offset 0 in its layout. Therefore, if the flag signalling that the value is actually elsewhere was not set to 1 by the casting and the value fit in the inline storage everything would still work. This is not always the case however and can lead to crashes. Therefore, treat value type arguments as plain non-wrapped values when populating function arguments. Amends 8bf5aae19b77b618f3f7a55a59e87c8a319475a8 Fixes: QTBUG-127009 Pick-to: 6.8 Change-Id: I495bcff7631399f207d87fea698d7e921e8e4721 Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>