https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101539
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- I think the implementation of is_corresponding_member heavily depends on layout-compatibility ensuring the same sizes and alignments of the members, otherwise any comparison of the OFFSET_TYPE values (which just hold at runtime byte offset from the start of struct and at compile time hold also the type of the pointed non-static data member and type of the object the offset is relative to) is going to be a nighmare. So I think we first need a clarification of the standard for the various alignas cases or the [[no_unique_address]] cases that are shown e.g. in the #c1 testcase and only when we can count on the corresponding members to have the exact same offset we can move further on.
