https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70526
--- Comment #19 from rguenther at suse dot de <rguenther at suse dot de> --- On April 29, 2016 5:24:00 PM GMT+02:00, "amonakov at gcc dot gnu.org" <gcc-bugzi...@gcc.gnu.org> wrote: >https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70526 > >Alexander Monakov <amonakov at gcc dot gnu.org> changed: > > What |Removed |Added >---------------------------------------------------------------------------- > CC| |amonakov at gcc dot gnu.org > >--- Comment #18 from Alexander Monakov <amonakov at gcc dot gnu.org> >--- >Richard -- please correct if I'm wrong -- means here: > >> You can't refer to that part of the storage by copying *this. > >... that the implicitly instantiated copy constructor (as well as >assignment >operator, for that matter) will copy this->typed as a char[]/uint64_t >union, >while it actually contains a value of type Register. You need an >explicit copy >constructor that would assign this->typed with the correct type via >'typed.addr() = ...' like the existing constructor does. Yes. In fact the C++ FE for the copy constructor emits a simple aggregate assignment which may be a problem on its own (regarding TBAA if this case is supposed to be not invalid) >(If T was POD, you could have had it in the union in the first place, >and this >issue wouldn't arise)
