https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78495
--- Comment #2 from Nathan Sidwell <nathan at gcc dot gnu.org> --- Created attachment 40543 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40543&action=edit reduced testcase The problem is not with unnamed union members, but with inheriting ctors passing by value. The temporary 'Ptr' object is passed by implicit reference, but in the inheriting ctor we pass the address of that reference to the Base ctor. In this case that means we end up initializing Base::val with a pointer into the stack frame, rather than NULL. Note the original testcase has a typo ': val(static_cast<canary&&>(val))' -- the ctor parm and the member variable have the same name, so that's doing self initialization -- not copying the incoming parm. (not that that;s the bug being exposed).
