On Mon, May 04, 2026 at 12:13:39PM -0400, Eric Pimentel Aguiar wrote: > I believe that is for those cases where X is a non-union class, but > contains an anonymous union. The members of X not within an anonymous union > would be those non-variant non-static data members referred in that clause.
What I mean is that the C++23 "any non-variant non-static data member of const-qualified type (or array thereof) with no brace-or-equal-initializer is not const-default-constructible" and C++26 "X is a non-union class and any non-variant non-static data member of const-qualified type (or possibly multidimensional array thereof) with no brace-or-equal-initializer is not const-default-constructible" IMHO say exactly the same. A union doesn't have any non-variant non-static data members, only variant non-static data members, so the C++23 wording implies that if the bullet is true, then X must be a non-union class. > > More importantly, defaulted dtor would be previously deleted if it had some > > variant subobject with deleted or inaccessible or non-trivial dtor, my > > understanding is that the paper wants to intentionally limit that to > > variant > > members with default initializer, but > > https://eel.is/c++draft/class.mem#class.dtor-7.2.2 > > doesn't seem to do that. For one, it doesn't apply to variant members in > > anonymous unions because it only talks about union classes, so I believe > > struct A { A (int); ~A () = delete; int a; }; > > struct B { union { A a = 42; int b; }; }; > > B::~B () per the new rules isn't deleted. And for unions, guess whether > > > > I believe that's because due to > https://eel.is/c++draft/class.default.ctor#2.4 > Because "a" has a default member initializer and its class A has a deleted > destructor, Ah, the anonymous union itself then has deleted dtor and since it is a non-variant member of B class, B has deleted dtor because of that. The only thing I'm wondering about is that the dtor is then deleted because the subobject dtor is not accessible inside of the default ctor and wonder whether that has to always mean that it is also inaccessible inside of the dtor. Jakub
