[Bug c++/94569] New: alignas(object) with a weaker (smaller) alignment than the alignas(type) of it's type compiles, inconsistent with the C++ standard

["sinbal2l at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94569

            Bug ID: 94569
           Summary: alignas(object) with a weaker (smaller) alignment than
                    the alignas(type) of it's type compiles, inconsistent
                    with the C++ standard
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sinbal2l at gmail dot com
  Target Milestone: ---

The standard specifies:

>From the standard: [9.12.2 Alignment specifier, section 6, pg 226]

If the defining declaration of an entity has an alignment-specifier, any
non-defining declaration of that entity shall either specify equivalent
alignment or have no alignment-specifier. Conversely, if any declaration of an
entity has an alignment-specifier, every defining declaration of that entity
shall specify an equivalent alignment. 

But on the latest revision, this compiles:

typedef struct alignas(32){
    int i;
}U; 

int main() {
    alignas(16) U my_u;     // alignas(obj) of a weaker alignment than the
type.

    cout << "alignof(my_u): " << alignof(my_u) << endl;
    cout << "alignof (decltype(my_u))" << alignof (decltype(my_u)) << endl;
}

https://godbolt.org/z/2uNAag 

P.S. thank you very much for doing such a great job!