-Wglobal-constructors is silenced for derived classes with a virtual base destructor in c++2b mode

[apache-hb]

When a class that contains a non trivial member inherits from a pure virtual base class that has an explicitly declared virtual destructor in c++2b mode -Wglobal-constructors is not raised, but an entry is still added to the .init_array to initialize the objects vtable before main. This behaviour is not present in c++20 mode. The entry is only added at -O0, at -O2 and higher __cxx_global_var_init is elided and the vtable is placed directly in the data section which makes this very hard to track down.

Godbolt reproducer link: https://godbolt.org/z/W355314dK

[frederick-vs-ja]

Before C++23 (P2448R2) the program is ill-formed, no diagnostic required, and Clang rejects it in old modes for that reason.