[Bug c++/93209] What is a bitfield's "underlying type"?

[John.Adriaan at BigPond dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93209

--- Comment #2 from John Adriaan <John.Adriaan at BigPond dot com> ---
Wow: I just realised. The following code for my proposal is problematic:

    struct S {
        bool     b : 1;
        unsigned i : 1;
        unsigned   : 0;
        char     c : 8;
    }; // S

Should `c` be aligned at one byte (its field) or four bytes (the padding field)
after the beginning of `S`?

According to the current implementation, it's four bytes - so again, the
padding `: 0` operator seems to be the overriding by its own type, not that of
the following field.

Also note that removing the `: 0` field pulls `c` back to a (padded) position
six bits _after_ `i`