[Bug libstdc++/56785] std::tuple of two elements does not apply empty base class optimization when one of its elements is a std::tuple with two elements

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56785

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #1)
> I assume (needs to be checked) this is related to the issue, reported
> elsewhere, that makes the size of
> std::tuple<std::tuple<std::tuple<std::tuple<>>>> grow linearly with the
> nesting depth.

That's PR51653. With the attached patch that occupies a single byte, for any
depth.