[Bug libstdc++/51653] More compact std::tuple

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51653

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #3)
> The suggestion in this PR is quite wild, but the fact that
> sizeof(tuple<tuple<tuple<tuple<tuple<int>>>>>)==20 is a real issue that
> could probably be solved with less trouble (still ABI-breaking). Maybe I
> should have split the PR...

That's fixed by the patch attached to PR56785