[Bug libstdc++/80811] out-of-line string members less efficient than they could be

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80811

--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
Reminds me of PR 59048 and some others, except that in that one adding "pure"
was not sufficient.

Is "pure" true for all legal template parameters of basic_string?