[Bug libstdc++/80676] [DR 2995] basic_stringbuf does not use initial capacity of SSO string

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80676

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |SUSPENDED
                 CC|                            |paolo.carlini at oracle dot com
   Target Milestone|---                         |8.0
            Summary|basic_stringbuf does not    |[DR 2995] basic_stringbuf
                   |use initial capacity of SSO |does not use initial
                   |string                      |capacity of SSO string

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This change would break a number of tests which were added specifically to
ensure that the sequence pointers are all null after construction:
https://gcc.gnu.org/ml/libstdc++/2004-09/msg00247.html

I've reported a new issue to relax the requirements so we can make this change:
https://wg21.link/lwg2995

This change would also fix Bug 81338 but for now I'll have to fix that in
stringbuf::overflow, rather than optimising it to not call overflow.