[Bug libstdc++/119037] Incorrect calculations of max_size involving basic_strings

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119037

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2025-02-27

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Halalaluyafail3 from comment #0)
> Issue two is caused by the subtraction of one not considering that max_size
> of the allocator can return zero, which causes wraparound to the maximum
> value.

Such an allocator is so silly I'm not sure it's worth considering.

> Theoretically, unintended wraparound could also happen in __diffmax if
> PTRDIFF_MAX/sizeof(_CharT) is greater than SIZE_MAX and sizeof(_CharT) is
> not a positive integer power of two. However, I'm not sure any targets exist
> where this combination can arise so it's probably not worth considering

I don't think there are any such targets.

There is a bug here, but it seems incredibly low priority to fix.