[Bug libstdc++/101587] ranges::uninitialized_copy/move incorrectly uses std::min

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101587

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
In theory yes, but it's unlikely to be a problem in practice because the
library doesn't need to compare unsigned types with negative values. If it does
need to do that, it is either already doing so carefully and correctly, or this
helper wouldn't make things worse.

I'm not suggesting designing a general purpose replacement for std::min that
handles all the possible corner cases, I'm just suggesting a convenience
function for our own internal needs.

All the uses in <bits/ranges_uninitialized.h> are with iterator difference
types, which had better be signed, and distance(first, last) had better be
non-negative too.


include/bits/hashtable_policy.h does:

      const auto __max_width = std::min<size_t>(sizeof(size_t), 8);

This is mixing unsigned and signed, but both positive.


include/bits/locale_conv.h:

       auto __nn = std::min<streamsize>(this->epptr() - this->pptr(),
                                        __n - __done);

This compares ptrdiff_t with streamsize, which are both signed (and both values
here are guaranteed to be non-negative by construction).