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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/101587] ranges::uninitialized_copy/move incorrectly
 uses std::min
Date: Fri, 23 Jul 2021 10:34:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101587

--- 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 =3D std::min<size_t>(sizeof(size_t), 8);

This is mixing unsigned and signed, but both positive.


include/bits/locale_conv.h:

       auto __nn =3D std::min<streamsize>(this->epptr() - this->pptr(),
                                        __n - __done);

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