[Bug libstdc++/93059] char and char8_t does not talk with each other with memcpy. std::copy std::copy_n, std::fill, std::fill_n, std::uninitialized_copy std::uninitialized_copy_n, std::fill, std::uninitialized_fill_n fails to convert to memxxx functions

[euloanty at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93059

--- Comment #41 from fdlbxtqi <euloanty at live dot com> ---
(In reply to Jonathan Wakely from comment #38)
> We could also use memcmp for std::equal when it's using std::equal_to<> or
> std::equal_to<_ValueType1> or std::equal_to<_ValueType2>, and for
> std::lexicographical_compare when it's using std::less<> or
> std::less<_ValueType1> or std::less<_ValueType2> (as long as the existing
> conditions are also met).
> 
> Currently we only use memcmp when those algos are used without a comparison
> function.

And the volatile bugs haven't fixed either. The code works fine in GCC 9.0. Now
it failed to work. Even I swap the standard to C++17, it still does not work.
Does deprecate volatile work in this case in C++20?? However, even that is the
case, C++17 should still work.

#include<array>
auto f(std::array<int volatile,3> arr)
{
    decltype(arr) arr2;
    std::copy(arr.begin(),arr.end(),arr2.begin());
}

https://godbolt.org/z/Tn87r5