[Bug libstdc++/119970] [16 Regression] mingw builds fail as libstdc++-v3/include/ostream:224:65: error: could not convert '__out' since r16-142-g01e5ef3e8b9128

[tkaminsk at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119970

--- Comment #6 from Tomasz Kamiński <tkaminsk at gcc dot gnu.org> ---
Yes, this allows us to avoid a separate allocation when transcoding to valid
Unicode. For reference in libstdc++-v3/src/c++23/print.cc, to_valid_unicode
will edit sequence in-situ:
```
  // If sizeof(_CharT) == 1 and the input is valid UTF-8, both s and out will
  // be unchanged. Otherwise, each invalid sequence in s will be overwritten
  // with a single 0xFF byte followed by zero or more 0xFE bytes, and then
  // a valid UTF-8 string will be produced in out (replacing invalid
  // sequences with U+FFFD).
  template<typename _CharT>
    bool
    to_valid_unicode(span<char> s, basic_string<_CharT>& out)

```