https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86465
--- Comment #3 from Pavel Roskin <proski at gnu dot org> --- Created attachment 44770 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44770&action=edit Futher reduced example I was able to reduce the example to just 55 lines, removing almost all the code that came from the standard headers. The code complies with C++ standards all the way back to C++03. As I suspected, the implementation of std::optional in libstdc++ uses a trick to avoid initializing the payload when the optional value default initialized, and that code turns out to be essential for reproducing the issue. Try uncommenting _empty_char, and the warning goes away.
