https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103726
--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> --- Ah it was left out of libstdc++'s freestanding builds intentionally: > When the final <coroutines> header is added it will need to be in > libsupc++ so that it's included for freestanding builds (and at that > point it won't be able to use <bits/stl_function.h>, but that will be > OK as the final header will be C++20-only and can rely on <compare> > unconditionally, which is also freestanding). The current experimental implementation supports C++14 and C++17, but to do that it needs to include some non-freestanding stuff.
