https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103626
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- If a header doesn't depend on any of <ios>, <thread> etc and could work for freestanding, do we want to explicitly disable out with #error, or make it available as an extension? Since the direction in the standard is to enable anything that can work freestanding, we could be liberal in freestanding extensions. That was my thinking anyway.
