https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110343
--- Comment #10 from Ed Smith-Rowland <emsr at gcc dot gnu.org> --- Sorry I was out for a while. I was trying to figure out if there was some table of allowed characters we should use. Also, C23 needs this too IIUC and I was wondering if we should coordinate. It looks like you got it though.
