https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81122
--- Comment #30 from Jonathan Wakely <redi at gcc dot gnu.org> --- Correct, that's how std::from_chars works. It never parses a prefix, and you need to use the hex format if you want to parse hex floats. There is no bug with from_chars, and it's nothing to do with this bug report for istream. https://eel.is/c++draft/text#charconv.from.chars-6.4
