https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81395
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- PR 45708 suggested that _M_reading and _M_writing aren't needed. I haven't found a patch to implement that, but I haven't looked too hard. You make a good point that going into uncommitted mode with _M_reading == true isn't done elsewhere. I don't understand the state machine, so I'm very unsure about changing anything here. But _M_set_buffer(0) seems wrong, since that causes an unwanted(?) call to this->setp(_M_buf, _M_buf + _M_buf_size - 1); from xsgetn.
