https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102909
--- Comment #2 from Iru Cai <mytbk920423 at gmail dot com> --- So it looks something like https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44677 GCC thinks ``a`` is set but not used in ``a = 1 + b;``, but is used in ``a = 1; a += b;``.
