https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67433
--- Comment #12 from xuejuncao <xuejuncao at gmail dot com> ---
(In reply to Richard Biener from comment #11)
> (In reply to xuejuncao from comment #10)
> > when bool value read from unpacked stream or file, wen can not ensure it's 1
> > or 0;
> > so maybe the best solution is compile with "-D_Bool=char" for now :-/
>
> You can always do the read with 'char' and then convert to _Bool.
>
> You can also "fix" your testcase (I think, didn't try) by using
>
> union u {
> bool b : 1;
> char c;
> } u;
>
> (in case unions allow bitfield members)
yes, it works, but likes a trick:-)
bit operation to bool is also undefined
int i = (u.b & 1 ? 1 : 0); // works without -O2, useless with -O2
