[Bug c/67433] ?: expression returns unexpected value when condition is a bool variable which memory is not true/false

[xuejuncao at gmail dot com]

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