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

["trippels at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67433

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |trippels at gcc dot gnu.org

--- Comment #9 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to xuejuncao from comment #8)
> thanks, i get the below result with -fsanitize=undefined 
> 
> boolmagic.c:12:16: runtime error: load of value 255, which is not a valid
> value for type '_Bool'
> boolmagic.c:13:15: runtime error: load of value 255, which is not a valid
> value for type '_Bool'
> boolmagic.c:14:15: runtime error: load of value 255, which is not a valid
> value for type '_Bool'
> b = 1, i = 1, j = 1
> 
> but, can i say the "-fsanitize=undefined" will _corrects_ the undefined
> behaviour?
> 
> or replace the code by if/else, which works fine (lucky?)
> 
>     int i; // = (u.b ? 1 : 0);
>     if (u.b) i = 1; else i = 0;

No, you're still invoking undefined behavior. -fsanitize=undefined will not
fix this at all; it just points out the issues.

You need to get rid of the underlying problem, but this is not the place
to discuss this further.