[Bug c++/104359] GCC Treats bool with value != 1 as falsey when picking branches

2022-02-03 Thread msebor at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104359

Martin Sebor  changed:

   What|Removed |Added

 CC||msebor at gcc dot gnu.org

--- Comment #5 from Martin Sebor  ---
It is undefined but the issue/question keeps coming up.  The store that makes
the subsequent read undefined is clearly visible in the IL at all optimization
levels so it would be quite easy to issue a helpful warning for the code.

[Bug c++/104359] GCC Treats bool with value != 1 as falsey when picking branches

2022-02-03 Thread redi at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104359

--- Comment #4 from Jonathan Wakely  ---
(In reply to Will Usher from comment #0)
> However, b's "value" is 255, which should evaluate to "true".

No. The only valid values of bool are true and false. If you set its bits to
some other value representation which does not correspond to either the 'true'
value or the 'false' value, you do not have an object of type bool, you have
garbage.

It's possible that a C++ implementation would use 0x for one of true or
false, in which case your memcpy would be valid. But that's not the case for
GCC.

[Bug c++/104359] GCC Treats bool with value != 1 as falsey when picking branches

2022-02-02 Thread pinskia at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104359

Andrew Pinski  changed:

   What|Removed |Added

 Resolution|--- |INVALID
 Status|WAITING |RESOLVED

--- Comment #3 from Andrew Pinski  ---
Closing as requested.

[Bug c++/104359] GCC Treats bool with value != 1 as falsey when picking branches

2022-02-02 Thread will at willusher dot io via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104359

--- Comment #2 from Will Usher  ---
Oh gotcha, then this can be closed.

[Bug c++/104359] GCC Treats bool with value != 1 as falsey when picking branches

2022-02-02 Thread pinskia at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104359

Andrew Pinski  changed:

   What|Removed |Added

 Ever confirmed|0   |1
   Last reconfirmed||2022-02-03
 Status|UNCONFIRMED |WAITING

--- Comment #1 from Andrew Pinski  ---
This is undefined behavior so anything can happen.
Why do you think GCC should act consistent here?

Using -fsanitize=undefined, I get:
/app/example.cpp:9:9: runtime error: load of value 255, which is not a valid
value for type 'bool'
/app/example.cpp:14:5: runtime error: load of value 255, which is not a valid
value for type 'bool'