[Bug sanitizer/88479] sanitizer should provide an option to detect conversion to signed integer that overflows

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88479

--- Comment #3 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Jakub Jelinek from comment #2)
> Note, it is no longer implementation-defined behavior in C++20, but well
> defined:
> 
> "Otherwise, the result is the unique value of the destination type that is
> congruent to the source integer modulo 2^N, where N is the range exponent of
> the destination type.", see wg21.link/p1236 .  It wouldn't surprise me if
> next C standard changes similarly.

The C standard would have to drop ones' complement and sign-magnitude first.

In any case, this is not a good programming practice, and for some projects, it
is reasonable to avoid such cases (a function to do such a conversion
explicitly would have been a better choice). So, a new feature in the sanitizer
would be a good thing, just like -Werror=... can make the compilation of valid
programs fail but is useful to detect bugs.