Em seg., 31 de ago. de 2020 às 14:00, Alvaro Herrera <
[email protected]> escreveu:
> On 2020-Aug-31, Ranier Vilela wrote:
>
> > More troubles with undefined-behavior.
> >
> > This type of code can leaves overflow:
> > var = (cast) (expression);
> > diff = (int32) (id1 - id2);
> >
> > See:
> > diff64 = ((long int) d1 - (long int) d2);
> > diff64=-4294901760
>
> Did you compile this with gcc -fwrapv?
>
gcc 10.2 -O2 -fwrapv
bool test1()
{
unsigned int d1 = 3;
unsigned int d2 = 4294901763;
long int diff64 = 0;
diff64 = ((long int) d1 - (long int) d2);
return (diff64 < 0);
}
output:
mov eax, 1
ret
What is a workaround for msvc 2019 (64 bits) and clang 64 bits (linux)?
transam.c:311:22: runtime error: unsigned integer overflow: 3 - 4294901763
cannot be represented in type 'unsigned int'
Ranier Vilela
