Eric Chamberland <eric.chamberl...@giref.ulaval.ca> writes:
> int main() {
> int a=1741445953; // my number of unknowns...
> int b=2*(a+2);
> unsigned long int c = b;
> std::cout << " a: " << a << " b: " << b << " c: " << c <<std::endl;
> return 0;
> }
>
> and it gives:
>
> a: 1741445953 b: -812075386 c: 18446744072897476230
This comes from the integer casting rules.
$ cat overflow.c
#include <stdio.h>
int main(int argc,char **argv) {
int a=1741445953;
size_t a1 = 2*(a+2);
size_t a2 = 2ll*(a+2);
printf("%zd %zd\n", a1, a2);
return 0;
}
$ make overflow && ./overflow
cc overflow.c -o overflow
-812075386 3482891910
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