🚀 go-pugleaf

a_rubin@dsg4.dse.beckman.com (Arthur Rubin) writes:

>>	int a, b;
>>	long c;

>>	c = a * b;

>(peter commented further that this works on a PDP-11).
>Aside from there being no guarantee that "long" is longer than "int", I
>don't think it is LEGAL for ANSI C to do this

No, a conforming C implementation can use an n*n -> 2n multiplication
primitive in this case.  If (int) (a*b) would not overflow, then you
get the same answer either way, so the `as-if' rule applies; and if
(int) (a*b) would overflow, then the result is undefined, so the
implementation can do what it pleases, including delivering the
mathematically correct answer!