unsigned long long int with os-x

[Segher Boessenkool]

Nicholas Strauss wrote:
> 
> Hi,
> 
> I'm trying to use gcc in darwin os-x. I've written the following piece of code:
> 
> int main(int argc, char *argv[])
> {
> unsigned long long int u;
> 
> u = 1<<63;

This is the int 1 shifted by 63 bits to the left; that's "undefined behaviour"
by the C standard (and will probably result in 0).

Write

	u = 1LL << 63;

instead.

> printf("u: %ld uu: %ld\n", u, u-1);
> printf("maxint %ld\n", INT64_MAX);
> }
> 
> What compiler/linker options should I use with gcc?

No special options are needed.  But try out -Wall and -W.

> What format should I use with printf?

"%lld" if I remember correctly.


Have fun,

Segher