uint64_t to int

Question

I'm writing a java binding for a C code and I'm not really familiar with C.

I have a uint64_t and need to cast it to a int. Does anyone know how to do that? (My binding returns then a jint...)

Answer 1

The short answer:

uint64_t foo;
int bar;
bar = foo;

Technically this has undefined behavior if the value of foo does not fit in an int. In practice, it will always simply truncate the upper bits. If you want to be more correct, then:

if (foo-INT_MIN <= (uint64_t)INT_MAX-INT_MIN)
    bar = foo;
else
    /* error case here */

Answer 2

Usually, using an exact width integer like 'uint64_t' is for a good reason. If you cast it to an int, which may not be 64bits long, you may have serious problems...