copy to void* pointer

Question

I have a function getData(void* data) which should copy to data some internal calculated values for example int r = getRadius(); r should be copied to data ,and is such a way returned from function getData what is the correct way to do it? I tried *(int*)data = r; but I am not sure this is a best solution.

Solution

If you are certain that the memory referenced by the void pointer is an int, then you can be confident in

*(int *)data = r;

However a better general solution is:

memcpy(data, &r, sizeof(int));

This way you don't have to worry about byte alignment or other potential gotchas.