Question

I’m trying to write a function that takes a void pointer to an int and then doubles the int, and puts it back into the memory location:

void doubleNumber(void *number){
    number = &((*((int*)(number))) * 2);

} 

So first I cast it into an int * from a void *, then I deference the int * to get the value, then I multiply by 2 and then I get the address of that to put it back into the pointer.

Can anyone give me tips on why my logic is not working?

Thanks

Answer 1

I’d write it like this:

void doubleNumber(void *number){
    *(int*)number *= 2;
}

First of all cast number to be of type int*. Then dereference the pointer. Then double it.

The problem with your code is that you are assigning the pointer rather than the pointee.