Question

does any one know if, for example, I’m writing in c++ the following code:

int a;
void *ptr = &a;
ptr = (char *)ptr + 1; //<-- this is the interesting line;

Does the (char *) only tells the compiler how to address this variable?
Or does it actually add more calculations in run time?

Thanks.

Answer 1

In this case, no extra calculations are done.

However, there are some cases where a cast is technically a conversion, mostly with numeric input. For example the following could introduce runtime code (provided it is not optimised out, which in a small example like this you’d expect it to be):

int x = 42;
double d = (double)x;

Here the internal representation of an int and a double means you cannot just change how the compiler sees the variable, you have to change the data as well.