Question

I write more and more C applications, and now I wonder something about casts. In C++, a dynamic cast is a very costly operation (for instance a down-cast), but I don’t even know for static one.

In C, I had to write something like that:

assert ( p ); /* p is void* */
int v = *(int*)p;

Is it a « C dynamic-cast »? Is it quite the same as the static_cast<int*>(p) of C++? How much does it cost?

Thanks in advance.

Answer 1

A cast in C is only meaningful at compile time because it tells the compiler how you want to manipulate a piece of data. It does not change the actual value of the data. For example, (int*)p tells the compiler to treat p as a memory address to an integer. However this costs nothing at run time, the processor just deals with raw numbers the way they are given to it.