Question

The following code is from The Practice of Programming:

int scmp(const void *p1, const void *p2)
{
    char *v1, *v2;
    v1 = *(char **) p1;
    v2 = *(char **) p2;
    return strcmp(v1, v2);
}

I don’t understand why using the expression *(char **) p1. Can we use (char *)p1 instead?
What is the difference between them?

Thanks!

Answer 1

No. The (char **) is a type cast, and the unary * which precedes the cast dereferences the pointer. If you simply take v1 = (char *) p1, then v1 will be set equal to p1, when what you want is for v1 to be equal to the char* to which p1 points.