c - Pointer manipulation inside function

Question

Let's say I have a pointer pointing to memory

0x10000000

I want to add to it so it traverses down memory, for example:

0x10000000 + 5 = 0x10000005

How would I do this inside a function? How would I pass in the address that the pointer points to, and inside the function add 5 to it, then after the function's complete, I can use that value?

Answer 1

You have two options:

1. The function can return the updated pointer.

   char *f(char *ptr) {
       ptr += 5;
       return ptr;
   }
   

The caller then does:

    char *p = some_initialization;
    p = f(p);

2. The function argument can be a pointer to a pointer, which it indirects through:

   void f(char **ptr_ptr) {
       *ptr += 5;
   }
   

The caller then does:

    char *p = some_initialization;
    f(&p);