Question

I can’t seem to understand the difference between the following to pointer notations, can someone please guide me?

 typedef struct some_struct struct_name;
  struct_name this;
  char buf[50];
  this = *((some_struct *)(buf));

Now I tried to play around a bit and did the above thing like:

  struct some_struct * this;
     char buf[50];
     this=(struct some_struct *)buf; 

As far as I am concerned I think both the implementations should generate the same result, Can someone guide me whether there is a difference between the two and if yes can some one point it out?

Thanks.

Answer 1

In your first snippet, this is not a pointer, it’s an instance of some_struct. The assignment you made did a shallow copy (i.e. memcpy()) of what’s in buf as if it were an instance of some_struct as well.

In the second snippet, this is a pointer, and it’s just pointed to the address of buf.

So, basically to sum up, first snippet this is not a pointer and the struct is copied into it. In the second, it’s a pointer and assigned to the same memory as buf (i.e. not a copy).