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Comment by codegeek

4 days ago

"Are pointers really that hard for so many people to understand?"

The * vs & always gets me and not to mention if I ever have to deal with Pointer Math.

6 comments

codegeek

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bionsystem  4 days ago

Think of it as types. All of the following are the same thing (declare p as an int* type). It's important for the end :

  int * p;
  int *p;
  int* p;

Now remember that the type is a memory address. I'm sure it is semantically wrong for whatever reason somebody will explain but it helps to think about it. So you can do :

  int my_number = 6;
  int* p = &my_number;

Both sides of the "=" are the same type (int* is an address, and &my_number is also an address, the one of my_number).

Now p is a pointer (or an int* or an address), and *p is... an int ! So this is totally valid :

  printf("%d\n", *p)

and for anything else than int you need to malloc that so you will see a lot of :

  my_struct* s = malloc(sizeof(my_struct);

which makes sense because malloc returns an address (the beginning address of the content of s ; yet again somebody will tell me I'm wrong to call it "the content of s" so sorry for that).

  my_struct* // is the type of s, it is an address
  my_struct // is the type of *s (some custom type of size sizeof(my_struct))

  • 1718627440  4 days ago

    > int* p

    I don't like that syntax, because it confuses people. It might be sensible to think of the type as (int *), but C just doesn't work this way. You might never declare more that a single variable in a statement, but it still gives people the wrong intuition.

    • usefulcat  3 days ago

      > int* p

      I very much prefer that syntax, because the '*' is part of the type, not part of the variable name.

      > You might never declare more that a single variable in a statement

          int a, *b, c, *d;

      Yes, you can do that, and in fact if you want to declare multiple pointers on the same line, you are required to put a '*' in front of every pointer variable name.

      Personally, I've always considered this to be a defect of the language. Would it really be so awful to have to write instead:

          // Both are of type 'int'. Pretty straightforward.
    int  a, c;
    // In my fantasy world, both of these would be of type 'pointer to int',
    // but IRL b is a pointer and d is an int. fun!
    int* b, d;

      But of course that's not the language we have.

      I'd be very curious to know the motivation for requiring a '*' in front of each pointer variable name, as opposed to once with the type. So far the only ones I've thought of (not mutually exclusive) are:

      a) we REALLY love terseness, and

      b) ooh look at this clever hack I came up with for variable declaration syntax.

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