• bleistift2@sopuli.xyzEnglish
    28·
    6 days ago

    linked lists, trees, objects with references to other objects

    That’s not a pointer to another pointer, but a pointer to a data structure that happens to contain another pointer.

    • Lightfire228@pawb.social
      16·
      6 days ago

      The distinction is meaningless in the land of Opcode’s and memory addresses

      For example, a struct is just an imaginary “overlay” on top of a contiguous section of memory

      Say you have a struct

      struct Thing {
  int a;
  int b;
  Thing* child;
}

Thing foo {}

      You could easily get a reference to foo->child->b by doing pointer arithmetic

      *((*((*foo) + size(int)*2)) +size(int))

      (I’ve not used C much so I’ve probably got the syntax wrong)

      • bleistift2@sopuli.xyzEnglish
        1·
        6 days ago

        Yes, you can do crazy shit if you try hard enough, but every reasonable programmer would access foo->child->b als foo->child->b and not via that crazy LISPy expression.

        By question was: Why would you have a pointer to a memory address that itself only holds a pointer somewhere else?

        So far the only reasonable explanation is from @Victoria@lemmy.blahaj.zone:

        • arrays of function pointers
        • pass by reference of a pointer
        • Lightfire228@pawb.social
          1·
          5 days ago

          I’m more talking about theory than practical.

          I’ve not developed anything in C/C++, so I don’t know practical uses for a double pointer, aside from multidimensional arrays, or arrays of pointers

          My point was that, conceptually, pointers to pointers is how most complex data structures work. Even if the C representation of said code doesn’t have a int** somewhere