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347

I love new features (lemmy.zip)

submitted 3 months ago by Maven@lemmy.zip to c/programmer_humor@programming.dev

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[–] bleistift2@sopuli.xyz 2 points 3 months ago (1 children)

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 points 3 months ago* (last edited 3 months ago) (2 children)

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.xyz 1 points 3 months ago (1 children)

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 points 3 months 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

[–] bane_killgrind@slrpnk.net 1 points 3 months ago

Magic.

Blasphemy.