C array types are weird

(anselmschueler.com)

54 points | by signa11 1 day ago

8 comments

  • fooker 44 minutes ago
    C array types are weird because C doesn't really need arrays. It's not what C was about.

    But if you designed a language in the era where Fortran, THE array language, reigned supreme, nobody would use your language. The mindshare Fortran had is difficult to convey now, half a century later.

    Think of it like making a chatbot today and not mentioning AI or LLMs, that's what making a language without arrays would have felt like in 1970.

  • uecker 1 day ago
    In practice, the [static n] notation can give you useful warnings and bounds checking.

    https://godbolt.org/z/PzcjW4zKK

    And while the (*array_ptr)[3] notation take a moment to get used to, it is very logical. If you have a pointer to an array, you dereference it first and then indx into it. Again, useful for bounds checking: https://godbolt.org/z/ao1so9KP7

    • keyle 2 hours ago
      I know of this notations but I don't see many people using [static n].

      Not sure why, maybe it doesn't feel like C anymore, maybe it feels hacky?

      typically if you're passed an array you'd want to get more anyway, so you'd get passed a struct. Not sure.

    • dnautics 3 hours ago
      What is **int[3][5]
      • thrance 2 hours ago
        A pointer to a pointer to a pointer to a pointer of integers.
      • ori_b 2 hours ago
        A syntax error. You need a variable name, not a type name, in the middle.
        • ori_b 2 hours ago
          And if you want 'int **arr[a][b]', it's a value that when you say 'x = **arr[m][n]', will evaluate to an int and assign it to x. Postfix has higher precedence than prefix.
        • fusslo 1 hour ago
          or a rejected PR
  • kazinator 1 hour ago
    There is a history to it; in one of the predecessor languages, like B, Ritchie actually had arrays that had a hidden pointer to their start. The "array to pointer decay" was actually a real operation that loaded an address from memory, and it was possible to twiddle the bits to relocate an array. One problem with it was no way to initialize such a pointer field that would allow an array to live in dynamically allocated storage (no constructors in the language).

    So in short, the bad design (array values produce pointers) was informed by conceptual compability with an earlier design in which that was literally happening.

  • the__alchemist 3 hours ago
    This is one of the things that I feel is an inappropriate abstraction that is around for historical reasons. When I do FFI to call C from rust, I usually wrap the generated API (Which is pointer based) into rust's &[] array syntax. Arrays/lists/Vecs etc in most non-C languages feel like an abstraction over a collection of items; I feel like C's exposing the pointer directly is taking a low-level memory/MMIO operation and inserting it into business logic. Conceptually, I like to keep them separate; pointers for writing drivers, accessing registers, writing to flash memory etc. Arrays/lists/vecs for higher level operations on collections.

    Tangent: I have a pet theory that part of Zig's raison d'etre is to fix some of the problems with C, while accommodating its pointer-based data structures, and the resulting patterns.

    • vulcan01 3 hours ago
      This talk – "Programming without pointers" – by Andrew Kelley may be interesting to you.

      https://www.hytradboi.com/2025/05c72e39-c07e-41bc-ac40-85e83...

      • throwaway27448 2 hours ago
        Learning to program with pointers is enormously useful. It's simply bad software engineering to not use typing to enforce constraints on access to pointers (or addresses, or however you'd like to term them)
        • doyougnu 13 minutes ago
          IIRC that talk of about using indices (u32) to represent data in an array. That is orthogonal to representing that information in the type system since you can just type the index
  • mlmonkey 25 minutes ago
    It still cracks me up that 3[x] and x[3] mean the same thing in C.
  • fatty_patty89 3 hours ago
    there's no array type in c
    • colejohnson66 3 hours ago
      Yes it does. It just decays to a pointer at the slightest touch.
      • throwaway27448 2 hours ago
        So why are we discussing it
        • dwattttt 2 hours ago
          Because doing a dance to avoid it decaying conveys better information to both the compiler and downstream users of your code.
  • IncreasePosts 3 hours ago
    Paging walter bright
    • glouwbug 3 hours ago
      C's biggest mistake.

      But in other news most don't know that a[3] == 3[a]

  • throwaway27448 2 hours ago
    Why are we still discussing c in 2026? Why are you intentionally hamstringing yourself unless you're using fucking hp-ux
    • smackeyacky 1 hour ago
      Embedded programming is still in C for a lot of micro controllers and whatnot. If you’re programming with limited resources it’s essential to understand pointers and arrays. Likely you won’t be doing anything useful without them
    • cartoonfoxes 2 hours ago
      • pdpi 1 hour ago
        As always, the TIOBE Index is of dubious value. The fact that it ranks Delphi above both Go and Rust should give you an idea of why.
      • mianos 2 hours ago
        p.s. in case you don't want to follow the link, number 2 on the list