HN

Comments (100)

• Menu

  Animats
  The real lack is that C doesn't have slices. Slices can do most of what pointers into arrays can do, with sane semantics. Slices were invented surprisingly late. They were implementable in the 1970s, but didn't really show up until the 1990s. Now that we have slices, the demand for pointers into the middle of an array has much decreased.I had a go at retrofitting C with slices over a decade ago.[1] Too much political hassle.[1] https://www.animats.com/papers/languages/safearraysforc43.pd...
• Menu

  alexey-salmin
  Interestingly the article doesn't mention two-dimensional arrays and they're curios because they bring a certain asymmetry with them. It always tripped me over the most in C because I otherwise find the language very "symmetrical". It often feels like in design of this language the beauty of expressing certain things took priority over readability or safety which I admire in a way. But somehow not in the case of the two-dimensional arrays.If you see a[i][j] it could mean two completely different things:1) "a" is a continuous chunk of memory of N*M bytes, so it behaves as char*; a[i][j] == *(a + i*M + j)2) "a" is an array of char* pointers that point to N completely distinct memory chunks of size M, so it behaves as char**; a[i][j] == *(*(a + i) + j)With flat arrays the difference between an array as a variable and a pointer to the first element is literally negligible because you won't even see the difference in the assembly. This is why the automatic decay-to-pointer makes a lot of sense.But that breaks completely with multiple dimensions. You definitely see the difference in the assembly because the memory layout is so different.
• Menu

  uecker
  In practice, the [static n] notation can give you useful warnings and bounds checking.https://godbolt.org/z/PzcjW4zKKAnd 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
• Menu

  kazinator
  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.
• Menu

  fooker
  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.
• danborn26
  C's array decay into pointers still catches me off guard sometimes. It is definitely one of those quirks you just have to memorize.
• Menu

  mlmonkey
  It still cracks me up that 3[x] and x[3] mean the same thing in C.
• Menu

  the__alchemist
  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.
• Menu

  RobotToaster
  It's still weird to me that you can declare an array with the register keyword.Then it (understandably) becomes UB to attempt to get the pointer.(It also probably isn't stored in a register, since the keyword is just asking the compiler nicely.)
• moktonar
  int x[n] and int *x are very different things when it comes to defining memory layout tho. In one case you end up with n int sized slots of memory, in the second with one register sized slot. That makes all the difference when defining structs for example.
• jason_s
  From the title, I thought they were going to point out that `a[2]` and `2[a]` have identical meaning in C.
• Menu

  IncreasePosts
  Paging walter bright
• Menu

  fatty_patty89
  there's no array type in c
• Menu

  throwaway27448
  Why are we still discussing c in 2026? Why are you intentionally hamstringing yourself unless you're using fucking hp-ux