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Comment by unnouinceput | Hacker News Reader

Quote: "4. Flexible array members ..... int elems[]; // <-- flexible array member"

TIL that a dynamic array is also called flexible. This generation, out of boringness, is trying to redefine well established paradigms? Because, for me, a 90's formed developer, "flexible" means maybe inheritance, or even better polymorphism. There is nothing flexible about a dynamic array. Its structure is well defined in the stack/heap, and with current compiler optimizations can even be demoted to a simple static array for faster access within CPU registries.

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"Dynamic array" refers to block of memory allocated via malloc() which you just happen to use as array.

"Flexible array member" [0] is when you have a struct and its last member is an array with unspecified size.

An example:

  #include <stdio.h>
  #include <stdlib.h>
  
  struct Foo {
      int len;
      int* arr; // dynamic "array"
  };
  
  struct Bar {
      int len;
      int arr[]; // FAM
  };
  
  int main()
  {
      const int n = 12;
  
      // have to allocate myself; no guarante it will be nearby the rest of struct
      struct Foo* a = malloc(sizeof a);
      a->arr = malloc(n * sizeof *(a->arr));
  
      // array is part of the memory allocated for struct
      struct Bar* x = malloc((sizeof x) + n*(sizeof *(x->arr)));
  
      return 0;
  }

[0]: https://en.wikipedia.org/wiki/Flexible_array_member

>"Dynamic array" refers to block of memory allocated via malloc() which you just happen to use as array.<

No. A dynamic array is an array which can be expanded or shrinked during its runtime life. The fact that C/C++ uses malloc for that (and btw, it's not the only way to do it) it's her problem. In other languages you have dynamic arrays that can be expanded/shrinked without using an extra line - main reason why nowadays Rust is a replacement for C/C++

>[0]< From you own wiki reference: "the flexible array member must be last"

LMAO, really? Well, that indeed is a bigger C quirk. In Pascal, as an example, I can have it anywhere inside the record (struct equivalent of C), and it can be just as "flexible".

It has to be last because it's not a pointer to the array, it is the array. The array elements are immediately after the struct in memory. You can't resize it without reallocating the whole struct.

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