Re: technology discussion → does the world need a "new" C ?

On 09/07/2024 23:32, Kaz Kylheku wrote:

On 2024-07-09, bart <bc@freeuk.com> wrote:

On 09/07/2024 16:58, Ben Bacarisse wrote:

bart <bc@freeuk.com> writes:
>

Arrays are passed by reference:
>
    void F(int a[20]) {}
>
    int main(void) {
      int x[20];
      F(x);
    }

>
This is the sort of thing that bad tutors say to students so that they
never learn C properly.  All parameter passing in C is by value.  All of
it.  You just have to know (a) what the syntax means and (b) what values
get passed.

>
The end result is that a parameter declared with value-array syntax is
passed using a reference rather than by value.
>
And it does so because the language says, not because the ABI requires
it. A 2-byte array is also passed by reference.

 In C, arrays are not passed to functions, period.

Arrays can be passed by explicit reference:
   void F(int(*A)[20]) {
       printf("%zu\n", sizeof(*A)/sizeof((*A)[0]));    // shows 20
   }
That can be called like this:
   int a[20];
   F(&a);
Here, an actual array type is involved, which is passed by an actual pointer to array, not a pointer to its elements.

Therefore ABIs do not say anything about array parameters,
(or if they do, it's not in relation to C).

That makes a change; most people think that C invented ABIs, which were created in its image.
The Win64 ABI talks about aggregate types.