Static hint in variable length arrays

Question

I'm a bit confused at the difference here, in C99:

int myfunc (int array[n], int n) { ... }

will not compile. As far as I know you must always put the reference to the array size first, so it has to be written:

int myfunc (int n, int array[n]) { ... }

But if you supply the static keyword, this works absolutely fine:

int myfunc (int array[static 1], int n) { ... }

This order if far preferable to me, as I'm used to having arrays come first in a function call, but why is this possible?

Edit: Realising that the third example isn't actually a VLA helps...

For reference, this was the piece of code I was looking at that led to the question:

int sum_array(int n, int m, int a[n][m])
{
  int i, j, sum = 0;
  for (i = 0; i < n; i++)
    for (j = 0; j < m; j++)
      sum += a[i][j];
  return sum;
}

Answer 1

The reason why

int myfunc (int n, int array[n]) { ... }

is valid and

int myfunc (int array[n], int n) { ... }

is not is due to the lexical scoping rules of C. An identifier cannot be used before it has been introduced in the scope. There are a few exceptions to this rule but this one is not one of them.

EDIT: here is the relevant paragraph of the C Standard:

(C99, 6.2.1p7) "Any other identifier has scope that begins just after the completion of its declarator."

This rule also applies to parameters declaration at function prototype scope.