array declared with static keyword: what is static, the pointer or the whole array?

Question

Simple but tricky question:

void f() {
    static int a[3] = {1, 2, 3};
    ...

What is static here? The pointer to array or the whole array?

Can anybody point me to definition of that in the C standard?

Thanks!

Answer 1

From the ISO C99 standard (section 6.2.1, "Scopes of identifiers"):

3 If the declaration of a file scope identifier for an object or a function contains the storage-class specifier static, the identifier has internal linkage.22)

In your example it's the a identifier that becomes static (i.e. the symbol in the object file is not exported).

EDIT:

For non-file scope static declarations (section 6.2.4, "Storage durations of objects")

3 An object whose identifier is declared with external or internal linkage, or with the storage-class specifier static has static storage duration. Its lifetime is the entire execution of the program and its stored value is initialized only once, prior to program startup.

I take it this to mean that the array itself becomes static in this case, which makes sense, since the identifier would have invalid contents otherwise.

Answer 2

It applies to the array. There is no pointer in your code. Array is not pointer.

#include <stdlib.h>
#include <stdio.h>

void f() {
    static int a[3] = {1, 2, 3};
        a[1]++;
        printf("%d\n", a[1]);
}

main()
{
        int i;
        for (i = 0; i < 5; i++)
        {
                f();
        }
}

outputs

3
4
5
6
7