extern declaration and global scope

Question

I'm wondering why is this code compiles and run. I thought that if a variable is declared as static (in global scope) it will be accessible only within the file it is declared.

functions.h

static int x = 10;

main.c

#include <stdio.h>
#include "functions.h"

extern int x;

int main()
{
   printf("%d", x);
}

Answer 1

Technically, it is indeed declared within the main.c, as this includes the functions.h. If it was a sparate compilation module, you'd be right.

But I'd have suspected that within the same compilation unit extern and staticwould collide with each other. At least it would be worth a warning.