initializing static variable with a function call gives compilation error?

Question

#include 
int foo(){
    return 1;
}
int main(void) {
    static int q = foo(); 
    return 0;
}

Here is a link for the same. This i

Answer 1

All the static variables are compile time and the function is giving the output at run time so you are initializing a compile time variable with a run time variable which is not possible so it is giving error.

Another example may be as follows

int main()
{
int p=9;
static int x=p;
}

the above code is also gives you compile time error,The cause is same as above.