Are the members of a global structure initialized to zero by default in C?

Question

Are the members of a global or static structure in C guaranteed to be automatically initialized to zero, in the same way that uninitialized global or static variables are?

Answer 1

Local variables are not initialized.

struct foobar {
    int x;
};

int main(void) {
    struct foobar qux;
    /* qux is uninitialized. It is a local variable */
    return 0;
}

static local variables are initialized to 0 (zero)

struct foobar {
    int x;
};

int main(void) {
    static struct foobar qux;
    /* qux is initialized (to 0). It is a static local variable */
    return 0;
}

Global variables are initialized to 0 (zero)

struct foobar {
    int x;
};
struct foobar qux;
/* qux is initialized (to 0). It is a global variable */

int main(void) {
    return 0;
}