struct vector {
    float x;
    float y;
};

struct ship {
    struct vector *position;
};

struct game {
    struct ship *ship;
} game;

static void
create_ship(struct ship *ship)
{
    ship = malloc(sizeof(struct ship));
    ship->position = malloc(sizeof(struct vector));
    ship->position->x = 10.0;
}

int main() {
    create_ship(game.ship);
    printf("%fn", game.ship->position->x); // <-- SEGFAULT
}

static void
create_ship(struct ship **ship)
{
    *ship = malloc(sizeof(struct ship));
    (*ship)->position = malloc(sizeof(struct vector));
    (*ship)->position->x = 10.0;
}

create_ship(&game.ship);

static struct ship* create_ship()
{
    struct ship* s = malloc(sizeof(struct ship));
    s->position = malloc(sizeof(struct vector));
    s->position->x = 10.0;

    return s;
}

game.ship = create_ship();

static void create_ship(struct ship **ship);

create_ship(&game.ship);

static void create_ship(struct ship **ship)
{
    *ship = malloc(sizeof(struct ship));
    // ...

static ship *create_ship()
{
    struct ship *ship = malloc(sizeof(struct ship));
    // ...

    return ship;
}

// ...

game.ship = create_ship();