You have been able to return a struct by value in C since at least C89:

    typedef struct {
        double d;
        int err;
    } Ret;

    Ret foo(void) {
        Ret r = { 0.0, 43};
        return r;
    }

    int main() {
        Ret r = foo();
    }

You can't return a bare fixed-size array though.