static char * sk_proxy_socket_error (Socket s)
static const char * sk_proxy_socket_error (Socket s)
static char * sk_proxy_socket_error (Socket s){    Proxy_Socket ps = (Proxy_Socket) s;    if (ps->error != NULL || ps->sub_socket == NULL) {	return ps->error;    }    return sk_socket_error(ps->sub_socket);}