void owl_print_error(const char *s, int n)
{
    if(n < 0) printf("%s: %d\n", s, n);
    else if(n == OWL_NO_ERROR) printf("%s: No Error\n", s);
    else if(n == OWL_INVALID_VALUE) printf("%s: Invalid Value\n", s);
    else if(n == OWL_INVALID_ENUM) printf("%s: Invalid Enum\n", s);
    else if(n == OWL_INVALID_OPERATION) printf("%s: Invalid Operation\n", s);
    else printf("%s: 0x%x\n", s, n);
}