static char *genstr(char *prefix, int i) {
    static char result[64] = {0};
    snprintf(result, sizeof(result), "%s%d", prefix, i);
    return result;
}
static char *genstr(char *prefix, int i) {
    static char result[64] = {0};
    snprintf(result, sizeof(result), "%s%d", prefix, i);
    return result;
}