调试手段

#define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__)

main()
{
    char *p ="it is:"
    debug("%s %d", p, num);
    return 0;
}

int main(int argc, char **argv)
{
    printf("%s(%d)-%s: this is main\n",__FILE__,__LINE__,__FUNCTION__);
    funca();
    printf("%s(%d)-%s: this is main\n",__FILE__,__LINE__,__FUNCTION__);
    funcb();
    printf("%s(%d)-%s: this is main\n",__FILE__,__LINE__,__FUNCTION__);
    return 0;
}