warning: comparison between pointer and integer ？？

Question

代码

标签 ：my_fgets.c

#include<stdio.h>

char *my_fgets(char *s,int maxlen,FILE *fp)
{
    register int c;
    register char *cs;
    
    cs = s;
    while(--maxlen >0 && (c = getc(fp)) != EOF)
        if((*cs++ = c) == '\n')
            break;
    *cs = '\0';
    return (c == EOF && cs == s)? NULL: cs;
}

标签 ： my_getline.c

#include<stdio.h>
#include<string.h>

/* getline : read a line, return lenght */ 
int my_getline(char *line, int max,FILE *fp)
{
    if ( (my_fgets(line, max, fp)) == NULL)
        return 0;
    else
        return strlen(line);
}

错误

[root@server0 fgets]# gcc -c my_getline.c
my_getline.c: In function ‘my_getline’:
my_getline.c:7:36: warning: comparison between pointer and integer [enabled by default]
     if ( (my_fgets(line, max, fp)) == NULL)
                                    ^

请问为什么会有这错误？

Answer 1

我在stackoverflow上提问得到了答案：
https://stackoverflow.com/que...

Answer 2

你贴的代码和报错的代码都不是同一个好吗！