在网上复制了几个字符串截取的函数，请问下下图这个警告如何优雅消除。
顺便说一下最近用了clang编译器，错误和警告的提示信息确实要更人性化点

https://

abstraction:
Most compilers will warn about assignments as the top-level operation inside a while or if control expression. To the compiler it looks like you're writing while (x = y) and it thinks maybe you meant while (x == y). To tell it you really want while (x = y), you can add extra parentheses while ((x = y)), or to make it even more explicit, while ((x = y) != 0)

good luck!

感谢，已经没有警告了

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

char* str_l(char* src, char* dst, int n)
{
    char *p=src;
    char *q=dst;
    int len=strlen(src);
    if(n>len) n=len;
    while(n--) *(q++)=*(p++);
    *(q++)='\0';
    return dst;
}

char* str_r(char* src, char* dst, int n)
{
    char *p=src;
    char *q=dst;
    int len=strlen(src);
    if(n>len) n=len;
    p+=(len-n);
    while((*(q++)=*(p++)) != 0);
    return dst;
}

char* sub_str(char* src, char* dst, int start, int len)
{
    char* p=dst;
    char* q=src;
    int length=strlen(src);
    if(start >= length || start<0) return 0; 
    if(len>length) len=length-start; 
    q+=start;
    while(len--){   
        *(p++)=*(q++); 
    }  
    *(p++)='\0';  
    return dst;
}

int main(int argc, char ** argv)
{
    //str_l
    char* str = "dlrow olleh";
    char nstr[strlen(str)-2+1];
    str_l(str, nstr, strlen(str)-2);
    printf("%s\n", nstr);
    
    //str_r
    char* str1 = "dlrow olle-h";
    char nstr1[2+1];
    str_r(str1, nstr1, 2);
    printf("%s\n", nstr1);
    
    //sub_str
    char* str2 = "dlrow olle-h";
    char nstr2[5+1];
    sub_str(str2, nstr2, 3, 5);
    printf("%s\n", nstr2);

 
    return 0;   
}

[此贴子已经被作者于2021-9-5 22:17编辑过]