C : 警告:赋值使指针从整数而不进行强制转换 [默认启用] [英] C : warning: assignment makes pointer from integer without a cast [enabled by default]

问题描述

这是我的代码

#include<stdio.h>
#include<stdlib.h>

void main() {
    FILE *fp;
    char * word;
    char line[255];
    fp=fopen("input.txt","r");
    while(fgets(line,255,fp)){
        word=strtok(line," ");
        while(word){
            printf("%s",word);
            word=strtok(NULL," ");
        }
    }
}

这是我收到的警告.

token.c:10:7: warning: assignment makes pointer from integer without a cast [enabled by default]
   word=strtok(line," ");
       ^

token.c:13:8: warning: assignment makes pointer from integer without a cast [enabled by default]
    word=strtok(NULL," ");
        ^

word 被声明为 char*.那为什么会出现这个警告?

The word is declared as char*. Then why this warning arises?

推荐答案

Include #include 以获得 strtok() 的原型.

Include #include <string.h> to get the prototype for strtok().

您的编译器(如在 C99 之前的 C 中)假定 strtok() 会因此返回 int.但不提供函数声明/原型在现代 C(自 C99)中无效.

Your compiler (like in pre-C99 C) assumed strtok() returns an int because of that. But not providing function declaration/prototype is not valid in modern C (since C99).

在 C 中使用了一个旧规则，允许隐式函数声明.但是 implicit int rule 从 C99 开始就从 C 语言中删除了.

There used an old rule in C which allowed implicit function declarations. But implicit int rule has been removed from C language since C99.

参见:C 函数调用:理解隐式 int"；规则

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