[英]Conflicting types for 'reverse_string' function
I was using this SO question as part of a program that needs to reverse a string. 我正在使用这个SO问题作为需要反转字符串的程序的一部分。 The problem I am having is that I cannot seem to get the function to work.
我遇到的问题是我似乎无法使功能发挥作用。 Here is the code I have:
这是我的代码:
int main(int argc, char *argv[]){
char *test = "Testing";
fputs(test, stdout);
fputs(reverse_string(test), stdout);
}
char* reverse_string(char *str){
char temp;
size_t len = strlen(str) - 1;
size_t i;
size_t k = len;
for(i = 0; i < (len +1)/2; i++){
temp = str[k];
str[k] = str[i];
str[i] = temp;
k--;
}
return str;
}
I am getting an error that there is conflicting types for 'reverse_string'
我收到一个错误,即
conflicting types for 'reverse_string'
存在conflicting types for 'reverse_string'
Edit: For anyone wondering here is the code that works. 编辑:对于任何想知道这里的人来说,代码是有效的。 See @chux's answer for an explanation.
请参阅@ chux的答案以获得解释。
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
char* reverse_string(char *str){
char temp;
size_t len = strlen(str) - 1;
size_t i;
size_t k = len;
for(i = 0; i < (len +1)/2; i++){
temp = str[k];
str[k] = str[i];
str[i] = temp;
k--;
}
return str;
}
int main(int argc, char *argv[]){
char test[] = "Testing";
fputs(test, stdout);
fputs(reverse_string(test), stdout);
}
You can not pass a const char *
to a char *
你不能将
const char *
传递给char *
char *test = "Testing";
fputs(reverse_string(test), ... // bad, attempting to change constant data.
// bad as reverse_string() is assumed to return int, but fputs() expects char *
char* reverse_string(char *str) { // Bad, there's now a function conflict
Instead 代替
char* reverse_string(char *str); // Need to declare/define function first
char test[] = "Testing";
fputs(reverse_string(test), ... // good
[Edit] [编辑]
You problem was well identified (missing function declaration) by others. 其他人很好地识别了您的问题(缺少函数声明)。 My suggestion takes care of the next problem.
我的建议处理下一个问题。 In C, a missing declaration of a function will assume
int reverse_string(...)
which does not match char* reverse_string(char *str)
. 在C中,函数的缺失声明将假定
int reverse_string(...)
与char* reverse_string(char *str)
不匹配。
[Edit] [编辑]
As @Shafik Yaghmou suggests, modifying a string literal char *test = "Testing"
will result in undefined behavior. 正如@Shafik Yaghmou所建议的那样,修改字符串文字
char *test = "Testing"
将导致未定义的行为。 Hence the char test[] = "Testing"
which initializes test
with "Testing\\0", but may be modified. 因此
char test[] = "Testing"
用“Testing \\ 0”初始化test
,但可以修改。
[Edit] [编辑]
@GreenAsJade correctly points out OP's original error message is due to the assumed int reverse_string(...)
supplying an int
to s
in int fputs(const char * s, FILE * stream);
@GreenAsJade正确地指出OP的原始错误消息是由于假定的
int reverse_string(...)
在int fputs(const char * s, FILE * stream);
为s
提供了一个int
int fputs(const char * s, FILE * stream);
char *test1 = "Testing"
is not the same thing as char test2[] = "Testing"
. char *test1 = "Testing"
与char test2[] = "Testing"
。 test1
becomes a char *
with the size of a pointer. test1
变成一个带有指针大小的char *
。 The initial pointer value is to a string "Testing" located elsewhere in memory. 初始指针值是位于内存中其他位置的字符串“Testing”。
test2
is a char
array with size 8: length of "Testing" + 1 for '\\0'. test2
是一个大小为8的char
数组:长度为“Testing”+ 1为'\\ 0'。 The array test2
is initialized with 'T', 'e', ... '\\0' etc. 数组
test2
初始化为'T','e',...'\\ 0'等。
FWIW: FWIW:
(h2hh)momerath:Documents mgregory$ cat test.c
char* reverse_string(char *str) {
return str;
}
char *test = "Testing";
int main() {
reverse_string(test);
}
(h2hh)momerath:Documents mgregory$ gcc test.c
(h2hh)momerath:Documents mgregory$
I think that the answer to the OP's question is that reverse_string has to be declared before being used, to be not int. 我认为OP问题的答案是必须在使用之前声明reverse_string,而不是int。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.