为什么这code会崩溃吗？ [英] why does this code crash?

问题描述

为什么这code会崩溃吗？
使用 strcat的非法的字符指针？

why does this code crash? is using strcat illegal on character pointers?

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

int main()
{
   char *s1 = "Hello, ";
   char *s2 = "world!";
   char *s3 = strcat(s1, s2);
   printf("%s",s3);
   return 0;
}

请给一个适当的方式，参照这两个数组和指针。

please give a proper way with referring to both array and pointers.

推荐答案

的问题是， S1 指向一个字符串文字，你试图通过追加到修改 S2 它。你不允许修改字符串。您需要创建一个字符数组和两个字符串复制到它，像这样：

The problem is that s1 points to a string literal and you are trying to modify it by appending s2 to it. You are not allowed to modify string literals. You need to create a character array and copy both strings into it, like so:

char *s1 = "Hello, ";
char *s2 = "world!";

char s3[100] = ""; /* note that it must be large enough! */
strcat(s3, s1);
strcat(s3, s2);
printf("%s", s3);

足够大是指至少的strlen（S1）+ strlen的（S2）+ 1 。在 + 1 是占空终止符。

虽然这样说，你应该认真考虑使用 strncat函数（或者可以说是更好，但非标准 strlcat提供，如果它是可用），这是边界检查，因而远远优于 strcat的。

That having been said, you should seriously consider using strncat (or the arguably better but nonstandard strlcat, if it is available), which are bounds-checked, and thus are far superior to strcat.

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