不以N结尾的C样式字符串 [英] Not null-terminating a C-style string

问题描述

给出一个字符串，比如说，

Given a string , say ,

char *str = "Hello,StackOverflow!"
char newStr[30];
int l = strlen(str);
for(int i =0 ; i<l ; i ++ )
   newStr[i] = str[i];
printf("%s" , newStr);

现在，我们知道c字符串的最后一个字符必须是'\0'，因为这里我们还没有明确地做同样的事情（将'\0'存储在字符串newStr的最后一个索引中），该程序应该崩溃，因为printf找不到

Now , we know that the last character of a c-string has to be '\0' , Since here we haven't explicitly done the same ( store '\0' at last index of string newStr) , this program should crash since printf won't find the end of string.

但是我注意到有时它工作得很好，有时却不行。可能是什么问题呢 ？实际上，它几乎每次都在工作。它不是应该崩溃还是给出一些运行时错误？

But I noticed that it was working fine sometimes and sometimes it wasn't. What could be the problem ? It was working almost everytime actually. Isn't it supposed to crash or give some run-time error?

在C ++中也是如此吗？

Will it be the same case in C++ too ?

推荐答案

没有。它会调用未定义的行为-这意味着它不会必须崩溃-它可以执行任何操作，例如鼻恶魔。

No. It invokes undefined behavior - it means it doesn't have to crash - it can do literally anything, like nasal demons.

此外，给出运行时错误-好吧，这取决于做什么您的意思是运行时错误。 C没有动态运行时-如果您期望异常产生格式正确的错误消息，则不会发生这种情况。可能会发生分段错误。

Also, "gives a runtime error" - well, that depends on what do you mean by a runtime error. There's no dynamic runtime for C - if you expect a nicely formatted error message from an exception, that wouldn't happen. What would happen is most likely a segmentation fault.

总而言之，如果一个人导致/使用了未定义的行为，他一定不能依靠它崩溃或不崩溃。

All in all, if one causes/uses undefined behavior, he must not rely on it crashing or not crashing.

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