Strlen返回不合理的数字 [英] Strlen returns unreasonable number

问题描述

如果我写：

char  lili [3];
cout<<strlen(lili)<<endl;

那么打印的是：11

但是如果我写：

char  lili [3];
lili [3]='\0';
cout<<strlen(lili)<<endl;

那么我得到3。

不理解为什么它在第一部分返回11？

不是strlen应该返回3，因为我为 lili 分配了3个字符？

I don't understand why it returns 11 on the first part?
Isn't strlen supposed to return 3, since I allocated 3 chars for lili?

推荐答案

这是因为 strlen 终止字符串。如果你给它一个简单的指针或未初始化的缓冲区，如你在第一个例子中，它将继续前进通过内存，直到它a）找到一个 \0 ，在这一点它会返回那个字符串的长度，或b）直到它到达受保护的内存位置并产生错误。

It is because strlen works with "C-style" null terminated strings. If you give it a plain pointer or uninitialised buffer as you did in your first example, it will keep marching through memory until it a) finds a \0, at which point it will return the length of that "string", or b) until it reaches a protected memory location and generates an error.

由于你已经标记了这个C ++，也许你应该考虑使用 std :: array 或更好， std :: string 。两者都提供长度返回函数（ size（）），并且都有一些额外的范围检查逻辑，这将有助于防止你的代码漫游到未初始化的内存区域。

Given that you've tagged this C++, perhaps you should consider using std::array or better yet, std::string. Both provide length-returning functions (size()) and both have some additional range checking logic that will help prevent your code from wandering into uninitialised memory regions as you're doing here.

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