std :: string :: c_str（）如何返回不会导致内存泄漏或未定义的c字符串内容的c字符串？ [英] How does std::string::c_str() return a c-string that does not cause a memory leak or undefined c-string contents?

问题描述

我正在写一个类似于std :: string的字符串类作为家庭作业，但我不知道如何返回一个不会导致内存泄漏的c字符串，并保证保持不变直到它不再使用。我目前有：

I'm writing a string class that is similar to std::string for a homework assignment, but I cannot figure out how to return a c-string that does not cause a memory leak and is guaranteed to stay the same until it is no longer in use. I currently have:

const char* string::c_str()
{
    char c[_size+1];
    strncpy(c,_data,_size);
    c[_size]='\0';
    return c;
}

但内容在调用后不久就会覆盖。如果我做动态分配，我将有一个内存泄漏或任何时候只有一个c字符串可以存在从给定的字符串。如何避免这种情况？

but the contents are overridden shortly after it is called. If I do dynamic allocation, I'll have either a memory leak or only one c-string can exist from a given string at any time. How can I avoid this?

推荐答案

但是 c_str指向的字符串只有在下一次修改（或销毁） std :: string 之前才有明确定义。

But the string pointed to by c_str is only well-defined until the std::string is next modified (or destroyed).

实现这可能是简单地返回一个指针到你的内部缓冲区（假设它是null终止）。请记住，符合标准的 c_str 必须在O（1）次操作;因此不允许复制。

One way to achieve this might be simply to return a pointer to your internal buffer (assuming it's null-terminated). Bear in mind that a standards-compliant c_str has to operate in O(1) time; so copying is not permitted.

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