C ++ 11字符串的分配要求 [英] C++11 Allocation Requirement on Strings

问题描述

我听说C ++ 11需要 string s在连续内存中分配。我甚至认为我看到一个堆栈溢出问题，但我似乎找不到它。

I had heard that C++11 was going to require strings to be allocated in contiguous memory. I even thought I saw a stack overflow question on it, but I can't seem to find it.

我知道在实践中，gcc和Visual Studio做分配<

I know that in practice both gcc and Visual Studio do allocate strings contiguously, I'm just asking as to the standard's requirements.

推荐答案

p> 2011年标准的第21.4.1.5节规定：

Section 21.4.1.5 of the 2011 standard states:

basic_string 对象应该连续存储
。也就是说，对于任何 basic_string 对象 s ，标识
& （s.begin（）+ n）==& * s.begin（）+ n 将适用于
n 使得 0 <= n < s.size（）。

The char-like objects in a basic_string object shall be stored contiguously. That is, for any basic_string object s, the identity &*(s.begin() + n) == &*s.begin() + n shall hold for all values of n such that 0 <= n < s.size().

身份表达式的两部分是

1. 以 begin（）迭代器前进 n ，然后取消引用并获取结果元素的地址。


2. 使用 begin（）迭代器，的所得元素。将 n 添加到此指针。

1. Take the begin() iterator, advance by n, then dereference and take the address of the resulting element.
2. Take the begin() iterator, dereference and take the address of the resulting element. Add n to this pointer.

由于两者都必须相同，这将强制执行连续存储;也就是说，迭代器不能在不违反这个要求的情况下移动任何不连续的存储。

Since both are required to be identical, this enforces contiguous storage; that is, the iterator cannot move over any non-contiguous storage without violating this requirement.

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