从同一个向量push_back一个元素是安全的吗？ [英] Is it safe to push_back an element from the same vector?

问题描述

vector<int> v;
v.push_back(1);
v.push_back(v[0]);

如果第二个push_back导致重新分配，向量中第一个整数的引用将不再有效。这是不安全的吗？

If the second push_back causes a reallocation, the reference to the first integer in the vector will no longer be valid. So this isn't safe?

vector<int> v;
v.push_back(1);
v.reserve(v.size() + 1);
v.push_back(v[0]);

这样安全吗？

推荐答案

它看起来像是 http：// www.open-std.org/jtc1/sc22/wg21/docs/lwg-closed.html#526 将此问题（或与其非常相似的内容）视为标准中的潜在缺陷：

It looks like http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-closed.html#526 addressed this problem (or something very similar to it) as a potential defect in the standard:

1）可以在执行期间更改const引用所执行的参数
函数

1) Parameters taken by const reference can be changed during execution of the function

例如：

给定std :: vector v：

Given std::vector v:

v.begin ，v [2]）;

v.insert(v.begin(), v[2]);

可以更改

建议的解决方案是这不是缺陷：

The proposed resolution was that this was not a defect:

vector :: insert（iter，value）因为标准
不允许它不工作。

vector::insert(iter, value) is required to work because the standard doesn't give permission for it not to work.

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