保证向量指针位置? [英] vector pointer locations guaranteed?

问题描述

假设我有一个整数向量，

Suppose I have a vector of ints,

std::vector<int> numbers;

用一堆值填充，然后我说这样做(其中条目存在于 43)

that is populated with a bunch of values, then I say do this (where an entry exists at 43)

int *oneNumber = &numbers[43];

oneNumber 是否保证始终指向索引 43 处的 int，即使我将数字调整为 numbers.resize(46) 之类的内容?

Is oneNumber guaranteed to always be pointing at the int at index 43, even if say I resize numbers to something like numbers.resize(46)?

我不是 100% 确定这里的预期行为是什么，我知道向量保证是连续的，但不确定这种连续性是否也意味着向量中的所有索引在其整个生命周期中都将保持在同一位置.

I'm not 100% sure what expected behaviour is here, I know vectors are guaranteed to be contiguous but not sure if that continuity would also mean all the indices in the vector will remain in the same place throughout its life.

推荐答案

oneNumber 是否保证始终指向索引 43 处的 int

Is oneNumber guaranteed to always be pointing at the int at index 43

是的，这是由标准保证的.

Yes, this is guaranteed by the standard.

即使说我将数字调整为 numbers.resize(46) 之类的东西?

even if say I resize numbers to something like numbers.resize(46)?

没有.一旦您对向量调整大小、添加或删除任何内容，它的所有地址和迭代器都将失效.这是因为向量可能需要重新分配新的内存位置.

No. Once you resize, add, or remove anything to the vector, all addresses and iterators to it are invalidated. This is because the vector may need to be reallocated with new memory locations.

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