为什么我得到“向量迭代器不兼容"?

为什么这个代码

#include <algorithm>
#include <iterator>
#include <vector>

int main()
{
    std::vector<int> v;
    v.push_back(1);
    v.push_back(2);
    v.push_back(3);
    v.reserve(v.size() * 2);  // Reserve enough space to keep iterators valid
    std::copy(v.begin(), v.end(), std::back_inserter(v));
    return 0;
}

给我调试断言失败，表达式:向量迭代器不兼容(Visual C++ 2008)?

give me the debug assertion failure, Expression: vector iterators incompatible (Visual C++ 2008)?

推荐答案

只有当向量必须重新分配时，对应于元素的迭代器才会失效，reserve 避免了这种情况.

Iterators corresponding to elements are only invalidated when the vector has to be reallocated, which reserve avoids.

然而，v.end() 不会保持有效.

However, v.end() won't stay valid.

标准对push_back 和insert 的描述保证

The Standard's description of push_back and insert guarantees that

如果新容量大于旧容量，则导致重新分配.如果没有重新分配发生，插入点之前的所有迭代器和引用都保持有效.

Causes reallocation if the new size is greater than the old capacity. If no reallocation happens, all the iterators and references before the insertion point remain valid.

v.end() 不是插入点之前".