c++ - 如何在两个 boost::intrusive::slist 对象之间传输节点

Question

在两个boost::intrusive::slist<boost::intrusive::cache_last<true>>之间转移节点是否有效对象？类似下面的内容

auto one = boost::intrusive::slist<Node, boost::intrusive::cache_last<true>>{};
auto two = boost::intrusive::slist<Node, boost::intrusive::cache_last<true>>{};

auto node = std::make_unique<Node>();
one.push_back(*node);

auto& front = one.front();
one.pop_front();
two.push_back(front);

我遇到了段错误，以及 boost 版本 1.70.0 的断言失败 https://wandbox.org/permlink/nWHakTYUiVBGKH6I .我该如何解决这个问题？

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注意:我无法分配新节点并复制旧节点，因为我正在使用侵入式列表来控制分配发生的时间和地点。

Answer 1

这似乎是splice的目的方法:

Effects: Transfers all the elements of list x to this list, before the the element pointed by it. No destructors or copy constructors are called.

two.splice(two.end(), one, one.begin());

完整的工作演示:

#include <iostream>
#include <string>
#include <boost/intrusive/slist.hpp>

struct Node : public boost::intrusive::slist_base_hook<>
{
    int         i;
    std::string s;

    Node(int i, std::string s) : i(i), s(std::move(s)) {}
};

using NodeList = boost::intrusive::slist<Node, boost::intrusive::cache_last<true>>;

int main()
{
    NodeList one;
    NodeList two;

    auto show = [&](auto text){
        std::cout <<text <<"\n  one\n";
        for (auto & item : one) { std::cout <<"    " <<item.i <<' ' <<item.s <<'\n'; }
        std::cout <<"  two\n";
        for (auto & item : two) { std::cout <<"    " <<item.i <<' ' <<item.s <<'\n'; }
    };


    one.push_back(*new Node(42, "hello"));
    show("before splice");

    two.splice(two.end(), one, one.begin());
    show("after splice");

    one.clear_and_dispose([](Node * ptr){ delete ptr; });
    two.clear_and_dispose([](Node * ptr){ delete ptr; });
    return 0;
}

运行时，会写:

before splice
  one
    42 hello
  two
after splice
  one
  two
    42 hello