贴个之前用coze写的代码的例子（gpt4），各位可以试试找找它的bug在哪里（人工搞不定的话，可以喂给AI找bug试试）

我下的提示指令是两句话：
1、可否实现一个C++模板类，该类实现LRU缓存的功能，能指定最大缓存的消息个数，以及需要淘汰的时间间隔TTL。
2、请给这个类加上读写锁。

#include <unordered_map>
#include <chrono>
#include <utility>
#include <shared_mutex>

template<typename Key, typename Value>
class LRUCache {
public:
    LRUCache(size_t max_size, long long ttl) : _max_size(max_size), _ttl(ttl) {}

    void put(const Key& key, const Value& value) {
        std::unique_lock<std::shared_timed_mutex> lock(_mutex);
        auto now = std::chrono::system_clock::now();
        auto item = _cache.find(key);
        if (item != _cache.end()) {
            _lru_list.erase(item->second.second);
            _cache.erase(item);
        }
        _lru_list.push_front(key);
        _cache[key] = {std::make_pair(value, now), _lru_list.begin()};

        if (_cache.size() > _max_size) {
            auto last = _lru_list.end();
            last--;
            _cache.erase(*last);
            _lru_list.pop_back();
        }

        remove_expired(now);
    }

    std::pair<bool, Value> get(const Key& key) {
        std::shared_lock<std::shared_timed_mutex> lock(_mutex);
        auto item = _cache.find(key);
        if (item == _cache.end()) {
            return std::make_pair(false, Value());
        }

        auto now = std::chrono::system_clock::now();
        auto duration = std::chrono::duration_cast<std::chrono::seconds>(now - item->second.first.second).count();

        if (duration > _ttl) {
            lock.unlock(); // Need to unlock here since remove_expired() requires unique_lock
            std::unique_lock<std::shared_timed_mutex> ulock(_mutex);
            _lru_list.erase(item->second.second);
            _cache.erase(item);
            return std::make_pair(false, Value());
        }

        // To modify the list, we need to upgrade to unique lock
        lock.unlock();
        std::unique_lock<std::shared_timed_mutex> ulock(_mutex);
        _lru_list.erase(item->second.second);
        _lru_list.push_front(key);
        item->second.second = _lru_list.begin();

        return std::make_pair(true, item->second.first.first);
    }

private:
    size_t _max_size;
    long long _ttl; // seconds
    std::list<Key> _lru_list;
    std::unordered_map<Key, std::pair<std::pair<Value, std::chrono::time_point<std::chrono::system_clock>>, typename std::list<Key>::iterator>> _cache;
    mutable std::shared_timed_mutex _mutex;

    void remove_expired(const std::chrono::time_point<std::chrono::system_clock>& now) {
        for (auto it = _lru_list.rbegin(); it != _lru_list.rend();) {
            auto cache_it = _cache.find(*it);
            if (cache_it != _cache.end()) {
                auto duration = std::chrono::duration_cast<std::chrono::seconds>(now - cache_it->second.first.second).count();
                if (duration > _ttl) {
                    _cache.erase(cache_it);
                    it = std::list<Key>::reverse_iterator(_lru_list.erase(std::next(it).base()));
                } else {
                    ++it;
                }
            } else {
                ++it;
            }
        }
    }
};

【 在 misskiss 的大作中提到: 】
: 试试4o，不一样的感受。
:
: #发自zSMTH@BKL-AL20
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