关于用timeSetEvent c++多线程时的空悬指针来探讨解决办法

实际开发中遇到的情况，为了简便写了个简单demo

#include<cstdio>
#include<Windows.h>
#pragma comment(lib, "winmm.lib") 
class Test {
    int x = 888;
public:
    static void CALLBACK funproc(UINT uID, UINT uMsg, DWORD dwUser, DWORD dw1, DWORD dw2) {
        Test* pthis = (Test*)dwUser;
        Sleep(100);//为了特殊情况产生
        pthis->fun();
    }

    void fun() {
        printf("x=%d\n", x);

    }

};



int main() {
    Test* pt = new Test();
    UINT timeruid= timeSetEvent(10, 0, Test::funproc, (DWORD_PTR)pt, (UINT)TIME_PERIODIC);
    Sleep(20);//为了特殊情况产生
    timeKillEvent(timeruid);
    if (pt) {
        delete pt;
        pt = nullptr;
    }
    getchar();
    return 0;
}

主线程执行了delete pt;后，定时器线程调用pthis->fun()，此时pthis指向的空间已经被删除。注意:实际开发中定时器延时是随机的，pt是收到网络信息ack应答后马上删除自身

建议使用shared_ptr来包裹pt，然后timeSetEvent里面传shared_ptr即可，这样pt的生命周期就是自动的

shared_ptr 和 weak_ptr
参考：

class SupportWeakCallback {
 public:
  virtual ~SupportWeakCallback() {
  }

  template<typename CallbackType>
  auto ToWeakCallback(const CallbackType& closure)
    ->WeakCallback < CallbackType > {
    return WeakCallback<CallbackType>(GetWeakFlag(), closure);
  }

  std::weak_ptr<WeakFlag> GetWeakFlag() {
    if (m_weakFlag.use_count() == 0) {
      m_weakFlag.reset((WeakFlag*)NULL);
    }
    return m_weakFlag;
  }

 private:
  template<typename ReturnValue, typename... Param, typename WeakFlag>
  static std::function<ReturnValue(Param...)> ConvertToWeakCallback(
    const std::function<ReturnValue(Param...)>& callback, std::weak_ptr<WeakFlag> expiredFlag) {
    auto weakCallback = [expiredFlag, callback](Param... p) {
      if (!expiredFlag.expired()) {
        return callback(p...);
      }
      return ReturnValue();
    };

    return weakCallback;
  }

 protected:
  std::shared_ptr<WeakFlag> m_weakFlag;
};