C++線程無法正常工作？

Question

我作出更大的計劃，我想使首先我試圖找出如何線程實際工作，所以我創建了一個簡單的程序來使用線程，我不明白爲什麼我沒有得到消息比"The bomb has just detonated.""Bomberman has just put a bomb. Wait for the boom."更早。

任何人都可以指導我，爲什麼它不按我期望的那樣工作？

#include <unistd.h> 
#include <chrono> 
#include <iostream> 
#include <thread> 

using namespace std; 

class CBomberman; 

class CBomb { 
public: 
    CBomb(void) : m_Owner(nullptr) { 
    thread other_thread(&CBomb::Timer, this); 
    other_thread.join(); 
    } 

private: 
    void Timer(void) { 
    this_thread::sleep_for(chrono::seconds(3)); 
    cout << "The bomb has just detonated." << endl; 
    } 

    CBomberman* m_Owner; 
}; 

class CBomberman { 
public: 
    CBomberman(void) : m_Bomb(nullptr) {} 

    bool PutBomb(void) { 
    if (m_Bomb == nullptr) { 
     m_Bomb = new CBomb(); 
     delete m_Bomb; 
     return true; 
    } else { 
     cout << "The bomb has already been put." << endl; 
     return false; 
    } 
    } 

private: 
    CBomb* m_Bomb; 
}; 

int main() { 
    CBomberman bomberman; 

    bomberman.PutBomb(); 
    cout << "Bomberman has just put a bomb. Wait for the boom." << endl; 

    return 0; 
} 

Answer 1

你的問題是，你要加入線程創建後立即，這意味着你只使用多線程在一個非常技術性的感覺：你肯定創建另一個線程，它的（可能）會工作在另一個CPU內核上，但主機線程只是在另一個線程工作時閒置。

您需要在本地存儲thread對象，以便您可以在以後加入。

class CBomb 
{ 
public: 
    CBomb (void) 
    : m_Owner (nullptr), 
    bomb_thread(&CBomb::Timer, this) 
    { 
    } 
    std::thread bomb_thread; //This needs to be a member of this object. Whether you make it public or not is a matter of your design approach. 
private: 
    void Timer (void) 
    { 
     this_thread::sleep_for(chrono::seconds(3)); 
     cout << "The bomb has just detonated." << endl; 
    } 

    CBomberman * m_Owner; 
}; 

class CBomberman 
{ 
public: 
    CBomberman (void) 
    : m_Bomb (nullptr) 
    { 

    } 

    bool PutBomb (void) 
    { 
     if(m_Bomb == nullptr) 
     { 
      m_Bomb = new CBomb();//Don't delete the object immediately after creating it. What were you expecting to have happen if you did? 
      return true; 
     } 
     else 
     { 
      cout << "The bomb has already been put." << endl; 
      return false; 
     } 
    } 
    CBomb * m_Bomb; 
}; 

int main() 
{ 
    CBomberman bomberman; 

    bomberman.PutBomb(); 
    cout << "Bomberman has just put a bomb. Wait for the boom." << endl; 
    bomberman.m_bomb->bomb_thread.join(); //If we hit the end before the thread concludes, there could be some errors. 

    return 0; 
} 

Answer 2

因爲你創造other_thread後，立即致電other_threadjoin。 join調用會阻塞主線程，並等待other_thread退出。有關std :: thread :: join的文檔，請參見http://en.cppreference.com/w/cpp/thread/thread/join。