multithreading - C++ Inheritance : Calling virtual method when it has been overridden -

i trying build service object can run (i.e. execute it's run() function) in separate thread. service object

#include <boost/noncopyable.hpp> #include <atomic> #include <thread> #include <iostream>  class service : public boost::noncopyable {  public:   service() : stop_(false), started_(false) { }    virtual ~service() {     stop();     if (thread_.joinable()) {       thread_.join();     }   }    virtual void stop() { stop_ = true; }    virtual void start() {     if (started_.load() == false) {       started_ = true;       thread_ = std::thread([&] () {         run();       });     }   }   protected:   virtual void run() = 0;    std::atomic<bool> stop_;    std::atomic<bool> started_;    std::thread thread_; }; 

i creating test class inherits abstract class , called in main() function

class test : public service {  public:   test() : service() {     std::cout<< "ctor" << std::endl;     start();   }    ~test() {     std::cout<< "dtor" << std::endl;   }   protected:   void run() override {     std::cout << "hello world" <<std::endl;   } };   int main() {   test test1;   return 0; } 

now when execute this, why error saying pure virtual function called? run() function overridden in test class. whats worse runs correctly sometimes?

$ ./a.out ctor dtor pure virtual method called terminate called without active exception  $ ./a.out ctor dtor pure virtual method called terminate called without active exception  $ ./a.out ctor dtor pure virtual method called terminate called without active exception  $ ./a.out ctor dtor hello world  $ ./a.out ctor dtor pure virtual method called terminate called without active exception 

what going wrong here?

follow along, step step:

1) construct object.

2) execute following piece of code:

if (started_.load() == false) {   started_ = true;   thread_ = std::thread([&] () {     run();   }); } 

the parent thread returns main() immediately exits , destroys object.

here's bug:

• you not guaranteed thread started in start() going reach call run(), above, before parent thread terminates process. both child thread, , parent thread runs concurrently.

so, every once in while, parent thread destroy object before child thread gets in gear, , calls run().

at point, object run() method gets invoked, destroyed.

undefined behavior.

the assertion you're hitting, every once in while, 1 possible result of undefined behavior.