deferred thread start

deferthread.cpp

#include <iostream>
#define PROCESS (std::cout<<"do"<<std::endl)
//#define PROCESS (throw 42)

//--------------------------------
#ifdef TEST1
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>

class X {
  boost::shared_ptr<boost::thread> thread_;

  void do_() { PROCESS; }

public:
  ~X()
  {
    if (thread_)
      thread_->join();
  }

  void start()
  {
    thread_.reset(new boost::thread([this] { do_(); }));
  }
};
#endif

//--------------------------------
#ifdef TEST2
#include <boost/thread.hpp>

class X {
  boost::thread thread_;

  void do_() { PROCESS; }

public:
  ~X()
  {
    if (thread_.joinable())
      thread_.join();
  }

  void start()
  {
    boost::thread th([this] { do_(); });
    thread_.swap(th);
  }
};
#endif

//--------------------------------
#ifdef TEST3
#include <thread>

class X {
  std::thread thread_;

  void do_() { PROCESS; }

public:
  ~X()
  {
    if (thread_.joinable())
      thread_.join();
  }

  void start()
  {
    thread_ = std::thread([this] { do_(); });
  }
};
#endif

//--------------------------------
#ifdef TEST4
#include <boost/optional.hpp>
#include <boost/utility/in_place_factory.hpp>
#include <boost/thread.hpp>

class X {
  boost::optional<boost::thread> thread_;

  void do_() { PROCESS; }

public:
  ~X()
  {
    if (thread_)
      thread_->join();
  }

  void start()
  {
    thread_ = boost::in_place([this] { do_(); });
  }
};
#endif

//--------------------------------
#ifdef TEST5
#include <future>
class X
{
  std::future<void> task_;

  void do_() { PROCESS; }

public:
  void start()
  {
    task_ = std::async(std::launch::async, [this]{ do_(); });
  }
};
#endif


int main()
{
  X x;
  x.start();
}