Question

I am using VS2012 and I want to set thread priority from within a running thread. The goal is to initialize all threads with the highest priority state. To do this I want to get a HANDLE to the thread.

I am having some trouble accessing the pointer that corresponds to the thread object.

Is this possible?

From the calling main thread, the pointer is valid and from the C++11 thread it is set to CCCCCCCC. Predictably dereferencing some nonsense memory location causes a crash.

The code below is a simplified version showing the problem.

#include "stdafx.h"
#include <Windows.h>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <iostream>
#include <atomic>
using namespace std;
class threadContainer
    {
    thread* mT;
    condition_variable* con;
    void lockMe()
        {
        mutex m;
        unique_lock<std::mutex> lock(m);
        con->wait(lock);//waits for host thread
        cout << mT << endl;//CCCCCCCC
        auto h = mT->native_handle();//causes a crash
        con->wait(lock);//locks forever
        }
    public:
        void run()
            {
            con = new condition_variable();
            mT = new thread(&threadContainer::lockMe,*this);
            cout << mT << endl; //00326420
            con->notify_one();// Without this line everything locks as expected
            mT->join();
            }
    };
int _tmain(int argc, _TCHAR* argv[])
    {
    threadContainer mContainer;
    mContainer.run();
    return 0;
    }

Answer 1

#include <mutex>
#include <condition_variable>
#include <iostream>
#include <atomic>
#include <thread>

class threadContainer {
   std::thread* mT;
  std::mutex m;
  void lockMe() {
    // wait for mT to be assigned:
    {
      std::unique_lock<std::mutex> lock(m);
    }
    std::cout << "lockMe():" << mT << "\n";
    auto h = mT->native_handle();//causes a crash
    std::cout << "Done lockMe!\n";
  }
  public:
    void run() {
      // release lock only after mT assigned:
      {
        std::unique_lock<std::mutex> lock(m);
        mT = new std::thread( [&](){ this->lockMe(); } );
      }
      std::cout << "run():" << mT << "\n"; //00326420
      mT->join();
    }
};

int main() {
  threadContainer mContainer;
  mContainer.run();
  return 0;
}

Try that.