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std::thread - DESPERATE NEED HELP!!!

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Hi all!

[What I want]
I want write reliable and modern Semaphore class.
I want write unit test to validate it.

[What I do]
I visited some education institution pages and inspired by it
I rewrote their examples. Addresses are:
http://sandbox.mc.edu/~bennet/cs422b/notes/semaphore_h.html
http://sandbox.mc.edu/~bennet/cs422b/notes/semaphore_cpp.html

As you can see this class is simple and silly as hell.
But it not works for me.
I have race conditions for unknown reasons.
It works in debuger. It works when I add some:
cout << "message" << endl << flush;
But not works in stand alone (debug and release both).
My system is Linux KDE Neon (based on Ubuntu 18.04 LTS).
My processor is Intel Core Duo (released in 2009).

[How to reproduce]
I paste here my code with complete minimal example.
It will compile in release mode.
It is fully automatic you need only to create 3 small files
and run: run.sh form commad line.
After 2-3 executions it hangs for unknown reasons.

Please help me! Thanks in advance and best regards!
Szyk Cech

[Files]
=============================================================
BEGIN: run.sh

#!/bin/bash

./make.sh

lCounter=0

while [ 1 ]; do
     lCounter=$[lCounter + 1]
     echo "Run: $lCounter"
     ./semtest
done

END:  run.sh

=============================================================

BEGIN: make.sh

#!/bin/bash
g++ -std=c++17 -pthread -O2 -s -DNDEBUG ./Main.cpp -o semtest

END: make.sh

=============================================================

BEGIN: Main.cpp

#include <mutex>
#include <condition_variable>
#include <chrono>
#include <thread>
#include <vector>
#include <iostream>


using namespace std;

class Semaphore
{
public:
     Semaphore(int aCounter);

public:
     int value();
     void up();
     void down();

protected:
     int mCounter;
     std::mutex mAccessMutex;
     std::condition_variable mWaitingCondition;
};

Semaphore::Semaphore(int aCounter)
     : mCounter(aCounter)
{
}

int Semaphore::value()
{
     return mCounter;
}

void Semaphore::down()
{
     unique_lock lock(mAccessMutex);
     --mCounter;
     if(mCounter < 0)
         mWaitingCondition.wait(lock);
}

void Semaphore::up()
{
     unique_lock lock(mAccessMutex);
     ++mCounter;
     if(mCounter <= 0)
         mWaitingCondition.notify_one();
}

void SemTestThread(Semaphore* aSem)
{
     aSem->down();
}

int main()
{
     Semaphore lSem(5);
     vector<thread> lArray;
     lArray.resize(15);

     for(unsigned long i(0); i < lArray.size(); ++i)
         lArray[i] = thread(SemTestThread, &lSem);

     bool lResult(true);

     for(int i(0); i < 5; ++i)
         lArray[i].join();

     lResult = lResult && (lSem.value() == -10);

     for(int i(10); i > 0; --i)
     {
         lSem.up();
         lArray[15 - i].join();
         lResult = lResult && (lSem.value() == -i + 1);
     }

     cout << "lResult: " << lResult << endl << flush;
//    return EXIT_SUCCESS;
}

END: Main.cpp

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Thread

std::thread - DESPERATE NEED HELP!!! Szyk Cech <szykcech@spoko.pl> - 2019-09-11 20:16 +0200
  Re: std::thread - DESPERATE NEED HELP!!! "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-09-11 23:01 -0700
  Re: std::thread - DESPERATE NEED HELP!!! Ralf Fassel <ralfixx@gmx.de> - 2019-09-12 11:14 +0200
  Re: std::thread - DESPERATE NEED HELP!!! "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-09-13 12:53 -0700
  Re: std::thread - DESPERATE NEED HELP!!! Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2019-09-13 23:38 -0400
    Re: std::thread - DESPERATE NEED HELP!!! "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-09-13 22:07 -0700
      Re: std::thread - DESPERATE NEED HELP!!! "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-09-13 22:17 -0700
        Re: std::thread - DESPERATE NEED HELP!!! "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-09-13 23:01 -0700

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