Not able to set conditional Variable

in the below code I am waiting inside function waitingForWork() on a condition variable, butdoTheCleanUp() is never called.

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <iostream>           // std::cout
#include <thread>          // std::thread
#include <mutex>              // std::mutex, std::unique_lock
#include <condition_variable> // std::condition_variable


std::mutex mtx;
std::condition_variable cv;
bool stop=false;

void stopTheWait()
{
    sleep(5);
    printf("stopping the wait.. \n\n");
    std::lock_guard<std::mutex> lck(mtx);
    stop = true;
    cv.notify_all();
}

void doTheCleanUp()/* is never called*/ {
    printf("clean up... \n\n");
}

void waitingForWork(){
    printf("wait for ever... \n\n");

    std::unique_lock<std::mutex> lck(mtx);
    cv.wait(lck, []{ return stop;});
    doTheCleanUp();
    printf("clean Up Done, now end wait... \n\n");
}


int main()
{
    printf("in main... \n");
   
   std::unique_lock<std::mutex> lck(mtx);

   std::thread t1(stopTheWait);
   
   waitingForWork();
   
   printf("exiting main...\n");
   sleep(1);
   
   return 0;
}