Modern C++ Concurrency: Get the most out of any machine/

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Thread Local Data

Thread Local Data

This lesson explains how data that is local to a thread is created

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Thread-local data, also known as thread-local storage, will be created for each thread separately. It behaves like static data because it’s bound for the lifetime of the thread and it will be created at its first usage. Also, thread-local data belongs exclusively to the thread.

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// threadLocal.cpp
#include <iostream>
#include <string>
#include <mutex>
#include <thread>
std::mutex coutMutex;
thread_local std::string s("hello from ");
void addThreadLocal(std::string const& s2){
  s += s2;
  // protect std::cout
  std::lock_guard<std::mutex> guard(coutMutex);
  std::cout << s << std::endl;
  std::cout << "&s: " << &s << std::endl;
  std::cout << std::endl;
}
int main(){
  std::cout << std::endl;
  std::thread t1(addThreadLocal,"t1"); 
  std::thread t2(addThreadLocal,"t2"); 
  std::thread t3(addThreadLocal,"t3"); 
  std::thread t4(addThreadLocal,"t4"); 
  t1.join();
  t2.join();
  t3.join();
  t4.join();
}

By using the keyword ...