CPP threads does not work on Unix-like machines!

[morchalabi]

Hi, i cannot run the following program with MSVS.NET c++, gcc on Linux or LLVM Clang on MAC. If you have any idea where it goes wrong please let me know :(

This code is taken from this page:
http://www.cplusplus.com/reference/thread/thread/thread/
-------------------------------------------

// constructing threads
#include <iostream>       // std::cout
#include <atomic>         // std::atomic
#include <thread>         // std::thread
#include <vector>         // std::vector

std::atomic<int> global_counter (0);

void increase_global (int n) { for (int i=0; i<n; ++i) ++global_counter; }

void increase_reference (std::atomic<int>& variable, int n) { for (int i=0; i<n; ++i) ++variable; }

struct C : std::atomic<int> {
  C() : std::atomic<int>(0) {}
  void increase_member (int n) { for (int i=0; i<n; ++i) fetch_add(1); }
};

int main ()
{
  std::vector<std::thread> threads;

  std::cout << "increase global counter with 10 threads...\n";
  for (int i=1; i<=10; ++i)
    threads.push_back(std::thread(increase_global,1000));

  std::cout << "increase counter (foo) with 10 threads using reference...\n";
  std::atomic<int> foo(0);
  for (int i=1; i<=10; ++i)
    threads.push_back(std::thread(increase_reference,std::ref(foo),1000));

  std::cout << "increase counter (bar) with 10 threads using member...\n";
  C bar;
  for (int i=1; i<=10; ++i)
    threads.push_back(std::thread(&C::increase_member,std::ref(bar),1000));

  std::cout << "synchronizing all threads...\n";
  for (auto& th : threads) th.join();

  std::cout << "global_counter: " << global_counter << '\n';
  std::cout << "foo: " << foo << '\n';
  std::cout << "bar: " << bar << '\n';

  return 0;
}

[Peter87]

It works if you pass a pointer instead of a reference_wrapper.

threads.push_back(std::thread(&C::increase_member,&bar,1000));

http://stackoverflow.com/questions/21059115/c11-thread-class-how-to-use-a-class-member-function

[morchalabi]

Thank you Peter87, I just saw that post. You are right the bug should be in the code!

[Peter87]

Did you read the answer by Casey? Visual Studio is the one that has a bug. GCC and LLVM just follows how the C++ standard says it should work.

[morchalabi]

I think I found a clearer answer! I will post it there on stackoverflow!

http://goo.gl/W6BmcG