Thread local test on mac

thread_local.cpp

// Compile with: c++ -std=c++1y -stdlib=libc++ -pthread thread_loc.cpp

#include <thread>
#include <future>
#include <iostream>
#include <mutex>


namespace {

__thread size_t a = 0;

} // anonymous


int main(int argc, char const *argv[])
{
    std::mutex mut;

    auto fut1 = std::async(std::launch::async, [&mut]() {
        std::lock_guard<std::mutex> lock(mut);
        std::cout << "Th 1: " << ++a << std::endl;
    });

    auto fut2 = std::async(std::launch::async, [&mut]() {
        std::lock_guard<std::mutex> lock(mut);
        std::cout << "Th 2: " << ++a << std::endl;
    });

    fut1.get();
    fut2.get();

    std::cout << "Main: " << a << std::endl;

    return 0;
}