mingw-w64-crt/testcases/t_tls_cpp.cpp

// CRT headers
#include <process.h>

// Standard C++ headers
#include <iostream>

#define WIN32_LEAN_AND_MEAN
#include <windows.h>

int __thread tls_value = 0;

unsigned __stdcall thread_fn(void*)
{
    ++tls_value;
    return 0;
}

// This is derived from the jig that I setup to explore the problems with
// MT exception handling - you could probably just as easily set processors to
// some value rather than tying it to the actual # of cores...
int main()
{
    // Get the number of processors available to use
    SYSTEM_INFO si;
    GetSystemInfo(&si);
    const unsigned processors = si.dwNumberOfProcessors;

    // Make a thread for every processor and assign the thread to it
    HANDLE *threads = new HANDLE[processors];

    for (unsigned i = 0; i < processors; i++) {
        threads[i] = (HANDLE)_beginthreadex(0, 0, thread_fn, 0, CREATE_SUSPENDED, 0);
        SetThreadAffinityMask(threads[i], 1 << i);
    }

    // Restart all the threads
    for (unsigned i = 0; i < processors; i++)
        ResumeThread(threads[i]);

    // Rejoin those threads
    WaitForMultipleObjects(processors, threads, 1, INFINITE);
    for (unsigned i = 0; i < processors; i++)
        CloseHandle(threads[i]);

    delete[] threads;

    if (tls_value != 0) {
        std::cout << "How is it possible that tls_value is " << tls_value << " != 0 ?" << std::endl;
        std::terminate ();
    }

    return 0;
}