#include <windows.h>
#include <stdio.h>
#include <process.h>

#if defined(_MSC_VER)
static __declspec(thread) int tlsvar = 1;
#else
static __thread int tlsvar = 1;
#endif

static unsigned __stdcall threadfunc(void* arg) {
    int id = (int)arg;
    printf("thread %d, tlsvar %p initially %d\n", id, &tlsvar, tlsvar);
    tlsvar = id + 100;
    for (int i = 0; i < 4; i++) {
        printf("thread %d, tlsvar %p %d\n", id, &tlsvar, tlsvar);
        tlsvar += 10;
        Sleep(500);
    }
    return 0;
}

int main(int argc, char* argv[]) {
    HANDLE threads[3];

    for (int i = 0; i < 3; i++) {
        printf("mainthread, tlsvar %p %d\n", &tlsvar, tlsvar);
        tlsvar += 10;
        threads[i] = (HANDLE)_beginthreadex(NULL, 0, threadfunc, (void*)(intptr_t) (i + 1), 0, NULL);
        Sleep(350);
    }
    for (int i = 0; i < 3; i++) {
        WaitForSingleObject(threads[i], INFINITE);
        CloseHandle(threads[i]);
    }
    return 0;
}