relaxed_ordering.cpp

#include <atomic>
#include <thread>
#include <assert.h>

std::atomic<bool> x,y;
std::atomic<int> z;

void write_x_then_y(){
    x.store(true,std::memory_order_relaxed);
    y.store(true,std::memory_order_relaxed);
}

void read_y_then_x(){
    while(!y.load(std::memory_order_relaxed));
    if(x.load(std::memory_order_relaxed))
        ++z;
}

int main (){
    x = false;
    y = false;
    z = 0;
    
    std::thread a (write_x_then_y);
    std::thread b (read_y_then_x);
    
    a.join();
    b.join();
    
    assert(z.load()!= 0);
    
    return 0;
}