#include <atomic>
#include <cassert>
#include <iostream>
#include <thread>

struct Payload {
    int left = 0;
    int right = 0;
};

int main() {
    Payload payload;
    std::atomic<bool> ready{false};
    std::jthread producer([&] {
        payload.left = 6;
        payload.right = 7;
        ready.store(true, std::memory_order_release);
        ready.notify_one();
    });

    ready.wait(false, std::memory_order_acquire);
    const int result = payload.left * payload.right;
    assert(payload.left == 6 && payload.right == 7);
    assert(result == 42);
    producer.join();
    std::cout << result << '\n';
}