External conditions: is my code safe?

[Michał Zientkiewicz]

Hello,

I'm about to start using taskflow in a large project and my workflow would be greatly simplified if there was a way for a task to wait for some external condition.
I wrote the following piece of code - it seems to work in a toy example, but is it safe?

    tf::Executor exec;

    tf::Semaphore sem{1};
    tf::Taskflow f;
    auto a = f.emplace([](){
        sleep_s(0.5); printf("Tick\n");
    }).acquire(sem);

    // this task will have to wait, obviously
    f.emplace([](){
        printf("Tock\n");
    }).acquire(sem).release(sem).succeed(a);

    exec.run(f);

    sleep_s(1.0);

    std::thread([&]()
    {
        auto ff = std::make_shared<tf::Taskflow>();
        ff->emplace([](){
            printf("Release agent applied ;)\n");
        }).release(sem);
        std::condition_variable cv;
        bool done = false;
        std::mutex mtx;
        // run called from another thread!
        exec.run(*ff, [ff]() { /* captured for side-effects */});
        ff.reset();
    }).detach();

    exec.wait_for_all();

I'd be glad to hear about any pitfalls in this approach before I implement it in a large project.

Thanks,
Michał

[Tsung-Wei Huang]

@mzient this is safe code.