Le 11/10/15 20:43, Mikael Olenfalk a écrit :

Hi,

I have stumbled on a minor inconvenience when it comes to using boost::future. Below is a small example which first wraps an asio io_service as an Executor (see even further below) and then uses boost::async() to launch a simple task on the executor and tries to queue up a continuation using future::then(Ex, F):

1. the destructor of async_result does not block which is nice Hmm, I believe that the in the develop branch tis should block. 2. the destructor of continuation_result does block which is a bit of an annoyance as this future I do not care about at all

Is there a way to make the destructor not block?

/M The current implementation of feature is broken (at least respect to what the standard TS Concurrency says) as the future resulting from ::then() should not blocks.

I have a branch (https://github.com/boostorg/thread/tree/feature/non_blocking_futures) that don't blocks on any future, but this will break async. I have another branch that has copyable executors and non-blocking futures (https://github.com/boostorg/thread/tree/feature/make_executors_copyable). Please, could you try on these branches and tell me how it works? Vicente

int main(int argc, char* argv[]) { boost::asio::io_service io_service; asio_executor executor{ io_service };

auto async_result = boost::async(executor, []() { return 42; }); // hangs: // async_result.then(executor, &g);

// does not hang: auto continuation_result = async_result.then(executor, [](boost::future<int> r) { cout << r.get() << endl; });

cout << "start io_service" << endl;

io_service.run();

cout << "stop io_service" << endl;

return 0; }

class asio_executor : public boost::executors::executor { public: asio_executor(boost::asio::io_service &ios) : _ios(ios) {}

void close() override { _ios.stop(); }

bool closed() override { return _ios.stopped(); }

void submit(work&& w) override { // for some reason _ios.post(w); causes endless // recursion and eventually a crash

_ios.post(std::move(w)); }

bool try_executing_one() override { return _ios.run_one() > 0; }

private: boost::asio::io_service &_ios; };

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