Re: [Boost-bugs] [Boost C++ Libraries] #11256: future<>::is_ready() == false in continuation function

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11256: future<>::is_ready() == false in continuation function
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-05-02 19:10:29

#11256: future<>::is_ready() == false in continuation function
-------------------------------------+-------------------------------------
  Reporter:  Konrad Zemek            |      Owner:  viboes
  <konrad.zemek@…>                   |     Status:  assigned
      Type:  Bugs                    |  Component:  thread
 Milestone:  To Be Determined        |   Severity:  Problem
   Version:  Boost 1.58.0            |   Keywords:  then continuation
Resolution:                          |  is_ready
-------------------------------------+-------------------------------------

Comment (by Konrad Zemek <konrad.zemek@…>):

 Below is the simplest code I got to reproduce if anyone else is curious.
 This version fails on assert, but when you remove {{{.unwrap()}}} it
 deadlocks instead (in this particular version, {{{boost::lock}}} throws
 exception saying "resource deadlock avoided", but my other code just
 deadlocks).

 {{{#!c++
 #define BOOST_THREAD_VERSION 4
 #define BOOST_THREAD_PROVIDES_EXECUTORS

 #include <boost/thread.hpp>
 #include <boost/thread/thread_pool.hpp>
 #include <cassert>

 auto createFuture()
 {
     boost::promise<void> promise;
     promise.set_value();
     return promise.get_future();
 }

 auto stepOne(boost::basic_thread_pool &executor)
 {
     auto sendFuture = createFuture();
     auto wrappedFuture = sendFuture.then(executor, [](auto f) mutable {
         return createFuture();
     });

     return wrappedFuture.unwrap();
 }

 auto stepTwo(boost::basic_thread_pool &executor)
 {
     auto future = stepOne(executor);
     return future.then(executor, [](auto f) {
         assert(f.is_ready());
     });
 }

 int main()
 {
     boost::basic_thread_pool executor{1};
     stepTwo(executor).get();
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11256#comment:4>
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