Error using boost::asio::deadline_timer while execution

Question

I am trying to implement a basic deadline timer using this code:

          class Example
          {
              Example(boost::asio::io_service& ios, config& cfg)
                        : ios_(ios), cfg_(cfg), tcp_client_(ios) {
    
                state = new State();
                boost::asio::deadline_timer t(ios, boost::posix_time::seconds(5));
                t.async_wait(boost::bind(&bse_dummy_exchange::start_heartbeats,this,boost::asio::placeholders::error,boost::ref(t)));
              }
              ~Example() = default;
              void start_heartbeats(const boost::system::error_code& e,boost::asio::deadline_timer& t)
              {
                  std::cout << "Hello, world!\n";
                  t.expires_from_now(boost::posix_time::seconds(5));
     t.async_wait(boost::bind(&bse_dummy_exchange::start_heartbeats,this,boost::asio::placeholders::error,boost::ref(t)));
              }
          }

Compilation goes fine, but while executing I get this error message which I don't understand, can someone please help me with it:

    Hello, world!
    bse_dummy_exchange: ../nptl/pthread_mutex_lock.c:425: 
    __pthread_mutex_lock_full: Assertion `INTERNAL_SYSCALL_ERRNO (e, __err) 
    != ESRCH || !robust' failed.
    Aborted (core dumped)

Answer 1

You don't show the mutex - so we can't answer.

That said, about everything is going wrong with respect to async that can go wrong:

• you have a memory leak (state is an owned pointer member, but you defaulted the destructor? https://www.google.com/search?q=cppreference+rule+of+three&oq=cppreference+rule+of+three&aqs=chrome..69i57j69i64.2928j0j7&sourceid=chrome&ie=UTF-8)

• This is UB:

       boost::asio::deadline_timer t(ios, boost::posix_time::seconds(5));
       t.async_wait(boost::bind(&bse_dummy_exchange::start_heartbeats,this,boost::asio::placeholders::error,boost::ref(t)));
  

  async_ return immediately, but the operation runs ... well ... asynchronously. In your case t is a local variable that immediately goes out of scope after the constructor returns. So, that's not gonna work.

• exactly the same problem in start_heartbeats

(I'm for the sake of understanding your code assuming that Example was actually named use_dummy_exchange)

At the very least, the timer needs to have lifetime extending beyond the lifetime of the async_wait.

Minimal Fixed Version

Of course, not fixing anything related to the mutex error - that was not included:

Live On Coliru

#include <boost/asio.hpp>
#include <iostream>
struct config { };

struct TcpClient {
    TcpClient(boost::asio::io_service& ios) : ios_(ios){}
  private:
    boost::asio::io_service& ios_;
};

struct Example {
    struct State {};
    std::unique_ptr<State> state;

    Example(boost::asio::io_service& ios, config& cfg)
        : state(std::unique_ptr<State>()),
          ios_(ios),
          cfg_(cfg),
          tcp_client_(ios)
    {
        heartbeats();
    }

    void heartbeats(const boost::system::error_code& e = {}) {
        std::cout << "Hello, world!" << std::endl;
        if (!e) {
            t.expires_from_now(boost::posix_time::seconds(5));
            t.async_wait([this](auto ec) { heartbeats(ec); });
        }
    }

  private:
    boost::asio::io_service& ios_;
    config cfg_;
    TcpClient tcp_client_;
    boost::asio::deadline_timer t{ios_};
};

int main() {
    boost::asio::io_service ios;
    config cfg;
    Example ex(ios, cfg);

    ios.run_for(std::chrono::seconds(12));
}

Prints

Hello, world!
Hello, world!
Hello, world!

It has no memory leak, and runs clean under UBSan/ASan