Destroy io_context after plugin shutdown to clear it out before plugi…

…n destroy

examples/executor_example/application.hpp

@@ -22,7 +22,7 @@ class my_executor {
 public:
    template <typename Func>
    auto post( int priority, Func&& func ) {
-      return boost::asio::post(io_serv, pri_queue.wrap(priority, --order, std::forward<Func>(func)));
+      return boost::asio::post(*io_serv, pri_queue.wrap(priority, --order, std::forward<Func>(func)));
    }
 
    auto& get_priority_queue() { return pri_queue; }
@@ -31,11 +31,13 @@ class my_executor {
 
    void clear() { pri_queue.clear(); }
 
-   boost::asio::io_service& get_io_service() { return io_serv; }
+   void reset() { io_serv.emplace(); }
+
+   boost::asio::io_service& get_io_service() { return *io_serv; }
 
 private:
    // members are ordered taking into account that the last one is destructed first
-   boost::asio::io_service  io_serv;
+   std::optional<boost::asio::io_service> io_serv{std::in_place};
    appbase::execution_priority_queue pri_queue;
    std::size_t order = std::numeric_limits<size_t>::max(); // to maintain FIFO ordering in queue within priority
 };

include/appbase/application_base.hpp

@@ -152,13 +152,13 @@ class application_base {
          }
 
          work.reset();
-         io_serv.restart();
-         // plugins shutdown down, drain io_context of anything posted while shutting down before destroying plugins
-         while (io_serv.poll())
-            ;
 
          try {
+            // plugins shutdown down at this point,
             exec.clear(); // make sure the queue is empty
+            // Recreate the io_context since it doesn't provide a clear and we want the destructors of all the
+            // lambdas posted to the io_context to execute before destroying the plugins
+            exec.reset();
             destroy_plugins();
          } catch (...) {
             if (!eptr)

include/appbase/default_executor.hpp

@@ -9,7 +9,7 @@ class default_executor {
 public:
    template <typename Func>
    auto post(int priority, Func&& func) {
-      return boost::asio::post(io_serv, pri_queue.wrap(priority, --order, std::forward<Func>(func)));
+      return boost::asio::post(*io_serv, pri_queue.wrap(priority, --order, std::forward<Func>(func)));
    }
 
    /**
@@ -32,17 +32,21 @@ class default_executor {
       pri_queue.clear();
    }
 
+   void reset() {
+      io_serv.emplace();
+   }
+
    /**
     * Do not run io_service in any other threads, as application assumes single-threaded execution in exec().
     * @return io_serivice of application
     */
    boost::asio::io_service& get_io_service() {
-      return io_serv;
+      return *io_serv;
    }
 
 private:
    // members are ordered taking into account that the last one is destructed first
-   boost::asio::io_service io_serv;
+   std::optional<boost::asio::io_service> io_serv{std::in_place};
    execution_priority_queue pri_queue;
    std::size_t order = std::numeric_limits<size_t>::max(); // to maintain FIFO ordering in queue within priority
 };