Fix segfault when the handler is destructed from within a callback

include/libev.h

@@ -1,12 +1,12 @@
 /**
  *  LibEV.h
- * 
+ *
  *  Implementation for the AMQP::TcpHandler that is optimized for libev. You can
  *  use this class instead of a AMQP::TcpHandler class, just pass the event loop
  *  to the constructor and you're all set
- * 
+ *
  *  Compile with: "g++ -std=c++11 libev.cpp -lamqpcpp -lev -lpthread"
- * 
+ *
  *  @author Emiel Bruijntjes <emiel.bruijntjes@copernica.com>
  *  @copyright 2015 Copernica BV
  */
@@ -43,7 +43,7 @@ private:
          *  @var struct ev_loop
          */
         struct ev_loop *_loop;
-    
+
         /**
          *  The actual watcher structure
          *  @var struct ev_io
@@ -60,11 +60,11 @@ private:
         {
             // retrieve the connection
             TcpConnection *connection = static_cast<TcpConnection*>(watcher->data);
-            
+
-            // tell the connection that its filedescriptor is active 
+            // tell the connection that its filedescriptor is active
             connection->process(watcher->fd, revents);
         }
-    
+
     public:
         /**
          *  Constructor
@@ -77,14 +77,22 @@ private:
         {
             // initialize the libev structure
             ev_io_init(&_io, callback, fd, events);
-            
+
             // store the connection in the data "void*"
             _io.data = connection;
-            
+
             // start the watcher
             ev_io_start(_loop, &_io);
         }
-        
+
+        /**
+         *  Watchers cannot be copied or moved
+         *
+         *  @param  that    The object to not move or copy
+         */
+        Watcher(Watcher &&that) = delete;
+        Watcher(const Watcher &that) = delete;
+
         /**
          *  Destructor
          */
@@ -93,7 +101,7 @@ private:
             // stop the watcher
             ev_io_stop(_loop, &_io);
         }
-        
+
         /**
          *  Change the events for which the filedescriptor is monitored
          *  @param  events
@@ -102,10 +110,10 @@ private:
         {
             // stop the watcher if it was active
             ev_io_stop(_loop, &_io);
-            
+
             // set the events
             ev_io_set(&_io, _io.fd, events);
-            
+
             // and restart it
             ev_io_start(_loop, &_io);
         }
@@ -117,14 +125,14 @@ private:
      *  @var struct ev_loop*
      */
     struct ev_loop *_loop;
-    
+
     /**
      *  All I/O watchers that are active, indexed by their filedescriptor
      *  @var std::map<int,Watcher>
      */
     std::map<int,std::unique_ptr<Watcher>> _watchers;
-    
+
-    
+
     /**
      *  Method that is called by AMQP-CPP to register a filedescriptor for readability or writability
      *  @param  connection  The TCP connection object that is reporting
@@ -135,13 +143,13 @@ private:
     {
         // do we already have this filedescriptor
         auto iter = _watchers.find(fd);
-        
+
         // was it found?
         if (iter == _watchers.end())
         {
             // we did not yet have this watcher - but that is ok if no filedescriptor was registered
             if (flags == 0) return;
-            
+
             // construct a new watcher, and put it in the map
             _watchers[fd] = std::unique_ptr<Watcher>(new Watcher(_loop, connection, fd, flags));
         }
@@ -163,13 +171,13 @@ public:
      *  @param  loop    The event loop to wrap
      */
     LibEvHandler(struct ev_loop *loop) : _loop(loop) {}
-    
+
     /**
      *  Destructor
      */
     virtual ~LibEvHandler() = default;
 };
-    
+
 /**
  *  End of namespace
  */

include/tcpconnection.h

@@ -26,7 +26,9 @@ class TcpState;
 /**
  *  Class definition
  */
-class TcpConnection : private ConnectionHandler
+class TcpConnection :
+    private ConnectionHandler,
+    private Watchable
 {
 private:
     /**

src/tcpconnection.cpp

@@ -47,17 +47,23 @@ TcpConnection::~TcpConnection()
  */
 void TcpConnection::process(int fd, int flags)
 {
+    // monitor the object for destruction
+    Monitor monitor{ this };
+
     // pass on the the state, that returns a new impl
     auto *result = _state->process(fd, flags);
-    
+
+    // are we still valid
+    if (!monitor.valid()) return;
+
     // skip if the same state is continued to be used, or when the process()
     // method returns nullptr (which only happens when the object is destructed,
     // and "this" is no longer valid)
     if (!result || result == _state) return;
-    
+
     // remove old state
     delete _state;
-    
+
     // replace it with the new implementation
     _state = result;
 }
@@ -105,10 +111,10 @@ void TcpConnection::onError(Connection *connection, const char *message)
 {
     // current object is going to be removed, wrap it in a unique pointer to enforce that
     std::unique_ptr<TcpState> ptr(_state);
-    
+
     // object is now in a closed state
     _state = new TcpClosed(_state);
-    
+
     // tell the implementation to report the error
     ptr->reportError(message);
 }
@@ -131,10 +137,10 @@ void TcpConnection::onClosed(Connection *connection)
 {
     // current object is going to be removed, wrap it in a unique pointer to enforce that
     std::unique_ptr<TcpState> ptr(_state);
-    
+
     // object is now in a closed state
     _state = new TcpClosed(_state);
-    
+
     // tell the implementation to report the error
     ptr->reportClosed();
 }

src/tcpresolver.h

@@ -177,7 +177,7 @@ public:
     {
         // only works if the incoming pipe is readable
         if (fd != _pipe.in() || !(flags & readable)) return this;
-        
+
         // do we have a valid socket?
         if (_socket >= 0) return new TcpConnected(_connection, _socket, std::move(_buffer), _handler);