SharedPV ensure callback pairing

Ensure that onLastDisconnect() isn't called
unless onFirstConnect() is/has been called.

src/server/pva/sharedstate.h

@@ -202,6 +202,8 @@ private:
     //! Used for initial Monitor update and Get operations.
     epics::pvData::BitSet valid;
 
+    bool notifiedConn; // whether onFirstConnect() has been, or is being, called
+
     int debugLvl;
 
     EPICS_NOT_COPYABLE(SharedPV)

src/server/sharedstate_channel.cpp

@@ -51,6 +51,7 @@ SharedChannel::SharedChannel(const std::tr1::shared_ptr<SharedPV> &owner,
         if(owner->channels.empty())
             handler = owner->handler;
         owner->channels.push_back(this);
+        owner->notifiedConn = !!handler;
     }
     if(handler) {
         handler->onFirstConnect(owner);
@@ -64,8 +65,9 @@ SharedChannel::~SharedChannel()
         Guard G(owner->mutex);
         bool wasempty = owner->channels.empty();
         owner->channels.remove(this);
-        if(!wasempty && owner->channels.empty()) {
+        if(!wasempty && owner->channels.empty() && owner->notifiedConn) {
             handler = owner->handler;
+            owner->notifiedConn = false;
         }
     }
     if(handler) {

src/server/sharedstate_pv.cpp

@@ -74,6 +74,7 @@ SharedPV::shared_pointer SharedPV::buildMailbox(pvas::SharedPV::Config *conf)
 SharedPV::SharedPV(const std::tr1::shared_ptr<Handler> &handler, pvas::SharedPV::Config *conf)
     :config(conf ? *conf : Config())
     ,handler(handler)
+    ,notifiedConn(false)
     ,debugLvl(0)
 {
     REFTRACE_INCREMENT(num_instances);
@@ -264,8 +265,10 @@ void SharedPV::close(bool destroy)
             puts.clear();
             rpcs.clear();
             monitors.clear();
-            if(!channels.empty())
+            if(!channels.empty() && notifiedConn) {
                 p_handler = handler;
+                notifiedConn = false;
+            }
             channels.clear();
         }
     }