ICE-4982: correct fix for the UDP assert

1 files changed, 11 insertions, 3 deletions

diff --git a/cpp/src/Ice/UdpTransceiver.cpp b/cpp/src/Ice/UdpTransceiver.cpp
index 1147d6c45ce..60416db2311 100644
--- a/cpp/src/Ice/UdpTransceiver.cpp
+++ b/cpp/src/Ice/UdpTransceiver.cpp
@@ -446,12 +446,20 @@ IceInternal::UdpTransceiver::startWrite(Buffer& buf)
                         DataWriter^ writer = ref new DataWriter(task.get());
                         writer->WriteBytes(ref new Array<unsigned char>(&*buf.i, static_cast<int>(buf.b.size())));
                         DataWriterStoreOperation^ operation = writer->StoreAsync();
-                        if(checkIfErrorOrCompleted(SocketOperationWrite, operation))
+
+                        if(operation->Status == Windows::Foundation::AsyncStatus::Completed)
                         {
+                            //
+                            // NOTE: unlike other methods, it's important to modify _write.count
+                            // _before_ calling checkIfErrorOrCompleted since this isn't called
+                            // with the connection mutex but from a Windows thread pool thread.
+                            // So we can't modify the _write structure after calling the 
+                            // completed callback.
+                            //
                             _write.count = operation->GetResults();
-                            _completedHandler(SocketOperationWrite);
                         }
-                        else
+
+                        if(!checkIfErrorOrCompleted(SocketOperationWrite, operation))
                         {
                             operation->Completed = _writeOperationCompletedHandler;
                         }