From 41dc2e60493ff1f10a8d2c4c8ae41f55ee4c327e Mon Sep 17 00:00:00 2001
From: Martin Hurton <hurtonm@gmail.com>
Date: Fri, 2 Nov 2012 11:11:14 +0100
Subject: [PATCH] Resolve LIBZMQ-459

Ref: https://zeromq.jira.com/browse/LIBZMQ-459
---
 src/stream_engine.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/stream_engine.cpp b/src/stream_engine.cpp
index 94f8cd32..413b87ec 100644
--- a/src/stream_engine.cpp
+++ b/src/stream_engine.cpp
@@ -263,8 +263,15 @@ void zmq::stream_engine_t::out_event ()
     //  If write buffer is empty, try to read new data from the encoder.
     if (!outsize) {
 
+        //  Even when we stop polling as soon as there is no
+        //  data to send, the poller may invoke out_event one
+        //  more time due to 'speculative write' optimisation.
+        if (unlikely (encoder == NULL)) {
+            zmq_assert (handshaking);
+            return;
+        }
+
         outpos = NULL;
-        zmq_assert (encoder);
         encoder->get_data (&outpos, &outsize);
 
         //  If there is no data to send, stop polling for output.