From 79ca436b74e3d28f2f5e55e280c90f0b37f91e74 Mon Sep 17 00:00:00 2001
From: Alexey Rybalchenko <alexryba@gmail.com>
Date: Thu, 4 Jun 2020 23:27:11 +0200
Subject: [PATCH] Zmq: let GetData of an empty message return nullptr

---
 fairmq/zeromq/Message.h   | 12 ++++++++++--
 test/message/_message.cxx | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/fairmq/zeromq/Message.h b/fairmq/zeromq/Message.h
index 9e16e85a..64ed96f3 100644
--- a/fairmq/zeromq/Message.h
+++ b/fairmq/zeromq/Message.h
@@ -155,9 +155,17 @@ class Message final : public fair::mq::Message
     void* GetData() const override
     {
         if (!fViewMsg) {
-            return zmq_msg_data(fMsg.get());
+            if (zmq_msg_size(fMsg.get()) > 0) {
+                return zmq_msg_data(fMsg.get());
+            } else {
+                return nullptr;
+            }
         } else {
-            return zmq_msg_data(fViewMsg.get());
+            if (zmq_msg_size(fViewMsg.get()) > 0) {
+                return zmq_msg_data(fViewMsg.get());
+            } else {
+                return nullptr;
+            }
         }
     }
 
diff --git a/test/message/_message.cxx b/test/message/_message.cxx
index c9d4b01b..6cec36b6 100644
--- a/test/message/_message.cxx
+++ b/test/message/_message.cxx
@@ -91,6 +91,31 @@ void Alignment(const string& transport)
     ASSERT_EQ(reinterpret_cast<uintptr_t>(msg->GetData()) % 64, 0);
 }
 
+void EmptyMessage(const string& transport, const string& _address)
+{
+    size_t session{fair::mq::tools::UuidHash()};
+    std::string address(fair::mq::tools::ToString(_address, "_", transport));
+
+    fair::mq::ProgOptions config;
+    config.SetProperty<string>("session", to_string(session));
+
+    auto factory = FairMQTransportFactory::CreateTransportFactory(transport, fair::mq::tools::Uuid(), &config);
+
+    FairMQChannel push{"Push", "push", factory};
+    push.Bind(address);
+
+    FairMQChannel pull{"Pull", "pull", factory};
+    pull.Connect(address);
+
+    FairMQMessagePtr outMsg(push.NewMessage());
+    ASSERT_EQ(outMsg->GetData(), nullptr);
+    ASSERT_EQ(push.Send(outMsg), 0);
+
+    FairMQMessagePtr inMsg(pull.NewMessage());
+    ASSERT_EQ(pull.Receive(inMsg), 0);
+    ASSERT_EQ(inMsg->GetData(), nullptr);
+}
+
 TEST(Resize, zeromq)
 {
     RunPushPullWithMsgResize("zeromq", "ipc://test_message_resize");
@@ -116,4 +141,14 @@ TEST(Alignment, shmem) // TODO: add test for ZeroMQ once it is implemented
     Alignment("shmem");
 }
 
+TEST(EmptyMessage, zeromq)
+{
+    EmptyMessage("zeromq", "ipc://test_empty_message");
+}
+
+TEST(EmptyMessage, shmem)
+{
+    EmptyMessage("shmem", "ipc://test_empty_message");
+}
+
 } // namespace