Various cleanups in zmqnotificationinterface.

This is a pure refactoring of zmqnotificationinterface to make the
code easier to read and maintain.  It replaces explicit iterators
with C++11 for-each loops where appropriate and uses std::unique_ptr
to make memory ownership more explicit.

src/zmq/zmqnotificationinterface.cpp

@@ -20,33 +20,26 @@ CZMQNotificationInterface::CZMQNotificationInterface() : pcontext(nullptr)
 CZMQNotificationInterface::~CZMQNotificationInterface()
 {
     Shutdown();
-
-    for (std::list<CZMQAbstractNotifier*>::iterator i=notifiers.begin(); i!=notifiers.end(); ++i)
-    {
-        delete *i;
-    }
 }
 
 std::list<const CZMQAbstractNotifier*> CZMQNotificationInterface::GetActiveNotifiers() const
 {
     std::list<const CZMQAbstractNotifier*> result;
-    for (const auto* n : notifiers) {
-        result.push_back(n);
+    for (const auto& n : notifiers) {
+        result.push_back(n.get());
     }
     return result;
 }
 
 CZMQNotificationInterface* CZMQNotificationInterface::Create()
 {
-    CZMQNotificationInterface* notificationInterface = nullptr;
     std::map<std::string, CZMQNotifierFactory> factories;
-    std::list<CZMQAbstractNotifier*> notifiers;
-
     factories["pubhashblock"] = CZMQAbstractNotifier::Create<CZMQPublishHashBlockNotifier>;
     factories["pubhashtx"] = CZMQAbstractNotifier::Create<CZMQPublishHashTransactionNotifier>;
     factories["pubrawblock"] = CZMQAbstractNotifier::Create<CZMQPublishRawBlockNotifier>;
     factories["pubrawtx"] = CZMQAbstractNotifier::Create<CZMQPublishRawTransactionNotifier>;
 
+    std::list<std::unique_ptr<CZMQAbstractNotifier>> notifiers;
     for (const auto& entry : factories)
     {
         std::string arg("-zmq" + entry.first);
@@ -58,23 +51,21 @@ CZMQNotificationInterface* CZMQNotificationInterface::Create()
             notifier->SetType(entry.first);
             notifier->SetAddress(address);
             notifier->SetOutboundMessageHighWaterMark(static_cast<int>(gArgs.GetArg(arg + "hwm", CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM)));
-            notifiers.push_back(notifier);
+            notifiers.emplace_back(notifier);
         }
     }
 
     if (!notifiers.empty())
     {
-        notificationInterface = new CZMQNotificationInterface();
-        notificationInterface->notifiers = notifiers;
+        std::unique_ptr<CZMQNotificationInterface> notificationInterface(new CZMQNotificationInterface());
+        notificationInterface->notifiers = std::move(notifiers);
 
-        if (!notificationInterface->Initialize())
-        {
-            delete notificationInterface;
-            notificationInterface = nullptr;
+        if (notificationInterface->Initialize()) {
+            return notificationInterface.release();
         }
     }
 
-    return notificationInterface;
+    return nullptr;
 }
 
 // Called at startup to conditionally set up ZMQ socket(s)
@@ -95,26 +86,15 @@ bool CZMQNotificationInterface::Initialize()
         return false;
     }
 
-    std::list<CZMQAbstractNotifier*>::iterator i=notifiers.begin();
-    for (; i!=notifiers.end(); ++i)
-    {
-        CZMQAbstractNotifier *notifier = *i;
-        if (notifier->Initialize(pcontext))
-        {
+    for (auto& notifier : notifiers) {
+        if (notifier->Initialize(pcontext)) {
             LogPrint(BCLog::ZMQ, "zmq: Notifier %s ready (address = %s)\n", notifier->GetType(), notifier->GetAddress());
-        }
-        else
-        {
+        } else {
             LogPrint(BCLog::ZMQ, "zmq: Notifier %s failed (address = %s)\n", notifier->GetType(), notifier->GetAddress());
-            break;
+            return false;
         }
     }
 
-    if (i!=notifiers.end())
-    {
-        return false;
-    }
-
     return true;
 }
 
@@ -124,9 +104,7 @@ void CZMQNotificationInterface::Shutdown()
     LogPrint(BCLog::ZMQ, "zmq: Shutdown notification interface\n");
     if (pcontext)
     {
-        for (std::list<CZMQAbstractNotifier*>::iterator i=notifiers.begin(); i!=notifiers.end(); ++i)
-        {
-            CZMQAbstractNotifier *notifier = *i;
+        for (auto& notifier : notifiers) {
             LogPrint(BCLog::ZMQ, "zmq: Shutdown notifier %s at %s\n", notifier->GetType(), notifier->GetAddress());
             notifier->Shutdown();
         }
@@ -141,9 +119,9 @@ void CZMQNotificationInterface::UpdatedBlockTip(const CBlockIndex *pindexNew, co
     if (fInitialDownload || pindexNew == pindexFork) // In IBD or blocks were disconnected without any new ones
         return;
 
-    for (std::list<CZMQAbstractNotifier*>::iterator i = notifiers.begin(); i!=notifiers.end(); )
+    for (auto i = notifiers.begin(); i!=notifiers.end(); )
     {
-        CZMQAbstractNotifier *notifier = *i;
+        CZMQAbstractNotifier *notifier = i->get();
         if (notifier->NotifyBlock(pindexNew))
         {
             i++;
@@ -162,9 +140,9 @@ void CZMQNotificationInterface::TransactionAddedToMempool(const CTransactionRef&
     // all the same external callback.
     const CTransaction& tx = *ptx;
 
-    for (std::list<CZMQAbstractNotifier*>::iterator i = notifiers.begin(); i!=notifiers.end(); )
+    for (auto i = notifiers.begin(); i!=notifiers.end(); )
     {
-        CZMQAbstractNotifier *notifier = *i;
+        CZMQAbstractNotifier *notifier = i->get();
         if (notifier->NotifyTransaction(tx))
         {
             i++;

src/zmq/zmqnotificationinterface.h

@@ -7,6 +7,7 @@
 
 #include <validationinterface.h>
 #include <list>
+#include <memory>
 
 class CBlockIndex;
 class CZMQAbstractNotifier;
@@ -34,7 +35,7 @@ private:
     CZMQNotificationInterface();
 
     void *pcontext;
-    std::list<CZMQAbstractNotifier*> notifiers;
+    std::list<std::unique_ptr<CZMQAbstractNotifier>> notifiers;
 };
 
 extern CZMQNotificationInterface* g_zmq_notification_interface;

src/zmq/zmqpublishnotifier.cpp

@@ -10,6 +10,14 @@
 #include <util/system.h>
 #include <rpc/server.h>
 
+#include <zmq.h>
+
+#include <cstdarg>
+#include <cstddef>
+#include <map>
+#include <string>
+#include <utility>
+
 static std::multimap<std::string, CZMQAbstractPublishNotifier*> mapPublishNotifiers;
 
 static const char *MSG_HASHBLOCK = "hashblock";