click: Fix clang-tidy warnings

src/click/model/ipv4-click-routing.cc

@@ -61,7 +61,7 @@ Ipv4ClickRouting::GetTypeId()
 
 Ipv4ClickRouting::Ipv4ClickRouting()
     : m_nonDefaultName(false),
-      m_ipv4(0)
+      m_ipv4(nullptr)
 {
     m_random = CreateObject<UniformRandomVariable>();
     m_simNode = new simclick_node_t;
@@ -124,7 +124,7 @@ Ipv4ClickRouting::DoDispose()
     {
         simclick_click_kill(m_simNode);
     }
-    m_ipv4 = 0;
+    m_ipv4 = nullptr;
     delete m_simNode;
     Ipv4RoutingProtocol::DoDispose();
 }
@@ -441,8 +441,11 @@ Ipv4ClickRouting::Receive(Ptr<Packet> p, Mac48Address receiverAddr, Mac48Address
 std::string
 Ipv4ClickRouting::ReadHandler(std::string elementName, std::string handlerName)
 {
-    char* handle =
-        simclick_click_read_handler(m_simNode, elementName.c_str(), handlerName.c_str(), 0, 0);
+    char* handle = simclick_click_read_handler(m_simNode,
+                                               elementName.c_str(),
+                                               handlerName.c_str(),
+                                               nullptr,
+                                               nullptr);
     std::string ret(handle);
 
     // This is required because Click does not free
@@ -497,7 +500,7 @@ Ipv4ClickRouting::RouteOutput(Ptr<Packet> p,
     std::string s = ReadHandler(m_clickRoutingTableElement, addr.str());
     NS_LOG_DEBUG("string from click routing table: " << s);
 
-    size_t pos = s.find(" ");
+    size_t pos = s.find(' ');
     Ipv4Address destination;
     int interfaceId;
     if (pos == std::string::npos)

src/click/model/ipv4-l3-click-protocol.cc

@@ -82,13 +82,13 @@ Ipv4L3ClickProtocol::DoDispose()
     NS_LOG_FUNCTION(this);
     for (L4List_t::iterator i = m_protocols.begin(); i != m_protocols.end(); ++i)
     {
-        i->second = 0;
+        i->second = nullptr;
     }
     m_protocols.clear();
 
     for (Ipv4InterfaceList::iterator i = m_interfaces.begin(); i != m_interfaces.end(); ++i)
     {
-        *i = 0;
+        *i = nullptr;
     }
     m_interfaces.clear();
     m_reverseInterfacesContainer.clear();
@@ -137,7 +137,7 @@ Ipv4L3ClickProtocol::GetInterface(uint32_t index) const
     {
         return m_interfaces[index];
     }
-    return 0;
+    return nullptr;
 }
 
 uint32_t
@@ -320,7 +320,7 @@ Ipv4L3ClickProtocol::SetupLoopback()
     NS_LOG_FUNCTION_NOARGS();
 
     Ptr<Ipv4Interface> interface = CreateObject<Ipv4Interface>();
-    Ptr<LoopbackNetDevice> device = 0;
+    Ptr<LoopbackNetDevice> device = nullptr;
     // First check whether an existing LoopbackNetDevice exists on the node
     for (uint32_t i = 0; i < m_node->GetNDevices(); i++)
     {
@@ -889,7 +889,7 @@ Ipv4L3ClickProtocol::GetIcmp() const
     }
     else
     {
-        return 0;
+        return nullptr;
     }
 }
 
@@ -989,7 +989,7 @@ Ipv4L3ClickProtocol::GetProtocol(int protocolNumber, int32_t interfaceIndex) con
         return i->second;
     }
 
-    return 0;
+    return nullptr;
 }
 
 } // namespace ns3