diff --git a/example/rest_book_client/main.cc b/example/rest_book_client/main.cc
index f0e8173..0849646 100644
--- a/example/rest_book_client/main.cc
+++ b/example/rest_book_client/main.cc
@@ -9,7 +9,7 @@
 #include "webcc/http_response.h"
 #include "webcc/rest_client.h"
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 // Write a JSON object to string.
 std::string JsonToString(const Json::Value& json) {
@@ -17,7 +17,7 @@ std::string JsonToString(const Json::Value& json) {
   return Json::writeString(builder, json);
 }
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 class BookListClient {
 public:
@@ -62,7 +62,7 @@ private:
   webcc::RestClient rest_client_;
 };
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 class BookDetailClient {
 public:
@@ -118,7 +118,7 @@ private:
   webcc::RestClient rest_client_;
 };
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 void Help(const char* argv0) {
   std::cout << "Usage: " << argv0 << " <host> <port>" << std::endl;
diff --git a/example/rest_book_server/book_services.cc b/example/rest_book_server/book_services.cc
index af7a197..7cc15a5 100644
--- a/example/rest_book_server/book_services.cc
+++ b/example/rest_book_server/book_services.cc
@@ -2,10 +2,11 @@
 
 #include <list>
 #include <iostream>
+
 #include "boost/lexical_cast.hpp"
-#include "json/json.h"  // jsoncpp
+#include "json/json.h"
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 // In-memory test data.
 // There should be some database in a real product.
@@ -97,7 +98,7 @@ private:
 
 static BookStore g_book_store;
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 static bool BookFromJson(const std::string& json, Book* book) {
   Json::Value root;
@@ -142,7 +143,7 @@ bool BookListService::Post(const std::string& request_content,
   return false;
 }
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 bool BookDetailService::Get(const std::vector<std::string>& url_sub_matches,
                             const webcc::UrlQuery& query,
@@ -182,7 +183,8 @@ bool BookDetailService::Put(const std::vector<std::string>& url_sub_matches,
   return false;
 }
 
-bool BookDetailService::Delete(const std::vector<std::string>& url_sub_matches) {
+bool BookDetailService::Delete(
+    const std::vector<std::string>& url_sub_matches) {
   if (url_sub_matches.size() != 1) {
     return false;
   }
diff --git a/example/rest_book_server/book_services.h b/example/rest_book_server/book_services.h
index f124718..4bdd773 100644
--- a/example/rest_book_server/book_services.h
+++ b/example/rest_book_server/book_services.h
@@ -3,7 +3,7 @@
 
 #include "webcc/rest_service.h"
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 // BookListService handles the HTTP GET and returns the book list based on
 // query parameters specified in the URL.
@@ -25,7 +25,7 @@ class BookListService : public webcc::RestListService {
             std::string* response_content) final;
 };
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 // The URL is like '/books/{BookID}', and the 'url_sub_matches' parameter
 // contains the matched book ID.
diff --git a/example/soap_calc_client/main.cc b/example/soap_calc_client/main.cc
index 799df26..aeda68a 100644
--- a/example/soap_calc_client/main.cc
+++ b/example/soap_calc_client/main.cc
@@ -3,7 +3,7 @@
 #include "calc_client.h"
 
 int main() {
-  LOG_INIT(webcc::INFO, 0);
+  LOG_INIT(webcc::VERB, 0);
 
   CalcClient calc;
 
diff --git a/src/webcc/globals.cc b/src/webcc/globals.cc
index 41af1ff..2c64408 100644
--- a/src/webcc/globals.cc
+++ b/src/webcc/globals.cc
@@ -4,6 +4,8 @@
 
 namespace webcc {
 
+// -----------------------------------------------------------------------------
+
 // NOTE:
 // Field names are case-insensitive.
 // See: https://stackoverflow.com/a/5259004
@@ -27,7 +29,7 @@ const std::string kHttpPatch = "PATCH";
 const std::string kHttpPut = "PUT";
 const std::string kHttpDelete = "DELETE";
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 const char* GetErrorMessage(Error error) {
   switch (error) {
@@ -63,7 +65,7 @@ const char* GetErrorMessage(Error error) {
   }
 }
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 Parameter::Parameter(const std::string& key, const char* value)
     : key_(key), value_(value) {
diff --git a/src/webcc/http_client.cc b/src/webcc/http_client.cc
index 7226da7..c7b4a55 100644
--- a/src/webcc/http_client.cc
+++ b/src/webcc/http_client.cc
@@ -19,14 +19,10 @@
 
 namespace webcc {
 
-////////////////////////////////////////////////////////////////////////////////
-
 static const int kConnectMaxSeconds = 10;
 static const int kSendMaxSeconds = 10;
 static const int kReceiveMaxSeconds = 30;
 
-////////////////////////////////////////////////////////////////////////////////
-
 HttpClient::HttpClient()
     : socket_(io_context_),
       timeout_seconds_(kReceiveMaxSeconds),
@@ -38,7 +34,7 @@ HttpClient::HttpClient()
 }
 
 Error HttpClient::Request(const HttpRequest& request, HttpResponse* response) {
-  assert(response != NULL);
+  assert(response != nullptr);
 
   Error error = kNoError;
 
diff --git a/src/webcc/http_response.cc b/src/webcc/http_response.cc
index 68cdba9..2858c17 100644
--- a/src/webcc/http_response.cc
+++ b/src/webcc/http_response.cc
@@ -81,8 +81,6 @@ const char CRLF[] = { '\r', '\n' };
 
 }  // misc_strings
 
-////////////////////////////////////////////////////////////////////////////////
-
 // ATTENTION: The buffers don't hold the memory!
 std::vector<boost::asio::const_buffer> HttpResponse::ToBuffers() const {
   std::vector<boost::asio::const_buffer> buffers;
diff --git a/src/webcc/http_server.cc b/src/webcc/http_server.cc
index a4b7dfd..2ae9e59 100644
--- a/src/webcc/http_server.cc
+++ b/src/webcc/http_server.cc
@@ -38,7 +38,7 @@ HttpServer::HttpServer(unsigned short port, std::size_t workers)
 }
 
 void HttpServer::Run() {
-  assert(GetRequestHandler() != NULL);
+  assert(GetRequestHandler() != nullptr);
 
   LOG_INFO("Server is going to run...");
 
diff --git a/src/webcc/logger.cc b/src/webcc/logger.cc
index d4be330..9ef5323 100644
--- a/src/webcc/logger.cc
+++ b/src/webcc/logger.cc
@@ -11,8 +11,6 @@
 
 namespace webcc {
 
-////////////////////////////////////////////////////////////////////////////////
-
 static std::string GetThreadId() {
   boost::thread::id thread_id = boost::this_thread::get_id();
   std::stringstream ss;
@@ -20,8 +18,6 @@ static std::string GetThreadId() {
   return ss.str();
 }
 
-////////////////////////////////////////////////////////////////////////////////
-
 static const char* kLevelNames[] = {
   "VERB", "INFO", "WARN", "ERRO", "FATA"
 };
@@ -35,8 +31,6 @@ struct Logger {
 // Global logger.
 static Logger g_logger{ VERB };
 
-////////////////////////////////////////////////////////////////////////////////
-
 void LogInit(int level, int modes) {
   g_logger.modes = modes;
   g_logger.level = level;
diff --git a/src/webcc/rest_service.cc b/src/webcc/rest_service.cc
index 4817443..1dca6ad 100644
--- a/src/webcc/rest_service.cc
+++ b/src/webcc/rest_service.cc
@@ -4,6 +4,8 @@
 
 namespace webcc {
 
+// -----------------------------------------------------------------------------
+
 bool RestListService::Handle(const std::string& http_method,
                              const std::vector<std::string>& url_sub_matches,
                              const UrlQuery& query,
@@ -22,7 +24,7 @@ bool RestListService::Handle(const std::string& http_method,
   return false;
 }
 
-////////////////////////////////////////////////////////////////////////////////
+// -----------------------------------------------------------------------------
 
 bool RestDetailService::Handle(const std::string& http_method,
                                const std::vector<std::string>& url_sub_matches,
diff --git a/src/webcc/rest_service_manager.cc b/src/webcc/rest_service_manager.cc
index 626b2c2..af5bdf5 100644
--- a/src/webcc/rest_service_manager.cc
+++ b/src/webcc/rest_service_manager.cc
@@ -32,10 +32,8 @@ bool RestServiceManager::AddService(RestServicePtr service,
 }
 
 RestServicePtr RestServiceManager::GetService(
-    const std::string& url,
-    std::vector<std::string>* sub_matches) {
-
-  assert(sub_matches != NULL);
+    const std::string& url, std::vector<std::string>* sub_matches) {
+  assert(sub_matches != nullptr);
 
   for (ServiceItem& item : service_items_) {
     if (item.is_regex) {
diff --git a/src/webcc/soap_message.cc b/src/webcc/soap_message.cc
index 1d64653..54a194e 100644
--- a/src/webcc/soap_message.cc
+++ b/src/webcc/soap_message.cc
@@ -24,12 +24,11 @@ void SoapMessage::ToXml(std::string* xml_string) {
   //   pugi::xml_node xdecl = xdoc.prepend_child(pugi::node_declaration);
   //   xdecl.append_attribute("version").set_value("1.0");
 
-  pugi::xml_node xroot = soap_xml::AddChild(soapenv_ns_.name, "Envelope",
-                                            &xdoc);
+  pugi::xml_node xroot = soap_xml::AddChild(xdoc, soapenv_ns_.name, "Envelope");
 
   soap_xml::AddNSAttr(xroot, soapenv_ns_.name, soapenv_ns_.url);
 
-  pugi::xml_node xbody = soap_xml::AddChild(soapenv_ns_.name, "Body", &xroot);
+  pugi::xml_node xbody = soap_xml::AddChild(xroot, soapenv_ns_.name, "Body");
 
   ToXmlBody(xbody);
 
diff --git a/src/webcc/soap_request.cc b/src/webcc/soap_request.cc
index 0aa339b..ea7332b 100644
--- a/src/webcc/soap_request.cc
+++ b/src/webcc/soap_request.cc
@@ -24,11 +24,11 @@ const std::string& SoapRequest::GetParameter(const std::string& key) const {
 }
 
 void SoapRequest::ToXmlBody(pugi::xml_node xbody) {
-  pugi::xml_node xop = soap_xml::AddChild(service_ns_.name, operation_, &xbody);
+  pugi::xml_node xop = soap_xml::AddChild(xbody, service_ns_.name, operation_);
   soap_xml::AddNSAttr(xop, service_ns_.name, service_ns_.url);
 
   for (Parameter& p : parameters_) {
-    pugi::xml_node xparam = soap_xml::AddChild(service_ns_.name, p.key(), &xop);
+    pugi::xml_node xparam = soap_xml::AddChild(xop, service_ns_.name, p.key());
     xparam.text().set(p.value().c_str());
   }
 }
diff --git a/src/webcc/soap_response.cc b/src/webcc/soap_response.cc
index 383a1ef..0a2cec4 100644
--- a/src/webcc/soap_response.cc
+++ b/src/webcc/soap_response.cc
@@ -6,12 +6,12 @@
 namespace webcc {
 
 void SoapResponse::ToXmlBody(pugi::xml_node xbody) {
-  pugi::xml_node xop = soap_xml::AddChild(service_ns_.name,
-                                          operation_ + "Response", &xbody);
+  pugi::xml_node xop = soap_xml::AddChild(xbody, service_ns_.name,
+                                          operation_ + "Response");
   soap_xml::AddNSAttr(xop, service_ns_.name, service_ns_.url);
 
-  pugi::xml_node xresult = soap_xml::AddChild(service_ns_.name, result_name_,
-                                              &xop);
+  pugi::xml_node xresult = soap_xml::AddChild(xop, service_ns_.name,
+                                              result_name_);
   xresult.text().set(result_.c_str());
 }
 
@@ -20,7 +20,7 @@ bool SoapResponse::FromXmlBody(pugi::xml_node xbody) {
 
   pugi::xml_node xresponse = xbody.first_child();
   if (xresponse) {
-    soap_xml::SplitName(xresponse, &service_ns_.name, NULL);
+    soap_xml::SplitName(xresponse, &service_ns_.name, nullptr);
     service_ns_.url = soap_xml::GetNSAttr(xresponse, service_ns_.name);
 
     pugi::xml_node xresult = soap_xml::GetChildNoNS(xresponse, result_name_);
diff --git a/src/webcc/soap_xml.cc b/src/webcc/soap_xml.cc
index 98212ef..5ac7f9b 100644
--- a/src/webcc/soap_xml.cc
+++ b/src/webcc/soap_xml.cc
@@ -10,17 +10,17 @@ void SplitName(const pugi::xml_node& xnode, std::string* prefix,
   size_t pos = full_name.find(':');
 
   if (pos != std::string::npos) {
-    if (prefix != NULL) {
+    if (prefix != nullptr) {
       *prefix = full_name.substr(0, pos);
     }
-    if (name != NULL) {
+    if (name != nullptr) {
       *name = full_name.substr(pos + 1);
     }
   } else {
-    if (prefix != NULL) {
+    if (prefix != nullptr) {
       *prefix = "";
     }
-    if (name != NULL) {
+    if (name != nullptr) {
       *name = full_name;
     }
   }
@@ -38,9 +38,9 @@ std::string GetNameNoPrefix(const pugi::xml_node& xnode) {
   return name;
 }
 
-pugi::xml_node AddChild(const std::string& ns, const std::string& name,
-                        pugi::xml_node* xnode) {
-  return xnode->append_child((ns + ":" + name).c_str());
+pugi::xml_node AddChild(pugi::xml_node xnode,
+                        const std::string& ns, const std::string& name) {
+  return xnode.append_child((ns + ":" + name).c_str());
 }
 
 pugi::xml_node GetChild(const pugi::xml_node& xnode, const std::string& ns,
@@ -70,13 +70,13 @@ pugi::xml_node GetChildNoNS(const pugi::xml_node& xnode,
   return pugi::xml_node();
 }
 
-void AddAttr(pugi::xml_node& xnode, const std::string& ns,
+void AddAttr(pugi::xml_node xnode, const std::string& ns,
              const std::string& name, const std::string& value) {
   std::string ns_name = ns + ":" + name;
   xnode.append_attribute(ns_name.c_str()) = value.c_str();
 }
 
-void AddNSAttr(pugi::xml_node& xnode, const std::string& ns_name,
+void AddNSAttr(pugi::xml_node xnode, const std::string& ns_name,
                const std::string& ns_url) {
   AddAttr(xnode, "xmlns", ns_name, ns_url);
 }
diff --git a/src/webcc/soap_xml.h b/src/webcc/soap_xml.h
index 8a143fb..4f6b938 100644
--- a/src/webcc/soap_xml.h
+++ b/src/webcc/soap_xml.h
@@ -13,8 +13,8 @@ namespace soap_xml {
 // Split the node name into namespace prefix and real name.
 // E.g., if the node name is "soapenv:Envelope", it will be splitted to
 // "soapenv" and "Envelope".
-void SplitName(const pugi::xml_node& xnode, std::string* prefix = NULL,
-               std::string* name = NULL);
+void SplitName(const pugi::xml_node& xnode, std::string* prefix = nullptr,
+               std::string* name = nullptr);
 
 // Get the namespace prefix from node name.
 // E.g., if the node name is "soapenv:Envelope", NS prefix will be "soapenv".
@@ -26,18 +26,17 @@ std::string GetNameNoPrefix(const pugi::xml_node& xnode);
 // Add a child with the given name which is prefixed by a namespace.
 // E.g., AppendChild(xnode, "soapenv", "Envelope") will append a child with
 // name "soapenv:Envelope".
-pugi::xml_node AddChild(const std::string& ns, const std::string& name,
-                        pugi::xml_node* xnode);
+pugi::xml_node AddChild(pugi::xml_node xnode,
+                        const std::string& ns, const std::string& name);
 
 pugi::xml_node GetChild(const pugi::xml_node& xnode, const std::string& ns,
                         const std::string& name);
 
-// TODO: Remove
 pugi::xml_node GetChildNoNS(const pugi::xml_node& xnode,
                             const std::string& name);
 
 // Add an attribute with the given name which is prefixed by a namespace.
-void AddAttr(pugi::xml_node& xnode, const std::string& ns,
+void AddAttr(pugi::xml_node xnode, const std::string& ns,
              const std::string& name, const std::string& value);
 
 // Append "xmlns" attribute.
@@ -45,7 +44,7 @@ void AddAttr(pugi::xml_node& xnode, const std::string& ns,
 //   { "soapenv", "http://schemas.xmlsoap.org/soap/envelope/" }
 // the attribute added will be
 //   xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
-void AddNSAttr(pugi::xml_node& xnode, const std::string& ns_name,
+void AddNSAttr(pugi::xml_node xnode, const std::string& ns_name,
                const std::string& ns_url);
 
 // Get namespace attribute value.
@@ -67,7 +66,7 @@ class XmlStrRefWriter : public pugi::xml_writer {
     result_->clear();
   }
 
-  void write(const void* data, size_t size) override {
+  void write(const void* data, std::size_t size) override {
     result_->append(static_cast<const char*>(data), size);
   }