Fix function overload resolution.

src/client/WFKafkaClient.cc

@@ -312,7 +312,7 @@ void KafkaClientTask::kafka_rebalance_callback(__WFKafkaTask *task)
 		snprintf(name, 64, "%p.cgroup", member);
 		member->mutex.unlock();
 
-		WFTaskFactory::signal_by_name(name, NULL, max);
+		WFTaskFactory::signal_by_name(name, (void *)NULL, max);
 	}
 	else
 	{

src/factory/WFTaskFactory.h

@@ -382,6 +382,33 @@ class WFTaskFactory
 		task->sub_series()->set_last_task(last);
 		return task;
 	}
+
+public:
+	/* The following functions are for overload resolution only. */
+
+	static int send_by_name(const std::string& mailbox_name, intptr_t msg,
+							size_t max)
+	{
+		return WFTaskFactory::send_by_name(mailbox_name, (void *)msg, max);
+	}
+
+	static int send_by_name(const std::string& mailbox_name, std::nullptr_t msg,
+							size_t max)
+	{
+		return WFTaskFactory::send_by_name(mailbox_name, (void *)0, max);
+	}
+
+	static int signal_by_name(const std::string& cond_name, intptr_t msg,
+							  size_t max)
+	{
+		return WFTaskFactory::signal_by_name(cond_name, (void *)msg, max);
+	}
+
+	static int signal_by_name(const std::string& cond_name, std::nullptr_t msg,
+							  size_t max)
+	{
+		return WFTaskFactory::signal_by_name(cond_name, (void *)0, max);
+	}
 };
 
 template<class REQ, class RESP>

src/factory/WFTaskFactory.inl

@@ -18,6 +18,7 @@
            Li Yingxin (liyingxin@sogou-inc.com)
 */
 
+#include <stddef.h>
 #include <stdio.h>
 #include <errno.h>
 #include <string>