Allow multiple logging::LogMessage{Handler,Listener}s

remoting/host/logging_mac.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "remoting/host/logging.h"
 
 #include <asl.h>
 #include <stddef.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ skipping 15 matching lines @@
   }
   static void Free(aslmsg msg) {
     asl_free(msg);
   }
 };
 typedef base::ScopedGeneric<aslmsg, ScopedAslMsgTraits> ScopedAslMsg;
 
 // Logging message handler that writes to syslog.
 // The log can be obtained by running the following in a terminal:
 // syslog -k Facility org.chromium.chromoting
-bool LogMessageToAsl(
-    logging::LogSeverity severity,
-    const char* file,
-    int line,
-    size_t message_start,
-    const std::string& message) {
+class LogMessageListener : logging::LogMessageListener {
+  void OnMessage(logging::LogSeverity severity,
+                 const char* file,
+                 int line,
+                 size_t message_start,
+                 const std::string& message) override;
+};
+
+void LogMessageListener::OnMessage(logging::LogSeverity severity,
+                                   const char* file,
+                                   int line,
+                                   size_t message_start,
+                                   const std::string& message) {
   int level;
   switch(severity) {
     case logging::LOG_INFO:
       level = ASL_LEVEL_NOTICE;
       break;
     case logging::LOG_WARNING:
       level = ASL_LEVEL_WARNING;
       break;
     case logging::LOG_ERROR:
     case logging::LOG_FATAL:
       level = ASL_LEVEL_ERR;
       break;
     default:
       // 'notice' is the lowest priority that the asl libraries will log by
       // default.
       level = ASL_LEVEL_NOTICE;
       break;
   }
 
   ScopedAslMsg asl_message(asl_new(ASL_TYPE_MSG));
   if (!asl_message.is_valid())
-    return false;
+    return;
 
   if (asl_set(asl_message.get(), ASL_KEY_FACILITY,
               kChromotingLoggingFacility) != 0)
-    return false;
+    return;
 
   if (asl_set(asl_message.get(), ASL_KEY_LEVEL,
               base::IntToString(level).c_str()) != 0)
-    return false;
+    return;
 
   // Restrict read access to the message to root and the current user.
   if (asl_set(asl_message.get(), ASL_KEY_READ_UID,
               base::IntToString(geteuid()).c_str()) != 0)
-    return false;
+    return;
 
   if (asl_set(asl_message.get(), ASL_KEY_MSG,
               message.c_str() + message_start) != 0)
-    return false;
+    return;
 
   asl_send(nullptr, asl_message.get());
 
   // Don't prevent message from being logged by traditional means.
-  return false;
 }
 
 }  // namespace
 
 void InitHostLogging() {
   // Write logs to the system debug log.
   logging::LoggingSettings settings;
   settings.logging_dest = logging::LOG_TO_SYSTEM_DEBUG_LOG;
   logging::InitLogging(settings);
 
   // Write logs to syslog as well.
-  logging::SetLogMessageHandler(LogMessageToAsl);
+  // Intentionally leak the listener
+  auto* listener = new LogMessageListener();
+  CHECK(listener);
 }
 
 }  // namespace remoting