Make the name of the event source for SYSLOG configurable.

base/syslog_logging.cc

 // Copyright 2016 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 "base/debug/stack_trace.h"
 #include "base/syslog_logging.h"
 
 #if defined(OS_WIN)
+#include "base/bind.h"
+#include "base/callback_helpers.h"
 #include "base/win/eventlog_messages.h"
 
 #include <windows.h>
 #elif defined(OS_LINUX)
 #include <syslog.h>
 #endif
 
 #include <cstring>
 #include <ostream>
 #include <string>
 
 namespace logging {
 
+#if defined(OS_WIN)
+
+namespace {
+std::string* g_event_source_name = nullptr;
+}
+
+void SetEventSourceName(const std::string& name) {
+  DCHECK_EQ(nullptr, g_event_source_name);
+  g_event_source_name = new std::string(name);
+}
+#endif  // defined(OS_WIN)
+
 EventLogMessage::EventLogMessage(const char* file,
                                  int line,
                                  LogSeverity severity)
     : log_message_(file, line, severity) {
 }
 
 EventLogMessage::~EventLogMessage() {
 #if defined(OS_WIN)
-  const char kEventSource[] = "chrome";
-  HANDLE event_log_handle = RegisterEventSourceA(NULL, kEventSource);
+  // If g_event_source_name is nullptr (which it is per default) SYSLOG will
+  // degrade gracefully to regular LOG. If you see this happening most probably
+  // you are using SYSLOG before you called SetEventSourceName.
+  if (g_event_source_name == nullptr)
+    return;
+
+  HANDLE event_log_handle =
+      RegisterEventSourceA(NULL, g_event_source_name->c_str());
   if (event_log_handle == NULL) {
     stream() << " !!NOT ADDED TO EVENTLOG!!";
     return;
   }
 
+  base::ScopedClosureRunner auto_deregister(
+      base::Bind(base::IgnoreResult(&DeregisterEventSource), event_log_handle));
   std::string message(log_message_.str());
   WORD log_type = EVENTLOG_ERROR_TYPE;
   switch (log_message_.severity()) {
     case LOG_INFO:
       log_type = EVENTLOG_INFORMATION_TYPE;
       break;
     case LOG_WARNING:
       log_type = EVENTLOG_WARNING_TYPE;
       break;
     case LOG_ERROR:
     case LOG_FATAL:
       // The price of getting the stack trace is not worth the hassle for
       // non-error conditions.
       base::debug::StackTrace trace;
       message.append(trace.ToString());
       log_type = EVENTLOG_ERROR_TYPE;
       break;
   }
   LPCSTR strings[1] = {message.data()};
   if (!ReportEventA(event_log_handle, log_type, BROWSER_CATEGORY,
                     MSG_LOG_MESSAGE, NULL, 1, 0, strings, NULL)) {
     stream() << " !!NOT ADDED TO EVENTLOG!!";
   }
-  DeregisterEventSource(event_log_handle);
 #elif defined(OS_LINUX)
   const char kEventSource[] = "chrome";
   openlog(kEventSource, LOG_NOWAIT | LOG_PID, LOG_USER);
   // We can't use the defined names for the logging severity from syslog.h
   // because they collide with the names of our own severity levels. Therefore
   // we use the actual values which of course do not match ours.
   // See sys/syslog.h for reference.
   int priority = 3;
   switch (log_message_.severity()) {
     case LOG_INFO:
       priority = 6;
       break;
     case LOG_WARNING:
       priority = 4;
       break;
     case LOG_ERROR:
       priority = 3;
       break;
     case LOG_FATAL:
       priority = 2;
       break;
   }
   syslog(priority, "%s", log_message_.str().c_str());
   closelog();
 #endif  // defined(OS_WIN)
 }
 
 }  // namespace logging