Assertion failure when using --log-regexp

src/log.cc

Index: src/log.cc
diff --git a/src/log.cc b/src/log.cc
index c634d28e9dd572304a4b7e5901419067a7faa643..97f599e98e3096c38774cabcc2fab4695daf6f55 100644
--- a/src/log.cc
+++ b/src/log.cc
@@ -953,10 +953,10 @@ TIMER_EVENTS_LIST(V)
 #undef V
 
 
-void Logger::LogRegExpSource(Handle<JSRegExp> regexp) {
+void Logger::LogRegExpSource(Handle<JSRegExp> regexp,
+                             Log::MessageBuilder& msg) {
   // Prints "/" + re.source + "/" +
   //      (re.global?"g":"") + (re.ignorecase?"i":"") + (re.multiline?"m":"")
-  Log::MessageBuilder msg(log_);
 
   Handle<Object> source = Object::GetProperty(
       isolate_, regexp, "source").ToHandleChecked();
@@ -994,8 +994,6 @@ void Logger::LogRegExpSource(Handle<JSRegExp> regexp) {
   if (multiline->IsTrue()) {
     msg.Append('m');
   }
-
-  msg.WriteToLogFile();
 }
 
 
@@ -1003,7 +1001,7 @@ void Logger::RegExpCompileEvent(Handle<JSRegExp> regexp, bool in_cache) {
   if (!log_->IsEnabled() || !FLAG_log_regexp) return;
   Log::MessageBuilder msg(log_);
   msg.Append("regexp-compile,");
-  LogRegExpSource(regexp);
+  LogRegExpSource(regexp, msg);
   msg.Append(in_cache ? ",hit" : ",miss");
   msg.WriteToLogFile();
 }