Give a more informative message if we failed to write to mysql.general_log

table.

sql/log.cc

@@ -73,23 +73,28 @@ static int binlog_prepare(handlerton *hton, THD *thd, bool all);
 */
 class Silence_log_table_errors : public Internal_error_handler
 {
+  char m_message[MYSQL_ERRMSG_SIZE];
 public:
   Silence_log_table_errors()
-  {}
+  {
+    m_message[0]= '\0';
+  }
 
   virtual ~Silence_log_table_errors() {}
 
   virtual bool handle_error(uint sql_errno, const char *message,
                             MYSQL_ERROR::enum_warning_level level,
                             THD *thd);
+  const char *message() const { return m_message; }
 };
 
 bool
 Silence_log_table_errors::handle_error(uint /* sql_errno */,
-                                       const char * /* message */,
+                                       const char *message_arg,
                                        MYSQL_ERROR::enum_warning_level /* level */,
                                        THD * /* thd */)
 {
+  strmake(m_message, message_arg, sizeof(m_message));
   return TRUE;
 }
 
@@ -437,7 +442,8 @@ bool Log_to_csv_event_handler::
 
 err:
   if (result)
-    sql_print_error("Failed to write to mysql.general_log");
+    sql_print_error("Failed to write to mysql.general_log: %s",
+                    error_handler.message());
 
   if (need_rnd_end)
   {