Bug#17599 The server doesn't give a warning

when --log is specified but log table is used
(recommit after docs reviewed the text of warnings)

sql/mysqld.cc

@@ -2770,6 +2770,19 @@ static int init_common_variables(const char *conf_file_name, int argc,
   else
     sys_init_slave.value=my_strdup("",MYF(0));
 
+  /* check log options and issue warnings if needed */
+  if (opt_log && opt_logname && !(log_output_options & LOG_FILE) &&
+      !(log_output_options & LOG_NONE))
+    sql_print_warning("Although a path was specified for the "
+                      "--log option, log tables are used. "
+                      "To enable logging to file use the --log-output option.");
+
+  if (opt_slow_log && opt_slow_logname && !(log_output_options & LOG_FILE)
+      && !(log_output_options & LOG_NONE))
+    sql_print_warning("Although a path was specified for the "
+                      "--log-slow-queries option, log tables are used. "
+                      "To enable logging to file use the --log-output option.");
+
   if (!opt_logname)
     opt_logname= make_default_log_name(buff, ".log");
   sys_var_general_log_path.value= my_strdup(opt_logname, MYF(0));