Is ["unexpected `Flen` value(-1) in CONCAT's args"] ["arg's index"=0] warning a normal phenomenon

Appears many times in the log file, caused by SQL select concat(@@sql_mode,',STRICT_TRANS_TABLES');.

Do we have an issue for it?

Nope. Not sure this is a problem or not. So I’d like to first discuss here.

Of course, it is not.

I think you can file an issue on github and mark it as a bug, although its severity is low.