5.7.43 on Ubuntu. Start option --log-error works abnormally, causing mysqld start failed

[shen jevon]

I don't know why option --log-error works uncorrectly, following cmd shows how i start mysqld and debug


All Started by
jevon@Kubuntu:/mnt/WorkSpace/Source_Code/mysql-server-5.7$ ./Build/sql/mysqld --user=jevon --sql-mode=NO_AUTO_CREATE_USER --port=9200 --socket=/mnt/WorkSpace/Source_Code/mysql-server-5.7/Build/Runtime_Location/server.socket --pid-file=/mnt/WorkSpace/Source_Code/mysql-server-5.7/Build/Runtime_Location/server.pid --basedir=/mnt/WorkSpace/Source_Code/mysql-server-5.7/Build/Runtime_Location --datadir=/mnt/WorkSpace/Source_Code/mysql-server-5.7/Build/Runtime_Location/data --lc-messages-dir=/mnt/WorkSpace/Source_Code/mysql-server-5.7/Build/sql/share
2023-10-30T02:31:07.925426Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2023-10-30T02:31:07.927278Z 0 [Warning] Insecure configuration for --secure-file-priv: Location is accessible to all OS users. Consider choosing a different directory.
2023-10-30T02:31:07.927311Z 0 [Note] ./Build/sql/mysqld (mysqld 5.7.43-debug) starting as process 78003 ...
2023-10-30T02:31:07.928965Z 0 [ERROR] Could not open file '/var/log/mysql/error.log' for error logging: Permission denied
2023-10-30T02:31:07.928999Z 0 [ERROR] Aborting

2023-10-30T02:31:07.943199Z 0 [Note] Binlog end
2023-10-30T02:31:07.961609Z 0 [Note] ./Build/sql/mysqld: Shutdown complete


This is how i start the second instance mysqld which is Builted when i already have an existing mysqld8.0 running
This Log : [ERROR] Could not open file '/var/log/mysql/error.log' is caused by log-error option i think.
I want to log error message on stderr so i did't create error.log and did't use --log-error

I Checked mysqld.cc:3846（maybe）
bool log_errors_to_file = !opt_help && (log_error_dest != disabled_my_option);

According to the comment above :
/*
Enable old-fashioned error log, except when the user has requested
help information. Since the implementation of plugin server
variables the help output is now written much later.

log_error_dest can be:
disabled_my_option --log-error was not used or --log-error=
"" --log-error without arguments (no '=')
filename --log-error=filename
*/
i didn't used --log-error option, so variable: log_error_dest should be equal to variable: disabled_my_option whick is '0' and cause variable: log_errors_to_file = false.
But i checked variable: log_error_dest is still /var/log/mysql/error.log which is the default value of this option.
And i also tryed "--log-error=", but still /var/log/mysql/error.log
It does't work correctly

However i used --log-error="0", it works well
mysqld started with no problems.Because variable: log_errors_to_file = false and aviod open errorlogs.

So why does " --log-error was not used or --log-error=" doesn't work?
Is there anythis i did wrong or missing some step?
(I use vscode to debug and using args "--log-error=\"0\"",it works well)
Plz give me some advice Thx