Description:
Hi,
The current configuration parser allows empty value as the option value. However, the empty value causes inconsistent and indeterminate behavior which might confuse users.
=============================
Symptom
=============================
1. For numeric options including INT, UINT, LONG, ULONG, the parser translate the empty value to 0, because of using "strtoll()" call in "eval_num_suffix()", as follows,
/* mysys/my_getopt.c */
864 num= strtoll(argument, &endchar, 10);
When argument is "", the returned num will be 0.
For example, start mysqld with the empty value of "query_cache_limit"
$ mysqld --query_cache_limit=
Retrieve the system value:
$ mysqld
mysql> SHOW GLOBAL VARIABLES LIKE 'query\_cache\_limit';
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| query_cache_limit | 0 |
+-------------------+-------+
1 row in set (0.00 sec)
-----------------------------
2. For boolean value, the empty value is rejected and set to "OFF"
$ mysqld --performance-schema=
130109 0:27:31 [Warning] Buffered warning: option 'performance_schema': boolean value '' wasn't recognized. Set to OFF.
-----------------------------
3. For string value, the results are indeterminate.
3.1
$ mysqld --innodb_data_file_path=
130109 0:31:00 [ERROR] InnoDB: syntax error in innodb_data_file_path
130109 0:31:00 [ERROR] Plugin 'InnoDB' init function returned error.
130109 0:31:00 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
130109 0:31:00 [ERROR] Unknown/unsupported storage engine: InnoDB
130109 0:31:00 [ERROR] Aborting
3.2
$ mysqld --socket=
130109 0:33:17 InnoDB: The InnoDB memory heap is disabled
130109 0:33:17 InnoDB: Mutexes and rw_locks use GCC atomic builtins
130109 0:33:17 InnoDB: Compressed tables use zlib 1.2.3.4
130109 0:33:17 InnoDB: Initializing buffer pool, size = 8.0M
130109 0:33:17 InnoDB: Completed initialization of buffer pool
130109 0:33:17 InnoDB: highest supported file format is Barracuda.
130109 0:33:17 InnoDB: Waiting for the background threads to start
130109 0:33:18 InnoDB: 1.1.8 started; log sequence number 116061718
130109 0:33:18 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
130109 0:33:18 [Note] - '127.0.0.1' resolves to '127.0.0.1';
130109 0:33:18 [Note] Server socket created on IP: '127.0.0.1'.
130109 0:33:18 [Note] Event Scheduler: Loaded 1 event
130109 0:33:18 [Note] bin/mysqld: ready for connections.
Version: '5.5.29-log' socket: '' port: 3306 Source distribution
mysql --host=localhost --port=3306
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
=============================
Root Cause
=============================
The root cause is such empty value is never checked in the configuration parser, and it goes through all the checking and finally get used.
How to repeat:
Described in the "Description" section.
Suggested fix:
I suggest to check it in the very beginning in setval() in my_getopt.c. See the patch attached.
The behavior is to ignore the input and print out an error message, while keeping the option value unchanged. In this way, it has no side effect.
The patch is tested.
--- mysql-5.5.29/mysys/my_getopt.c 2012-08-29 01:50:46.000000000 -0700
+++ mysql-5.5.29/mysys/my_getopt.c 2013-01-09 00:57:10.020208478 -0800
@@ -642,6 +642,13 @@
if (!argument)
argument= enabled_my_option;
+
+ if(strlen(argument) == 0) {
+ my_getopt_error_reporter(ERROR_LEVEL,
+ "%s: Empty value of '%s' is specified. Keep the previous value unchanged",
+ my_progname, opts->name);
+ return 0;
+ }
if (value)
{
Description: Hi, The current configuration parser allows empty value as the option value. However, the empty value causes inconsistent and indeterminate behavior which might confuse users. ============================= Symptom ============================= 1. For numeric options including INT, UINT, LONG, ULONG, the parser translate the empty value to 0, because of using "strtoll()" call in "eval_num_suffix()", as follows, /* mysys/my_getopt.c */ 864 num= strtoll(argument, &endchar, 10); When argument is "", the returned num will be 0. For example, start mysqld with the empty value of "query_cache_limit" $ mysqld --query_cache_limit= Retrieve the system value: $ mysqld mysql> SHOW GLOBAL VARIABLES LIKE 'query\_cache\_limit'; +-------------------+-------+ | Variable_name | Value | +-------------------+-------+ | query_cache_limit | 0 | +-------------------+-------+ 1 row in set (0.00 sec) ----------------------------- 2. For boolean value, the empty value is rejected and set to "OFF" $ mysqld --performance-schema= 130109 0:27:31 [Warning] Buffered warning: option 'performance_schema': boolean value '' wasn't recognized. Set to OFF. ----------------------------- 3. For string value, the results are indeterminate. 3.1 $ mysqld --innodb_data_file_path= 130109 0:31:00 [ERROR] InnoDB: syntax error in innodb_data_file_path 130109 0:31:00 [ERROR] Plugin 'InnoDB' init function returned error. 130109 0:31:00 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed. 130109 0:31:00 [ERROR] Unknown/unsupported storage engine: InnoDB 130109 0:31:00 [ERROR] Aborting 3.2 $ mysqld --socket= 130109 0:33:17 InnoDB: The InnoDB memory heap is disabled 130109 0:33:17 InnoDB: Mutexes and rw_locks use GCC atomic builtins 130109 0:33:17 InnoDB: Compressed tables use zlib 1.2.3.4 130109 0:33:17 InnoDB: Initializing buffer pool, size = 8.0M 130109 0:33:17 InnoDB: Completed initialization of buffer pool 130109 0:33:17 InnoDB: highest supported file format is Barracuda. 130109 0:33:17 InnoDB: Waiting for the background threads to start 130109 0:33:18 InnoDB: 1.1.8 started; log sequence number 116061718 130109 0:33:18 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306 130109 0:33:18 [Note] - '127.0.0.1' resolves to '127.0.0.1'; 130109 0:33:18 [Note] Server socket created on IP: '127.0.0.1'. 130109 0:33:18 [Note] Event Scheduler: Loaded 1 event 130109 0:33:18 [Note] bin/mysqld: ready for connections. Version: '5.5.29-log' socket: '' port: 3306 Source distribution mysql --host=localhost --port=3306 ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2) ============================= Root Cause ============================= The root cause is such empty value is never checked in the configuration parser, and it goes through all the checking and finally get used. How to repeat: Described in the "Description" section. Suggested fix: I suggest to check it in the very beginning in setval() in my_getopt.c. See the patch attached. The behavior is to ignore the input and print out an error message, while keeping the option value unchanged. In this way, it has no side effect. The patch is tested. --- mysql-5.5.29/mysys/my_getopt.c 2012-08-29 01:50:46.000000000 -0700 +++ mysql-5.5.29/mysys/my_getopt.c 2013-01-09 00:57:10.020208478 -0800 @@ -642,6 +642,13 @@ if (!argument) argument= enabled_my_option; + + if(strlen(argument) == 0) { + my_getopt_error_reporter(ERROR_LEVEL, + "%s: Empty value of '%s' is specified. Keep the previous value unchanged", + my_progname, opts->name); + return 0; + } if (value) {