MySQL Bugs: #43233: Some server variables are clipped during "update," not "check" stage

Bug #43233	Some server variables are clipped during "update," not "check" stage
Submitted:	26 Feb 16:48	Modified:	26 Feb 17:05
Reporter:	Tatjana A. Nuernberg
Status:	Verified
Category:	Server: General	Severity:	S3 (Non-critical)
Version:	any	OS:	Any
Assigned to:		Target Version:
Triage:	Triaged: D4 (Minor)

Description:
The right way to do things: Check variable during check-stage (duh :-). If user-supplied
value is out of range, throw a warning, unless in strict mode, in which case we throw an
error and never proceed to the update stage. Most system variables are handled this way.
Hooray.

There are some (very few) exceptions; system-variables that bound their values during the
update phase. This arguably violates the model; it also means we can throw only warnings
(see Bug#40657) and not promote them to errors in strict mode without triggering an
assert -- we're simply supposed to already be sure by this time that the value is good.

How to repeat:
set @@global.key_cache_block_size=-1;

(should throw warning, but probably doesn't, depending on patchlevel of your version. 
Either way, now try

set sql_mode=strict_all_tables;
set @@global.key_cache_block_size=-1;

Depending on your patchlevel, this will either crash the server, or throw a warning
instead of an error.

Suggested fix:
Move said test/clipping from update() to check() functions. Create those check()
functions as needed.

Look at

sys_var_ulonglong_ptr: unused?

sys_var_thd_ha_rows: "max_join_size" et al.

sys_var_key_buffer_size: "key_buffer_size"

sys_var_key_cache_long: "key_cache_block_size" et al.

Thank you for the bug report. Verified just as described:

valeriy-kravchuks-macbook-pro:6.0 openxs$ bin/mysql -uroot test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 6.0.11-alpha-debug Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> set @@global.key_cache_block_size=-1;
Query OK, 0 rows affected, 1 warning (0.38 sec)

mysql> show warnings\G
*************************** 1. row ***************************
  Level: Warning
   Code: 1292
Message: Truncated incorrect key_cache_block_size value: '4294967295'
1 row in set (0.00 sec)

mysql> set sql_mode=strict_all_tables;
Query OK, 0 rows affected (0.00 sec)

mysql> set @@global.key_cache_block_size=-1;
ERROR 2013 (HY000): Lost connection to MySQL server during query
mysql> 090226 17:58:38 mysqld_safe mysqld restarted

mysql> exit
Bye
valeriy-kravchuks-macbook-pro:6.0 openxs$ tail -50
var/valeriy-kravchuks-macbook-pro.local.err 
090224 07:22:27 mysqld_safe mysqld from pid file
/Users/openxs/dbs/6.0/var/valeriy-kravchuks-macbook-pro.local.pid ended
090226 17:57:34 mysqld_safe Starting mysqld daemon with databases from
/Users/openxs/dbs/6.0/var
090226 17:57:34 [Warning] Setting lower_case_table_names=2 because file system for
/Users/openxs/dbs/6.0/var/ is case insensitive
090226 17:57:34 [Warning] One can only use the --user switch if running as root

090226 17:57:35  InnoDB: Started; log sequence number 0 54748
090226 17:57:35 [Note] Event Scheduler: Loaded 0 events
090226 17:57:35 [Note] /Users/openxs/dbs/6.0/libexec/mysqld: ready for connections.
Version: '6.0.11-alpha-debug'  socket: '/tmp/mysql.sock'  port: 3306  Source
distribution
Assertion failed: (! is_set()), function set_ok_status, file sql_error.cc, line 86.
090226 17:58:38 - mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help diagnose
the problem, but since we have already crashed, something is definitely wrong
and this may fail.

key_buffer_size=8384512
read_buffer_size=131072
max_used_connections=1
max_threads=151
thread_count=1
connection_count=1
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 337802 K
bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

thd: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0x0 thread_stack 0x30c00
0   mysqld                              0x0078efd0 my_print_stacktrace + 44
1   mysqld                              0x000f83c2 handle_segfault + 894
2   libSystem.B.dylib                   0x940472bb _sigtramp + 43
3   ???                                 0xffffffff 0x0 + 4294967295
4   mysqld                              0x001029e5 main + 1391
5   mysqld                              0x0000247a start + 54
The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.
090226 17:58:38 mysqld_safe mysqld restarted
090226 17:58:38 [Warning] Setting lower_case_table_names=2 because file system for
/Users/openxs/dbs/6.0/var/ is case insensitive
090226 17:58:38 [Warning] One can only use the --user switch if running as root

090226 17:58:39  InnoDB: Started; log sequence number 0 54748
090226 17:58:39 [Note] Event Scheduler: Loaded 0 events
090226 17:58:39 [Note] /Users/openxs/dbs/6.0/libexec/mysqld: ready for connections.
Version: '6.0.11-alpha-debug'  socket: '/tmp/mysql.sock'  port: 3306  Source distribution