Bug #45168 assertion with convert() and empty set value

Description:
from today's 5.1 bzr:

Version: '5.1.36-debug'  socket: '/tmp/mysql.sock'  port: 3306  yes
[New Thread -1271387248 (LWP 15336)]
mysqld: sql_string.cc:332: bool String::copy(const char*, uint32, CHARSET_INFO*, CHARSET_INFO*, uint*): Assertion `str != Ptr' failed.

#0 in __kernel_vsyscall ()
#1 in raise 
#2 in abort 
#3 in __assert_fail 
#4 in String::copy  at sql_string.cc:332
#5 in Item_func_conv_charset::val_str  at item_strfunc.cc:2724
#6 in Item::send at item.cc:5508
#7 in select_send::send_data  at sql_class.cc:1587
#8 in end_send  at sql_select.cc:11986
#9 in do_select  at sql_select.cc:10864
#10 in JOIN::exec  at sql_select.cc:2199
#11 in mysql_select  at sql_select.cc:2386
#12 in handle_select 
#13 in execute_sqlcom_select 
#14 in mysql_execute_command 
#15 in mysql_parse 
#16 in dispatch_command 
#17 in do_command 
#18 in handle_one_connection 

How to repeat:
drop table if exists `t1`;
create table `t1`(`a` set('a'));
insert into `t1` values ('');
select convert(`a` using latin1) from `t1` ;

Thank you for the report.

Verified as described.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/76106

2931 Martin Hansson	2009-06-11
      Bug#45168: assertion with convert() and empty set value
      
      The assertion in String::copy was added in order to avoid
      valgrind errors when the destination was the same as the source.
      Eased restriction to allow for the case when length is 0.
     @ mysql-test/r/func_set.result
        Bug#45168: Test Result
     @ mysql-test/t/func_set.test
        Bug#45168: Test case.
     @ sql/sql_string.cc
        Bug#45168: Fix and clarified comment.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/76399

2931 Martin Hansson	2009-06-16
      Bug#45168: assertion with convert() and empty set value
            
      The assertion in String::copy was added in order to avoid
      valgrind errors when the destination was the same as the source.
      Eased restriction to allow for the case when str == NULL.
     @ mysql-test/r/func_set.result
        Bug#45168: Test result
     @ mysql-test/t/func_set.test
        Bug#45168: Test case
     @ sql/item_strfunc.cc
        Bug#45168: Code cleanup and grammar correction in comment
     @ sql/sql_string.cc
        Bug#45168: Fix

Both reviewers are done.

Pushed into 5.1.37 (revid:joro@sun.com-20090708131116-kyz8iotbum8w9yic) (version source revid:mhansson@mysql.com-20090618072546-8ksflicrhzi8yuyw) (merge vers: 5.1.36) (pib:11)

Pushed into 5.1.37 (revid:joro@sun.com-20090708131116-kyz8iotbum8w9yic) (version source revid:mhansson@mysql.com-20090618072546-8ksflicrhzi8yuyw) (merge vers: 5.1.36) (pib:11)

Pushed into 5.4.4-alpha (revid:anozdrin@bk-internal.mysql.com-20090710111017-bnh2cau84ug1hvei) (version source revid:mhansson@mysql.com-20090618064925-hf8g6oscvrdjk3qs) (merge vers: 5.4.4-alpha) (pib:11)

Noted in 5.1.37, 5.4.4 changelogs.

Use of CONVERT() with an empty SET value could cause an assertion
failure.

Noted in 5.4.2 changelog because next 5.4 version will be 5.4.2 and not 5.4.4.

Ignore previous comment about 5.4.2.

Pushed into 5.1.37-ndb-7.0.8 (revid:jonas@mysql.com-20090826132541-yablppc59e3yb54l) (version source revid:jonas@mysql.com-20090826132541-yablppc59e3yb54l) (merge vers: 5.1.37-ndb-7.0.8) (pib:11)

Pushed into 5.1.37-ndb-6.3.27 (revid:jonas@mysql.com-20090826105955-bkj027t47gfbamnc) (version source revid:jonas@mysql.com-20090826105955-bkj027t47gfbamnc) (merge vers: 5.1.37-ndb-6.3.27) (pib:11)

Pushed into 5.1.37-ndb-6.2.19 (revid:jonas@mysql.com-20090825194404-37rtosk049t9koc4) (version source revid:jonas@mysql.com-20090825194404-37rtosk049t9koc4) (merge vers: 5.1.37-ndb-6.2.19) (pib:11)

Pushed into 5.1.35-ndb-7.1.0 (revid:magnus.blaudd@sun.com-20090827163030-6o3kk6r2oua159hr) (version source revid:jonas@mysql.com-20090826132541-yablppc59e3yb54l) (merge vers: 5.1.37-ndb-7.0.8) (pib:11)

The 5.4 fix has been pushed to 5.4.2.