4.1.21:
----------

[sbester@fc4 sqlthreads]$ ./sqlthreads 30 60 1 0 "drop table if exists t1;create table t1 (i int);lock tables t1 read;show open tables;unlock tables;" 127.0.0.1 3306 test root
Testing DB connection before spawning threads....
Connecting....
Connected....
Thread Safe is ON
Spawning 30 new threads
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 
Database connections are setup! Check above for errors.
Completed spawning new threads from the application!
Now running for 60 seconds (until 1153581873)
mysql_next_result returned 1, mysql error Lost connection to MySQL server during query, (2013)
Query failed (2013) - Lost connection to MySQL server during query: drop table if exists t1;create table t1 (i int);lock tables t1 read;show open tables;unlock tables;




/home/sbester/servers/4.1-bk/bin/mysqld: ready for connections.
Version: '4.1.21-debug'  socket: '/tmp/my.sock'  port: 3306  yes
mysqld: sql_base.cc:144: OPEN_TABLE_LIST* list_open_tables(THD*, const char*): Assertion `entry->real_name' failed.
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=8388572
read_buffer_size=131072
max_used_connections=30
max_connections=100
threads_connected=30
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_connections = 225788 K
bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

thd=0x8d2b668
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...
Cannot determine thread, fp=0x6253bc, backtrace may not be correct.
Stack range sanity check OK, backtrace follows:
0x80bdaed handle_segfault + 461
0x4da420 data.7108 + 5088244
0x8d67d74 __stop___libc_freeres_ptrs + 7786792
0x8380d8b __assert_fail + 167
0x80ece5c _Z16list_open_tablesP3THDPKc + 232
0x81732ae _Z23mysqld_show_open_tablesP3THDPKc + 798
0x80d4abc _Z21mysql_execute_commandP3THD + 12274
0x80d6ad1 _Z11mysql_parseP3THDPcj + 289
0x80d7419 _Z16dispatch_command19enum_server_commandP3THDPcj + 2181
0x80d8552 _Z10do_commandP3THD + 530
0x80d9033 handle_one_connection + 2617
0x8374252 start_thread + 98
0x83a4fbe __clone + 110

New value of fp=(nil) failed sanity check, terminating stack trace!
Please read http://dev.mysql.com/doc/mysql/en/Using_stack_trace.html and follow instructions on how to resolve the stack trace. Resolved
stack trace is much more helpful in diagnosing the problem, so please do 
resolve it
Trying to get some variables.
Some pointers may be invalid and cause the dump to abort...
thd->query at 0x8d2cacc = show open tables;unlock tables
thd->thread_id=27
The manual page at http://www.mysql.com/doc/en/Crashing.html contains
information that should help you find out what is causing the crash.