#5 0x08210bff in Bitmap<64u>::merge (this=0xe0, map2=...)
at sql_bitmap.h:161
#6 0x0835c044 in add_key_field (join=0x948f680, key_fields=0xae8fd8cc,
and_level=0, cond=0x94903d0, field=0x9492708, eq_func=true,
value=0xae8fd7bc, num_values=1, usable_tables=18446744073709551615,
sargables=0xae8fda90) at sql_select.cc:3956
#7 0x0835d108 in add_key_fields (join=0x948f680, key_fields=0xae8fd8cc,
and_level=0xae8fd8d0, cond=0x94903d0,
usable_tables=18446744073709551615, sargables=0xae8fda90)
at sql_select.cc:4365
#8 0x0835dd0e in update_ref_and_keys (thd=0x93f0728, keyuse=0x948f860,
join_tab=0x9490540, tables=2, cond=0x94903d0,
normal_tables=18446744073709551615, select_lex=0x9471764,
sargables=0xae8fda90) at sql_select.cc:4717
#9 0x0835a085 in make_join_statistics (join=0x948f680, tables_list=...,
conds=0x94903d0, keyuse_array=0x948f860) at sql_select.cc:3250
#10 0x083532c5 in JOIN::optimize (this=0x948f680) at sql_select.cc:1150
#11 0x08359140 in mysql_select (thd=0x93f0728, rref_pointer_array=0x94718a0,
tables=0x9472f48, wild_num=0, fields=..., conds=0x0, og_num=0,
order=0x0, group=0x0, having=0x0, proc_param=0x0,
select_options=3489942016, result=0x948f608, unit=0x9471484,
select_lex=0x9471764) at sql_select.cc:2938
#12 0x08350e43 in handle_select (thd=0x93f0728, lex=0x9471428,
result=0x948f608, setup_tables_done_option=1073741824)
at sql_select.cc:285
#13 0x082e6053 in mysql_execute_command (thd=0x93f0728) at sql_parse.cc:3304
#14 0x083a5da6 in Prepared_statement::execute (this=0x9471118,
expanded_query=0xae8fe71c, open_cursor=false) at sql_prepare.cc:3732
#15 0x083a52bb in Prepared_statement::execute_loop (this=0x9471118,
expanded_query=0xae8fe71c, open_cursor=false, packet=0x0, packet_end=0x0)
at sql_prepare.cc:3413
#16 0x083a3b83 in mysql_sql_stmt_execute (thd=0x93f0728)
at sql_prepare.cc:2638
#17 0x082e329b in mysql_execute_command (thd=0x93f0728) at sql_parse.cc:2293
#18 0x082ee4d4 in mysql_parse (thd=0x93f0728,
rawbuf=0x948f4c8 "EXECUTE stmt", length=12, found_semicolon=0xae8ff234)
at sql_parse.cc:6152
#19 0x082e0eb5 in dispatch_command (command=COM_QUERY, thd=0x93f0728,
packet=0x94478e9 "EXECUTE stmt", packet_length=12) at sql_parse.cc:1228
#20 0x082e035f in do_command (thd=0x93f0728) at sql_parse.cc:923
#21 0x082dd2e5 in handle_one_connection (arg=0x93f0728)
at sql_connect.cc:1193
#22 0xb782bb25 in start_thread () from /lib/libpthread.so.0

bzr version-info
revision-id: <email address hidden>
date: 2012-03-29 21:58:40 +0200
build-date: 2012-03-30 03:22:23 +0400
revno: 3482

Notes:
Also crashes on MariaDB 5.5 revno 3353.
No crash on MariaDB 5.2, MySQL trunk.
No crash when t1 has more than 1 row.
No crash if t1 is an InnoDB table.
No crash if FROM subquery is replaced with a view (either MERGE or TEMPTABLE).
No crash if executed as SELECT, without INSERT.
No if executed outside the prepared statement.

Minimal optimizer_switch: derived_merge=on
Full optimizer_switch (default): on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on,extended_keys=off

EXPLAIN for the SELECT part with minimal optimizer_switch (derived_merge=on, everything else OFF):

id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system a NULL NULL NULL 1 100.00
1 SIMPLE alias2 ref a a 5 const 1 100.00Using index
Warnings:
Note 1003 select 1 AS `a` from `test`.`t1` join `test`.`t2` `alias2` where (`test`.`alias2`.`a` = 1)

Test case:

SET optimizer_switch = 'derived_merge=on';

CREATE TABLE t1 ( a INT, INDEX(a) ) ENGINE=MyISAM;
INSERT INTO t1 VALUES (1);
CREATE TABLE t2 ( a INT, INDEX(a) );
INSERT INTO t2 VALUES (1),(2);

EXPLAIN EXTENDED
SELECT a FROM
( SELECT a FROM test.t1 ) AS alias1
NATURAL JOIN t2 AS alias2;

PREPARE stmt FROM "
INSERT INTO t1
SELECT a FROM
( SELECT a FROM test.t1 ) AS alias1
NATURAL JOIN t2 AS alias2
";

EXECUTE stmt;

1. End of test case