Server crashes in String::append on selecting sql_mode inside anonymous block

--delimiter |

BEGIN NOT ATOMIC SELECT @@sql_mode; END |

--delimiter ;

#3  <signal handler called>

#4  __strlen_sse2 () at ../sysdeps/x86_64/multiarch/../strlen.S:32

#5  0x00007fb006f20c02 in String::append (this=0x7fb0069a0ce0, s=0x0) at sql/sql_string.cc:479

#6  0x00007fb006f58123 in set_to_string (thd=0x7fafff7ec070, result=0x7fb0069a0cd0, set=2779096485, lib=0x7fb007f2e7e0) at sql/strfunc.cc:362

#7  0x00007fb006fcdc2a in Sys_var_set::session_value_ptr (this=0x7fb00810ab20, thd=0x7fafff7ec070, base=0x7faffc4e8158) at sql/sys_vars.h:1290

#8  0x00007fb006dd6a22 in sys_var::value_ptr (this=0x7fb00810ab20, thd=0x7fafff7ec070, type=OPT_DEFAULT, base=0x7faffc4e8158) at sql/set_var.cc:250

#9  0x00007fb0070ef4f5 in Item_func_get_system_var::fix_length_and_dec (this=0x7faffc4e8088) at sql/item_func.cc:5854

#10 0x00007fb0070dc6c4 in Item_func::fix_fields (this=0x7faffc4e8088, thd=0x7fafff7ec070, ref=0x7faffc4e81b8) at sql/item_func.cc:229

#11 0x00007fb006e23dda in setup_fields (thd=0x7fafff7ec070, ref_pointer_array=0x7faffc4e82b8, fields=..., mark_used_columns=MARK_COLUMNS_READ, sum_func_list=0x7faffc4eb4e0, allow_sum_func=true) at sql/sql_base.cc:7790

#12 0x00007fb006eb1494 in JOIN::prepare (this=0x7faffc4eb1a8, rref_pointer_array=0x7faffc45c660, tables_init=0x0, wild_num=0, conds_init=0x0, og_num=0, order_init=0x0, skip_order_by=false, group_init=0x0, having_init=0x0, proc_param_init=0x0, select_lex_arg=0x7faffc45c3e8, unit_arg=0x7faffc45bd00) at sql/sql_select.cc:785

#13 0x00007fb006eba747 in mysql_select (thd=0x7fafff7ec070, rref_pointer_array=0x7faffc45c660, tables=0x0, wild_num=0, fields=..., conds=0x0, og_num=0, order=0x0, group=0x0, having=0x0, proc_param=0x0, select_options=2147749632, result=0x7faffc4eb188, unit=0x7faffc45bd00, select_lex=0x7faffc45c3e8) at sql/sql_select.cc:3298

#14 0x00007fb006eb076e in handle_select (thd=0x7fafff7ec070, lex=0x7faffc45bc38, result=0x7faffc4eb188, setup_tables_done_option=0) at sql/sql_select.cc:372

#15 0x00007fb006e835b1 in execute_sqlcom_select (thd=0x7fafff7ec070, all_tables=0x0) at sql/sql_parse.cc:5313

#16 0x00007fb006e7b55b in mysql_execute_command (thd=0x7fafff7ec070) at sql/sql_parse.cc:2599

#17 0x00007fb0071c3f78 in sp_instr_stmt::exec_core (this=0x7faffc4e81e0, thd=0x7fafff7ec070, nextp=0x7fb0069a25c0) at sql/sp_head.cc:3193

#18 0x00007fb0071c36d1 in sp_lex_keeper::reset_lex_and_exec_core (this=0x7faffc4e8220, thd=0x7fafff7ec070, nextp=0x7fb0069a25c0, open_tables=false, instr=0x7faffc4e81e0) at sql/sp_head.cc:2963

#19 0x00007fb0071c3c8a in sp_instr_stmt::execute (this=0x7faffc4e81e0, thd=0x7fafff7ec070, nextp=0x7fb0069a25c0) at sql/sp_head.cc:3112

#20 0x00007fb0071bf764 in sp_head::execute (this=0x7faffc45b088, thd=0x7fafff7ec070, merge_da_on_success=true) at sql/sp_head.cc:1364

#21 0x00007fb0071c162a in sp_head::execute_procedure (this=0x7faffc45b088, thd=0x7fafff7ec070, args=0x7fafff7f0a28) at sql/sp_head.cc:2153

#22 0x00007fb006e7a992 in do_execute_sp (thd=0x7fafff7ec070, sp=0x7faffc45b088) at sql/sql_parse.cc:2213

#23 0x00007fb006e818ba in mysql_execute_command (thd=0x7fafff7ec070) at sql/sql_parse.cc:4740

#24 0x00007fb006e85ec6 in mysql_parse (thd=0x7fafff7ec070, rawbuf=0x7faffc456088 "BEGIN NOT ATOMIC SELECT @@sql_mode; END", length=39, parser_state=0x7fb0069a35e0) at sql/sql_parse.cc:6466

#25 0x00007fb006e7857b in dispatch_command (command=COM_QUERY, thd=0x7fafff7ec070, packet=0x7fb0003f9071 "BEGIN NOT ATOMIC SELECT @@sql_mode; END ", packet_length=40) at sql/sql_parse.cc:1310

#26 0x00007fb006e778c0 in do_command (thd=0x7fafff7ec070) at sql/sql_parse.cc:1007

#27 0x00007fb006fa083d in do_handle_one_connection (thd_arg=0x7fafff7ec070) at sql/sql_connect.cc:1379

#28 0x00007fb006fa0590 in handle_one_connection (arg=0x7fafff7ec070) at sql/sql_connect.cc:1293

#29 0x00007fb007504ba6 in pfs_spawn_thread (arg=0x7faffdaae970) at storage/perfschema/pfs.cc:1860

#30 0x00007fb00658fb50 in start_thread (arg=<optimized out>) at pthread_create.c:304

#31 0x00007fb00486720d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112

commit 6502f42f679e605fcdbd6c8b49d2813f553001b0

Author: Sergei Golubchik <serg@mariadb.org>

Date:   Mon Aug 18 14:28:48 2014 +0200