SIGSEGV in Opt_trace_context::is_started & SIGSEGV in Json_writer::add_table_name (on optimized builds)

# Keep testcase repeating until mysqld crashes (one time often if not always enough on debug, optimized may take 2-x attempts)

USE test;

SET SQL_MODE='';

SET SESSION enforce_storage_engine=MEMORY;

SET SESSION optimizer_trace='enabled=on';

CREATE TABLE t1( a INT, b INT, KEY( a ) ) ;

SELECT MAX(a), SUM(MAX(a)) OVER () FROM t1 WHERE a > 10;

SELECT * FROM information_schema.session_variables WHERE variable_name='innodb_ft_min_token_size';

UPDATE t1 SET b=REPEAT(LEFT(b,1),200) WHERE a=1;

Core was generated by `/test/MD150620-mariadb-10.5.4-linux-x86_64-dbg/bin/mysqld --no-defaults --core-'.

Program terminated with signal SIGSEGV, Segmentation fault.

#0  __pthread_kill (threadid=<optimized out>, signo=signo@entry=11)

    at ../sysdeps/unix/sysv/linux/pthread_kill.c:57

[Current thread is 1 (Thread 0x14e11810c700 (LWP 1655068))]

(gdb) bt

#0  __pthread_kill (threadid=<optimized out>, signo=signo@entry=11) at ../sysdeps/unix/sysv/linux/pthread_kill.c:57

#1  0x000055565b1b74c6 in my_write_core (sig=sig@entry=11) at /test/10.5_dbg/mysys/stacktrace.c:518

#2  0x000055565a959d60 in handle_fatal_signal (sig=11) at /test/10.5_dbg/sql/signal_handler.cc:330

#3  <signal handler called>

#4  Opt_trace_context::is_started (this=<error reading variable: Cannot access memory at address 0x8f8f8f8f8f8f910f>) at /test/10.5_dbg/sql/opt_trace_context.h:108

#5  THD::trace_started (this=<error reading variable: Cannot access memory at address 0x8f8f8f8f8f8f910f>) at /test/10.5_dbg/sql/sql_class.h:3407

#6  Json_writer::add_table_name (this=0x14e0ff471600, tab=tab@entry=0x14e0ff478710) at /test/10.5_dbg/sql/opt_trace.cc:561

#7  0x000055565aaf562f in Json_value_helper::add_table_name (tab=0x14e0ff478710, this=0x14e118108438) at /test/10.5_dbg/sql/my_json_writer.h:300

#8  Json_writer_object::add_table_name (tab=0x14e0ff478710, this=0x14e118108430) at /test/10.5_dbg/sql/my_json_writer.h:474

#9  SQL_SELECT::test_quick_select (this=this@entry=0x14e0ff4754f0, thd=thd@entry=0x14e0ff415088, keys_to_use={static BITS_PER_ELEMENT = 64, static ARRAY_ELEMENTS = 1, static ALL_BITS_SET = 18446744073709551615, buffer = {18446744073709551615}}, prev_tables=prev_tables@entry=0, limit=limit@entry=18446744073709551615, force_quick_range=force_quick_range@entry=false, ordered_output=false, remove_false_parts_of_where=false, only_single_index_range_scan=false) at /test/10.5_dbg/sql/opt_range.cc:2695

#10 0x000055565a7a59ad in SQL_SELECT::check_quick (limit=18446744073709551615, force_quick_range=<optimized out>, thd=0x14e0ff415088, this=0x14e0ff4754f0) at /test/10.5_dbg/sql/opt_range.h:1655

#11 mysql_update (thd=thd@entry=0x14e0ff415088, table_list=<optimized out>, fields=@0x14e0ff4199f0: {<base_list> = {<Sql_alloc> = {<No data fields>}, first = 0x14e0ff474e30, last = 0x14e0ff474e30, elements = 1}, <No data fields>}, values=@0x14e0ff419f68: {<base_list> = {<Sql_alloc> = {<No data fields>}, first = 0x14e0ff474e40, last = 0x14e0ff474e40, elements = 1}, <No data fields>}, conds=<optimized out>, order_num=<optimized out>, order=0x0, limit=18446744073709551615, ignore=false, found_return=0x14e11810aca0, updated_return=0x14e11810ad70) at /test/10.5_dbg/sql/sql_update.cc:555

#12 0x000055565a6b062c in mysql_execute_command (thd=thd@entry=0x14e0ff415088) at /test/10.5_dbg/sql/sql_parse.cc:4401

#13 0x000055565a6bc15c in mysql_parse (thd=thd@entry=0x14e0ff415088, rawbuf=<optimized out>, length=<optimized out>, parser_state=parser_state@entry=0x14e11810b350, is_com_multi=is_com_multi@entry=false, is_next_command=is_next_command@entry=false) at /test/10.5_dbg/sql/sql_parse.cc:7993

#14 0x000055565a6a8c60 in dispatch_command (command=command@entry=COM_QUERY, thd=thd@entry=0x14e0ff415088, packet=packet@entry=0x14e0ff467089 "UPDATE t1 SET b=REPEAT(LEFT(b,1),200) WHERE a=1", packet_length=packet_length@entry=47, is_com_multi=is_com_multi@entry=false, is_next_command=is_next_command@entry=false) at /test/10.5_dbg/sql/sql_parse.cc:1874

#15 0x000055565a6a743a in do_command (thd=0x14e0ff415088) at /test/10.5_dbg/sql/sql_parse.cc:1355

#16 0x000055565a802c47 in do_handle_one_connection (connect=<optimized out>, connect@entry=0x14e10197a108, put_in_cache=put_in_cache@entry=true) at /test/10.5_dbg/sql/sql_connect.cc:1411

#17 0x000055565a803363 in handle_one_connection (arg=arg@entry=0x14e10197a108) at /test/10.5_dbg/sql/sql_connect.cc:1313

#18 0x000055565ac64902 in pfs_spawn_thread (arg=0x14e11f046c88) at /test/10.5_dbg/storage/perfschema/pfs.cc:2201

#19 0x000014e1211486db in start_thread (arg=0x14e11810c700) at pthread_create.c:463

#20 0x000014e12054688f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95