Memory leak in rec_copy_prefix_to_buf / btr_blob_log_check_t::check

--source include/have_innodb.inc

--source include/have_sequence.inc

CREATE TABLE t (f longtext, KEY(f(1024))) ENGINE=InnoDB;

INSERT INTO t SELECT REPEAT('a',100000) FROM seq_1_to_500;

--connect (con1,localhost,root,,test)

--send

  ALTER TABLE t FORCE;

--connection default

UPDATE t SET f = NULL LIMIT 1;

UPDATE t SET f = REPEAT('b',1000000) LIMIT 1;

--connection con1

--reap

DROP TABLE t;

--disconnect con1

==2740416==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 12 byte(s) in 1 object(s) allocated from:

    #0 0x7fcf72597e8f in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145

    #1 0x555e07787ea8 in rec_copy_prefix_to_buf(unsigned char const*, dict_index_t const*, unsigned long, unsigned char**, unsigned long*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/rem/rem0rec.cc:2002

    #2 0x555e07a9bf07 in btr_pcur_store_position(btr_pcur_t*, mtr_t*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/btr/btr0pcur.cc:200

    #3 0x555e07a90c78 in btr_blob_log_check_t::check() /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/btr/btr0cur.cc:7171

    #4 0x555e07a899ae in btr_store_big_rec_extern_fields(btr_pcur_t*, unsigned short*, big_rec_t const*, mtr_t*, blob_op) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/btr/btr0cur.cc:7372

    #5 0x555e07861d80 in row_log_table_apply_update /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/row/row0log.cc:2328

    #6 0x555e078647c7 in row_log_table_apply_op /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/row/row0log.cc:2671

    #7 0x555e07868c05 in row_log_table_apply_ops /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/row/row0log.cc:3041

    #8 0x555e07869a79 in row_log_table_apply(que_thr_t*, dict_table_t*, TABLE*, ut_stage_alter_t*, dict_table_t*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/row/row0log.cc:3150

    #9 0x555e075a9758 in ha_innobase::inplace_alter_table(TABLE*, Alter_inplace_info*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/innobase/handler/handler0alter.cc:7223

    #10 0x555e06a94373 in handler::ha_inplace_alter_table(TABLE*, Alter_inplace_info*) (/mnt8t/bld/10.3-nightly/bin/mysqld+0x12a7373)

    #11 0x555e06a77116 in mysql_inplace_alter_table /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_table.cc:7774

    #12 0x555e06a88631 in mysql_alter_table(THD*, st_mysql_const_lex_string const*, st_mysql_const_lex_string const*, HA_CREATE_INFO*, TABLE_LIST*, Alter_info*, unsigned int, st_order*, bool) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_table.cc:10159

    #13 0x555e06bf1905 in Sql_cmd_alter_table::execute(THD*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_alter.cc:512

    #14 0x555e0683d843 in mysql_execute_command(THD*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_parse.cc:6076

    #15 0x555e06849675 in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_parse.cc:7855

    #16 0x555e06820cc3 in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_parse.cc:1852

    #17 0x555e0681d87b in do_command(THD*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_parse.cc:1398

    #18 0x555e06be11ef in do_handle_one_connection(CONNECT*) /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_connect.cc:1403

    #19 0x555e06be0aeb in handle_one_connection /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/sql/sql_connect.cc:1308

    #20 0x555e0818e244 in pfs_spawn_thread /home/jenkins/workspace/sandbox-elenst/Nightly-Build-CS/src/storage/perfschema/pfs.cc:1869

    #21 0x7fcf71c91ea6 in start_thread nptl/pthread_create.c:477

SUMMARY: AddressSanitizer: 12 byte(s) leaked in 1 allocation(s).