Comment 1 for bug 534361

Another reason to eliminate these valgrind errors is that it would make it easier to distinguish the ones that are actual bugs. For example, this one, from testcase pbxt.multi_update, looks like a real problem:

==19278== Invalid write of size 1
==19278== at 0x4C270D8: memset (mc_replace_strmem.c:586)
==19278== by 0xA50298: XTDatabaseLog::xlog_append(XTThread*, unsigned long, unsigned char*, unsigned long, unsigned char*, int, unsigned int*, long*) (xactlog_xt.cc:1112)
==19278== by 0xA519A9: xt_xlog_modify_table(unsigned int, unsigned int, unsigned int, unsigned int, unsigned int, unsigned long, unsigned char*, XTThread*) (xactlog_xt.cc:1657)
==19278== by 0xA3778A: tab_add_record(XTOpenTable*, XTTabRecInfo*, unsigned int) (table_xt.cc:4017)
==19278== by 0xA38214: xt_tab_new_record(XTOpenTable*, unsigned char*) (table_xt.cc:4380)
==19278== by 0xA0489A: ha_pbxt::write_row(unsigned char*) (ha_pbxt.cc:2645)
==19278== by 0x7D7B29: handler::ha_write_row(unsigned char*) (handler.cc:4647)
==19278== by 0x72ECDC: write_record(THD*, st_table*, st_copy_info*) (sql_insert.cc:1632)
==19278== by 0x733425: select_insert::send_data(List<Item>&) (sql_insert.cc:3212)
==19278== by 0x71AAC2: end_send(JOIN*, st_join_table*, bool) (sql_select.cc:12455)
==19278== by 0x71897D: evaluate_join_record(JOIN*, st_join_table*, int) (sql_select.cc:11638)
==19278== by 0x718616: sub_select(JOIN*, st_join_table*, bool) (sql_select.cc:11518)
==19278== by 0x71812A: do_select(JOIN*, List<Item>*, st_table*, Procedure*) (sql_select.cc:11268)
==19278== by 0x7013BE: JOIN::exec() (sql_select.cc:2292)
==19278== by 0x701B0F: mysql_select(THD*, Item***, TABLE_LIST*, unsigned int, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) (sql_select.cc:2486)
==19278== by 0x6F9E07: handle_select(THD*, st_lex*, select_result*, unsigned long) (sql_select.cc:279)
==19278== Address 0xf1c13f0 is 0 bytes after a block of size 1,049,088 alloc'd
==19278== at 0x4C25153: malloc (vg_replace_malloc.c:195)
==19278== by 0xA159D3: xt_malloc(XTThread*, unsigned long) (memory_xt.cc:101)
==19278== by 0xA4F2FB: XTDatabaseLog::xlog_setup(XTThread*, XTDatabase*, long, unsigned long, int) (xactlog_xt.cc:632)
==19278== by 0xA4A5D9: xt_xn_init_db(XTThread*, XTDatabase*) (xaction_xt.cc:1107)
==19278== by 0xA5BF89: xt_get_database(XTThread*, char*, int) (database_xt.cc:471)
==19278== by 0xA5C806: xt_open_database(XTThread*, char*, int) (database_xt.cc:639)
==19278== by 0xA0044D: xt_ha_open_database_of_table(XTThread*, XTPathStr*) (ha_pbxt.cc:512)
==19278== by 0xA09781: ha_pbxt::create(char const*, st_table*, st_ha_create_information*) (ha_pbxt.cc:5438)
==19278== by 0x7D4DB9: handler::ha_create(char const*, st_table*, st_ha_create_information*) (handler.cc:3397)
==19278== by 0x7D554D: ha_create_table(THD*, char const*, char const*, char const*, st_ha_create_information*, bool) (handler.cc:3604)
==19278== by 0x77BA6C: rea_create_table(THD*, char const*, char const*, char const*, st_ha_create_information*, List<Create_field>&, unsigned int, st_key*, handler*) (unireg.cc:414)
==19278== by 0x7F9972: mysql_create_table_no_lock(THD*, char const*, char const*, st_ha_create_information*, Alter_info*, bool, unsigned int) (sql_table.cc:3958)
==19278== by 0x7F9DD1: mysql_create_table(THD*, char const*, char const*, st_ha_create_information*, Alter_info*, bool, unsigned int) (sql_table.cc:4055)
==19278== by 0x68F38A: mysql_execute_command(THD*) (sql_parse.cc:2791)
==19278== by 0x6994CF: mysql_parse(THD*, char const*, unsigned int, char const**) (sql_parse.cc:6034)
==19278== by 0x68B804: dispatch_command(enum_server_command, THD*, char*, unsigned int) (sql_parse.cc:1247)