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  1. MariaDB Server
  2. MDEV-5674

Valgrind warnings "Conditional jump or move depends on uninitialised value" in create_sort_index with small sort_buffer_size




      The failure happens in buildbot on main.order_by and main.filesort_debug tests.

      The warning started appearing with the following revision:

          revno: 3965.1.14
          revision-id: sergii@pisem.net-20140201083407-l6hg86u20byph3i7
          parent: sergii@pisem.net-20140201083326-wlzdm7dash8h58m8
          fixes bug: https://mariadb.atlassian.net/browse/MDEV-5549
          committer: Sergei Golubchik <sergii@pisem.net>
          branch nick: 10.0
          timestamp: Sat 2014-02-01 09:34:07 +0100
            MDEV-5549 Wrong row counter in found_rows() result
            only let filesort() count rows for SQL_CALC_ROWS if it's using priority queue

      Here is an excerpt from main.order_by which causes the failure (maybe it will be easier to debug, the whole test is rather big):

      create table t1(a int, b tinytext);
      insert into t1 values (1,2),(3,2);
      set session sort_buffer_size= 1000;
      select * from t1 order by b;

      ERROR HY001: Out of sort memory, consider increasing server sort buffer size

      ==23750== Thread 4:
      ==23750== Conditional jump or move depends on uninitialised value(s)
      ==23750==    at 0x6D2E5F: create_sort_index(THD*, JOIN*, st_order*, unsigned long long, unsigned long long, bool) (sql_select.cc:20393)
      ==23750==    by 0x6A8579: JOIN::exec_inner() (sql_select.cc:3035)
      ==23750==    by 0x6A5C8F: JOIN::exec() (sql_select.cc:2355)
      ==23750==    by 0x6A900E: 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:3292)
      ==23750==    by 0x69F76A: handle_select(THD*, LEX*, select_result*, unsigned long) (sql_select.cc:372)
      ==23750==    by 0x6747F0: execute_sqlcom_select(THD*, TABLE_LIST*) (sql_parse.cc:5301)
      ==23750==    by 0x66CB9B: mysql_execute_command(THD*) (sql_parse.cc:2587)
      ==23750==    by 0x676F7A: mysql_parse(THD*, char*, unsigned int, Parser_state*) (sql_parse.cc:6447)
      ==23750==    by 0x669D48: dispatch_command(enum_server_command, THD*, char*, unsigned int) (sql_parse.cc:1308)
      ==23750==    by 0x6690EA: do_command(THD*) (sql_parse.cc:1005)
      ==23750==    by 0x783394: do_handle_one_connection(THD*) (sql_connect.cc:1379)
      ==23750==    by 0x7830E7: handle_one_connection (sql_connect.cc:1293)
      ==23750==    by 0xAAB6E0: pfs_spawn_thread (pfs.cc:1853)
      ==23750==    by 0x4E35B4F: start_thread (pthread_create.c:304)
      ==23750==    by 0x6320A7C: clone (clone.S:112)

      Stack trace from:

      revision-id: svoj@mariadb.org-20140213071355-psk0jpsarx2u7myc
      revno: 4005
      branch-nick: 10.0




            serg Sergei Golubchik
            elenst Elena Stepanova
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