Bug #59060 Valgrind warning in Protocol_text::store()

Description:
==31898== Conditional jump or move depends on uninitialised value(s)
==31898==    at 0x4C21D66: strnlen (mc_replace_strmem.c:259)
==31898==    by 0xBC3B7E: process_str_arg (my_vsnprintf.c:195)
==31898==    by 0xBC587C: my_vsnprintf_ex (my_vsnprintf.c:605)
==31898==    by 0xBC5CBC: my_vsnprintf (my_vsnprintf.c:668)
==31898==    by 0xB8BCDE: DbugVfprintf (dbug.c:1350)
==31898==    by 0xB8BC81: _db_doprnt_ (dbug.c:1335)
==31898==    by 0x55F8E6: Protocol_text::store(char const*, unsigned long, charset_info_st*) (protocol.cc:986)
==31898==    by 0x74F688: Item::send(Protocol*, String*) (item.cc:5932)
==31898==    by 0x55DAD0: Protocol::send_result_set_row(List<Item>*) (protocol.cc:848)
==31898==    by 0x5AA672: select_send::send_data(List<Item>&) (sql_class.cc:1866)
==31898==    by 0x634C37: JOIN::exec() (sql_select.cc:2794)
==31898== by 0x63113A: 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:3554)
==31898==    by 0x637370: handle_select(THD*, LEX*, select_result*, unsigned long) (sql_select.cc:323)
==31898==    by 0x5D7835: execute_sqlcom_select(THD*, TABLE_LIST*) (sql_parse.cc:4513)
==31898==    by 0x5D879E: mysql_execute_command(THD*) (sql_parse.cc:2096)
==31898==    by 0x5DF6F8: mysql_parse(THD*, char*, unsigned int, Parser_state*) (sql_parse.cc:5550)

How to repeat:
The warning appears for the following tests:
  - rpl.rpl_corruption
  - rpl.rpl_get_master_version_and_clock

Check out PB for trunk-bugfixing (or trunk-stage).

See also Bug#52304.

Patch for BUG#49978, BUG#59037 has nothing to do with the warning.
The tests were modified, so this issue started to pop up.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/127408

3462 Alexander Nozdrin	2010-12-21
      A patch for Bug#59060 (Valgrind warning in Protocol_text::store()).
      
      We should not assume to have zero-terminated strings.

Pushed to trunk-bugfixing.

Pushed into mysql-trunk 5.6.1 (revid:alexander.nozdrin@oracle.com-20101222212842-y0t3ibtd32wd9qaw) (version source revid:alexander.nozdrin@oracle.com-20101222212842-y0t3ibtd32wd9qaw) (merge vers: 5.6.1) (pib:24)

Bug does not appear in any released version. No changelog entry needed.