bzr push into mysql-trunk branch (chaithra.gopalareddy:3916 to 3917)

[Chaithra Gopalareddy]

 3917 Chaithra Gopalareddy	2012-02-17 [merge]
      Null merge from 5.5 to 5.6

 3916 Rohit Kalhans	2012-02-17
      BUG#11766817: CRASH ON MYSQLD STARTUP WHEN USING LOG-BIN (STRMAKE ISSUE?)
      BUG#12929941: SEGFAULT IN STRMAKE/CONVERT_DIRNAME WHEN USING --RELAY-LOG=SLAVE-RELAY-BIN
            
      Problem Description: 
            The global variable 'char *mysql_real_data_home_ptr'
            is declared and initialized to the address of the
            global buffer char mysql_real_data_home[] in mysqld.cc.
            Then, the constructor for Sys_datadir overwrites
            mysql_real_data_home_ptr with NULL. In the case when value
            datadir is not given in both command-line as well as in
            cnf file and the default path (<basedir>/data) needs to be
            used, the mysql_real_data_home_ptr is not made to point to
            mysql_real_data_home and still has NULL value. 
            After WL#5465, we use mysql_real_data_home_ptr when it still
            holds NULL as no cli or cnf file arguments were given. In
            particular, rpl_make_log_name passes mysql_real_data_home_ptr
            to fn_format. This caused a coredump because fn_format did not
            expect NULL.
            The following combinations caused the core dump
            1.unspecified but existing empty default data dir and
              --log-bin 
            2.unspecified but existing empty default data dir and
              --relay-log=<some name for relay log>
            
                   
      Solution: 
            We solve this problem by making mysql_real_data_home_ptr to
            point to the mysql_real_data_home if it is null before passing
            it to fn_format function because by this time we know that
            mysql_real_data_home is correctly initialized and holds the 
            final value of datadir path. We have also added asserts in
            fn_format() to check if the dir is null.
     @ mysql-test/suite/binlog/t/binlog_server_start_options.test
        added file to check startup error when
        no value of datadir has been given.
     @ mysys/mf_format.c
        Assert that the dir passed to this function
        is not null.
     @ sql/mysqld.cc
        Make mysql_real_data_home_ptr point to
        mysql_real_data_home if mysql_real_data_home_ptr
        is null before passing it to the fn_format().

    added:
      mysql-test/suite/binlog/r/binlog_server_start_options.result
      mysql-test/suite/binlog/t/binlog_server_start_options.test
    modified:
      mysys/mf_format.c
      sql/mysqld.cc
No bundle (reason: useless for push emails).