Bug#53417 my_getwd() makes assumptions on the buffer sizes which not always hold true
      
The mysys library contains many functions for rewriting file paths. Most of these
functions makes implicit assumptions on the buffer sizes they write to. If a path is put
in my_realpath() it will propagate to my_getwd() which assumes that the buffer holding
the path name is greater than 2. This is not true in cases.
      
In the special case where a VARBIN_ITEM is passed as argument to the LOAD_FILE function
this can lead to a crash.
      
This patch fixes the issue by introduce more safe guards agaist buffer overruns.

This is the 5.1 merge and extension of the fix.
The server was happily accepting paths in table name in all places a table
name is accepted (e.g. a SELECT). This allowed all users that have some 
privilege over some database to read all tables in all databases in all
mysql server instances that the server file system has access to.
Fixed by :
1. making sure no path elements are allowed in quoted table name when
constructing the path (note that the path symbols are still valid in table names
when they're properly escaped by the server).
2. checking the #mysql50# prefixed names the same way they're checked for
path elements in mysql-5.0.

      
When issuing a 'SET GLOBAL SQL_SLAVE_SKIP_COUNTER' statement, the previous
position along with the new position is dumped into the error log. Namely,
the following information is printed out: skip_counter, group_relay_log_name
and group_relay_log_pos.

When split_rec==NULL, choose the correct node pointer key (first_rec).

      
When issuing a 'CHANGE MASTER TO' statement, key elements of the previous
state, namely the host, port, the master_log_file and the master_log_pos
are dumped into the error log.

Iterative patch improvement. Previously committed patch
caused wrong result on Windows. The previous patch also
broke secure_file_priv for symlinks since not all file
paths which must be compared against this variable are
normalized using the same norm.

The server variable opt_secure_file_priv wasn't
normalized properly and caused the operations
LOAD DATA INFILE .. INTO TABLE ..
and
SELECT load_file(..)
to do different interpretations of the 
--secure-file-priv option.
     
The patch moves code to the server initialization
routines so that the path always is normalized
once and only once.
      
It was also intended that setting the option
to an empty string should be equal to 
lifting all previously set restrictions. This
is also fixed by this patch.

The server was not checking the supplied to COM_FIELD_LIST table name
for validity and compliance to acceptable table names standards.
Fixed by checking the table name for compliance similar to how it's 
normally checked by the parser and returning an error message if 
it's not compliant.

buf_page_get_gen(): Assert that buf_zip_decompress() succeeds.
Callers are not prepared for a NULL return value. (Bug #53248)

WHERE predicates containing references to empty tables in a
subquery were handled incorrectly by the optimizer when
executing EXPLAIN. As a result, the optimizer could try to
evaluate such predicates rather than just stop with
"Impossible WHERE noticed after reading const tables" as 
it would do in a non-subquery case. This led to valgrind 
errors and crashes.

Fixed the code checking the above condition so that subqueries
are not excluded and hence are handled in the same way as top
level SELECTs.

mysql-tests because those emit (spurious?) valgrind warnings.

This addresses Bug #53122 in the built-in InnoDB.

recv_addr_t: Turn space,page_no into bitfields to save space on 64-bit.
This addresses Bug #53122 in the InnoDB Plugin.

READ COMMITTED in the built-in InnoDB. (Bug #48607)

The server could be tricked to read packets indefinitely if it
received a packet larger than the maximum size of one packet.
This problem is aggravated by the fact that it can be triggered
before authentication.

The solution is to no skip big packets for non-authenticated
sessions. If a big packet is sent before a session is authen-
ticated, a error is returned and the connection is closed.

READ COMMITTED in the InnoDB Plugin. (Bug #48607)

Problem: "COM_FIELD_LIST is an old command of the MySQL server, before there was real move to only
SQL. Seems that the data sent to COM_FIELD_LIST( mysql_list_fields() function) is not
checked for sanity. By sending long data for the table a buffer is overflown, which can
be used deliberately to include code that harms".

Fix: check incoming data length.

on same table

Followup to vasil.dimov@oracle.com-20100428102033-dt3caf531rs3lidr :

Add more asserions, which I forgot.

This is branches/zip@r6032 in SVN and _is part_ of
revid:svn-v4:16c675df-0fcb-4bc9-8058-dcc011a37293:branches/zip:6113
in BZR.

This is being reverted because now the code is serialized directly on
index->stat_n_diff_key_vals[] as the fix for
Bug#53046 dict_update_statistics_low can still be run concurrently on same table
goes.

Address Marko's suggestions wrt the fix of
Bug#53046 dict_update_statistics_low can still be run concurrently
on same table

on same table

Protect dict_index_t::stat_n_diff_key_vals[] with an array of
mutexes.

Testing: tested all code paths under UNIV_SYNC_DEBUG
for the one in dict_print() one has to enable the InnoDB table monitor:
CREATE TABLE innodb_table_monitor (a int) ENGINE=INNODB;

  ------------------------------------------------------------------------
  r6103 | marko | 2009-10-26 15:46:18 +0200 (Mon, 26 Oct 2009) | 4 lines
  Changed paths:
     M /branches/zip/row/row0ins.c

  branches/zip: row_ins_alloc_sys_fields(): Zero out the system columns
  DB_TRX_ID, DB_ROLL_PTR and DB_ROW_ID, in order to avoid harmless
  Valgrind warnings about uninitialized data.  (The warnings were
  harmless, because the fields would be initialized at a later stage.)
  ------------------------------------------------------------------------

any files.

this results in some valgrind errors.

Bug#53202 valgrind: uninitialized bytes in dtuple_print()
has been opened to track this.