strict aliasing violations.
Essentially, the problem is that large parts of the server were
developed in simpler times (last decades, pre C99 standard) when
strict aliasing and compilers supporting such optimizations were
rare to non-existent. Thus, when compiling the server with a modern
compiler that uses strict aliasing rules to perform optimizations,
there are several places in the code that might trigger undefined
behavior.
As evinced by some recent bugs, GCC does a somewhat good of job
misoptimizing such code, but on the other hand also gives warnings
about suspicious code. One problem is that the warnings aren't
always accurate, yet we can't afford to just shut them off as we
might miss real cases. False-positive cases are aggravated mostly
by casts that are likely to trigger undefined behavior.
The solution is to start a cleanup process focused on fixing and
reducing the amount of strict-aliasing related warnings produced
by GCC and others compilers. A good deal of noise reduction can
be achieved by just removing useless casts that are product of
historical cruft and are likely to trigger undefined behavior if
dereferenced.
Several items said to be deprecated in the 4.1 manual
have never been removed. This worklog adds deprecation
warnings when these items are used, and warns the user
that the items will be removed in MySQL 5.6.
A couple of previously deprecation decision have been
reversed (see single file comments)
strmov() is not guaranteed to work correctly on overlapping
source and destination buffers. On some OSes it may work,
but Fedora 12 has a stpcpy() that's not working correctly
on overlapping buffers.
Fixed to use the overlap-safe version of strmov instead.
Re-vitalized the overlap-safe version of strmov.
mysql client displays wrong character-set of server. When a user changes the
charset of a server, mysql client 'status' command displays wrong charset but
the command "SHOW VARIABLES LIKE "%charset%" displayed correct charset results.
The problem is only with the mysql client's 'status' command output.
In mysql client, the method mysql_store_lazy_result() returns 0 for
success and non-zero for failure. The method com_status() was using this method
wrongly. Fixed all such instances according to return value of the method
mysql_store_lazy_result().
When starting the (5.1+) mysql command-line client, we try to get
"select @@version_comment" from the server to present it to the
user. Recent clients are aware that older servers do not have that
variable and fall back on other info to be able to present *something*
at least. This fallback string was allocated through the POSIX interface,
but released through the my*() suite, which rightfully complained about
the imbalance in calls when compiled with --debug. While this wasn't
as bad as it looked (no double-free, use of uninitialized or freed
buffer, etc.), it did look funky.
Using my_strdup() now for what will be my_free()d later.
If a thread is killed in the server, we throw "shutdown" only if one is actually in
progress; otherwise, we throw "query interrupted".
Control-C in the mysql command-line client is "incremental" now.
First Control-C sends KILL QUERY (when connected to 5.0+ server, otherwise, see next)
Next Control-C sends KILL CONNECTION
Next Control-C aborts client.
As the first two steps only pertain to an existing query,
Control-C will abort the client right away if no query is running.
client will give more detailed/consistent feedback on Control-C now.
with gcc 4.3.2
This patch fixes a number of GCC warnings about variables used
before initialized. A new macro UNINIT_VAR() is introduced for
use in the variable declaration, and LINT_INIT() usage will be
gradually deprecated. (A workaround is used for g++, pending a
patch for a g++ bug.)
GCC warnings for unused results (attribute warn_unused_result)
for a number of system calls (present at least in later
Ubuntus, where the usual void cast trick doesn't work) are
also fixed.
server
If the server connection was lost during repeated status commands,
the client would fail to detect this and the client output would be inconsistent.
This patch fixes this issue by making sure that the server is online
before the client attempts to execute the status command.
The problem: described in the bug report.
The fix:
--increase buffers where it's necessary
(buffers which are used in stxnmov)
--decrease buffer lengths which are used
memory issue ?
The mysql command line client could misinterpret some character
sequences as commands under some circumstances.
The upper limit for internal readline buffer was raised to 1 GB
(the same as for server's max_allowed_packet) so that any input
line is processed by add_line() as a whole rather than in
chunks.
When asking what database is selected, client expected
to *always* get an answer from the server.
We now handle failure more gracefully.
See comments in ticket for a discussion of what happens,
and how things interlock.
mysql-client used static buffer to concatenate server-
version and version_comment. Sufficiently long comments
could get cut off. This was harmless, but looked daft.
Now using a dynamic buffer instead.
~40Mb after mysqldump/import
When the input string exceeds the maximum allowed size for the
internal buffer, batch_readline() returns a truncated string.
Since there was no way for a caller to determine whether the
string was truncated or not, the command line client assumed
batch_readline() to always return the whole input string and
appended a newline character. This resulted in garbled data
when importing dumps containing strings longer than the
maximum input buffer size.
Fixed by adding a flag to the batch_readline() interface to
signal a truncated string to the caller.
Other minor problems fixed during patch implementation:
- The maximum allowed buffer size for batch_readline() was set
up depending on the client's max_allowed_packet value. It does
not actully make any sense, as those variables are not
related. The input buffer size limit is now always set to 1
MB.
- fill_buffer() did not always set the EOF flag.
- The input buffer could actually grow twice as the specified
limit due to insufficient checks in intern_read_line().
