Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.
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.
added code to exit a tool if the forced config file wasn't found
per-file comments:
client/mysql.cc
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
client/mysql_upgrade.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
client/mysqladmin.cc
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
client/mysqlcheck.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
client/mysqldump.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
client/mysqlimport.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
client/mysqlshow.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
client/mysqlslap.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
mysql-test/t/mysql.test
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
test added
sql/mysqld.cc
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
storage/myisam/myisamchk.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
storage/myisam/myisampack.c
Bug#47216 programs should quit if the file specified by --defaults-file option isn't found
added code to exit a tool if the forced config file wasn't found
Options loaded from config files were added before command line
arguments, and they were parsed together, which could interprete
the following:
option-a
option-b
as --option-a=--option-b if 'option-a' requires a value, and
caused confusing.
Because all options that requires a value are always given in
the form '--option=value', so it's an error if there is no
'=value' part for such an option read from config file.
This patch added a separator to separate the arguments from
config files and that from command line, so that they can be
handled differently. And report an error for options loaded
from config files that requires a value and is not given in the
form '--option=value'.
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
Recognize the --no-defaults, --defaults-file and --defaults-extra-file
options. Treat old --config-file argument as if --defaults-extra-file
had been specified instead.
Plus a few other defaults-related cleanups.
- Removed not used variables and functions
- Added #ifdef around code that is not used
- Renamed variables and functions to avoid conflicts
- Removed some not used arguments
Fixed some class/struct warnings in ndb
Added define IS_LONGDATA() to simplify code in libmysql.c
I did run gcov on the changes and added 'purecov' comments on almost all lines that was not just variable name changes
Changed defaults option --instance to --defaults-group-suffix
Changed option handling to allow --defaults-file, --defaults-extra-file and --defaults-group-suffix to be given in any order
Changed MYSQL_INSTANCE to MYSQL_GROUP_SUFFIX
mysql_print_defaults now understands --defaults-group-suffix
Remove usage of my_tempnam() (not safe function)
if( -> if ( and while( to while (
used in the handle_options() function (instead of using additional
handle_option() parameter). The default value of the
my_getopt_error_reporter is default_reporter(). One can set it to
other functions if case of need.
Added declarations for print_msg_to_log and vprint_msg_to_log. sql_print_error are simple functions that wrap calls to print_msg_to_log. Define the different error types with MY_ERROR_TYPE, MY_WARNING_TYPE, and MY_INFORMATION_TYPE
gen_lex_hash.cc:
Added NULL error reporting parameter to handle_options
log.cc:
Add print_msg_to_log, print_buffer_to_log, and vprint_msg_to_log. Print_msg_to_log will write the message to the windows event log if on NT. We now have error, warning, and information versions of sql_print_xxxx. T his is a variation of a similar changeset WAX did.
mysqld.cc:
Added option_error_reporter callback function and pass that into handle_options
mysql.cc:
Added NULL as error reporter arg to the end of handle_options
Many files:
Added NULL error reporter parameter as the last paramter to handle_options
my_getopt.c:
Added second function pointer to server as an error reporting callback. Added local function report_option_error that will either write the error to stderr or to the error reporting callback. changed all calls in handle_options from fprintf(stderr, ... ) to report_option_error
my_getopt.h:
Changed declaration of handle_options to use typedefs for the two function pointers. added second function pointer to server as an error reporting callback
mysqld.dsp:
Added custom build step for compiling message file and added message resource file (output of mc)
Ensured that all projects compile
Removed compiler warnings
Better setting of server_version variable.
Fix that make_win_src_distribution creates the privilege tables.
Add pack_bits to pack_reclength for dynamic rows. This solves buffer a possible buffer overflow on update.
(This will probably solve bug #563)
Fix test for available file descriptors in mysqltest
Fixed core dump bug in replication tests when running without transactional table support
of an error in option handling. This can sometimes be useful in
scripts.
Changed some exit code names and corresponding numbers.
Fixed a bug in mysqld.cc, in replication related options.
Added a global flag in my_getopt, which can be set by any program
that is using my_getopt, which tells whether the client should
print the error message itself, or whether my_getopt should do it.
The default is that my_getopt will print the error messages.
Fixes for building MySQL with gcc 3.0
Added SIGNED / UNSIGNED casts
Fixed core dump bug in net_clear() with libmysqld.
Back to using semaphores in query cache.
Added 'Null' and 'Index_type' to SHOW INDEX.
