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Bug#42733: Type-punning warnings when compiling MySQL --

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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.
This commit is contained in:
Davi Arnaut
2010-06-10 17:16:43 -03:00
parent e3b4d33187
commit bb036c93b4
35 changed files with 1248 additions and 1111 deletions
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24
client/mysql_upgrade.c
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@ -68,7 +68,7 @@ static struct my_option my_long_options[]=
"Directory for character set files.", 0,
0, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"compress", OPT_COMPRESS, "Use compression in server/client protocol.",
(uchar**)&not_used, (uchar**)&not_used, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
&not_used, &not_used, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
{"datadir", 'd',
"Not used by mysql_upgrade. Only for backward compatibility.",
0, 0, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
@ -76,26 +76,26 @@ static struct my_option my_long_options[]=
{"debug", '#', "This is a non-debug version. Catch this and exit.",
0, 0, 0, GET_DISABLED, OPT_ARG, 0, 0, 0, 0, 0, 0},
#else
{"debug", '#', "Output debug log.", (uchar* *) & default_dbug_option,
(uchar* *) & default_dbug_option, 0, GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
{"debug", '#', "Output debug log.", &default_dbug_option,
&default_dbug_option, 0, GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
#endif
{"debug-check", OPT_DEBUG_CHECK, "Check memory and open file usage at exit.",
(uchar**) &debug_check_flag, (uchar**) &debug_check_flag, 0,
&debug_check_flag, &debug_check_flag, 0,
GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
{"debug-info", 'T', "Print some debug info at exit.", (uchar**) &debug_info_flag,
(uchar**) &debug_info_flag, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
{"debug-info", 'T', "Print some debug info at exit.", &debug_info_flag,
&debug_info_flag, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
{"default-character-set", OPT_DEFAULT_CHARSET,
"Set the default character set.", 0,
0, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"force", 'f', "Force execution of mysqlcheck even if mysql_upgrade "
"has already been executed for the current version of MySQL.",
(uchar**)&opt_force, (uchar**)&opt_force, 0,
&opt_force, &opt_force, 0,
GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
{"host",'h', "Connect to host.", 0,
0, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"password", 'p',
"Password to use when connecting to server. If password is not given,"
" it's solicited on the tty.", (uchar**) &opt_password,(uchar**) &opt_password,
" it's solicited on the tty.", &opt_password,&opt_password,
0, GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
#ifdef __WIN__
{"pipe", 'W', "Use named pipes to connect to server.", 0, 0, 0,
@ -121,15 +121,15 @@ static struct my_option my_long_options[]=
#include <sslopt-longopts.h>
{"tmpdir", 't', "Directory for temporary files.",
0, 0, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"user", 'u', "User for login if not current user.", (uchar**) &opt_user,
(uchar**) &opt_user, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"user", 'u', "User for login if not current user.", &opt_user,
&opt_user, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"verbose", 'v', "Display more output about the process.",
(uchar**) &opt_verbose, (uchar**) &opt_verbose, 0,
&opt_verbose, &opt_verbose, 0,
GET_BOOL, NO_ARG, 1, 0, 0, 0, 0, 0},
{"write-binlog", OPT_WRITE_BINLOG,
"All commands including mysqlcheck are binlogged. Enabled by default;"
"use --skip-write-binlog when commands should not be sent to replication slaves.",
(uchar**) &opt_write_binlog, (uchar**) &opt_write_binlog, 0, GET_BOOL, NO_ARG,
&opt_write_binlog, &opt_write_binlog, 0, GET_BOOL, NO_ARG,
1, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}
};