From 6f3a540c37bd1d84139c32a4b74844ff648c3b0c Mon Sep 17 00:00:00 2001 From: Davi Arnaut Date: Thu, 10 Jun 2010 17:16:43 -0300 Subject: Bug#42733: Type-punning warnings when compiling MySQL -- 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. client/mysql.cc: Remove now-unnecessary casts. Break up large strings. client/mysql_upgrade.c: Remove now-unnecessary casts. client/mysqladmin.cc: Remove now-unnecessary casts. Break up large strings. client/mysqlbinlog.cc: Remove now-unnecessary casts. client/mysqlcheck.c: Remove now-unnecessary casts. client/mysqldump.c: Remove now-unnecessary casts. client/mysqlimport.c: Remove now-unnecessary casts. client/mysqlshow.c: Remove now-unnecessary casts. client/mysqlslap.c: Remove now-unnecessary casts. client/mysqltest.cc: Remove now-unnecessary casts. extra/comp_err.c: Remove now-unnecessary casts. extra/my_print_defaults.c: Remove now-unnecessary casts. Break up large strings. extra/mysql_waitpid.c: Remove now-unnecessary casts. extra/perror.c: Remove now-unnecessary casts. extra/resolve_stack_dump.c: Remove now-unnecessary casts. extra/resolveip.c: Remove now-unnecessary casts. include/my_getopt.h: Use a void pointer type as the opaque type to avoid problems with type incompatibility -- GCC issues warnings when the type name is not type compatible with a operand. As a side bonus, a explicit cast won't be necessary anymore. include/sslopt-longopts.h: Remove now-unnecessary casts. Break up large strings. mysys/my_getopt.c: Update opaque type and introduce a type definition for the argument to my_getopt_register_get_addr. server-tools/instance-manager/options.cc: Remove now-unnecessary casts. sql/mysqld.cc: Remove now-unnecessary casts. Break up large strings. Update mysql_getopt_value prototype (the old prototype was different from the definition anyway). sql/sql_plugin.cc: The type of a pointer to a function must be compatible with the pointed-to function type, otherwise the behavior is undefined. sql/table.cc: The variable buf pointer to pointer to pointer to constant char could improperly alias a incompatible type in call to fix_type_ pointers. Since this was actually dead code, it is simply removed. sql/unireg.cc: Remove call to get_form_pos. The code creates a new FRM file which is always truncated and writes the form position as 0. Hence, no need to retrieve it, we now for sure it is 0. storage/archive/archive_reader.c: Remove now-unnecessary casts. storage/myisam/ft_nlq_search.c: Read weight directly from the buffer. storage/myisam/fulltext.h: Add explanation about the type duality of a key buffer. Add accessor macro to retrieve a FT float value. storage/myisam/mi_test1.c: Remove now-unnecessary casts. storage/myisam/myisam_ftdump.c: Read weight directly from the buffer. storage/myisam/myisamchk.c: Remove now-unnecessary casts. storage/myisam/myisamlog.c: A pointer to char was used to alias a pointer to pointer to unsigned char, thus violating strict aliasing rules. storage/myisam/myisampack.c: Remove now-unnecessary casts. strings/decimal.c: Remove aliasing violation, printing the value is enough for debugging purposes. tests/mysql_client_test.c: Remove now-unnecessary casts. --- extra/my_print_defaults.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) (limited to 'extra/my_print_defaults.c') diff --git a/extra/my_print_defaults.c b/extra/my_print_defaults.c index 06f7e51c380..cc74208b783 100644 --- a/extra/my_print_defaults.c +++ b/extra/my_print_defaults.c @@ -46,31 +46,36 @@ static struct my_option my_long_options[] = searched for a file of this name (and standard filename extensions are added if the file has no extension) */ - {"config-file", 'c', "Deprecated, please use --defaults-file instead. Name of config file to read; if no extension is given, default extension (e.g., .ini or .cnf) will be added", - (uchar**) &config_file, (uchar**) &config_file, 0, GET_STR, REQUIRED_ARG, + {"config-file", 'c', "Deprecated, please use --defaults-file instead. " + "Name of config file to read; if no extension is given, default " + "extension (e.g., .ini or .cnf) will be added", + &config_file, &config_file, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0}, #ifdef DBUG_OFF {"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 - {"defaults-file", 'c', "Like --config-file, except: if first option, then read this file only, do not read global or per-user config files; should be the first option", - (uchar**) &config_file, (uchar**) &config_file, 0, GET_STR, REQUIRED_ARG, + {"defaults-file", 'c', "Like --config-file, except: if first option, " + "then read this file only, do not read global or per-user config " + "files; should be the first option", + &config_file, &config_file, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0}, {"defaults-extra-file", 'e', - "Read this file after the global config file and before the config file in the users home directory; should be the first option", - (uchar**) &my_defaults_extra_file, (uchar**) &my_defaults_extra_file, 0, + "Read this file after the global config file and before the config " + "file in the users home directory; should be the first option", + &my_defaults_extra_file, &my_defaults_extra_file, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0}, {"defaults-group-suffix", 'g', "In addition to the given groups, read also groups with this suffix", - (uchar**) &my_defaults_group_suffix, (uchar**) &my_defaults_group_suffix, + &my_defaults_group_suffix, &my_defaults_group_suffix, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0}, {"extra-file", 'e', "Deprecated. Synonym for --defaults-extra-file.", - (uchar**) &my_defaults_extra_file, - (uchar**) &my_defaults_extra_file, 0, GET_STR, + &my_defaults_extra_file, + &my_defaults_extra_file, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0}, {"no-defaults", 'n', "Return an empty string (useful for scripts).", 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}, -- cgit v1.2.1