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.

1 files changed, 33 insertions, 34 deletions

diff --git a/client/mysqlbinlog.cc b/client/mysqlbinlog.cc
index c8b9a7d34c5..30bdb58153f 100644
--- a/client/mysqlbinlog.cc
+++ b/client/mysqlbinlog.cc
@@ -1004,9 +1004,8 @@ static struct my_option my_long_options[] =
    "events); 'always' prints base64 whenever possible. 'always' is for "
    "debugging only and should not be used in a production system. If this "
    "argument is not given, the default is 'auto'; if it is given with no "
-   "argument, 'always' is used."
-   ,(uchar**) &opt_base64_output_mode_str,
-   (uchar**) &opt_base64_output_mode_str,
+   "argument, 'always' is used.",
+   &opt_base64_output_mode_str, &opt_base64_output_mode_str,
    0, GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
   /*
     mysqlbinlog needs charsets knowledge, to be able to convert a charset
@@ -1015,43 +1014,43 @@ static struct my_option my_long_options[] =
     SET @`a`:=_cp850 0x4DFC6C6C6572 COLLATE `cp850_general_ci`;
   */
   {"character-sets-dir", OPT_CHARSETS_DIR,
-   "Directory for character set files.", (uchar**) &charsets_dir,
-   (uchar**) &charsets_dir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+   "Directory for character set files.", &charsets_dir,
+   &charsets_dir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"database", 'd', "List entries for just this database (local log only).",
-   (uchar**) &database, (uchar**) &database, 0, GET_STR_ALLOC, REQUIRED_ARG,
+   &database, &database, 0, GET_STR_ALLOC, REQUIRED_ARG,
    0, 0, 0, 0, 0, 0},
 #ifndef DBUG_OFF
-  {"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", OPT_DEBUG_INFO, "Print some debug info at exit.",
-   (uchar**) &debug_info_flag, (uchar**) &debug_info_flag,
+   &debug_info_flag, &debug_info_flag,
    0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
   {"disable-log-bin", 'D', "Disable binary log. This is useful, if you "
     "enabled --to-last-log and are sending the output to the same MySQL server. "
     "This way you could avoid an endless loop. You would also like to use it "
     "when restoring after a crash to avoid duplication of the statements you "
     "already have. NOTE: you will need a SUPER privilege to use this option.",
-   (uchar**) &disable_log_bin, (uchar**) &disable_log_bin, 0, GET_BOOL,
+   &disable_log_bin, &disable_log_bin, 0, GET_BOOL,
    NO_ARG, 0, 0, 0, 0, 0, 0},
   {"force-if-open", 'F', "Force if binlog was not closed properly.",
-   (uchar**) &force_if_open_opt, (uchar**) &force_if_open_opt, 0, GET_BOOL, NO_ARG,
+   &force_if_open_opt, &force_if_open_opt, 0, GET_BOOL, NO_ARG,
    1, 0, 0, 0, 0, 0},
   {"force-read", 'f', "Force reading unknown binlog events.",
-   (uchar**) &force_opt, (uchar**) &force_opt, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
+   &force_opt, &force_opt, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
    0, 0},
   {"hexdump", 'H', "Augment output with hexadecimal and ASCII event dump.",
-   (uchar**) &opt_hexdump, (uchar**) &opt_hexdump, 0, GET_BOOL, NO_ARG,
+   &opt_hexdump, &opt_hexdump, 0, GET_BOOL, NO_ARG,
    0, 0, 0, 0, 0, 0},
-  {"host", 'h', "Get the binlog from server.", (uchar**) &host, (uchar**) &host,
+  {"host", 'h', "Get the binlog from server.", &host, &host,
    0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"local-load", 'l', "Prepare local temporary files for LOAD DATA INFILE in the specified directory.",
-   (uchar**) &dirname_for_local_load, (uchar**) &dirname_for_local_load, 0,
+   &dirname_for_local_load, &dirname_for_local_load, 0,
    GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
-  {"offset", 'o', "Skip the first N entries.", (uchar**) &offset, (uchar**) &offset,
+  {"offset", 'o', "Skip the first N entries.", &offset, &offset,
    0, GET_ULL, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"password", 'p', "Password to connect to remote server.",
    0, 0, 0, GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
@@ -1061,10 +1060,10 @@ static struct my_option my_long_options[] =
    "/etc/services, "
 #endif
    "built-in default (" STRINGIFY_ARG(MYSQL_PORT) ").",
-   (uchar**) &port, (uchar**) &port, 0, GET_INT, REQUIRED_ARG,
+   &port, &port, 0, GET_INT, REQUIRED_ARG,
    0, 0, 0, 0, 0, 0},
   {"position", OPT_POSITION, "Deprecated. Use --start-position instead.",
-   (uchar**) &start_position, (uchar**) &start_position, 0, GET_ULL,
+   &start_position, &start_position, 0, GET_ULL,
    REQUIRED_ARG, BIN_LOG_HEADER_SIZE, BIN_LOG_HEADER_SIZE,
    /* COM_BINLOG_DUMP accepts only 4 bytes for the position */
    (ulonglong)(~(uint32)0), 0, 0, 0},
@@ -1072,31 +1071,31 @@ static struct my_option my_long_options[] =
    "The protocol to use for connection (tcp, socket, pipe, memory).",
    0, 0, 0, GET_STR,  REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"read-from-remote-server", 'R', "Read binary logs from a MySQL server.",
-   (uchar**) &remote_opt, (uchar**) &remote_opt, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
+   &remote_opt, &remote_opt, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
    0, 0},
   {"result-file", 'r', "Direct output to a given file.", 0, 0, 0, GET_STR,
    REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"server-id", OPT_SERVER_ID,
    "Extract only binlog entries created by the server having the given id.",
-   (uchar**) &server_id, (uchar**) &server_id, 0, GET_ULONG,
+   &server_id, &server_id, 0, GET_ULONG,
    REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"set-charset", OPT_SET_CHARSET,
-   "Add 'SET NAMES character_set' to the output.", (uchar**) &charset,
-   (uchar**) &charset, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+   "Add 'SET NAMES character_set' to the output.", &charset,
+   &charset, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
 #ifdef HAVE_SMEM
   {"shared-memory-base-name", OPT_SHARED_MEMORY_BASE_NAME,
-   "Base name of shared memory.", (uchar**) &shared_memory_base_name, 
-   (uchar**) &shared_memory_base_name, 
+   "Base name of shared memory.", &shared_memory_base_name,
+   &shared_memory_base_name,
    0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
 #endif
   {"short-form", 's', "Just show regular queries: no extra info and no "
    "row-based events. This is for testing only, and should not be used in "
    "production systems. If you want to suppress base64-output, consider "
    "using --base64-output=never instead.",
-   (uchar**) &short_form, (uchar**) &short_form, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
+   &short_form, &short_form, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
    0, 0},
   {"socket", 'S', "The socket file to use for connection.",
-   (uchar**) &sock, (uchar**) &sock, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 
+   &sock, &sock, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 
    0, 0},
   {"start-datetime", OPT_START_DATETIME,
    "Start reading the binlog at first event having a datetime equal or "
@@ -1104,12 +1103,12 @@ static struct my_option my_long_options[] =
    "in the local time zone, in any format accepted by the MySQL server "
    "for DATETIME and TIMESTAMP types, for example: 2004-12-25 11:25:56 "
    "(you should probably use quotes for your shell to set it properly).",
-   (uchar**) &start_datetime_str, (uchar**) &start_datetime_str,
+   &start_datetime_str, &start_datetime_str,
    0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"start-position", 'j',
    "Start reading the binlog at position N. Applies to the first binlog "
    "passed on the command line.",
-   (uchar**) &start_position, (uchar**) &start_position, 0, GET_ULL,
+   &start_position, &start_position, 0, GET_ULL,
    REQUIRED_ARG, BIN_LOG_HEADER_SIZE, BIN_LOG_HEADER_SIZE,
    /* COM_BINLOG_DUMP accepts only 4 bytes for the position */
    (ulonglong)(~(uint32)0), 0, 0, 0},
@@ -1119,22 +1118,22 @@ static struct my_option my_long_options[] =
    "in the local time zone, in any format accepted by the MySQL server "
    "for DATETIME and TIMESTAMP types, for example: 2004-12-25 11:25:56 "
    "(you should probably use quotes for your shell to set it properly).",
-   (uchar**) &stop_datetime_str, (uchar**) &stop_datetime_str,
+   &stop_datetime_str, &stop_datetime_str,
    0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"stop-position", OPT_STOP_POSITION,
    "Stop reading the binlog at position N. Applies to the last binlog "
    "passed on the command line.",
-   (uchar**) &stop_position, (uchar**) &stop_position, 0, GET_ULL,
+   &stop_position, &stop_position, 0, GET_ULL,
    REQUIRED_ARG, (ulonglong)(~(my_off_t)0), BIN_LOG_HEADER_SIZE,
    (ulonglong)(~(my_off_t)0), 0, 0, 0},
   {"to-last-log", 't', "Requires -R. Will not stop at the end of the \
 requested binlog but rather continue printing until the end of the last \
 binlog of the MySQL server. If you send the output to the same MySQL server, \
 that may lead to an endless loop.",
-   (uchar**) &to_last_remote_log, (uchar**) &to_last_remote_log, 0, GET_BOOL,
+   &to_last_remote_log, &to_last_remote_log, 0, GET_BOOL,
    NO_ARG, 0, 0, 0, 0, 0, 0},
   {"user", 'u', "Connect to the remote server as username.",
-   (uchar**) &user, (uchar**) &user, 0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0,
+   &user, &user, 0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0,
    0, 0},
   {"verbose", 'v', "Reconstruct SQL statements out of row events. "
                    "-v -v adds comments on column data types.",
@@ -1143,7 +1142,7 @@ that may lead to an endless loop.",
    0, 0, 0, 0, 0},
   {"open_files_limit", OPT_OPEN_FILES_LIMIT,
    "Used to reserve file descriptors for use by this program.",
-   (uchar**) &open_files_limit, (uchar**) &open_files_limit, 0, GET_ULONG,
+   &open_files_limit, &open_files_limit, 0, GET_ULONG,
    REQUIRED_ARG, MY_NFILE, 8, OS_FILE_LIMIT, 0, 1, 0},
   {0, 0, 0, 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}
 };