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.

1 files changed, 31 insertions, 29 deletions

diff --git a/client/mysqladmin.cc b/client/mysqladmin.cc
index 8a8e8ec2db5..fe3e51a4d61 100644
--- a/client/mysqladmin.cc
+++ b/client/mysqladmin.cc
@@ -122,37 +122,37 @@ static struct my_option my_long_options[] =
 #endif
   {"count", 'c',
    "Number of iterations to make. This works with -i (--sleep) only.",
-   (uchar**) &nr_iterations, (uchar**) &nr_iterations, 0, GET_UINT,
+   &nr_iterations, &nr_iterations, 0, GET_UINT,
    REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
 #ifndef DBUG_OFF
   {"debug", '#', "Output debug log. Often this is 'd:t:o,filename'.",
    0, 0, 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},
   {"force", 'f',
    "Don't ask for confirmation on drop database; with multiple commands, continue even if an error occurs.",
-   (uchar**) &option_force, (uchar**) &option_force, 0, GET_BOOL, NO_ARG, 0, 0,
+   &option_force, &option_force, 0, GET_BOOL, NO_ARG, 0, 0,
    0, 0, 0, 0},
   {"compress", 'C', "Use compression in server/client protocol.",
-   (uchar**) &opt_compress, (uchar**) &opt_compress, 0, GET_BOOL, NO_ARG, 0, 0, 0,
+   &opt_compress, &opt_compress, 0, GET_BOOL, NO_ARG, 0, 0, 0,
    0, 0, 0},
   {"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},
   {"default-character-set", OPT_DEFAULT_CHARSET,
-   "Set the default character set.", (uchar**) &default_charset,
-   (uchar**) &default_charset, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+   "Set the default character set.", &default_charset,
+   &default_charset, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"help", '?', "Display this help and exit.", 0, 0, 0, GET_NO_ARG,
    NO_ARG, 0, 0, 0, 0, 0, 0},
-  {"host", 'h', "Connect to host.", (uchar**) &host, (uchar**) &host, 0, GET_STR,
+  {"host", 'h', "Connect to host.", &host, &host, 0, GET_STR,
    REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
-  {"no-beep", 'b', "Turn off beep on error.", (uchar**) &opt_nobeep,
-   (uchar**) &opt_nobeep, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0}, 
+  {"no-beep", 'b', "Turn off beep on error.", &opt_nobeep,
+   &opt_nobeep, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0}, 
   {"password", 'p',
    "Password to use when connecting to server. If password is not given it's asked from the tty.",
    0, 0, 0, GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
@@ -166,50 +166,52 @@ static struct my_option my_long_options[] =
    "/etc/services, "
 #endif
    "built-in default (" STRINGIFY_ARG(MYSQL_PORT) ").",
-   (uchar**) &tcp_port,
-   (uchar**) &tcp_port, 0, GET_UINT, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+   &tcp_port,
+   &tcp_port, 0, GET_UINT, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"protocol", OPT_MYSQL_PROTOCOL, "The protocol to use for connection (tcp, socket, pipe, memory).",
     0, 0, 0, GET_STR,  REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"relative", 'r',
-   "Show difference between current and previous values when used with -i. Currently only works with extended-status.",
-   (uchar**) &opt_relative, (uchar**) &opt_relative, 0, GET_BOOL, NO_ARG, 0, 0, 0,
+   "Show difference between current and previous values when used with -i. "
+   "Currently only works with extended-status.",
+   &opt_relative, &opt_relative, 0, GET_BOOL, NO_ARG, 0, 0, 0,
   0, 0, 0},
   {"set-variable", 'O',
-   "Change the value of a variable. Please note that this option is deprecated; you can set variables directly with --variable-name=value.",
+   "Change the value of a variable. Please note that this option is "
+   "deprecated; you can set variables directly with --variable-name=value.",
    0, 0, 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_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
 #endif
   {"silent", 's', "Silently exit if one can't connect to server.",
    0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0},
   {"socket", 'S', "The socket file to use for connection.",
-   (uchar**) &unix_port, (uchar**) &unix_port, 0, GET_STR, REQUIRED_ARG, 0, 0, 0,
+   &unix_port, &unix_port, 0, GET_STR, REQUIRED_ARG, 0, 0, 0,
    0, 0, 0},
   {"sleep", 'i', "Execute commands repeatedly with a sleep between.",
-   (uchar**) &interval, (uchar**) &interval, 0, GET_INT, REQUIRED_ARG, 0, 0, 0, 0,
+   &interval, &interval, 0, GET_INT, REQUIRED_ARG, 0, 0, 0, 0,
    0, 0},
 #include <sslopt-longopts.h>
 #ifndef DONT_ALLOW_USER_CHANGE
-  {"user", 'u', "User for login if not current user.", (uchar**) &user,
-   (uchar**) &user, 0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+  {"user", 'u', "User for login if not current user.", &user,
+   &user, 0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
 #endif
-  {"verbose", 'v', "Write more information.", (uchar**) &opt_verbose,
-   (uchar**) &opt_verbose, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
+  {"verbose", 'v', "Write more information.", &opt_verbose,
+   &opt_verbose, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
   {"version", 'V', "Output version information and exit.", 0, 0, 0, GET_NO_ARG,
    NO_ARG, 0, 0, 0, 0, 0, 0},
   {"vertical", 'E',
    "Print output vertically. Is similar to --relative, but prints output vertically.",
-   (uchar**) &opt_vertical, (uchar**) &opt_vertical, 0, GET_BOOL, NO_ARG, 0, 0, 0,
+   &opt_vertical, &opt_vertical, 0, GET_BOOL, NO_ARG, 0, 0, 0,
    0, 0, 0},
   {"wait", 'w', "Wait and retry if connection is down.", 0, 0, 0, GET_UINT,
    OPT_ARG, 0, 0, 0, 0, 0, 0},
-  {"connect_timeout", OPT_CONNECT_TIMEOUT, "", (uchar**) &opt_connect_timeout,
-   (uchar**) &opt_connect_timeout, 0, GET_ULONG, REQUIRED_ARG, 3600*12, 0,
+  {"connect_timeout", OPT_CONNECT_TIMEOUT, "", &opt_connect_timeout,
+   &opt_connect_timeout, 0, GET_ULONG, REQUIRED_ARG, 3600*12, 0,
    3600*12, 0, 1, 0},
-  {"shutdown_timeout", OPT_SHUTDOWN_TIMEOUT, "", (uchar**) &opt_shutdown_timeout,
-   (uchar**) &opt_shutdown_timeout, 0, GET_ULONG, REQUIRED_ARG,
+  {"shutdown_timeout", OPT_SHUTDOWN_TIMEOUT, "", &opt_shutdown_timeout,
+   &opt_shutdown_timeout, 0, GET_ULONG, REQUIRED_ARG,
    SHUTDOWN_DEF_TIMEOUT, 0, 3600*12, 0, 1, 0},
   { 0, 0, 0, 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}
 };