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, 20 insertions, 19 deletions

diff --git a/client/mysqlshow.c b/client/mysqlshow.c
index 370efe83f10..2f5582cb668 100644
--- a/client/mysqlshow.c
+++ b/client/mysqlshow.c
@@ -164,35 +164,35 @@ static struct my_option my_long_options[] =
    0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0},
 #endif
   {"character-sets-dir", 'c', "Directory for character set files.",
-   (uchar**) &charsets_dir, (uchar**) &charsets_dir, 0, GET_STR, REQUIRED_ARG, 0,
+   &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},
   {"count", OPT_COUNT,
    "Show number of rows per table (may be slow for non-MyISAM tables).",
-   (uchar**) &opt_count, (uchar**) &opt_count, 0, GET_BOOL, NO_ARG, 0, 0, 0,
+   &opt_count, &opt_count, 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},
   {"debug", '#', "Output debug log. Often this is 'd:t:o,filename'.",
    0, 0, 0, GET_STR, OPT_ARG, 0, 0, 0, 0, 0, 0},
   {"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},
   {"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},
   {"status", 'i', "Shows a lot of extra information about each table.",
-   (uchar**) &opt_status, (uchar**) &opt_status, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
+   &opt_status, &opt_status, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0,
    0, 0},
-  {"keys", 'k', "Show keys for table.", (uchar**) &opt_show_keys,
-   (uchar**) &opt_show_keys, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
+  {"keys", 'k', "Show keys for table.", &opt_show_keys,
+   &opt_show_keys, 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 "
    "solicited on the tty.",
@@ -203,8 +203,8 @@ static struct my_option my_long_options[] =
    "/etc/services, "
 #endif
    "built-in default (" STRINGIFY_ARG(MYSQL_PORT) ").",
-   (uchar**) &opt_mysql_port,
-   (uchar**) &opt_mysql_port, 0, GET_UINT, REQUIRED_ARG, 0, 0, 0, 0, 0,
+   &opt_mysql_port,
+   &opt_mysql_port, 0, GET_UINT, REQUIRED_ARG, 0, 0, 0, 0, 0,
    0},
 #ifdef __WIN__
   {"pipe", 'W', "Use named pipes to connect to server.", 0, 0, 0, GET_NO_ARG,
@@ -215,19 +215,20 @@ static struct my_option my_long_options[] =
    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,
-   0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+   "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
   {"show-table-type", 't', "Show table type column.",
-   (uchar**) &opt_table_type, (uchar**) &opt_table_type, 0, GET_BOOL,
+   &opt_table_type, &opt_table_type, 0, GET_BOOL,
    NO_ARG, 0, 0, 0, 0, 0, 0},
   {"socket", 'S', "The socket file to use for connection.",
-   (uchar**) &opt_mysql_unix_port, (uchar**) &opt_mysql_unix_port, 0, GET_STR,
+   &opt_mysql_unix_port, &opt_mysql_unix_port, 0, GET_STR,
    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, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+  {"user", 'u', "User for login if not current user.", &user,
+   &user, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
 #endif
   {"verbose", 'v',
    "More verbose output; you can use this multiple times to get even more "