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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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33
tests/mysql_client_test.c
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@ -18220,17 +18220,17 @@ static char **defaults_argv;
static struct my_option client_test_long_options[] =
{
{"basedir", 'b', "Basedir for tests.", (uchar**) &opt_basedir,
(uchar**) &opt_basedir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"count", 't', "Number of times test to be executed", (uchar **) &opt_count,
(uchar **) &opt_count, 0, GET_UINT, REQUIRED_ARG, 1, 0, 0, 0, 0, 0},
{"database", 'D', "Database to use", (uchar **) &opt_db, (uchar **) &opt_db,
{"basedir", 'b', "Basedir for tests.", &opt_basedir,
&opt_basedir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"count", 't', "Number of times test to be executed", &opt_count,
&opt_count, 0, GET_UINT, REQUIRED_ARG, 1, 0, 0, 0, 0, 0},
{"database", 'D', "Database to use", &opt_db, &opt_db,
0, GET_STR_ALLOC, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"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},
{"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 **) &opt_host, (uchar **) &opt_host,
{"host", 'h', "Connect to host", &opt_host, &opt_host,
0, GET_STR_ALLOC, REQUIRED_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.",
@ -18241,8 +18241,7 @@ static struct my_option client_test_long_options[] =
"/etc/services, "
#endif
"built-in default (" STRINGIFY_ARG(MYSQL_PORT) ").",
(uchar **) &opt_port,
(uchar **) &opt_port, 0, GET_UINT, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
&opt_port, &opt_port, 0, GET_UINT, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"server-arg", 'A', "Send embedded server this as a parameter.",
0, 0, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"show-tests", 'T', "Show all tests' names", 0, 0, 0, GET_NO_ARG, NO_ARG,
@ -18251,23 +18250,23 @@ static struct my_option client_test_long_options[] =
0},
#ifdef HAVE_SMEM
{"shared-memory-base-name", 'm', "Base name of shared memory.",
(uchar**) &shared_memory_base_name, (uchar**)&shared_memory_base_name, 0,
&shared_memory_base_name, (uchar**)&shared_memory_base_name, 0,
GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
#endif
{"socket", 'S', "Socket file to use for connection",
(uchar **) &opt_unix_socket, (uchar **) &opt_unix_socket, 0, GET_STR,
&opt_unix_socket, &opt_unix_socket, 0, GET_STR,
REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"testcase", 'c',
"May disable some code when runs as mysql-test-run testcase.",
0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0},
#ifndef DONT_ALLOW_USER_CHANGE
{"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},
#endif
{"vardir", 'v', "Data dir for tests.", (uchar**) &opt_vardir,
(uchar**) &opt_vardir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"vardir", 'v', "Data dir for tests.", &opt_vardir,
&opt_vardir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
{"getopt-ll-test", 'g', "Option for testing bug in getopt library",
(uchar **) &opt_getopt_ll_test, (uchar **) &opt_getopt_ll_test, 0,
&opt_getopt_ll_test, &opt_getopt_ll_test, 0,
GET_LL, REQUIRED_ARG, 0, 0, LONGLONG_MAX, 0, 0, 0},
{ 0, 0, 0, 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}
};