mariadb/extra/mysql_waitpid.c
Davi Arnaut bb036c93b4 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.
2010-06-10 17:16:43 -03:00

117 lines
3 KiB
C

/* Copyright (C) 2003 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/* Wait until a program dies */
#ifndef __NETWARE__
#include <my_global.h>
#include <m_string.h>
#include <my_sys.h>
#include <my_getopt.h>
#include <signal.h>
#include <errno.h>
static const char *VER= "1.1";
static char *progname;
static my_bool verbose;
void usage(void);
static struct my_option my_long_options[] =
{
{"help", '?', "Display this help and exit.", 0, 0, 0, GET_NO_ARG, NO_ARG, 0,
0, 0, 0, 0, 0},
{"help", 'I', "Synonym for -?.", 0, 0, 0, GET_NO_ARG, NO_ARG, 0,
0, 0, 0, 0, 0},
{"verbose", 'v',
"Be more verbose. Give a warning, if kill can't handle signal 0.",
&verbose, &verbose, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
{"version", 'V', "Print version information and exit.", 0, 0, 0,
GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0},
{ 0, 0, 0, 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}
};
static my_bool
get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
char *argument __attribute__((unused)))
{
switch(optid) {
case 'V':
printf("%s version %s by Jani Tolonen\n", progname, VER);
exit(-1);
case 'I':
case '?':
usage();
}
return 0;
}
int main(int argc, char *argv[])
{
int pid= 0, t= 0, sig= 0;
progname= argv[0];
if (handle_options(&argc, &argv, my_long_options, get_one_option))
exit(-1);
if (!argv[0] || !argv[1] || (pid= atoi(argv[0])) <= 0 ||
(t= atoi(argv[1])) <= 0)
usage();
for (; t > 0; t--)
{
if (kill((pid_t) pid, sig))
{
if (errno == EINVAL)
{
if (verbose)
printf("WARNING: kill couldn't handle signal 0, using signal 1.\n");
sig= 1;
t++;
continue;
}
return 0;
}
sleep(1);
}
return 1;
}
void usage(void)
{
printf("%s version %s by Jani Tolonen\n\n", progname, VER);
printf("usage: %s [options] #pid #time\n\n", progname);
printf("Description: Waits for a program, which program id is #pid, to\n");
printf("terminate within #time seconds. If the program terminates within\n");
printf("this time, or if the #pid no longer exists, value 0 is returned.\n");
printf("Otherwise 1 is returned. Both #pid and #time must be positive\n");
printf("integer arguments.\n\n");
printf("Options:\n");
my_print_help(my_long_options);
exit(-1);
}
#else
#include <stdio.h>
main()
{
fprintf(stderr,"This tool has not been ported to NetWare\n");
return 0;
}
#endif /* __NETWARE__ */