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c-posix-signals.c
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c-posix-signals.c
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/*----------------------------------------------------------------------------
-- --
-- FLORIST (FSU Implementation of POSIX.5) COMPONENTS --
-- --
-- --
-- C - P O S I X - S I G N A L S . C --
-- --
-- --
-- Copyright (C) 1998, Florida State University --
-- Copyright (C) 1998-2014, AdaCore --
-- --
-- --
-- This file is a component of FLORIST, an implementation of an Ada API --
-- for the POSIX OS services, for use with the GNAT Ada compiler and --
-- the FSU Gnu Ada Runtime Library (GNARL). The interface is intended --
-- to be close to that specified in IEEE STD 1003.5: 1990 and IEEE STD --
-- 1003.5b: 1996. --
-- --
-- FLORIST is free software; you can redistribute it and/or modify it --
-- under terms of the GNU General Public License as published by the --
-- Free Software Foundation; either version 2, or (at your option) any --
-- later version. FLORIST 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 distributed with GNARL; see --
-- file COPYING. If not, write to the Free Software Foundation, 59 --
-- Temple Place - Suite 330, Boston, MA 02111-1307, USA --
-- --
-- --
-- --
-- --
-- --
-- --
-- --
-- --
----------------------------------------------------------------------------*/
/* file: c-posix-signals.c
=======================
[$Revision: 232963 $]
This program generates the file
posix-implementation-ok_signals.ads,
which is an Ada package specification that defines a
list of signals that seem to work correctly with sigwait().
The test is to mask a given signal, then use kill () to send the
signal to the current process, then call sigwait () to receive the
signal.
The observed behavior for some signals is that the process hangs
on sigwait, notably for signals whose default action is to ignore
the signal or stop the process.
In order to allow testing of more than one signal, the program
tries to recover if sigwait() hangs.
The first attempt was to use alarm() to arrange for another
signal to be delivered, if sigwait() did not receive the tested
signal within one second. This seemed to have worked for SIGCHLD
and SIGCONT, i.e. the signals whose default action is to ignore
them. It did not seem to work for SIGSTOP, SITTSTP, SIGTTIN,
SIGTTOU, whose default action is to stop the process.
In order to recover for these cases, we moved the test of
sigwait() into a child process, and arranged for the parent
process to send SIGCONT to the child if it stops. This seems to
solve the problem.
When linking this test don't forget to use "-lpthread",
or the appropriate thread library.
*/
#define _POSIX_C_SIGNALS_C
#include "confsrc/pconfig.h"
#define _POSIX_C_SOURCE 199506L
#define _REENTRANT
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include <string.h>
/* Uncomment the following only for debugging. */
/* #define DEBUG */
int sigs [] = {
0,
#ifdef SIG32
SIG32,
#endif
#ifdef SIGABRT
SIGABRT,
#endif
#ifdef SIGALRM
SIGALRM,
#endif
#ifdef SIGBUS
SIGBUS,
#endif
#ifdef SIGCANCEL
SIGCANCEL,
#endif
#ifdef SIGCHLD
SIGCHLD,
#endif
#ifdef SIGCLD
SIGCLD,
#endif
#ifdef SIGCONT
SIGCONT,
#endif
#ifdef SIGEMT
SIGEMT,
#endif
#ifdef SIGFPE
SIGFPE,
#endif
#ifdef SIGFREEZE
SIGFREEZE,
#endif
#ifdef SIGHUP
SIGHUP,
#endif
#ifdef SIGILL
SIGILL,
#endif
#ifdef SIGINT
SIGINT,
#endif
#ifdef SIGIO
SIGIO,
#endif
#ifdef SIGIOT
SIGIOT,
#endif
#ifdef SIGKILL
SIGKILL,
#endif
#ifdef SIGLOST
SIGLOST,
#endif
#ifdef SIGLWP
SIGLWP,
#endif
#ifdef SIGPIPE
SIGPIPE,
#endif
#ifdef SIGPOLL
SIGPOLL,
#endif
#ifdef SIGPROF
SIGPROF,
#endif
#ifdef SIGQUIT
SIGQUIT,
#endif
#ifdef SIGSEGV
SIGSEGV,
#endif
#ifdef SIGSTKFLT
SIGSTKFLT,
#endif
#ifdef SIGSYS
SIGSYS,
#endif
#ifdef SIGTERM
SIGTERM,
#endif
#ifdef SIGUSR1
SIGUSR1,
#endif
#ifdef SIGUSR2
SIGUSR2,
#endif
#ifdef SIGTRAP
SIGTRAP,
#endif
#ifdef SIGSTOP
SIGSTOP,
#endif
#ifdef SIGTHAW
SIGTHAW,
#endif
#ifdef SIGTSTP
SIGTSTP,
#endif
#ifdef SIGTTIN
SIGTTIN,
#endif
#ifdef SIGTTOU
SIGTTOU,
#endif
#ifdef SIGPWR
SIGPWR,
#endif
#ifdef SIGURG
SIGURG,
#endif
#ifdef SIGUNUSED
SIGUNUSED,
#endif
#ifdef SIGVTALRM
SIGVTALRM,
#endif
#ifdef SIGWAITING
SIGWAITING,
#endif
#ifdef SIGWINCH
SIGWINCH,
#endif
#ifdef SIGXCPU
SIGXCPU,
#endif
#ifdef SIGXFSZ
SIGXFSZ,
#endif
0};
char *signames [] = {
"SIGNONE",
#ifdef SIG32
"SIG32",
#endif
#ifdef SIGABRT
"SIGABRT",
#endif
#ifdef SIGALRM
"SIGALRM",
#endif
#ifdef SIGBUS
"SIGBUS",
#endif
#ifdef SIGCANCEL
"SIGCANCEL",
#endif
#ifdef SIGCHLD
"SIGCHLD",
#endif
#ifdef SIGCLD
"SIGCLD",
#endif
#ifdef SIGCONT
"SIGCONT",
#endif
#ifdef SIGEMT
"SIGEMT",
#endif
#ifdef SIGFPE
"SIGFPE",
#endif
#ifdef SIGFREEZE
"SIGFREEZE",
#endif
#ifdef SIGHUP
"SIGHUP",
#endif
#ifdef SIGILL
"SIGILL",
#endif
#ifdef SIGINT
"SIGINT",
#endif
#ifdef SIGIO
"SIGIO",
#endif
#ifdef SIGIOT
"SIGIOT",
#endif
#ifdef SIGKILL
"SIGKILL",
#endif
#ifdef SIGLOST
"SIGLOST",
#endif
#ifdef SIGLWP
"SIGLWP",
#endif
#ifdef SIGPIPE
"SIGPIPE",
#endif
#ifdef SIGPOLL
"SIGPOLL",
#endif
#ifdef SIGPROF
"SIGPROF",
#endif
#ifdef SIGQUIT
"SIGQUIT",
#endif
#ifdef SIGSEGV
"SIGSEGV",
#endif
#ifdef SIGSTKFLT
"SIGSTKFLT",
#endif
#ifdef SIGSYS
"SIGSYS",
#endif
#ifdef SIGTERM
"SIGTERM",
#endif
#ifdef SIGUSR1
"SIGUSR1",
#endif
#ifdef SIGUSR2
"SIGUSR2",
#endif
#ifdef SIGTRAP
"SIGTRAP",
#endif
#ifdef SIGSTOP
"SIGSTOP",
#endif
#ifdef SIGTHAW
"SIGTHAW",
#endif
#ifdef SIGTSTP
"SIGTSTP",
#endif
#ifdef SIGTTIN
"SIGTTIN",
#endif
#ifdef SIGTTOU
"SIGTTOU",
#endif
#ifdef SIGPWR
"SIGPWR",
#endif
#ifdef SIGURG
"SIGURG",
#endif
#ifdef SIGUNUSED
"SIGUNUSED",
#endif
#ifdef SIGVTALRM
"SIGVTALRM",
#endif
#ifdef SIGWAITING
"SIGWAITING",
#endif
#ifdef SIGWINCH
"SIGWINCH",
#endif
#ifdef SIGXCPU
"SIGXCPU",
#endif
#ifdef SIGXFSZ
"SIGXFSZ",
#endif
"SIGNONE"};
int namedsigs = sizeof (sigs) / sizeof (int);
int nsigs;
int *oksigs;
int *oksigs_nodefault;
int *oksigs_stop;
void comment (char const *msg) {
#ifdef DEBUG
fprintf (stderr, "%s\n", msg);
fflush (stderr);
#endif
}
void handler (int sig) {
if (sig == SIGALRM) {
comment ("==> in handler for SIGALRM");
} else {
comment ("==> in handler: unexpected signal");
exit (-1);
}
}
void handler_parent (int sig) {
if (sig == SIGALRM) {
comment ("==> PARENT: in handler for SIGALRM");
} else {
comment ("==> PARENT: in handler: unexpected signal");
kill (0, SIGKILL);
exit (-1);
}
}
void print_package
(int *oksigs, int *oksigs_nodefault, int *oksigs_stop) {
int sig;
FILE *fp;
fprintf (stderr,"creating package POSIX.Implementation.OK_Signals\n");
if (! (fp = fopen (GENDIR "/posix-implementation-ok_signals.ads", "w"))) {
perror ("posix-implemenation-ok_signals.ads");
exit (-1);
}
fprintf (fp, "package POSIX.Implementation.OK_Signals is\n");
fprintf (fp, "\n");
fprintf (fp, " -- OK (Sig) = True iff we can use Sig"
" with sigwait ().\n\n");
fprintf (fp, " OK : constant array (0 .. %d) of Boolean :=\n",
nsigs - 1);
fprintf (fp, " (");
for (sig = 0; sig < nsigs; sig++) {
if (oksigs_nodefault[sig] == 1) fprintf (fp, " True");
else fprintf (fp, "False");
if (sig == nsigs - 1) fprintf (fp, ");\n");
else if (sig % 10 == 9) fprintf (fp, ",\n ");
else fprintf (fp, ", ");
}
fprintf (fp, "\n");
fprintf (fp, " -- Default_Is_Ignore (Sig) = True iff we need to"
" override the default\n");
fprintf (fp, " -- treatment of Sig with a do-nothing handler"
" before we try to\n");
fprintf (fp, " -- use sigwait() with it.\n\n");
fprintf (fp, " Default_Is_Ignore : constant array"
" (0 .. %d) of Boolean :=\n",
nsigs - 1);
fprintf (fp, " (");
for (sig = 0; sig < nsigs; sig++) {
if ((oksigs[sig] != 1) && (oksigs_nodefault[sig] == 1))
fprintf (fp, " True");
else fprintf (fp, "False");
if (sig == nsigs - 1) fprintf (fp, ");\n");
else if (sig % 10 == 9) fprintf (fp, ",\n ");
else fprintf (fp, ", ");
}
fprintf (fp, "\n -- Default_Is_Stop (Sig) = True iff the default"
" action of Sig\n -- is to stop the process.\n\n");
fprintf (fp, " Default_Is_Stop : constant array (0 .. %d)"
" of Boolean :=\n",
nsigs - 1);
fprintf (fp, " (");
for (sig = 0; sig < nsigs; sig++) {
if (oksigs_stop[sig] == 1)
fprintf (fp, " True");
else fprintf (fp, "False");
if (sig == nsigs - 1) fprintf (fp, ");\n");
else if (sig % 10 == 9) fprintf (fp, ",\n ");
else fprintf (fp, ", ");
}
fprintf (fp, "\nend POSIX.Implementation.OK_Signals;\n");
fclose (fp);
}
int guess_nsigs () {
/* Try to find out the range of valid signals.
We have not yet discovered a portable C way of doing this.
We assume the range starts at 0 and is continuous up to some
limit.
We need this becuase we want to represent sets of signals as
Boolean arrays.
We considered using sigset_t directly, and would have liked
to do so, but had two problems:
(1) sigset_t apparently allows the use of dynamically allocated memory
(2) we could not figure out how to check for signal validity;
in particular, we needed a way to check for whether a given signal
is reserved by the Ada runtime system.
*/
// Take care: similar code in c-posix.c
sigset_t set;
int sig;
int result;
int last_good = -1;
int first_bad = -1;
sigfillset (&set);
for (sig = 0; sig < 1024; sig++) {
result = sigismember (&set, sig);
if (result == 1) {
last_good = sig;
first_bad = -1;
} else if (first_bad == -1) {
if (sig == 0) {
fprintf (stderr, "WARNING: C library problem? "
"sigfillset does not include zero\n");
} else first_bad = sig;
}
}
if (last_good == 1023)
fprintf (stderr, "WARNING: signal range estimate probably too small\n");
if (first_bad < last_good) {
fprintf (stderr, "WARNING: signal range estimate may be invalid\n");
last_good = first_bad - 1;
}
#if defined(NSIG)
if (last_good >= NSIG) return NSIG;
else return last_good + 1;
#else
return last_good + 1;
#endif
}
void parent_process(pid_t child, int *oksigs, int sig) {
/* Monitor the child process until it terminates.
If the child process stops, wake it up.
If the child process dies via signal, restart it and tell it to
skip the last signal it was trying.
*/
pid_t ret;
int status;
struct sigaction act;
act.sa_flags = 0;
act.sa_handler = handler_parent;
if (sigaction (SIGALRM, &act, NULL)) perror ("sigaction (handler_parent)");
while (1) {
alarm (30);
comment (" PARENT: awaiting child status");
fflush (stderr);
ret = waitpid ( (pid_t) -1, &status, WUNTRACED);
fflush (stderr);
if (ret == -1) {
if (errno == EINTR) {
comment (" PARENT: timed out, sending SIGCONT");
fflush (stderr);
kill (child, SIGCONT);
alarm (0);
sleep (1);
continue;
}
comment (" PARENT: waitpid failed");
kill (0, SIGKILL);
exit (-1);
}
if (ret != child) {
comment (" PARENT: unknown child");
kill (0, SIGKILL);
exit (-1);
}
if (WIFSTOPPED (status)) {
oksigs_stop [sig] = 1;
comment (" PARENT: sending SIGCONT to stopped child");
kill (child, SIGCONT);
alarm (0);
sleep (1);
continue;
}
if (WIFEXITED (status)) {
if (WEXITSTATUS (status) != 1)
comment (" PARENT: child exited abnormally");
else {
oksigs [sig] = 1;
comment (" PARENT: child exited normally");
}
return;
}
if (WIFSIGNALED (status)) {
comment(" PARENT: child killed by signal");
fprintf (stderr, "child process killed by signal %d\n", WTERMSIG (status));
return;
}
comment (" PARENT: invalid child status %x");
kill (0, SIGKILL);
exit (-1);
}
}
void test_signal (int nodefaults, int signal) {
struct sigaction act;
int sig;
sigset_t set, oset;
int ret;
act.sa_flags = 0;
act.sa_handler = handler;
#ifdef LYNX_SIGTHREADKILL_HACK
/*
Attempting to test SIGTHREADKILL on LynxOS will kill both
the child and the parent process: The call to sigaction fails
and falls through to kill (0, SIGKILL).
This code works around a problem specific to LynxOS, where
signal 24 is reserved by the user space portion of the
pthreads implementation. It should be replaced by a general
mechanism for skipping problematic signals.
*/
if (signal == SIGTHREADKILL) {
fprintf (stderr, "Reserved by C library.\n");
fflush (stderr);
exit (-1);
}
#endif /* LYNX_SIGTHREADKILL_HACK */
if (sigaction (signal, &act, NULL)) {
if (errno == EINVAL) {
fprintf (stderr, "cannot be caught\n");
fflush (stderr);
exit (-1);
} else {
fprintf (stderr, " *** sigaction: %s\n", strerror (errno));
fflush (stderr);
kill (0, SIGKILL);
exit (-1);
}
}
if (! nodefaults) {
act.sa_handler = SIG_IGN;
if (sigaction (signal, &act, NULL)) {
if (errno == EINVAL) {
fprintf (stderr, "cannot be ignored\n");
fflush (stderr);
exit (-1);
} else {
fprintf (stderr, " *** sigaction: %s\n", strerror (errno));
fflush (stderr);
kill (0, SIGKILL);
exit (-1);
}
}
}
if (! nodefaults) {
act.sa_handler = SIG_DFL;
if (sigaction (signal, &act, NULL)) {
fprintf (stderr, " *** sigaction: %s\n", strerror (errno));
fflush (stderr);
kill (0, SIGKILL);
exit (-1);
}
}
if (sigemptyset (&set)) perror ("sigemptyset");
if (sigaddset (&set, signal)) perror ("sigaddset");
if (sigaddset (&set, SIGALRM)) perror ("sigaddset");
comment (" masking signal");
if ((ret = pthread_sigmask (SIG_BLOCK, &set, NULL)))
fprintf (stderr, " *** pthread_sigmask (SIG_BLOCK): %s\n",
strerror (ret));
if ((ret = pthread_sigmask (SIG_BLOCK, &set, &oset)))
fprintf (stderr, " *** pthread_sigmask (SIG_BLOCK 2): %s\n",
strerror (ret));
if (sigismember (&oset, signal) == 0) {
/* we are unable to mask this signal */
fprintf (stderr, "cannot be masked.\n");
exit (-1);
}
comment (" sending signal to self");
if (kill (getpid (), signal)) perror ("kill");
comment (" setting one second timeout");
alarm (1);
comment (" doing sigwait");
#ifndef _CMA_OS_
if (ret = sigwait (&set, &sig)) {
#else
ret = sigwait (&set);
if (ret == -1)
ret = errno;
else {
sig = ret;
ret = 0;
}
if (ret) {
#endif
fprintf (stderr, "*** sigwait: %s\n", strerror (ret));
} else if (sig == signal) {
fprintf (stderr, "works OK.\n");
exit (1); /* signal is OK */
} else if (sig == SIGALRM) {
fprintf (stderr, "*** timed out\n");
} else {
fprintf (stderr, "*** wrong signal: %d\n", sig);
}
exit (-1);
}
void test_signals (int nodefaults, int *oksigs) {
/* Test each signal, to see if it works with sigwait().
If nodefault != 0 then override the default treatment
by installing a dummy handler.
*/
int i;
int signal;
pid_t child;
if (nodefaults)
fprintf (stderr, "testing signals without default treatments\n");
else
fprintf (stderr, "testing signals with default treatments\n");
for (signal = 1; signal < nsigs; signal++) {
for (i = 0; i < namedsigs; i++)
if (sigs[i] == signal) break;
if (i < namedsigs)
fprintf (stderr, "testing signal: %2d %10s ...", signal, signames[i]);
else
fprintf (stderr, "testing signal: %2d ...", signal);
fflush (stderr);
if ((child = fork ()))
parent_process (child, oksigs, signal);
else {
test_signal (nodefaults, signal);
fprintf (stderr, "*** should never return ***");
exit (-1);
}
}
}
int main (int argc, char *argv[]){
int i;
struct sigaction act;
nsigs = guess_nsigs();
fprintf (stderr, "nsigs: %d\n", nsigs);
oksigs = (int *) malloc (nsigs * sizeof (int));
oksigs_nodefault = (int *) malloc (nsigs * sizeof (int));
oksigs_stop = (int *) malloc (nsigs * sizeof (int));
for (i = 0; i < nsigs; i++)
oksigs[i] = oksigs_nodefault[i] = oksigs_stop[i]= 0;
act.sa_flags = 0;
act.sa_handler = handler;
if (sigaction (SIGALRM, &act, NULL)) perror ("sigaction (handler)");
#ifdef DEBUG
comment ("sending 3 SIGALRM's, to test handler");
fflush (stderr);
kill (getpid (), SIGALRM);
kill (getpid (), SIGALRM);
kill (getpid (), SIGALRM);
#endif
test_signals (0, oksigs);
test_signals (1, oksigs_nodefault);
print_package (oksigs, oksigs_nodefault, oksigs_stop);
fprintf (stderr, "done.\n");
return 0;
}