/
signal.c
1188 lines (1073 loc) · 24.4 KB
/
signal.c
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/**********************************************************************
signal.c -
$Author$
created at: Tue Dec 20 10:13:44 JST 1994
Copyright (C) 1993-2007 Yukihiro Matsumoto
Copyright (C) 2000 Network Applied Communication Laboratory, Inc.
Copyright (C) 2000 Information-technology Promotion Agency, Japan
**********************************************************************/
#include "ruby/ruby.h"
#include "vm_core.h"
#include <signal.h>
#include <stdio.h>
#include <errno.h>
#include "ruby_atomic.h"
#include "eval_intern.h"
#if defined(__native_client__) && defined(NACL_NEWLIB)
# include "nacl/signal.h"
#endif
#ifdef NEED_RUBY_ATOMIC_OPS
rb_atomic_t
ruby_atomic_exchange(rb_atomic_t *ptr, rb_atomic_t val)
{
rb_atomic_t old = *ptr;
*ptr = val;
return old;
}
rb_atomic_t
ruby_atomic_compare_and_swap(rb_atomic_t *ptr, rb_atomic_t cmp,
rb_atomic_t newval)
{
rb_atomic_t old = *ptr;
if (old == cmp) {
*ptr = newval;
}
return old;
}
#endif
#if defined(__BEOS__) || defined(__HAIKU__)
#undef SIGBUS
#endif
#ifndef NSIG
# define NSIG (_SIGMAX + 1) /* For QNX */
#endif
static const struct signals {
const char *signm;
int signo;
} siglist [] = {
{"EXIT", 0},
#ifdef SIGHUP
{"HUP", SIGHUP},
#endif
{"INT", SIGINT},
#ifdef SIGQUIT
{"QUIT", SIGQUIT},
#endif
#ifdef SIGILL
{"ILL", SIGILL},
#endif
#ifdef SIGTRAP
{"TRAP", SIGTRAP},
#endif
#ifdef SIGIOT
{"IOT", SIGIOT},
#endif
#ifdef SIGABRT
{"ABRT", SIGABRT},
#endif
#ifdef SIGEMT
{"EMT", SIGEMT},
#endif
#ifdef SIGFPE
{"FPE", SIGFPE},
#endif
#ifdef SIGKILL
{"KILL", SIGKILL},
#endif
#ifdef SIGBUS
{"BUS", SIGBUS},
#endif
#ifdef SIGSEGV
{"SEGV", SIGSEGV},
#endif
#ifdef SIGSYS
{"SYS", SIGSYS},
#endif
#ifdef SIGPIPE
{"PIPE", SIGPIPE},
#endif
#ifdef SIGALRM
{"ALRM", SIGALRM},
#endif
#ifdef SIGTERM
{"TERM", SIGTERM},
#endif
#ifdef SIGURG
{"URG", SIGURG},
#endif
#ifdef SIGSTOP
{"STOP", SIGSTOP},
#endif
#ifdef SIGTSTP
{"TSTP", SIGTSTP},
#endif
#ifdef SIGCONT
{"CONT", SIGCONT},
#endif
#ifdef SIGCHLD
{"CHLD", SIGCHLD},
#endif
#ifdef SIGCLD
{"CLD", SIGCLD},
#else
# ifdef SIGCHLD
{"CLD", SIGCHLD},
# endif
#endif
#ifdef SIGTTIN
{"TTIN", SIGTTIN},
#endif
#ifdef SIGTTOU
{"TTOU", SIGTTOU},
#endif
#ifdef SIGIO
{"IO", SIGIO},
#endif
#ifdef SIGXCPU
{"XCPU", SIGXCPU},
#endif
#ifdef SIGXFSZ
{"XFSZ", SIGXFSZ},
#endif
#ifdef SIGVTALRM
{"VTALRM", SIGVTALRM},
#endif
#ifdef SIGPROF
{"PROF", SIGPROF},
#endif
#ifdef SIGWINCH
{"WINCH", SIGWINCH},
#endif
#ifdef SIGUSR1
{"USR1", SIGUSR1},
#endif
#ifdef SIGUSR2
{"USR2", SIGUSR2},
#endif
#ifdef SIGLOST
{"LOST", SIGLOST},
#endif
#ifdef SIGMSG
{"MSG", SIGMSG},
#endif
#ifdef SIGPWR
{"PWR", SIGPWR},
#endif
#ifdef SIGPOLL
{"POLL", SIGPOLL},
#endif
#ifdef SIGDANGER
{"DANGER", SIGDANGER},
#endif
#ifdef SIGMIGRATE
{"MIGRATE", SIGMIGRATE},
#endif
#ifdef SIGPRE
{"PRE", SIGPRE},
#endif
#ifdef SIGGRANT
{"GRANT", SIGGRANT},
#endif
#ifdef SIGRETRACT
{"RETRACT", SIGRETRACT},
#endif
#ifdef SIGSOUND
{"SOUND", SIGSOUND},
#endif
#ifdef SIGINFO
{"INFO", SIGINFO},
#endif
{NULL, 0}
};
static int
signm2signo(const char *nm)
{
const struct signals *sigs;
for (sigs = siglist; sigs->signm; sigs++)
if (strcmp(sigs->signm, nm) == 0)
return sigs->signo;
return 0;
}
static const char*
signo2signm(int no)
{
const struct signals *sigs;
for (sigs = siglist; sigs->signm; sigs++)
if (sigs->signo == no)
return sigs->signm;
return 0;
}
/*
* call-seq:
* Signal.signame(signo) -> string
*
* convert signal number to signal name
*
* Signal.trap("INT") { |signo| puts Signal.signame(signo) }
* Process.kill("INT", 0)
*
* <em>produces:</em>
*
* INT
*/
static VALUE
sig_signame(VALUE recv, VALUE signo)
{
const char *signame = signo2signm(NUM2INT(signo));
return rb_str_new_cstr(signame);
}
const char *
ruby_signal_name(int no)
{
return signo2signm(no);
}
/*
* call-seq:
* SignalException.new(sig_name) -> signal_exception
* SignalException.new(sig_number [, name]) -> signal_exception
*
* Construct a new SignalException object. +sig_name+ should be a known
* signal name.
*/
static VALUE
esignal_init(int argc, VALUE *argv, VALUE self)
{
int argnum = 1;
VALUE sig = Qnil;
int signo;
const char *signm;
if (argc > 0) {
sig = rb_check_to_integer(argv[0], "to_int");
if (!NIL_P(sig)) argnum = 2;
else sig = argv[0];
}
rb_check_arity(argc, 1, argnum);
if (argnum == 2) {
signo = NUM2INT(sig);
if (signo < 0 || signo > NSIG) {
rb_raise(rb_eArgError, "invalid signal number (%d)", signo);
}
if (argc > 1) {
sig = argv[1];
}
else {
signm = signo2signm(signo);
if (signm) {
sig = rb_sprintf("SIG%s", signm);
}
else {
sig = rb_sprintf("SIG%u", signo);
}
}
}
else {
signm = SYMBOL_P(sig) ? rb_id2name(SYM2ID(sig)) : StringValuePtr(sig);
if (strncmp(signm, "SIG", 3) == 0) signm += 3;
signo = signm2signo(signm);
if (!signo) {
rb_raise(rb_eArgError, "unsupported name `SIG%s'", signm);
}
sig = rb_sprintf("SIG%s", signm);
}
rb_call_super(1, &sig);
rb_iv_set(self, "signo", INT2NUM(signo));
return self;
}
/*
* call-seq:
* signal_exception.signo -> num
*
* Returns a signal number.
*/
static VALUE
esignal_signo(VALUE self)
{
return rb_iv_get(self, "signo");
}
/* :nodoc: */
static VALUE
interrupt_init(int argc, VALUE *argv, VALUE self)
{
VALUE args[2];
args[0] = INT2FIX(SIGINT);
rb_scan_args(argc, argv, "01", &args[1]);
return rb_call_super(2, args);
}
void
ruby_default_signal(int sig)
{
signal(sig, SIG_DFL);
raise(sig);
}
/*
* call-seq:
* Process.kill(signal, pid, ...) -> fixnum
*
* Sends the given signal to the specified process id(s) if _pid_ is positive.
* If _pid_ is zero _signal_ is sent to all processes whose group ID is equal
* to the group ID of the process. _signal_ may be an integer signal number or
* a POSIX signal name (either with or without a +SIG+ prefix). If _signal_ is
* negative (or starts with a minus sign), kills process groups instead of
* processes. Not all signals are available on all platforms.
*
* pid = fork do
* Signal.trap("HUP") { puts "Ouch!"; exit }
* # ... do some work ...
* end
* # ...
* Process.kill("HUP", pid)
* Process.wait
*
* <em>produces:</em>
*
* Ouch!
*
* If _signal_ is an integer but wrong for signal,
* <code>Errno::EINVAL</code> or +RangeError+ will be raised.
* Otherwise unless _signal_ is a +String+ or a +Symbol+, and a known
* signal name, +ArgumentError+ will be raised.
*
* Also, <code>Errno::ESRCH</code> or +RangeError+ for invalid _pid_,
* <code>Errno::EPERM</code> when failed because of no privilege,
* will be raised. In these cases, signals may have been sent to
* preceding processes.
*/
VALUE
rb_f_kill(int argc, VALUE *argv)
{
#ifndef HAVE_KILLPG
#define killpg(pg, sig) kill(-(pg), (sig))
#endif
int negative = 0;
int sig;
int i;
volatile VALUE str;
const char *s;
rb_secure(2);
rb_check_arity(argc, 2, UNLIMITED_ARGUMENTS);
switch (TYPE(argv[0])) {
case T_FIXNUM:
sig = FIX2INT(argv[0]);
break;
case T_SYMBOL:
s = rb_id2name(SYM2ID(argv[0]));
if (!s) rb_raise(rb_eArgError, "bad signal");
goto str_signal;
case T_STRING:
s = RSTRING_PTR(argv[0]);
str_signal:
if (s[0] == '-') {
negative++;
s++;
}
if (strncmp("SIG", s, 3) == 0)
s += 3;
if ((sig = signm2signo(s)) == 0)
rb_raise(rb_eArgError, "unsupported name `SIG%s'", s);
if (negative)
sig = -sig;
break;
default:
str = rb_check_string_type(argv[0]);
if (!NIL_P(str)) {
s = RSTRING_PTR(str);
goto str_signal;
}
rb_raise(rb_eArgError, "bad signal type %s",
rb_obj_classname(argv[0]));
break;
}
if (sig < 0) {
sig = -sig;
for (i=1; i<argc; i++) {
if (killpg(NUM2PIDT(argv[i]), sig) < 0)
rb_sys_fail(0);
}
}
else {
for (i=1; i<argc; i++) {
if (kill(NUM2PIDT(argv[i]), sig) < 0)
rb_sys_fail(0);
}
}
return INT2FIX(i-1);
}
static struct {
rb_atomic_t cnt[RUBY_NSIG];
rb_atomic_t size;
} signal_buff;
#ifdef __dietlibc__
#define sighandler_t sh_t
#endif
typedef RETSIGTYPE (*sighandler_t)(int);
#ifdef USE_SIGALTSTACK
typedef void ruby_sigaction_t(int, siginfo_t*, void*);
#define SIGINFO_ARG , siginfo_t *info, void *ctx
#else
typedef RETSIGTYPE ruby_sigaction_t(int);
#define SIGINFO_ARG
#endif
#ifdef USE_SIGALTSTACK
int rb_sigaltstack_size(void)
{
/* XXX: BSD_vfprintf() uses >1500KiB stack and x86-64 need >5KiB stack. */
int size = 8192;
#ifdef MINSIGSTKSZ
if (size < MINSIGSTKSZ)
size = MINSIGSTKSZ;
#endif
#if defined(HAVE_SYSCONF) && defined(_SC_PAGE_SIZE)
{
int pagesize;
pagesize = (int)sysconf(_SC_PAGE_SIZE);
if (size < pagesize)
size = pagesize;
}
#endif
return size;
}
/* alternate stack for SIGSEGV */
void
rb_register_sigaltstack(rb_thread_t *th)
{
stack_t newSS, oldSS;
if (!th->altstack)
rb_bug("rb_register_sigaltstack: th->altstack not initialized\n");
newSS.ss_sp = th->altstack;
newSS.ss_size = rb_sigaltstack_size();
newSS.ss_flags = 0;
sigaltstack(&newSS, &oldSS); /* ignore error. */
}
#endif /* USE_SIGALTSTACK */
#ifdef POSIX_SIGNAL
static sighandler_t
ruby_signal(int signum, sighandler_t handler)
{
struct sigaction sigact, old;
#if 0
rb_trap_accept_nativethreads[signum] = 0;
#endif
sigemptyset(&sigact.sa_mask);
#ifdef USE_SIGALTSTACK
sigact.sa_sigaction = (ruby_sigaction_t*)handler;
sigact.sa_flags = SA_SIGINFO;
#else
sigact.sa_handler = handler;
sigact.sa_flags = 0;
#endif
#ifdef SA_NOCLDWAIT
if (signum == SIGCHLD && handler == SIG_IGN)
sigact.sa_flags |= SA_NOCLDWAIT;
#endif
#if defined(SA_ONSTACK) && defined(USE_SIGALTSTACK)
if (signum == SIGSEGV
#ifdef SIGBUS
|| signum == SIGBUS
#endif
)
sigact.sa_flags |= SA_ONSTACK;
#endif
if (sigaction(signum, &sigact, &old) < 0) {
if (errno != 0 && errno != EINVAL) {
rb_bug_errno("sigaction", errno);
}
}
return old.sa_handler;
}
sighandler_t
posix_signal(int signum, sighandler_t handler)
{
return ruby_signal(signum, handler);
}
#else /* !POSIX_SIGNAL */
#define ruby_signal(sig,handler) (/* rb_trap_accept_nativethreads[(sig)] = 0,*/ signal((sig),(handler)))
#if 0 /* def HAVE_NATIVETHREAD */
static sighandler_t
ruby_nativethread_signal(int signum, sighandler_t handler)
{
sighandler_t old;
old = signal(signum, handler);
rb_trap_accept_nativethreads[signum] = 1;
return old;
}
#endif
#endif
static RETSIGTYPE
sighandler(int sig)
{
ATOMIC_INC(signal_buff.cnt[sig]);
ATOMIC_INC(signal_buff.size);
rb_thread_wakeup_timer_thread();
#if !defined(BSD_SIGNAL) && !defined(POSIX_SIGNAL)
ruby_signal(sig, sighandler);
#endif
}
int
rb_signal_buff_size(void)
{
return signal_buff.size;
}
#if HAVE_PTHREAD_H
#include <pthread.h>
#endif
static void
rb_disable_interrupt(void)
{
#ifdef HAVE_PTHREAD_SIGMASK
sigset_t mask;
sigfillset(&mask);
pthread_sigmask(SIG_SETMASK, &mask, NULL);
#endif
}
static void
rb_enable_interrupt(void)
{
#ifdef HAVE_PTHREAD_SIGMASK
sigset_t mask;
sigemptyset(&mask);
pthread_sigmask(SIG_SETMASK, &mask, NULL);
#endif
}
int
rb_get_next_signal(void)
{
int i, sig = 0;
if (signal_buff.size != 0) {
for (i=1; i<RUBY_NSIG; i++) {
if (signal_buff.cnt[i] > 0) {
ATOMIC_DEC(signal_buff.cnt[i]);
ATOMIC_DEC(signal_buff.size);
sig = i;
break;
}
}
}
return sig;
}
#ifdef USE_SIGALTSTACK
static void
check_stack_overflow(const void *addr)
{
int ruby_stack_overflowed_p(const rb_thread_t *, const void *);
NORETURN(void ruby_thread_stack_overflow(rb_thread_t *th));
rb_thread_t *th = GET_THREAD();
if (ruby_stack_overflowed_p(th, addr)) {
ruby_thread_stack_overflow(th);
}
}
#define CHECK_STACK_OVERFLOW() check_stack_overflow(info->si_addr)
#else
#define CHECK_STACK_OVERFLOW() (void)0
#endif
#ifdef SIGBUS
static RETSIGTYPE
sigbus(int sig SIGINFO_ARG)
{
/*
* Mac OS X makes KERN_PROTECTION_FAILURE when thread touch guard page.
* and it's delivered as SIGBUS instaed of SIGSEGV to userland. It's crazy
* wrong IMHO. but anyway we have to care it. Sigh.
*/
#if defined __APPLE__
CHECK_STACK_OVERFLOW();
#endif
rb_bug("Bus Error");
}
#endif
#ifdef SIGSEGV
static void ruby_abort(void)
{
#ifdef __sun
/* Solaris's abort() is async signal unsafe. Of course, it is not
* POSIX compliant.
*/
raise(SIGABRT);
#else
abort();
#endif
}
static int segv_received = 0;
extern int ruby_disable_gc_stress;
static RETSIGTYPE
sigsegv(int sig SIGINFO_ARG)
{
if (segv_received) {
ssize_t RB_UNUSED_VAR(err);
char msg[] = "SEGV received in SEGV handler\n";
err = write(2, msg, sizeof(msg));
ruby_abort();
}
CHECK_STACK_OVERFLOW();
segv_received = 1;
ruby_disable_gc_stress = 1;
rb_bug("Segmentation fault");
}
#endif
static void
signal_exec(VALUE cmd, int safe, int sig)
{
rb_thread_t *cur_th = GET_THREAD();
volatile unsigned long old_interrupt_mask = cur_th->interrupt_mask;
int state;
cur_th->interrupt_mask |= TRAP_INTERRUPT_MASK;
TH_PUSH_TAG(cur_th);
if ((state = EXEC_TAG()) == 0) {
VALUE signum = INT2NUM(sig);
rb_eval_cmd(cmd, rb_ary_new3(1, signum), safe);
}
TH_POP_TAG();
cur_th = GET_THREAD();
cur_th->interrupt_mask = old_interrupt_mask;
if (state) {
/* XXX: should be replaced with rb_threadptr_pending_interrupt_enque() */
JUMP_TAG(state);
}
}
void
rb_trap_exit(void)
{
rb_vm_t *vm = GET_VM();
VALUE trap_exit = vm->trap_list[0].cmd;
if (trap_exit) {
vm->trap_list[0].cmd = 0;
signal_exec(trap_exit, vm->trap_list[0].safe, 0);
}
}
void
rb_signal_exec(rb_thread_t *th, int sig)
{
rb_vm_t *vm = GET_VM();
VALUE cmd = vm->trap_list[sig].cmd;
int safe = vm->trap_list[sig].safe;
if (cmd == 0) {
switch (sig) {
case SIGINT:
rb_interrupt();
break;
#ifdef SIGHUP
case SIGHUP:
#endif
#ifdef SIGQUIT
case SIGQUIT:
#endif
#ifdef SIGTERM
case SIGTERM:
#endif
#ifdef SIGALRM
case SIGALRM:
#endif
#ifdef SIGUSR1
case SIGUSR1:
#endif
#ifdef SIGUSR2
case SIGUSR2:
#endif
rb_threadptr_signal_raise(th, sig);
break;
}
}
else if (cmd == Qundef) {
rb_threadptr_signal_exit(th);
}
else {
signal_exec(cmd, safe, sig);
}
}
static sighandler_t
default_handler(int sig)
{
sighandler_t func;
switch (sig) {
case SIGINT:
#ifdef SIGHUP
case SIGHUP:
#endif
#ifdef SIGQUIT
case SIGQUIT:
#endif
#ifdef SIGTERM
case SIGTERM:
#endif
#ifdef SIGALRM
case SIGALRM:
#endif
#ifdef SIGUSR1
case SIGUSR1:
#endif
#ifdef SIGUSR2
case SIGUSR2:
#endif
func = sighandler;
break;
#ifdef SIGBUS
case SIGBUS:
func = (sighandler_t)sigbus;
break;
#endif
#ifdef SIGSEGV
case SIGSEGV:
func = (sighandler_t)sigsegv;
break;
#endif
#ifdef SIGPIPE
case SIGPIPE:
func = SIG_IGN;
break;
#endif
default:
func = SIG_DFL;
break;
}
return func;
}
static sighandler_t
trap_handler(VALUE *cmd, int sig)
{
sighandler_t func = sighandler;
VALUE command;
if (NIL_P(*cmd)) {
func = SIG_IGN;
}
else {
command = rb_check_string_type(*cmd);
if (NIL_P(command) && SYMBOL_P(*cmd)) {
command = rb_id2str(SYM2ID(*cmd));
if (!command) rb_raise(rb_eArgError, "bad handler");
}
if (!NIL_P(command)) {
SafeStringValue(command); /* taint check */
*cmd = command;
switch (RSTRING_LEN(command)) {
case 0:
goto sig_ign;
break;
case 14:
if (strncmp(RSTRING_PTR(command), "SYSTEM_DEFAULT", 14) == 0) {
func = SIG_DFL;
*cmd = 0;
}
break;
case 7:
if (strncmp(RSTRING_PTR(command), "SIG_IGN", 7) == 0) {
sig_ign:
func = SIG_IGN;
*cmd = 0;
}
else if (strncmp(RSTRING_PTR(command), "SIG_DFL", 7) == 0) {
sig_dfl:
func = default_handler(sig);
*cmd = 0;
}
else if (strncmp(RSTRING_PTR(command), "DEFAULT", 7) == 0) {
goto sig_dfl;
}
break;
case 6:
if (strncmp(RSTRING_PTR(command), "IGNORE", 6) == 0) {
goto sig_ign;
}
break;
case 4:
if (strncmp(RSTRING_PTR(command), "EXIT", 4) == 0) {
*cmd = Qundef;
}
break;
}
}
else {
rb_proc_t *proc;
GetProcPtr(*cmd, proc);
(void)proc;
}
}
return func;
}
static int
trap_signm(VALUE vsig)
{
int sig = -1;
const char *s;
switch (TYPE(vsig)) {
case T_FIXNUM:
sig = FIX2INT(vsig);
if (sig < 0 || sig >= NSIG) {
rb_raise(rb_eArgError, "invalid signal number (%d)", sig);
}
break;
case T_SYMBOL:
s = rb_id2name(SYM2ID(vsig));
if (!s) rb_raise(rb_eArgError, "bad signal");
goto str_signal;
default:
s = StringValuePtr(vsig);
str_signal:
if (strncmp("SIG", s, 3) == 0)
s += 3;
sig = signm2signo(s);
if (sig == 0 && strcmp(s, "EXIT") != 0)
rb_raise(rb_eArgError, "unsupported signal SIG%s", s);
}
return sig;
}
static VALUE
trap(int sig, sighandler_t func, VALUE command)
{
sighandler_t oldfunc;
VALUE oldcmd;
rb_vm_t *vm = GET_VM();
/*
* Be careful. ruby_signal() and trap_list[sig].cmd must be changed
* atomically. In current implementation, we only need to don't call
* RUBY_VM_CHECK_INTS().
*/
oldfunc = ruby_signal(sig, func);
oldcmd = vm->trap_list[sig].cmd;
switch (oldcmd) {
case 0:
if (oldfunc == SIG_IGN) oldcmd = rb_str_new2("IGNORE");
else if (oldfunc == sighandler) oldcmd = rb_str_new2("DEFAULT");
else oldcmd = Qnil;
break;
case Qundef:
oldcmd = rb_str_new2("EXIT");
break;
}
vm->trap_list[sig].cmd = command;
vm->trap_list[sig].safe = rb_safe_level();
return oldcmd;
}
static int
reserved_signal_p(int signo)
{
/* Synchronous signal can't deliver to main thread */
#ifdef SIGSEGV
if (signo == SIGSEGV)
return 1;
#endif
#ifdef SIGBUS
if (signo == SIGBUS)
return 1;
#endif
#ifdef SIGILL
if (signo == SIGILL)
return 1;
#endif
#ifdef SIGFPE
if (signo == SIGFPE)
return 1;
#endif
/* used ubf internal see thread_pthread.c. */
#ifdef SIGVTALRM
if (signo == SIGVTALRM)
return 1;
#endif
return 0;
}
/*
* call-seq:
* Signal.trap( signal, command ) -> obj
* Signal.trap( signal ) {| | block } -> obj
*
* Specifies the handling of signals. The first parameter is a signal
* name (a string such as ``SIGALRM'', ``SIGUSR1'', and so on) or a
* signal number. The characters ``SIG'' may be omitted from the
* signal name. The command or block specifies code to be run when the
* signal is raised.
* If the command is the string ``IGNORE'' or ``SIG_IGN'', the signal
* will be ignored.
* If the command is ``DEFAULT'' or ``SIG_DFL'', the Ruby's default handler
* will be invoked.
* If the command is ``EXIT'', the script will be terminated by the signal.
* If the command is ``SYSTEM_DEFAULT'', the operating system's default
* handler will be invoked.
* Otherwise, the given command or block will be run.
* The special signal name ``EXIT'' or signal number zero will be
* invoked just prior to program termination.
* trap returns the previous handler for the given signal.
*
* Signal.trap(0, proc { puts "Terminating: #{$$}" })
* Signal.trap("CLD") { puts "Child died" }
* fork && Process.wait
*
* produces:
* Terminating: 27461
* Child died
* Terminating: 27460
*/
static VALUE
sig_trap(int argc, VALUE *argv)
{
int sig;
sighandler_t func;
VALUE cmd;
rb_secure(2);
rb_check_arity(argc, 1, 2);