srclib/sigprocmask.c - nest-hello/libiconv - Git at Google

 /* POSIX compatible signal blocking.
    Copyright (C) 2006-2011 Free Software Foundation, Inc.
    Written by Bruno Haible <bruno@clisp.org>, 2006.

    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; either version 3 of the License, or
    (at your option) any later version.

    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, see <http://www.gnu.org/licenses/>.  */

 #include <config.h>

 /* Specification.  */
 #include <signal.h>

 #include <errno.h>
 #include <stdint.h>
 #include <stdlib.h>

 /* We assume that a platform without POSIX signal blocking functions
    also does not have the POSIX sigaction() function, only the
    signal() function.  We also assume signal() has SysV semantics,
    where any handler is uninstalled prior to being invoked.  This is
    true for Woe32 platforms.  */

 /* We use raw signal(), but also provide a wrapper rpl_signal() so
    that applications can query or change a blocked signal.  */
 #undef signal

 /* Provide invalid signal numbers as fallbacks if the uncatchable
    signals are not defined.  */
 #ifndef SIGKILL
 # define SIGKILL (-1)
 #endif
 #ifndef SIGSTOP
 # define SIGSTOP (-1)
 #endif

 /* On native Windows, as of 2008, the signal SIGABRT_COMPAT is an alias
    for the signal SIGABRT.  Only one signal handler is stored for both
    SIGABRT and SIGABRT_COMPAT.  SIGABRT_COMPAT is not a signal of its own.  */
 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
 # undef SIGABRT_COMPAT
 # define SIGABRT_COMPAT 6
 #endif
 #ifdef SIGABRT_COMPAT
 # define SIGABRT_COMPAT_MASK (1U << SIGABRT_COMPAT)
 #else
 # define SIGABRT_COMPAT_MASK 0
 #endif

 typedef void (*handler_t) (int);

 /* Handling of gnulib defined signals.  */

 #if GNULIB_defined_SIGPIPE
 static handler_t SIGPIPE_handler = SIG_DFL;
 #endif

 #if GNULIB_defined_SIGPIPE
 static handler_t
 ext_signal (int sig, handler_t handler)
 {
   switch (sig)
     {
     case SIGPIPE:
       {
         handler_t old_handler = SIGPIPE_handler;
         SIGPIPE_handler = handler;
         return old_handler;
       }
     default: /* System defined signal */
       return signal (sig, handler);
     }
 }
 # define signal ext_signal
 #endif

 int
 sigismember (const sigset_t *set, int sig)
 {
   if (sig >= 0 && sig < NSIG)
     {
       #ifdef SIGABRT_COMPAT
       if (sig == SIGABRT_COMPAT)
         sig = SIGABRT;
       #endif

       return (*set >> sig) & 1;
     }
   else
     return 0;
 }

 int
 sigemptyset (sigset_t *set)
 {
   *set = 0;
   return 0;
 }

 int
 sigaddset (sigset_t *set, int sig)
 {
   if (sig >= 0 && sig < NSIG)
     {
       #ifdef SIGABRT_COMPAT
       if (sig == SIGABRT_COMPAT)
         sig = SIGABRT;
       #endif

       *set |= 1U << sig;
       return 0;
     }
   else
     {
       errno = EINVAL;
       return -1;
     }
 }

 int
 sigdelset (sigset_t *set, int sig)
 {
   if (sig >= 0 && sig < NSIG)
     {
       #ifdef SIGABRT_COMPAT
       if (sig == SIGABRT_COMPAT)
         sig = SIGABRT;
       #endif

       *set &= ~(1U << sig);
       return 0;
     }
   else
     {
       errno = EINVAL;
       return -1;
     }
 }


 int
 sigfillset (sigset_t *set)
 {
   *set = ((2U << (NSIG - 1)) - 1) & ~ SIGABRT_COMPAT_MASK;
   return 0;
 }

 /* Set of currently blocked signals.  */
 static volatile sigset_t blocked_set /* = 0 */;

 /* Set of currently blocked and pending signals.  */
 static volatile sig_atomic_t pending_array[NSIG] /* = { 0 } */;

 /* Signal handler that is installed for blocked signals.  */
 static void
 blocked_handler (int sig)
 {
   /* Reinstall the handler, in case the signal occurs multiple times
      while blocked.  There is an inherent race where an asynchronous
      signal in between when the kernel uninstalled the handler and
      when we reinstall it will trigger the default handler; oh
      well.  */
   signal (sig, blocked_handler);
   if (sig >= 0 && sig < NSIG)
     pending_array[sig] = 1;
 }

 int
 sigpending (sigset_t *set)
 {
   sigset_t pending = 0;
   int sig;

   for (sig = 0; sig < NSIG; sig++)
     if (pending_array[sig])
       pending |= 1U << sig;
   *set = pending;
   return 0;
 }

 /* The previous signal handlers.
    Only the array elements corresponding to blocked signals are relevant.  */
 static volatile handler_t old_handlers[NSIG];

 int
 sigprocmask (int operation, const sigset_t *set, sigset_t *old_set)
 {
   if (old_set != NULL)
     *old_set = blocked_set;

   if (set != NULL)
     {
       sigset_t new_blocked_set;
       sigset_t to_unblock;
       sigset_t to_block;

       switch (operation)
         {
         case SIG_BLOCK:
           new_blocked_set = blocked_set | *set;
           break;
         case SIG_SETMASK:
           new_blocked_set = *set;
           break;
         case SIG_UNBLOCK:
           new_blocked_set = blocked_set & ~*set;
           break;
         default:
           errno = EINVAL;
           return -1;
         }
       to_unblock = blocked_set & ~new_blocked_set;
       to_block = new_blocked_set & ~blocked_set;

       if (to_block != 0)
         {
           int sig;

           for (sig = 0; sig < NSIG; sig++)
             if ((to_block >> sig) & 1)
               {
                 pending_array[sig] = 0;
                 if ((old_handlers[sig] = signal (sig, blocked_handler)) != SIG_ERR)
                   blocked_set |= 1U << sig;
               }
         }

       if (to_unblock != 0)
         {
           sig_atomic_t received[NSIG];
           int sig;

           for (sig = 0; sig < NSIG; sig++)
             if ((to_unblock >> sig) & 1)
               {
                 if (signal (sig, old_handlers[sig]) != blocked_handler)
                   /* The application changed a signal handler while the signal
                      was blocked, bypassing our rpl_signal replacement.
                      We don't support this.  */
                   abort ();
                 received[sig] = pending_array[sig];
                 blocked_set &= ~(1U << sig);
                 pending_array[sig] = 0;
               }
             else
               received[sig] = 0;

           for (sig = 0; sig < NSIG; sig++)
             if (received[sig])
               raise (sig);
         }
     }
   return 0;
 }

 /* Install the handler FUNC for signal SIG, and return the previous
    handler.  */
 handler_t
 rpl_signal (int sig, handler_t handler)
 {
   /* We must provide a wrapper, so that a user can query what handler
      they installed even if that signal is currently blocked.  */
   if (sig >= 0 && sig < NSIG && sig != SIGKILL && sig != SIGSTOP
       && handler != SIG_ERR)
     {
       #ifdef SIGABRT_COMPAT
       if (sig == SIGABRT_COMPAT)
         sig = SIGABRT;
       #endif

       if (blocked_set & (1U << sig))
         {
           /* POSIX states that sigprocmask and signal are both
              async-signal-safe.  This is not true of our
              implementation - there is a slight data race where an
              asynchronous interrupt on signal A can occur after we
              install blocked_handler but before we have updated
              old_handlers for signal B, such that handler A can see
              stale information if it calls signal(B).  Oh well -
              signal handlers really shouldn't try to manipulate the
              installed handlers of unrelated signals.  */
           handler_t result = old_handlers[sig];
           old_handlers[sig] = handler;
           return result;
         }
       else
         return signal (sig, handler);
     }
   else
     {
       errno = EINVAL;
       return SIG_ERR;
     }
 }

 #if GNULIB_defined_SIGPIPE
 /* Raise the signal SIG.  */
 int
 rpl_raise (int sig)
 # undef raise
 {
   switch (sig)
     {
     case SIGPIPE:
       if (blocked_set & (1U << sig))
         pending_array[sig] = 1;
       else
         {
           handler_t handler = SIGPIPE_handler;
           if (handler == SIG_DFL)
             exit (128 + SIGPIPE);
           else if (handler != SIG_IGN)
             (*handler) (sig);
         }
       return 0;
     default: /* System defined signal */
       return raise (sig);
     }
 }
 #endif
	/* POSIX compatible signal blocking.
	Copyright (C) 2006-2011 Free Software Foundation, Inc.
	Written by Bruno Haible <bruno@clisp.org>, 2006.

	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; either version 3 of the License, or
	(at your option) any later version.

	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, see <http://www.gnu.org/licenses/>. */

	#include <config.h>

	/* Specification. */
	#include <signal.h>

	#include <errno.h>
	#include <stdint.h>
	#include <stdlib.h>

	/* We assume that a platform without POSIX signal blocking functions
	also does not have the POSIX sigaction() function, only the
	signal() function. We also assume signal() has SysV semantics,
	where any handler is uninstalled prior to being invoked. This is
	true for Woe32 platforms. */

	/* We use raw signal(), but also provide a wrapper rpl_signal() so
	that applications can query or change a blocked signal. */
	#undef signal

	/* Provide invalid signal numbers as fallbacks if the uncatchable
	signals are not defined. */
	#ifndef SIGKILL
	# define SIGKILL (-1)
	#endif
	#ifndef SIGSTOP
	# define SIGSTOP (-1)
	#endif

	/* On native Windows, as of 2008, the signal SIGABRT_COMPAT is an alias
	for the signal SIGABRT. Only one signal handler is stored for both
	SIGABRT and SIGABRT_COMPAT. SIGABRT_COMPAT is not a signal of its own. */
	#if (defined _WIN32 \|\| defined __WIN32__) && ! defined __CYGWIN__
	# undef SIGABRT_COMPAT
	# define SIGABRT_COMPAT 6
	#endif
	#ifdef SIGABRT_COMPAT
	# define SIGABRT_COMPAT_MASK (1U << SIGABRT_COMPAT)
	#else
	# define SIGABRT_COMPAT_MASK 0
	#endif

	typedef void (*handler_t) (int);

	/* Handling of gnulib defined signals. */

	#if GNULIB_defined_SIGPIPE
	static handler_t SIGPIPE_handler = SIG_DFL;
	#endif

	#if GNULIB_defined_SIGPIPE
	static handler_t
	ext_signal (int sig, handler_t handler)
	{
	switch (sig)
	{
	case SIGPIPE:
	{
	handler_t old_handler = SIGPIPE_handler;
	SIGPIPE_handler = handler;
	return old_handler;
	}
	default: /* System defined signal */
	return signal (sig, handler);
	}
	}
	# define signal ext_signal
	#endif

	int
	sigismember (const sigset_t *set, int sig)
	{
	if (sig >= 0 && sig < NSIG)
	{
	#ifdef SIGABRT_COMPAT
	if (sig == SIGABRT_COMPAT)
	sig = SIGABRT;
	#endif

	return (*set >> sig) & 1;
	}
	else
	return 0;
	}

	int
	sigemptyset (sigset_t *set)
	{
	*set = 0;
	return 0;
	}

	int
	sigaddset (sigset_t *set, int sig)
	{
	if (sig >= 0 && sig < NSIG)
	{
	#ifdef SIGABRT_COMPAT
	if (sig == SIGABRT_COMPAT)
	sig = SIGABRT;
	#endif

	*set \|= 1U << sig;
	return 0;
	}
	else
	{
	errno = EINVAL;
	return -1;
	}
	}

	int
	sigdelset (sigset_t *set, int sig)
	{
	if (sig >= 0 && sig < NSIG)
	{
	#ifdef SIGABRT_COMPAT
	if (sig == SIGABRT_COMPAT)
	sig = SIGABRT;
	#endif

	*set &= ~(1U << sig);
	return 0;
	}
	else
	{
	errno = EINVAL;
	return -1;
	}
	}


	int
	sigfillset (sigset_t *set)
	{
	*set = ((2U << (NSIG - 1)) - 1) & ~ SIGABRT_COMPAT_MASK;
	return 0;
	}

	/* Set of currently blocked signals. */
	static volatile sigset_t blocked_set /* = 0 */;

	/* Set of currently blocked and pending signals. */
	static volatile sig_atomic_t pending_array[NSIG] /* = { 0 } */;

	/* Signal handler that is installed for blocked signals. */
	static void
	blocked_handler (int sig)
	{
	/* Reinstall the handler, in case the signal occurs multiple times
	while blocked. There is an inherent race where an asynchronous
	signal in between when the kernel uninstalled the handler and
	when we reinstall it will trigger the default handler; oh
	well. */
	signal (sig, blocked_handler);
	if (sig >= 0 && sig < NSIG)
	pending_array[sig] = 1;
	}

	int
	sigpending (sigset_t *set)
	{
	sigset_t pending = 0;
	int sig;

	for (sig = 0; sig < NSIG; sig++)
	if (pending_array[sig])
	pending \|= 1U << sig;
	*set = pending;
	return 0;
	}

	/* The previous signal handlers.
	Only the array elements corresponding to blocked signals are relevant. */
	static volatile handler_t old_handlers[NSIG];

	int
	sigprocmask (int operation, const sigset_t set, sigset_t old_set)
	{
	if (old_set != NULL)
	*old_set = blocked_set;

	if (set != NULL)
	{
	sigset_t new_blocked_set;
	sigset_t to_unblock;
	sigset_t to_block;

	switch (operation)
	{
	case SIG_BLOCK:
	new_blocked_set = blocked_set \| *set;
	break;
	case SIG_SETMASK:
	new_blocked_set = *set;
	break;
	case SIG_UNBLOCK:
	new_blocked_set = blocked_set & ~*set;
	break;
	default:
	errno = EINVAL;
	return -1;
	}
	to_unblock = blocked_set & ~new_blocked_set;
	to_block = new_blocked_set & ~blocked_set;

	if (to_block != 0)
	{
	int sig;

	for (sig = 0; sig < NSIG; sig++)
	if ((to_block >> sig) & 1)
	{
	pending_array[sig] = 0;
	if ((old_handlers[sig] = signal (sig, blocked_handler)) != SIG_ERR)
	blocked_set \|= 1U << sig;
	}
	}

	if (to_unblock != 0)
	{
	sig_atomic_t received[NSIG];
	int sig;

	for (sig = 0; sig < NSIG; sig++)
	if ((to_unblock >> sig) & 1)
	{
	if (signal (sig, old_handlers[sig]) != blocked_handler)
	/* The application changed a signal handler while the signal
	was blocked, bypassing our rpl_signal replacement.
	We don't support this. */
	abort ();
	received[sig] = pending_array[sig];
	blocked_set &= ~(1U << sig);
	pending_array[sig] = 0;
	}
	else
	received[sig] = 0;

	for (sig = 0; sig < NSIG; sig++)
	if (received[sig])
	raise (sig);
	}
	}
	return 0;
	}

	/* Install the handler FUNC for signal SIG, and return the previous
	handler. */
	handler_t
	rpl_signal (int sig, handler_t handler)
	{
	/* We must provide a wrapper, so that a user can query what handler
	they installed even if that signal is currently blocked. */
	if (sig >= 0 && sig < NSIG && sig != SIGKILL && sig != SIGSTOP
	&& handler != SIG_ERR)
	{
	#ifdef SIGABRT_COMPAT
	if (sig == SIGABRT_COMPAT)
	sig = SIGABRT;
	#endif

	if (blocked_set & (1U << sig))
	{
	/* POSIX states that sigprocmask and signal are both
	async-signal-safe. This is not true of our
	implementation - there is a slight data race where an
	asynchronous interrupt on signal A can occur after we
	install blocked_handler but before we have updated
	old_handlers for signal B, such that handler A can see
	stale information if it calls signal(B). Oh well -
	signal handlers really shouldn't try to manipulate the
	installed handlers of unrelated signals. */
	handler_t result = old_handlers[sig];
	old_handlers[sig] = handler;
	return result;
	}
	else
	return signal (sig, handler);
	}
	else
	{
	errno = EINVAL;
	return SIG_ERR;
	}
	}

	#if GNULIB_defined_SIGPIPE
	/* Raise the signal SIG. */
	int
	rpl_raise (int sig)
	# undef raise
	{
	switch (sig)
	{
	case SIGPIPE:
	if (blocked_set & (1U << sig))
	pending_array[sig] = 1;
	else
	{
	handler_t handler = SIGPIPE_handler;
	if (handler == SIG_DFL)
	exit (128 + SIGPIPE);
	else if (handler != SIG_IGN)
	(*handler) (sig);
	}
	return 0;
	default: /* System defined signal */
	return raise (sig);
	}
	}
	#endif