signal.c   [plain text]


/* signal.c
   Signal handling routines.

   Copyright (C) 1992 Ian Lance Taylor

   This file is part of the Taylor UUCP package.

   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 2 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, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.

   The author of the program may be contacted at ian@airs.com.
   */

#include "uucp.h"

#include "uudefs.h"
#include "sysdep.h"
#include "system.h"

#include <errno.h>

/* Signal handling routines.  When we catch a signal, we want to set
   the appropriate elements of afSignal and afLog_signal to TRUE.  If
   we are on a system which restarts system calls, we may also want to
   longjmp out.  On a system which does not restart system calls,
   these signal handling routines are well-defined by ANSI C.  */

#if HAVE_RESTARTABLE_SYSCALLS
volatile sig_atomic_t fSjmp;
volatile jmp_buf sSjmp_buf;
#endif /* HAVE_RESTARTABLE_SYSCALLS */

/* Some systems, such as SunOS, have a SA_INTERRUPT bit that must be
   set in the sigaction structure to force system calls to be
   interrupted.  */
#ifndef SA_INTERRUPT
#define SA_INTERRUPT 0
#endif

/* The SVR3 sigset function can be called just like signal, unless
   system calls are restarted which is extremely unlikely; we prevent
   this case in sysh.unx.  */
#if HAVE_SIGSET && ! HAVE_SIGACTION && ! HAVE_SIGVEC
#define signal sigset
#endif

/* The sigvec structure changed from 4.2BSD to 4.3BSD.  These macros
   make the 4.3 code backward compatible.  */
#ifndef SV_INTERRUPT
#define SV_INTERRUPT 0
#endif
#if ! HAVE_SIGVEC_SV_FLAGS
#define sv_flags sv_onstack
#endif

/* Catch a signal.  Reinstall the signal handler if necessary, set the
   appropriate variables, and do a longjmp if necessary.  */

RETSIGTYPE
ussignal (isig)
     int isig;
{
  int iindex;

#if ! HAVE_SIGACTION && ! HAVE_SIGVEC && ! HAVE_SIGSET
  (void) signal (isig, ussignal);
#endif

  switch (isig)
    {
    default: iindex = INDEXSIG_SIGHUP; break;
#ifdef SIGINT
    case SIGINT: iindex = INDEXSIG_SIGINT; break;
#endif
#ifdef SIGQUIT
    case SIGQUIT: iindex = INDEXSIG_SIGQUIT; break;
#endif
#ifdef SIGTERM
    case SIGTERM: iindex = INDEXSIG_SIGTERM; break;
#endif
#ifdef SIGPIPE
    case SIGPIPE: iindex = INDEXSIG_SIGPIPE; break;
#endif
    }

  afSignal[iindex] = TRUE;
  afLog_signal[iindex] = TRUE;

#if HAVE_RESTARTABLE_SYSCALLS
  if (fSjmp)
    longjmp (sSjmp_buf, 1);
#endif /* HAVE_RESTARTABLE_SYSCALLS */
}

/* Prepare to catch a signal.  This is basically the ANSI C routine
   signal, but it uses sigaction or sigvec instead if they are
   available.  If fforce is FALSE, we do not set the signal if it is
   currently being ignored.  If pfignored is not NULL and fforce is
   FALSE, then *pfignored will be set to TRUE if the signal was
   previously being ignored (if fforce is TRUE the value returned in
   *pfignored is meaningless).  If we can't change the signal handler
   we give a fatal error.  */

void
usset_signal (isig, pfn, fforce, pfignored)
     int isig;
     RETSIGTYPE (*pfn) P((int));
     boolean fforce;
     boolean *pfignored;
{
#if HAVE_SIGACTION

  struct sigaction s;

  if (! fforce)
    {
      (void) (sigemptyset (&s.sa_mask));
      if (sigaction (isig, (struct sigaction *) NULL, &s) != 0)
	ulog (LOG_FATAL, "sigaction (%d): %s", isig, strerror (errno));

      if (s.sa_handler == SIG_IGN)
	{
	  if (pfignored != NULL)
	    *pfignored = TRUE;
	  return;
	}

      if (pfignored != NULL)
	*pfignored = FALSE;
    }

  s.sa_handler = pfn;
  (void) (sigemptyset (&s.sa_mask));
  s.sa_flags = SA_INTERRUPT;

  if (sigaction (isig, &s, (struct sigaction *) NULL) != 0)
    ulog (LOG_FATAL, "sigaction (%d): %s", isig, strerror (errno));

#else /* ! HAVE_SIGACTION */
#if HAVE_SIGVEC

  struct sigvec s;

  if (! fforce)
    {
      if (sigvec (isig, (struct sigvec *) NULL, &s) != 0)
	ulog (LOG_FATAL, "sigvec (%d): %s", isig, strerror (errno));

      if (s.sv_handler == SIG_IGN)
	{
	  if (pfignored != NULL)
	    *pfignored = TRUE;
	  return;
	}

      if (pfignored != NULL)
	*pfignored = FALSE;
    }

  s.sv_handler = pfn;
  s.sv_mask = 0;
  s.sv_flags = SV_INTERRUPT;

  if (sigvec (isig, &s, (struct sigvec *) NULL) != 0)
    ulog (LOG_FATAL, "sigvec (%d): %s", isig, strerror (errno));

#else /* ! HAVE_SIGVEC */

  if (! fforce)
    {
      if (signal (isig, SIG_IGN) == SIG_IGN)
	{
	  if (pfignored != NULL)
	    *pfignored = TRUE;
	  return;
	}

      if (pfignored != NULL)
	*pfignored = FALSE;
    }

  (void) signal (isig, pfn);

#endif /* ! HAVE_SIGVEC */
#endif /* ! HAVE_SIGACTION */
}

/* The routine called by the system independent code, which always
   uses the same signal handler.  */

void
usysdep_signal (isig)
     int isig;
{
  usset_signal (isig, ussignal, FALSE, (boolean *) NULL);
}