sighandlers.cc

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/*

Copyright (C) 1993-2018 John W. Eaton

This file is part of Octave.

Octave 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.

Octave 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 Octave; see the file COPYING.  If not, see
<https://www.gnu.org/licenses/>.

*/

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include <csignal>
#include <cstdlib>

#include <iostream>
#include <new>

#if defined (OCTAVE_USE_WINDOWS_API)
#  define WIN32_LEAN_AND_MEAN
#  include <windows.h>
#endif

#include "child-list.h"
#include "cmd-edit.h"
#include "oct-syscalls.h"
#include "quit.h"
#include "signal-wrappers.h"

#include "bp-table.h"
#include "defun.h"
#include "error.h"
#include "input.h"
#include "interpreter-private.h"
#include "interpreter.h"
#include "load-save.h"
#include "octave.h"
#include "oct-map.h"
#include "pager.h"
#include "pt-bp.h"
#include "pt-eval.h"
#include "sighandlers.h"
#include "sysdep.h"
#include "utils.h"
#include "variables.h"

namespace octave
{
  // Nonzero means we have already printed a message for this series of
  // SIGPIPES.  We assume that the writer will eventually give up.
  int pipe_handler_error_count = 0;

  // TRUE means we can be interrupted.
  bool can_interrupt = false;

  // TRUE means we should try to enter the debugger on SIGINT.
  bool Vdebug_on_interrupt = false;

  // Allow users to avoid writing octave-workspace for SIGHUP (sent by
  // closing gnome-terminal, for example).  Note that this variable has
  // no effect if Vcrash_dumps_octave_core is FALSE.
  static bool Vsighup_dumps_octave_core = true;

  // Similar to Vsighup_dumps_octave_core, but for SIGQUIT signal.
  static bool Vsigquit_dumps_octave_core = true;

  // Similar to Vsighup_dumps_octave_core, but for SIGTERM signal.
  static bool Vsigterm_dumps_octave_core = true;

  // List of signals we have caught since last call to signal_handler.
  static bool *signals_caught = nullptr;

  static void
  my_friendly_exit (int sig, bool save_vars = true)
  {
    std::cerr << "fatal: caught signal "
              << octave_strsignal_wrapper (sig)
              << " -- stopping myself..." << std::endl;

    if (save_vars)
      dump_octave_core ();

    sysdep_cleanup ();

    throw exit_exception (1);
  }

  // Called from octave_quit () to actually do something about the signals
  // we have caught.

  void
  respond_to_pending_signals (void)
  {
    // The list of signals is relatively short, so we will just go
    // linearly through the list.

    // Interrupt signals are currently handled separately.

    static int sigint;
    static const bool have_sigint
      = octave_get_sig_number ("SIGINT", &sigint);

    static int sigbreak;
    static const bool have_sigbreak
      = octave_get_sig_number ("SIGBREAK", &sigbreak);

    // Termination signals.

    static int sighup;
    static const bool have_sighup
      = octave_get_sig_number ("SIGHUP", &sighup);

    static int sigquit;
    static const bool have_sigquit
      = octave_get_sig_number ("SIGQUIT", &sigquit);

    static int sigterm;
    static const bool have_sigterm
      = octave_get_sig_number ("SIGTERM", &sigterm);

    // Alarm signals.

    static int sigalrm;
    static const bool have_sigalrm
      = octave_get_sig_number ("SIGALRM", &sigalrm);

    static int sigvtalrm;
    static const bool have_sigvtalrm
      = octave_get_sig_number ("SIGVTALRM", &sigvtalrm);

    // I/O signals.

    static int sigio;
    static const bool have_sigio
      = octave_get_sig_number ("SIGIO", &sigio);

    static int siglost;
    static const bool have_siglost
      = octave_get_sig_number ("SIGLOST", &siglost);

    static int sigpipe;
    static const bool have_sigpipe
      = octave_get_sig_number ("SIGPIPE", &sigpipe);

    // Job control signals.

    static int sigchld;
    static const bool have_sigchld
      = octave_get_sig_number ("SIGCHLD", &sigchld);

    static int sigcld;
    static const bool have_sigcld
      = octave_get_sig_number ("SIGCLD", &sigcld);

    // Resource limit signals.

    static int sigxcpu;
    static const bool have_sigxcpu
      = octave_get_sig_number ("SIGXCPU", &sigxcpu);

    static int sigxfsz;
    static const bool have_sigxfsz
      = octave_get_sig_number ("SIGXFSZ", &sigxfsz);

    // User signals.

    static int sigusr1;
    static const bool have_sigusr1
      = octave_get_sig_number ("SIGUSR1", &sigusr1);

    static int sigusr2;
    static const bool have_sigusr2
      = octave_get_sig_number ("SIGUSR2", &sigusr2);

    octave::child_list& kids
      = octave::__get_child_list__ ("respond_to_pending_signals");

    for (int sig = 0; sig < octave_num_signals (); sig++)
      {
        if (signals_caught[sig])
          {
            signals_caught[sig] = false;

            if ((have_sigchld && sig == sigchld)
                || (have_sigcld && sig == sigcld))
              {
                // FIXME: should we block or ignore?
                volatile interrupt_handler saved_interrupt_handler
                  = ignore_interrupts ();

                void *context = octave_block_child ();

                kids.wait ();

                set_interrupt_handler (saved_interrupt_handler);

                octave_unblock_child (context);

                kids.reap ();
              }
            else if (have_sigpipe && sig == sigpipe)
              {
                std::cerr << "warning: broken pipe" << std::endl;

                // Don't loop forever on account of this.
                // FIXME: is this really needed?  Does it do anything
                // useful now?

                if (pipe_handler_error_count++ > 100
                    && octave_interrupt_state >= 0)
                  octave_interrupt_state++;
              }
            else if (have_sighup && sig == sighup)
              my_friendly_exit (sighup, Vsighup_dumps_octave_core);
            else if (have_sigquit && sig == sigquit)
              my_friendly_exit (sigquit, Vsigquit_dumps_octave_core);
            else if (have_sigterm && sig == sigterm)
              my_friendly_exit (sigterm, Vsigterm_dumps_octave_core);
            else if ((have_sigalrm && sig == sigalrm)
                     || (have_sigvtalrm && sig == sigvtalrm)
                     || (have_sigio && sig == sigio)
                     || (have_siglost && sig == siglost)
                     || (have_sigxcpu && sig == sigxcpu)
                     || (have_sigxfsz && sig == sigxfsz)
                     || (have_sigusr1 && sig == sigusr1)
                     || (have_sigusr2 && sig == sigusr2))
              std::cerr << "warning: ignoring signal: "
                        << octave_strsignal_wrapper (sig)
                        << std::endl;
            else if ((have_sigint && sig == sigint)
                     || (have_sigbreak && sig == sigbreak))
              ; // Handled separately; do nothing.
            else
              std::cerr << "warning: ignoring unexpected signal: "
                        << octave_strsignal_wrapper (sig)
                        << std::endl;
          }
      }
  }

  sig_handler *
  set_signal_handler (int sig, sig_handler *handler, bool restart_syscalls)
  {
    return octave_set_signal_handler_internal (sig, handler, restart_syscalls);
  }

  sig_handler *
  set_signal_handler (const char *signame, sig_handler *handler,
                      bool restart_syscalls)
  {
    return octave_set_signal_handler_by_name (signame, handler,
                                              restart_syscalls);
  }

  static void
  generic_sig_handler (int sig)
  {
    // FIXME: this function may execute in a separate signal handler or
    // signal watcher thread so it should probably be more careful about
    // how it accesses global objects.

    octave_signal_caught = 1;

    signals_caught[sig] = true;

    static int sigint;
    static const bool have_sigint
      = octave_get_sig_number ("SIGINT", &sigint);

    static int sigbreak;
    static const bool have_sigbreak
      = octave_get_sig_number ("SIGBREAK", &sigbreak);

    if ((have_sigint && sig == sigint)
        || (have_sigbreak && sig == sigbreak))
      {
        if (! octave_initialized)
          exit (1);

        if (can_interrupt)
          {
            octave_signal_caught = 1;
            octave_interrupt_state++;
          }
      }
  }

  static void
  deadly_sig_handler (int sig)
  {
    std::cerr << "fatal: caught signal "
              << octave_strsignal_wrapper (sig)
              << " -- stopping myself..." << std::endl;

    octave_set_default_signal_handler (sig);

    octave_raise_wrapper (sig);
  }

  static void
  fpe_sig_handler (int)
  {
    // FIXME: is there something better we can do?

    std::cerr << "warning: floating point exception" << std::endl;
  }

  interrupt_handler
  catch_interrupts (void)
  {
    interrupt_handler retval;

    retval.int_handler = set_signal_handler ("SIGINT", generic_sig_handler);
    retval.brk_handler = set_signal_handler ("SIGBREAK", generic_sig_handler);

    return retval;
  }

  interrupt_handler
  ignore_interrupts (void)
  {
    interrupt_handler retval;

    retval.int_handler = set_signal_handler ("SIGINT", SIG_IGN);
    retval.brk_handler = set_signal_handler ("SIGBREAK", SIG_IGN);

    return retval;
  }

  interrupt_handler
  set_interrupt_handler (const volatile interrupt_handler& h,
                         bool restart_syscalls)
  {
    interrupt_handler retval;

    retval.int_handler = set_signal_handler ("SIGINT", h.int_handler,
                                             restart_syscalls);

    retval.brk_handler = set_signal_handler ("SIGBREAK", h.brk_handler,
                                             restart_syscalls);

    return retval;
  }

  // Install all the handlers for the signals we might care about.

  void
  install_signal_handlers (void)
  {
    if (! signals_caught)
      signals_caught = new bool [octave_num_signals ()];

    for (int i = 0; i < octave_num_signals (); i++)
      signals_caught[i] = false;

    // Interrupt signals.

    catch_interrupts ();

    // Program Error signals.  These are most likely unrecoverable for
    // us.

    set_signal_handler ("SIGABRT", deadly_sig_handler);
    set_signal_handler ("SIGBUS", deadly_sig_handler);
    set_signal_handler ("SIGEMT", deadly_sig_handler);
    set_signal_handler ("SIGILL", deadly_sig_handler);
    // SIGIOT is normally another name for SIGABRT.
    set_signal_handler ("SIGIOT", deadly_sig_handler);
    set_signal_handler ("SIGSEGV", deadly_sig_handler);
    set_signal_handler ("SIGSYS", deadly_sig_handler);
    set_signal_handler ("SIGTRAP", deadly_sig_handler);

    // Handle SIGFPE separately.

    set_signal_handler ("SIGFPE", fpe_sig_handler);

    // Handle other signals for which the default action is to terminate
    // the program.

    // Termination signals.

    set_signal_handler ("SIGHUP", generic_sig_handler);
    set_signal_handler ("SIGQUIT", generic_sig_handler);
    set_signal_handler ("SIGTERM", generic_sig_handler);

    // Alarm signals.

    set_signal_handler ("SIGALRM", generic_sig_handler);
    set_signal_handler ("SIGVTALRM", generic_sig_handler);

    // I/O signals.

    set_signal_handler ("SIGLOST", generic_sig_handler);
    set_signal_handler ("SIGPIPE", generic_sig_handler);

    // Job control signals.  We only recognize signals about child
    // processes.

    set_signal_handler ("SIGCHLD", generic_sig_handler);
    set_signal_handler ("SIGCLD", generic_sig_handler);

    // Resource limit signals.

    // FIXME: does it really make sense to try to handle the CPU limit
    // signal?

    set_signal_handler ("SIGXCPU", generic_sig_handler);
    set_signal_handler ("SIGXFSZ", generic_sig_handler);

    // User signals.

    set_signal_handler ("SIGUSR1", generic_sig_handler);
    set_signal_handler ("SIGUSR2", generic_sig_handler);

    // This does nothing on Windows systems.
    octave_create_interrupt_watcher_thread (generic_sig_handler);
  }

  static void
  set_sig_struct_field (octave_scalar_map& m, const char *signame)
  {
    int signum;

    // The names in the struct do not include the leading "SIG" prefix.

    if (octave_get_sig_number (signame, &signum))
      m.assign (&signame[3], signum);
  }

  static octave_scalar_map
  make_sig_struct (void)
  {
    octave_scalar_map m;

    set_sig_struct_field (m, "SIGABRT");
    set_sig_struct_field (m, "SIGALRM");
    set_sig_struct_field (m, "SIGBUS");
    set_sig_struct_field (m, "SIGCHLD");
    set_sig_struct_field (m, "SIGCLD");
    set_sig_struct_field (m, "SIGCONT");
    set_sig_struct_field (m, "SIGEMT");
    set_sig_struct_field (m, "SIGFPE");
    set_sig_struct_field (m, "SIGHUP");
    set_sig_struct_field (m, "SIGILL");
    set_sig_struct_field (m, "SIGINFO");
    set_sig_struct_field (m, "SIGINT");
    set_sig_struct_field (m, "SIGIO");
    set_sig_struct_field (m, "SIGIOT");
    set_sig_struct_field (m, "SIGKILL");
    set_sig_struct_field (m, "SIGLOST");
    set_sig_struct_field (m, "SIGPIPE");
    set_sig_struct_field (m, "SIGPOLL");
    set_sig_struct_field (m, "SIGPROF");
    set_sig_struct_field (m, "SIGPWR");
    set_sig_struct_field (m, "SIGQUIT");
    set_sig_struct_field (m, "SIGSEGV");
    set_sig_struct_field (m, "SIGSTKFLT");
    set_sig_struct_field (m, "SIGSTOP");
    set_sig_struct_field (m, "SIGSYS");
    set_sig_struct_field (m, "SIGTERM");
    set_sig_struct_field (m, "SIGTRAP");
    set_sig_struct_field (m, "SIGTSTP");
    set_sig_struct_field (m, "SIGTTIN");
    set_sig_struct_field (m, "SIGTTOU");
    set_sig_struct_field (m, "SIGUNUSED");
    set_sig_struct_field (m, "SIGURG");
    set_sig_struct_field (m, "SIGUSR1");
    set_sig_struct_field (m, "SIGUSR2");
    set_sig_struct_field (m, "SIGVTALRM");
    set_sig_struct_field (m, "SIGWINCH");
    set_sig_struct_field (m, "SIGXCPU");
    set_sig_struct_field (m, "SIGXFSZ");

    return m;
  }
}

DEFUN (SIG, args, ,
       doc: /* -*- texinfo -*-
@deftypefn {} {} SIG ()
Return a structure containing Unix signal names and their defined values.
@end deftypefn */)
{
  if (args.length () != 0)
    print_usage ();

  static octave_scalar_map m = octave::make_sig_struct ();

  return ovl (m);
}

/*
%!assert (isstruct (SIG ()))
%!assert (! isempty (SIG ()))

%!error SIG (1)
*/

DEFUN (debug_on_interrupt, args, nargout,
       doc: /* -*- texinfo -*-
@deftypefn  {} {@var{val} =} debug_on_interrupt ()
@deftypefnx {} {@var{old_val} =} debug_on_interrupt (@var{new_val})
@deftypefnx {} {} debug_on_interrupt (@var{new_val}, "local")
Query or set the internal variable that controls whether Octave will try
to enter debugging mode when it receives an interrupt signal (typically
generated with @kbd{C-c}).

If a second interrupt signal is received before reaching the debugging mode,
a normal interrupt will occur.

When called from inside a function with the @qcode{"local"} option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
@seealso{debug_on_error, debug_on_warning}
@end deftypefn */)
{
  return set_internal_variable (octave::Vdebug_on_interrupt, args, nargout,
                                "debug_on_interrupt");
}

/*
%!test
%! orig_val = debug_on_interrupt ();
%! old_val = debug_on_interrupt (! orig_val);
%! assert (orig_val, old_val);
%! assert (debug_on_interrupt (), ! orig_val);
%! debug_on_interrupt (orig_val);
%! assert (debug_on_interrupt (), orig_val);

%!error (debug_on_interrupt (1, 2))
*/

DEFUN (sighup_dumps_octave_core, args, nargout,
       doc: /* -*- texinfo -*-
@deftypefn  {} {@var{val} =} sighup_dumps_octave_core ()
@deftypefnx {} {@var{old_val} =} sighup_dumps_octave_core (@var{new_val})
@deftypefnx {} {} sighup_dumps_octave_core (@var{new_val}, "local")
Query or set the internal variable that controls whether Octave tries
to save all current variables to the file @file{octave-workspace} if it
receives a hangup signal.

When called from inside a function with the @qcode{"local"} option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
@end deftypefn */)
{
  return set_internal_variable (octave::Vsighup_dumps_octave_core,
                                args, nargout,
                                "sighup_dumps_octave_core");
}

/*
%!test
%! orig_val = sighup_dumps_octave_core ();
%! old_val = sighup_dumps_octave_core (! orig_val);
%! assert (orig_val, old_val);
%! assert (sighup_dumps_octave_core (), ! orig_val);
%! sighup_dumps_octave_core (orig_val);
%! assert (sighup_dumps_octave_core (), orig_val);

%!error (sighup_dumps_octave_core (1, 2))
*/

DEFUN (sigquit_dumps_octave_core, args, nargout,
       doc: /* -*- texinfo -*-
@deftypefn  {} {@var{val} =} sigquit_dumps_octave_core ()
@deftypefnx {} {@var{old_val} =} sigquit_dumps_octave_core (@var{new_val})
@deftypefnx {} {} sigquit_dumps_octave_core (@var{new_val}, "local")
Query or set the internal variable that controls whether Octave tries
to save all current variables to the file @file{octave-workspace} if it
receives a quit signal.

When called from inside a function with the @qcode{"local"} option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
@end deftypefn */)
{
  return set_internal_variable (octave::Vsigquit_dumps_octave_core,
                                args, nargout,
                                "sigquit_dumps_octave_core");
}

/*
%!test
%! orig_val = sigquit_dumps_octave_core ();
%! old_val = sigquit_dumps_octave_core (! orig_val);
%! assert (orig_val, old_val);
%! assert (sigquit_dumps_octave_core (), ! orig_val);
%! sigquit_dumps_octave_core (orig_val);
%! assert (sigquit_dumps_octave_core (), orig_val);

%!error (sigquit_dumps_octave_core (1, 2))
*/

DEFUN (sigterm_dumps_octave_core, args, nargout,
       doc: /* -*- texinfo -*-
@deftypefn  {} {@var{val} =} sigterm_dumps_octave_core ()
@deftypefnx {} {@var{old_val} =} sigterm_dumps_octave_core (@var{new_val})
@deftypefnx {} {} sigterm_dumps_octave_core (@var{new_val}, "local")
Query or set the internal variable that controls whether Octave tries
to save all current variables to the file @file{octave-workspace} if it
receives a terminate signal.

When called from inside a function with the @qcode{"local"} option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
@end deftypefn */)
{
  return set_internal_variable (octave::Vsigterm_dumps_octave_core,
                                args, nargout,
                                "sigterm_dumps_octave_core");
}

/*
%!test
%! orig_val = sigterm_dumps_octave_core ();
%! old_val = sigterm_dumps_octave_core (! orig_val);
%! assert (orig_val, old_val);
%! assert (sigterm_dumps_octave_core (), ! orig_val);
%! sigterm_dumps_octave_core (orig_val);
%! assert (sigterm_dumps_octave_core (), orig_val);

%!error (sigterm_dumps_octave_core (1, 2))
*/