Adding upstream version 5.2.15.upstream/5.2.15upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1580 insertions, 0 deletions

diff --git a/trap.c b/trap.c
new file mode 100644
index 0000000..e56f6cc
--- /dev/null
+++ b/trap.c
@@ -0,0 +1,1580 @@
+/* trap.c -- Not the trap command, but useful functions for manipulating
+   those objects.  The trap command is in builtins/trap.def. */
+
+/* Copyright (C) 1987-2021 Free Software Foundation, Inc.
+
+   This file is part of GNU Bash, the Bourne Again SHell.
+
+   Bash 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.
+
+   Bash 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 Bash.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "config.h"
+
+#if defined (HAVE_UNISTD_H)
+#  include <unistd.h>
+#endif
+
+#include "bashtypes.h"
+#include "bashansi.h"
+
+#include <stdio.h>
+#include <errno.h>
+
+#include "bashintl.h"
+
+#include <signal.h>
+
+#include "trap.h"
+
+#include "shell.h"
+#include "execute_cmd.h"
+#include "flags.h"
+#include "parser.h"
+#include "input.h"	/* for save_token_state, restore_token_state */
+#include "jobs.h"
+#include "signames.h"
+#include "builtins.h"
+#include "builtins/common.h"
+#include "builtins/builtext.h"
+
+#if defined (READLINE)
+#  include <readline/readline.h>
+#  include "bashline.h"
+#endif
+
+#ifndef errno
+extern int errno;
+#endif
+
+/* Flags which describe the current handling state of a signal. */
+#define SIG_INHERITED   0x0	/* Value inherited from parent. */
+#define SIG_TRAPPED     0x1	/* Currently trapped. */
+#define SIG_HARD_IGNORE 0x2	/* Signal was ignored on shell entry. */
+#define SIG_SPECIAL     0x4	/* Treat this signal specially. */
+#define SIG_NO_TRAP     0x8	/* Signal cannot be trapped. */
+#define SIG_INPROGRESS	0x10	/* Signal handler currently executing. */
+#define SIG_CHANGED	0x20	/* Trap value changed in trap handler. */
+#define SIG_IGNORED	0x40	/* The signal is currently being ignored. */
+
+#define SPECIAL_TRAP(s)	((s) == EXIT_TRAP || (s) == DEBUG_TRAP || (s) == ERROR_TRAP || (s) == RETURN_TRAP)
+
+/* An array of such flags, one for each signal, describing what the
+   shell will do with a signal.  DEBUG_TRAP == NSIG; some code below
+   assumes this. */
+static int sigmodes[BASH_NSIG];
+
+static void free_trap_command (int);
+static void change_signal (int, char *);
+
+static int _run_trap_internal (int, char *);
+
+static void free_trap_string (int);
+static void reset_signal (int);
+static void restore_signal (int);
+static void reset_or_restore_signal_handlers (sh_resetsig_func_t *);
+static void reinit_trap (int);
+
+static void trap_if_untrapped (int, char *);
+
+/* Variables used here but defined in other files. */
+
+extern volatile int from_return_trap;
+extern int waiting_for_child;
+
+extern WORD_LIST *subst_assign_varlist;
+
+/* The list of things to do originally, before we started trapping. */
+SigHandler *original_signals[NSIG];
+
+/* For each signal, a slot for a string, which is a command to be
+   executed when that signal is received.  The slot can also contain
+   DEFAULT_SIG, which means do whatever you were going to do before
+   you were so rudely interrupted, or IGNORE_SIG, which says ignore
+   this signal. */
+char *trap_list[BASH_NSIG];
+
+/* A bitmap of signals received for which we have trap handlers. */
+int pending_traps[NSIG];
+
+/* Set to the number of the signal we're running the trap for + 1.
+   Used in execute_cmd.c and builtins/common.c to clean up when
+   parse_and_execute does not return normally after executing the
+   trap command (e.g., when `return' is executed in the trap command). */
+int running_trap;
+
+/* Set to last_command_exit_value before running a trap. */
+int trap_saved_exit_value;
+
+/* The (trapped) signal received while executing in the `wait' builtin */
+int wait_signal_received;
+
+int trapped_signal_received;
+
+/* Set to 1 to suppress the effect of `set v' in the DEBUG trap. */
+int suppress_debug_trap_verbose = 0;
+
+#define GETORIGSIG(sig) \
+  do { \
+    original_signals[sig] = (SigHandler *)set_signal_handler (sig, SIG_DFL); \
+    set_signal_handler (sig, original_signals[sig]); \
+    if (original_signals[sig] == SIG_IGN) \
+      sigmodes[sig] |= SIG_HARD_IGNORE; \
+  } while (0)
+
+#define SETORIGSIG(sig,handler) \
+  do { \
+    original_signals[sig] = handler; \
+    if (original_signals[sig] == SIG_IGN) \
+      sigmodes[sig] |= SIG_HARD_IGNORE; \
+  } while (0)
+
+#define GET_ORIGINAL_SIGNAL(sig) \
+  if (sig && sig < NSIG && original_signals[sig] == IMPOSSIBLE_TRAP_HANDLER) \
+    GETORIGSIG(sig)
+
+void
+initialize_traps ()
+{
+  register int i;
+
+  initialize_signames();
+
+  trap_list[EXIT_TRAP] = trap_list[DEBUG_TRAP] = trap_list[ERROR_TRAP] = trap_list[RETURN_TRAP] = (char *)NULL;
+  sigmodes[EXIT_TRAP] = sigmodes[DEBUG_TRAP] = sigmodes[ERROR_TRAP] = sigmodes[RETURN_TRAP] = SIG_INHERITED;
+  original_signals[EXIT_TRAP] = IMPOSSIBLE_TRAP_HANDLER;
+
+  for (i = 1; i < NSIG; i++)
+    {
+      pending_traps[i] = 0;
+      trap_list[i] = (char *)DEFAULT_SIG;
+      sigmodes[i] = SIG_INHERITED;	/* XXX - only set, not used */
+      original_signals[i] = IMPOSSIBLE_TRAP_HANDLER;
+    }
+
+  /* Show which signals are treated specially by the shell. */
+#if defined (SIGCHLD)
+  GETORIGSIG (SIGCHLD);
+  sigmodes[SIGCHLD] |= (SIG_SPECIAL | SIG_NO_TRAP);
+#endif /* SIGCHLD */
+
+  GETORIGSIG (SIGINT);
+  sigmodes[SIGINT] |= SIG_SPECIAL;
+
+#if defined (__BEOS__)
+  /* BeOS sets SIGINT to SIG_IGN! */
+  original_signals[SIGINT] = SIG_DFL;
+  sigmodes[SIGINT] &= ~SIG_HARD_IGNORE;
+#endif
+
+  GETORIGSIG (SIGQUIT);
+  sigmodes[SIGQUIT] |= SIG_SPECIAL;
+
+  if (interactive)
+    {
+      GETORIGSIG (SIGTERM);
+      sigmodes[SIGTERM] |= SIG_SPECIAL;
+    }
+
+  get_original_tty_job_signals ();
+}
+
+#ifdef DEBUG
+/* Return a printable representation of the trap handler for SIG. */
+static char *
+trap_handler_string (sig)
+     int sig;
+{
+  if (trap_list[sig] == (char *)DEFAULT_SIG)
+    return "DEFAULT_SIG";
+  else if (trap_list[sig] == (char *)IGNORE_SIG)
+    return "IGNORE_SIG";
+  else if (trap_list[sig] == (char *)IMPOSSIBLE_TRAP_HANDLER)
+    return "IMPOSSIBLE_TRAP_HANDLER";
+  else if (trap_list[sig])
+    return trap_list[sig];
+  else
+    return "NULL";
+}
+#endif
+
+/* Return the print name of this signal. */
+char *
+signal_name (sig)
+     int sig;
+{
+  char *ret;
+
+  /* on cygwin32, signal_names[sig] could be null */
+  ret = (sig >= BASH_NSIG || sig < 0 || signal_names[sig] == NULL)
+	? _("invalid signal number")
+	: signal_names[sig];
+
+  return ret;
+}
+
+/* Turn a string into a signal number, or a number into
+   a signal number.  If STRING is "2", "SIGINT", or "INT",
+   then (int)2 is returned.  Return NO_SIG if STRING doesn't
+   contain a valid signal descriptor. */
+int
+decode_signal (string, flags)
+     char *string;
+     int flags;
+{
+  intmax_t sig;
+  char *name;
+
+  if (legal_number (string, &sig))
+    return ((sig >= 0 && sig < NSIG) ? (int)sig : NO_SIG);
+
+#if defined (SIGRTMIN) && defined (SIGRTMAX)
+  if (STREQN (string, "SIGRTMIN+", 9) || ((flags & DSIG_NOCASE) && strncasecmp (string, "SIGRTMIN+", 9) == 0))
+    {
+      if (legal_number (string+9, &sig) && sig >= 0 && sig <= SIGRTMAX - SIGRTMIN)
+	return (SIGRTMIN + sig);
+      else
+	return NO_SIG;
+    }
+  else if (STREQN (string, "RTMIN+", 6) || ((flags & DSIG_NOCASE) && strncasecmp (string, "RTMIN+", 6) == 0))
+    {
+      if (legal_number (string+6, &sig) && sig >= 0 && sig <= SIGRTMAX - SIGRTMIN)
+	return (SIGRTMIN + sig);
+      else
+	return NO_SIG;
+    }
+#endif /* SIGRTMIN && SIGRTMAX */
+
+  /* A leading `SIG' may be omitted. */
+  for (sig = 0; sig < BASH_NSIG; sig++)
+    {
+      name = signal_names[sig];
+      if (name == 0 || name[0] == '\0')
+	continue;
+
+      /* Check name without the SIG prefix first case sensitively or
+	 insensitively depending on whether flags includes DSIG_NOCASE */
+      if (STREQN (name, "SIG", 3))
+	{
+	  name += 3;
+
+	  if ((flags & DSIG_NOCASE) && strcasecmp (string, name) == 0)
+	    return ((int)sig);
+	  else if ((flags & DSIG_NOCASE) == 0 && strcmp (string, name) == 0)
+	    return ((int)sig);
+	  /* If we can't use the `SIG' prefix to match, punt on this
+	     name now. */
+	  else if ((flags & DSIG_SIGPREFIX) == 0)
+	    continue;
+	}
+
+      /* Check name with SIG prefix case sensitively or insensitively
+	 depending on whether flags includes DSIG_NOCASE */
+      name = signal_names[sig];
+      if ((flags & DSIG_NOCASE) && strcasecmp (string, name) == 0)
+	return ((int)sig);
+      else if ((flags & DSIG_NOCASE) == 0 && strcmp (string, name) == 0)
+	return ((int)sig);
+    }
+
+  return (NO_SIG);
+}
+
+/* Non-zero when we catch a trapped signal. */
+static int catch_flag;
+
+void
+run_pending_traps ()
+{
+  register int sig;
+  int x;
+  volatile int old_exit_value, old_running;
+  WORD_LIST *save_subst_varlist;
+  HASH_TABLE *save_tempenv;
+  sh_parser_state_t pstate;
+  volatile int save_return_catch_flag, function_code;
+  procenv_t save_return_catch;
+  char *trap_command, *old_trap;
+#if defined (ARRAY_VARS)
+  ARRAY *ps;
+#endif
+
+  if (catch_flag == 0)		/* simple optimization */
+    return;
+
+  if (running_trap > 0)
+    {
+      internal_debug ("run_pending_traps: recursive invocation while running trap for signal %d", running_trap-1);
+#if defined (SIGWINCH)
+      if (running_trap == SIGWINCH+1 && pending_traps[SIGWINCH])
+	return;			/* no recursive SIGWINCH trap invocations */
+#endif
+      /* could check for running the trap handler for the same signal here
+	 (running_trap == sig+1) */
+      if (evalnest_max > 0 && evalnest > evalnest_max)
+	{
+	  internal_error (_("trap handler: maximum trap handler level exceeded (%d)"), evalnest_max);
+	  evalnest = 0;
+	  jump_to_top_level (DISCARD);
+	}
+    }
+
+  catch_flag = trapped_signal_received = 0;
+
+  /* Preserve $? when running trap. */
+  trap_saved_exit_value = old_exit_value = last_command_exit_value;
+#if defined (ARRAY_VARS)
+  ps = save_pipestatus_array ();
+#endif
+  old_running = running_trap;
+
+  for (sig = 1; sig < NSIG; sig++)
+    {
+      /* XXX this could be made into a counter by using
+	 while (pending_traps[sig]--) instead of the if statement. */
+      if (pending_traps[sig])
+	{
+	  /* XXX - set last_command_exit_value = trap_saved_exit_value here? */
+	  running_trap = sig + 1;
+
+	  if (sig == SIGINT)
+	    {
+	      pending_traps[sig] = 0;	/* XXX */
+	      /* We don't modify evalnest here, since run_interrupt_trap() calls
+		 _run_trap_internal, which does. */
+	      run_interrupt_trap (0);
+	      CLRINTERRUPT;	/* interrupts don't stack */
+	    }
+#if defined (JOB_CONTROL) && defined (SIGCHLD)
+	  else if (sig == SIGCHLD &&
+		   trap_list[SIGCHLD] != (char *)IMPOSSIBLE_TRAP_HANDLER &&
+		   (sigmodes[SIGCHLD] & SIG_INPROGRESS) == 0)
+	    {
+	      sigmodes[SIGCHLD] |= SIG_INPROGRESS;
+	      /* We modify evalnest here even though run_sigchld_trap can run
+		 the trap action more than once */
+	      evalnest++;
+	      x = pending_traps[sig];
+	      pending_traps[sig] = 0;
+	      run_sigchld_trap (x);	/* use as counter */
+	      running_trap = 0;
+	      evalnest--;
+	      sigmodes[SIGCHLD] &= ~SIG_INPROGRESS;
+	      /* continue here rather than reset pending_traps[SIGCHLD] below in
+		 case there are recursive calls to run_pending_traps and children
+		 have been reaped while run_sigchld_trap was running. */
+	      continue;
+	    }
+	  else if (sig == SIGCHLD &&
+		   trap_list[SIGCHLD] == (char *)IMPOSSIBLE_TRAP_HANDLER &&
+		   (sigmodes[SIGCHLD] & SIG_INPROGRESS) != 0)
+	    {
+	      /* This can happen when run_pending_traps is called while
+		 running a SIGCHLD trap handler. */
+	      running_trap = 0;
+	      /* want to leave pending_traps[SIGCHLD] alone here */
+	      continue;					/* XXX */
+	    }
+	  else if (sig == SIGCHLD && (sigmodes[SIGCHLD] & SIG_INPROGRESS))
+	    {
+	      /* whoops -- print warning? */
+	      running_trap = 0;		/* XXX */
+	      /* want to leave pending_traps[SIGCHLD] alone here */
+	      continue;
+	    }
+#endif
+	  else if (trap_list[sig] == (char *)DEFAULT_SIG ||
+		   trap_list[sig] == (char *)IGNORE_SIG ||
+		   trap_list[sig] == (char *)IMPOSSIBLE_TRAP_HANDLER)
+	    {
+	      /* This is possible due to a race condition.  Say a bash
+		 process has SIGTERM trapped.  A subshell is spawned
+		 using { list; } & and the parent does something and kills
+		 the subshell with SIGTERM.  It's possible for the subshell
+		 to set pending_traps[SIGTERM] to 1 before the code in
+		 execute_cmd.c eventually calls restore_original_signals
+		 to reset the SIGTERM signal handler in the subshell.  The
+		 next time run_pending_traps is called, pending_traps[SIGTERM]
+		 will be 1, but the trap handler in trap_list[SIGTERM] will
+		 be invalid (probably DEFAULT_SIG, but it could be IGNORE_SIG).
+		 Unless we catch this, the subshell will dump core when
+		 trap_list[SIGTERM] == DEFAULT_SIG, because DEFAULT_SIG is
+		 usually 0x0. */
+	      internal_warning (_("run_pending_traps: bad value in trap_list[%d]: %p"),
+				sig, trap_list[sig]);
+	      if (trap_list[sig] == (char *)DEFAULT_SIG)
+		{
+		  internal_warning (_("run_pending_traps: signal handler is SIG_DFL, resending %d (%s) to myself"), sig, signal_name (sig));
+		  kill (getpid (), sig);
+		}
+	    }
+	  else
+	    {
+	      old_trap = trap_list[sig];
+	      trap_command = savestring (old_trap);
+
+	      save_parser_state (&pstate);
+	      save_subst_varlist = subst_assign_varlist;
+	      subst_assign_varlist = 0;
+	      save_tempenv = temporary_env;
+	      temporary_env = 0;	/* traps should not run with temporary env */
+
+#if defined (JOB_CONTROL)
+	      save_pipeline (1);	/* XXX only provides one save level */
+#endif
+	      /* XXX - set pending_traps[sig] = 0 here? */
+	      pending_traps[sig] = 0;
+	      evalnest++;
+
+	      function_code = 0;
+	      save_return_catch_flag = return_catch_flag;
+	      if (return_catch_flag)
+		{
+		  COPY_PROCENV (return_catch, save_return_catch);
+		  function_code = setjmp_nosigs (return_catch);
+		}
+
+	      if (function_code == 0)
+	        /* XXX is x always last_command_exit_value? */
+		x = parse_and_execute (trap_command, "trap", SEVAL_NONINT|SEVAL_NOHIST|SEVAL_RESETLINE|SEVAL_NOOPTIMIZE);
+	      else
+		{
+		  parse_and_execute_cleanup (sig + 1);	/* XXX - could use -1 */
+		  x = return_catch_value;
+		}
+
+	      evalnest--;
+#if defined (JOB_CONTROL)
+	      restore_pipeline (1);
+#endif
+
+	      subst_assign_varlist = save_subst_varlist;
+	      restore_parser_state (&pstate);
+	      temporary_env = save_tempenv;
+
+	      if (save_return_catch_flag)
+		{
+		  return_catch_flag = save_return_catch_flag;
+		  return_catch_value = x;
+		  COPY_PROCENV (save_return_catch, return_catch);
+		  if (function_code)
+		    {
+		      running_trap = old_running;		/* XXX */
+		      /* caller will set last_command_exit_value */
+		      sh_longjmp (return_catch, 1);
+		    }
+		}
+	    }
+
+	  pending_traps[sig] = 0;	/* XXX - move before evalstring? */
+	  running_trap = old_running;
+	}
+    }
+
+#if defined (ARRAY_VARS)
+  restore_pipestatus_array (ps);
+#endif
+  last_command_exit_value = old_exit_value;
+}
+
+/* Set the private state variables noting that we received a signal SIG
+   for which we have a trap set. */
+void
+set_trap_state (sig)
+     int sig;
+{
+  catch_flag = 1;
+  pending_traps[sig]++;
+  trapped_signal_received = sig;
+}
+    
+sighandler
+trap_handler (sig)
+     int sig;
+{
+  int oerrno;
+
+  if ((sigmodes[sig] & SIG_TRAPPED) == 0)
+    {
+      internal_debug ("trap_handler: signal %d: signal not trapped", sig);
+      SIGRETURN (0);
+    }
+
+  /* This means we're in a subshell, but have not yet reset the handler for
+     trapped signals. We're not supposed to execute the trap in this situation;
+     we should restore the original signal and resend the signal to ourselves
+     to preserve the Posix "signal traps that are not being ignored shall be
+     set to the default action" semantics. */
+  if ((subshell_environment & SUBSHELL_IGNTRAP) && trap_list[sig] != (char *)IGNORE_SIG)
+    {
+      sigset_t mask;
+
+      /* Paranoia */
+      if (original_signals[sig] == IMPOSSIBLE_TRAP_HANDLER)
+	original_signals[sig] = SIG_DFL;
+
+      restore_signal (sig);
+
+      /* Make sure we let the signal we just caught through */
+      sigemptyset (&mask);
+      sigprocmask (SIG_SETMASK, (sigset_t *)NULL, &mask);
+      sigdelset (&mask, sig);
+      sigprocmask (SIG_SETMASK, &mask, (sigset_t *)NULL);
+
+      kill (getpid (), sig);
+
+      SIGRETURN (0);
+    }
+
+  if ((sig >= NSIG) ||
+      (trap_list[sig] == (char *)DEFAULT_SIG) ||
+      (trap_list[sig] == (char *)IGNORE_SIG))
+    programming_error (_("trap_handler: bad signal %d"), sig);
+  else
+    {
+      oerrno = errno;
+#if defined (MUST_REINSTALL_SIGHANDLERS)
+#  if defined (JOB_CONTROL) && defined (SIGCHLD)
+      if (sig != SIGCHLD)
+#  endif /* JOB_CONTROL && SIGCHLD */
+      set_signal_handler (sig, trap_handler);
+#endif /* MUST_REINSTALL_SIGHANDLERS */
+
+      set_trap_state (sig);
+
+      if (this_shell_builtin && (this_shell_builtin == wait_builtin))
+	{
+	  wait_signal_received = sig;
+	  if (waiting_for_child && wait_intr_flag)
+	    sh_longjmp (wait_intr_buf, 1);
+	}
+
+#if defined (READLINE)
+      /* Set the event hook so readline will call it after the signal handlers
+	 finish executing, so if this interrupted character input we can get
+	 quick response. */
+      if (RL_ISSTATE (RL_STATE_SIGHANDLER))
+        bashline_set_event_hook ();
+#endif
+
+      errno = oerrno;
+    }
+  
+  SIGRETURN (0);
+}
+
+int
+next_pending_trap (start)
+     int start;
+{
+  register int i;
+
+  for (i = start; i < NSIG; i++)
+    if (pending_traps[i])
+      return i;
+  return -1;
+}
+
+int
+first_pending_trap ()
+{
+  return (next_pending_trap (1));
+}
+
+/* Return > 0 if any of the "real" signals (not fake signals like EXIT) are
+   trapped. */
+int
+any_signals_trapped ()
+{
+  register int i;
+
+  for (i = 1; i < NSIG; i++)
+    if ((sigmodes[i] & SIG_TRAPPED) && (sigmodes[i] & SIG_IGNORED) == 0)
+      return i;
+  return -1;
+}
+
+void
+clear_pending_traps ()
+{
+  register int i;
+
+  for (i = 1; i < NSIG; i++)
+    pending_traps[i] = 0;
+}
+
+void
+check_signals ()
+{
+  /* Add any other shell timeouts here */
+  check_read_timeout ();	/* set by the read builtin */
+  QUIT;
+}
+
+/* Convenience functions the rest of the shell can use */
+void
+check_signals_and_traps ()
+{
+  check_signals ();
+
+  run_pending_traps ();
+}
+
+#if defined (JOB_CONTROL) && defined (SIGCHLD)
+
+#ifdef INCLUDE_UNUSED
+/* Make COMMAND_STRING be executed when SIGCHLD is caught. */
+void
+set_sigchld_trap (command_string)
+     char *command_string;
+{
+  set_signal (SIGCHLD, command_string);
+}
+#endif
+
+/* Make COMMAND_STRING be executed when SIGCHLD is caught iff SIGCHLD
+   is not already trapped.  IMPOSSIBLE_TRAP_HANDLER is used as a sentinel
+   to make sure that a SIGCHLD trap handler run via run_sigchld_trap can
+   reset the disposition to the default and not have the original signal
+   accidentally restored, undoing the user's command. */
+void
+maybe_set_sigchld_trap (command_string)
+     char *command_string;
+{
+  if ((sigmodes[SIGCHLD] & SIG_TRAPPED) == 0 && trap_list[SIGCHLD] == (char *)IMPOSSIBLE_TRAP_HANDLER)
+    set_signal (SIGCHLD, command_string);
+}
+
+/* Temporarily set the SIGCHLD trap string to IMPOSSIBLE_TRAP_HANDLER.  Used
+   as a sentinel in run_sigchld_trap and maybe_set_sigchld_trap to see whether
+   or not a SIGCHLD trap handler reset SIGCHLD disposition to the default. */
+void
+set_impossible_sigchld_trap ()
+{
+  restore_default_signal (SIGCHLD);
+  change_signal (SIGCHLD, (char *)IMPOSSIBLE_TRAP_HANDLER);
+  sigmodes[SIGCHLD] &= ~SIG_TRAPPED;	/* maybe_set_sigchld_trap checks this */
+}
+
+/* Act as if we received SIGCHLD NCHILD times and increment
+   pending_traps[SIGCHLD] by that amount.  This allows us to still run the
+   SIGCHLD trap once for each exited child. */
+void
+queue_sigchld_trap (nchild)
+     int nchild;
+{
+  if (nchild > 0)
+    {
+      catch_flag = 1;
+      pending_traps[SIGCHLD] += nchild;
+      trapped_signal_received = SIGCHLD;
+    }
+}
+#endif /* JOB_CONTROL && SIGCHLD */
+
+/* Set a trap for SIG only if SIG is not already trapped. */
+static inline void
+trap_if_untrapped (sig, command)
+     int sig;
+     char *command;
+{
+  if ((sigmodes[sig] & SIG_TRAPPED) == 0)
+    set_signal (sig, command);
+}
+
+void
+set_debug_trap (command)
+     char *command;
+{
+  set_signal (DEBUG_TRAP, command);
+}
+
+/* Separate function to call when functions and sourced files want to restore
+   the original version of the DEBUG trap before returning.  Unless the -T
+   option is set, source and shell function execution save the old debug trap
+   and unset the trap.  If the function or sourced file changes the DEBUG trap,
+   SIG_TRAPPED will be set and we don't bother restoring the original trap string.
+   This is used by both functions and the source builtin. */
+void
+maybe_set_debug_trap (command)
+     char *command;
+{
+  trap_if_untrapped (DEBUG_TRAP, command);
+}
+
+void
+set_error_trap (command)
+     char *command;
+{
+  set_signal (ERROR_TRAP, command);
+}
+
+void
+maybe_set_error_trap (command)
+     char *command;
+{
+  trap_if_untrapped (ERROR_TRAP, command);
+}
+
+void
+set_return_trap (command)
+     char *command;
+{
+  set_signal (RETURN_TRAP, command);
+}
+
+void
+maybe_set_return_trap (command)
+     char *command;
+{
+  trap_if_untrapped (RETURN_TRAP, command);
+}
+
+#ifdef INCLUDE_UNUSED
+void
+set_sigint_trap (command)
+     char *command;
+{
+  set_signal (SIGINT, command);
+}
+#endif
+
+/* Reset the SIGINT handler so that subshells that are doing `shellsy'
+   things, like waiting for command substitution or executing commands
+   in explicit subshells ( ( cmd ) ), can catch interrupts properly. */
+SigHandler *
+set_sigint_handler ()
+{
+  if (sigmodes[SIGINT] & SIG_HARD_IGNORE)
+    return ((SigHandler *)SIG_IGN);
+
+  else if (sigmodes[SIGINT] & SIG_IGNORED)
+    return ((SigHandler *)set_signal_handler (SIGINT, SIG_IGN)); /* XXX */
+
+  else if (sigmodes[SIGINT] & SIG_TRAPPED)
+    return ((SigHandler *)set_signal_handler (SIGINT, trap_handler));
+
+  /* The signal is not trapped, so set the handler to the shell's special
+     interrupt handler. */
+  else if (interactive)	/* XXX - was interactive_shell */
+    return (set_signal_handler (SIGINT, sigint_sighandler));
+  else
+    return (set_signal_handler (SIGINT, termsig_sighandler));
+}
+
+/* Return the correct handler for signal SIG according to the values in
+   sigmodes[SIG]. */
+SigHandler *
+trap_to_sighandler (sig)
+     int sig;
+{
+  if (sigmodes[sig] & (SIG_IGNORED|SIG_HARD_IGNORE))
+    return (SIG_IGN);
+  else if (sigmodes[sig] & SIG_TRAPPED)
+    return (trap_handler);
+  else
+    return (SIG_DFL);
+}
+
+/* Set SIG to call STRING as a command. */
+void
+set_signal (sig, string)
+     int sig;
+     char *string;
+{
+  sigset_t set, oset;
+
+  if (SPECIAL_TRAP (sig))
+    {
+      change_signal (sig, savestring (string));
+      if (sig == EXIT_TRAP && interactive == 0)
+	initialize_terminating_signals ();
+      return;
+    }
+
+  /* A signal ignored on entry to the shell cannot be trapped or reset, but
+     no error is reported when attempting to do so.  -- Posix.2 */
+  if (sigmodes[sig] & SIG_HARD_IGNORE)
+    return;
+
+  /* Make sure we have original_signals[sig] if the signal has not yet
+     been trapped. */
+  if ((sigmodes[sig] & SIG_TRAPPED) == 0)
+    {
+      /* If we aren't sure of the original value, check it. */
+      if (original_signals[sig] == IMPOSSIBLE_TRAP_HANDLER)
+        GETORIGSIG (sig);
+      if (original_signals[sig] == SIG_IGN)
+	return;
+    }
+
+  /* Only change the system signal handler if SIG_NO_TRAP is not set.
+     The trap command string is changed in either case.  The shell signal
+     handlers for SIGINT and SIGCHLD run the user specified traps in an
+     environment in which it is safe to do so. */
+  if ((sigmodes[sig] & SIG_NO_TRAP) == 0)
+    {
+      BLOCK_SIGNAL (sig, set, oset);
+      change_signal (sig, savestring (string));
+      set_signal_handler (sig, trap_handler);
+      UNBLOCK_SIGNAL (oset);
+    }
+  else
+    change_signal (sig, savestring (string));
+}
+
+static void
+free_trap_command (sig)
+     int sig;
+{
+  if ((sigmodes[sig] & SIG_TRAPPED) && trap_list[sig] &&
+      (trap_list[sig] != (char *)IGNORE_SIG) &&
+      (trap_list[sig] != (char *)DEFAULT_SIG) &&
+      (trap_list[sig] != (char *)IMPOSSIBLE_TRAP_HANDLER))
+    free (trap_list[sig]);
+}
+
+/* If SIG has a string assigned to it, get rid of it.  Then give it
+   VALUE. */
+static void
+change_signal (sig, value)
+     int sig;
+     char *value;
+{
+  if ((sigmodes[sig] & SIG_INPROGRESS) == 0)
+    free_trap_command (sig);
+  trap_list[sig] = value;
+
+  sigmodes[sig] |= SIG_TRAPPED;
+  if (value == (char *)IGNORE_SIG)
+    sigmodes[sig] |= SIG_IGNORED;
+  else
+    sigmodes[sig] &= ~SIG_IGNORED;
+  if (sigmodes[sig] & SIG_INPROGRESS)
+    sigmodes[sig] |= SIG_CHANGED;
+}
+
+void
+get_original_signal (sig)
+     int sig;
+{
+  /* If we aren't sure the of the original value, then get it. */
+  if (sig > 0 && sig < NSIG && original_signals[sig] == (SigHandler *)IMPOSSIBLE_TRAP_HANDLER)
+    GETORIGSIG (sig);
+}
+
+void
+get_all_original_signals ()
+{
+  register int i;
+
+  for (i = 1; i < NSIG; i++)
+    GET_ORIGINAL_SIGNAL (i);
+}
+
+void
+set_original_signal (sig, handler)
+     int sig;
+     SigHandler *handler;
+{
+  if (sig > 0 && sig < NSIG && original_signals[sig] == (SigHandler *)IMPOSSIBLE_TRAP_HANDLER)
+    SETORIGSIG (sig, handler);
+}
+
+/* Restore the default action for SIG; i.e., the action the shell
+   would have taken before you used the trap command.  This is called
+   from trap_builtin (), which takes care to restore the handlers for
+   the signals the shell treats specially. */
+void
+restore_default_signal (sig)
+     int sig;
+{
+  if (SPECIAL_TRAP (sig))
+    {
+      if ((sig != DEBUG_TRAP && sig != ERROR_TRAP && sig != RETURN_TRAP) ||
+	  (sigmodes[sig] & SIG_INPROGRESS) == 0)
+	free_trap_command (sig);
+      trap_list[sig] = (char *)NULL;
+      sigmodes[sig] &= ~SIG_TRAPPED;
+      if (sigmodes[sig] & SIG_INPROGRESS)
+	sigmodes[sig] |= SIG_CHANGED;
+      return;
+    }
+
+  GET_ORIGINAL_SIGNAL (sig);
+
+  /* A signal ignored on entry to the shell cannot be trapped or reset, but
+     no error is reported when attempting to do so.  Thanks Posix.2. */
+  if (sigmodes[sig] & SIG_HARD_IGNORE)
+    return;
+
+  /* If we aren't trapping this signal, don't bother doing anything else. */
+  /* We special-case SIGCHLD and IMPOSSIBLE_TRAP_HANDLER (see above) as a
+     sentinel to determine whether or not disposition is reset to the default
+     while the trap handler is executing. */
+  if (((sigmodes[sig] & SIG_TRAPPED) == 0) &&
+      (sig != SIGCHLD || (sigmodes[sig] & SIG_INPROGRESS) == 0 || trap_list[sig] != (char *)IMPOSSIBLE_TRAP_HANDLER))
+    return;
+
+  /* Only change the signal handler for SIG if it allows it. */
+  if ((sigmodes[sig] & SIG_NO_TRAP) == 0)
+    set_signal_handler (sig, original_signals[sig]);
+
+  /* Change the trap command in either case. */
+  change_signal (sig, (char *)DEFAULT_SIG);
+
+  /* Mark the signal as no longer trapped. */
+  sigmodes[sig] &= ~SIG_TRAPPED;
+}
+
+/* Make this signal be ignored. */
+void
+ignore_signal (sig)
+     int sig;
+{
+  if (SPECIAL_TRAP (sig) && ((sigmodes[sig] & SIG_IGNORED) == 0))
+    {
+      change_signal (sig, (char *)IGNORE_SIG);
+      return;
+    }
+
+  GET_ORIGINAL_SIGNAL (sig);
+
+  /* A signal ignored on entry to the shell cannot be trapped or reset.
+     No error is reported when the user attempts to do so. */
+  if (sigmodes[sig] & SIG_HARD_IGNORE)
+    return;
+
+  /* If already trapped and ignored, no change necessary. */
+  if (sigmodes[sig] & SIG_IGNORED)
+    return;
+
+  /* Only change the signal handler for SIG if it allows it. */
+  if ((sigmodes[sig] & SIG_NO_TRAP) == 0)
+    set_signal_handler (sig, SIG_IGN);
+
+  /* Change the trap command in either case. */
+  change_signal (sig, (char *)IGNORE_SIG);
+}
+
+/* Handle the calling of "trap 0".  The only sticky situation is when
+   the command to be executed includes an "exit".  This is why we have
+   to provide our own place for top_level to jump to. */
+int
+run_exit_trap ()
+{
+  char *trap_command;
+  int code, function_code, retval;
+#if defined (ARRAY_VARS)
+  ARRAY *ps;
+#endif
+
+  trap_saved_exit_value = last_command_exit_value;
+#if defined (ARRAY_VARS)
+  ps = save_pipestatus_array ();
+#endif
+  function_code = 0;
+
+  /* Run the trap only if signal 0 is trapped and not ignored, and we are not
+     currently running in the trap handler (call to exit in the list of
+     commands given to trap 0). */
+  if ((sigmodes[EXIT_TRAP] & SIG_TRAPPED) &&
+      (sigmodes[EXIT_TRAP] & (SIG_IGNORED|SIG_INPROGRESS)) == 0)
+    {
+      trap_command = savestring (trap_list[EXIT_TRAP]);
+      sigmodes[EXIT_TRAP] &= ~SIG_TRAPPED;
+      sigmodes[EXIT_TRAP] |= SIG_INPROGRESS;
+
+      retval = trap_saved_exit_value;
+      running_trap = 1;
+
+      code = setjmp_nosigs (top_level);
+
+      /* If we're in a function, make sure return longjmps come here, too. */
+      if (return_catch_flag)
+	function_code = setjmp_nosigs (return_catch);
+
+      if (code == 0 && function_code == 0)
+	{
+	  reset_parser ();
+	  parse_and_execute (trap_command, "exit trap", SEVAL_NONINT|SEVAL_NOHIST|SEVAL_RESETLINE|SEVAL_NOOPTIMIZE);
+	}
+      else if (code == ERREXIT)
+	retval = last_command_exit_value;
+      else if (code == EXITPROG || code == EXITBLTIN)
+	retval = last_command_exit_value;
+      else if (function_code != 0)
+        retval = return_catch_value;
+      else
+	retval = trap_saved_exit_value;
+
+      running_trap = 0;
+#if defined (ARRAY_VARS)
+      array_dispose (ps);
+#endif
+
+      return retval;
+    }
+
+#if defined (ARRAY_VARS)
+  restore_pipestatus_array (ps);
+#endif
+  return (trap_saved_exit_value);
+}
+
+void
+run_trap_cleanup (sig)
+     int sig;
+{
+  /* XXX - should we clean up trap_list[sig] == IMPOSSIBLE_TRAP_HANDLER? */
+  sigmodes[sig] &= ~(SIG_INPROGRESS|SIG_CHANGED);
+}
+
+#define RECURSIVE_SIG(s) (SPECIAL_TRAP(s) == 0)
+
+/* Run a trap command for SIG.  SIG is one of the signals the shell treats
+   specially.  Returns the exit status of the executed trap command list. */
+static int
+_run_trap_internal (sig, tag)
+     int sig;
+     char *tag;
+{
+  char *trap_command, *old_trap;
+  int trap_exit_value;
+  volatile int save_return_catch_flag, function_code;
+  int old_modes, old_running, old_int;
+  int flags;
+  procenv_t save_return_catch;
+  WORD_LIST *save_subst_varlist;
+  HASH_TABLE *save_tempenv;
+  sh_parser_state_t pstate;
+#if defined (ARRAY_VARS)
+  ARRAY *ps;
+#endif
+
+  old_modes = old_running = -1;
+
+  trap_exit_value = function_code = 0;
+  trap_saved_exit_value = last_command_exit_value;
+  /* Run the trap only if SIG is trapped and not ignored, and we are not
+     currently executing in the trap handler. */
+  if ((sigmodes[sig] & SIG_TRAPPED) && ((sigmodes[sig] & SIG_IGNORED) == 0) &&
+      (trap_list[sig] != (char *)IMPOSSIBLE_TRAP_HANDLER) &&
+#if 1
+      /* Uncomment this to allow some special signals to recursively execute
+	 trap handlers. */
+      (RECURSIVE_SIG (sig) || (sigmodes[sig] & SIG_INPROGRESS) == 0))
+#else
+      ((sigmodes[sig] & SIG_INPROGRESS) == 0))
+#endif
+    {
+      old_trap = trap_list[sig];
+      old_modes = sigmodes[sig];
+      old_running = running_trap;
+
+      sigmodes[sig] |= SIG_INPROGRESS;
+      sigmodes[sig] &= ~SIG_CHANGED;		/* just to be sure */
+      trap_command =  savestring (old_trap);
+
+      running_trap = sig + 1;
+
+      old_int = interrupt_state;	/* temporarily suppress pending interrupts */
+      CLRINTERRUPT;
+
+#if defined (ARRAY_VARS)
+      ps = save_pipestatus_array ();
+#endif
+
+      save_parser_state (&pstate);
+      save_subst_varlist = subst_assign_varlist;
+      subst_assign_varlist = 0;
+      save_tempenv = temporary_env;
+      temporary_env = 0;	/* traps should not run with temporary env */
+
+#if defined (JOB_CONTROL)
+      if (sig != DEBUG_TRAP)	/* run_debug_trap does this */
+	save_pipeline (1);	/* XXX only provides one save level */
+#endif
+
+      /* If we're in a function, make sure return longjmps come here, too. */
+      save_return_catch_flag = return_catch_flag;
+      if (return_catch_flag)
+	{
+	  COPY_PROCENV (return_catch, save_return_catch);
+	  function_code = setjmp_nosigs (return_catch);
+	}
+
+      flags = SEVAL_NONINT|SEVAL_NOHIST|SEVAL_NOOPTIMIZE;
+      if (sig != DEBUG_TRAP && sig != RETURN_TRAP && sig != ERROR_TRAP)
+	flags |= SEVAL_RESETLINE;
+      evalnest++;
+      if (function_code == 0)
+        {
+	  parse_and_execute (trap_command, tag, flags);
+	  trap_exit_value = last_command_exit_value;
+        }
+      else
+        trap_exit_value = return_catch_value;
+      evalnest--;
+
+#if defined (JOB_CONTROL)
+      if (sig != DEBUG_TRAP)	/* run_debug_trap does this */
+	restore_pipeline (1);
+#endif
+
+      subst_assign_varlist = save_subst_varlist;
+      restore_parser_state (&pstate);
+
+#if defined (ARRAY_VARS)
+      restore_pipestatus_array (ps);
+#endif
+
+      temporary_env = save_tempenv;
+
+      if ((old_modes & SIG_INPROGRESS) == 0)
+	sigmodes[sig] &= ~SIG_INPROGRESS;
+
+      running_trap = old_running;
+      interrupt_state = old_int;
+
+      if (sigmodes[sig] & SIG_CHANGED)
+	{
+#if 0
+	  /* Special traps like EXIT, DEBUG, RETURN are handled explicitly in
+	     the places where they can be changed using unwind-protects.  For
+	     example, look at execute_cmd.c:execute_function(). */
+	  if (SPECIAL_TRAP (sig) == 0)
+#endif
+	    free (old_trap);
+	  sigmodes[sig] &= ~SIG_CHANGED;
+
+	  CHECK_TERMSIG;	/* some pathological conditions lead here */
+	}
+
+      if (save_return_catch_flag)
+	{
+	  return_catch_flag = save_return_catch_flag;
+	  return_catch_value = trap_exit_value;
+	  COPY_PROCENV (save_return_catch, return_catch);
+	  if (function_code)
+	    {
+#if 0
+	      from_return_trap = sig == RETURN_TRAP;
+#endif
+	      sh_longjmp (return_catch, 1);
+	    }
+	}
+    }
+
+  return trap_exit_value;
+}
+
+int
+run_debug_trap ()
+{
+  int trap_exit_value, old_verbose;
+  pid_t save_pgrp;
+#if defined (PGRP_PIPE)
+  int save_pipe[2];
+#endif
+
+  /* XXX - question:  should the DEBUG trap inherit the RETURN trap? */
+  trap_exit_value = 0;
+  if ((sigmodes[DEBUG_TRAP] & SIG_TRAPPED) && ((sigmodes[DEBUG_TRAP] & SIG_IGNORED) == 0) && ((sigmodes[DEBUG_TRAP] & SIG_INPROGRESS) == 0))
+    {
+#if defined (JOB_CONTROL)
+      save_pgrp = pipeline_pgrp;
+      pipeline_pgrp = 0;
+      save_pipeline (1);
+#  if defined (PGRP_PIPE)
+      save_pgrp_pipe (save_pipe, 1);
+#  endif
+      stop_making_children ();
+#endif
+
+      old_verbose = echo_input_at_read;
+      echo_input_at_read = suppress_debug_trap_verbose ? 0 : echo_input_at_read;
+
+      trap_exit_value = _run_trap_internal (DEBUG_TRAP, "debug trap");
+
+      echo_input_at_read = old_verbose;
+
+#if defined (JOB_CONTROL)
+      pipeline_pgrp = save_pgrp;
+      restore_pipeline (1);
+#  if defined (PGRP_PIPE)
+      close_pgrp_pipe ();
+      restore_pgrp_pipe (save_pipe);
+#  endif
+      if (pipeline_pgrp > 0 && ((subshell_environment & (SUBSHELL_ASYNC|SUBSHELL_PIPE)) == 0))
+	give_terminal_to (pipeline_pgrp, 1);
+
+      notify_and_cleanup ();
+#endif
+      
+#if defined (DEBUGGER)
+      /* If we're in the debugger and the DEBUG trap returns 2 while we're in
+	 a function or sourced script, we force a `return'. */
+      if (debugging_mode && trap_exit_value == 2 && return_catch_flag)
+	{
+	  return_catch_value = trap_exit_value;
+	  sh_longjmp (return_catch, 1);
+	}
+#endif
+    }
+  return trap_exit_value;
+}
+
+void
+run_error_trap ()
+{
+  if ((sigmodes[ERROR_TRAP] & SIG_TRAPPED) && ((sigmodes[ERROR_TRAP] & SIG_IGNORED) == 0) && (sigmodes[ERROR_TRAP] & SIG_INPROGRESS) == 0)
+    _run_trap_internal (ERROR_TRAP, "error trap");
+}
+
+void
+run_return_trap ()
+{
+  int old_exit_value;
+
+#if 0
+  if ((sigmodes[DEBUG_TRAP] & SIG_TRAPPED) && (sigmodes[DEBUG_TRAP] & SIG_INPROGRESS))
+    return;
+#endif
+
+  if ((sigmodes[RETURN_TRAP] & SIG_TRAPPED) && ((sigmodes[RETURN_TRAP] & SIG_IGNORED) == 0) && (sigmodes[RETURN_TRAP] & SIG_INPROGRESS) == 0)
+    {
+      old_exit_value = last_command_exit_value;
+      _run_trap_internal (RETURN_TRAP, "return trap");
+      last_command_exit_value = old_exit_value;
+    }
+}
+
+/* Run a trap set on SIGINT.  This is called from throw_to_top_level (), and
+   declared here to localize the trap functions. */
+void
+run_interrupt_trap (will_throw)
+     int will_throw;	/* from throw_to_top_level? */
+{
+  if (will_throw && running_trap > 0)
+    run_trap_cleanup (running_trap - 1);
+  pending_traps[SIGINT] = 0;	/* run_pending_traps does this */
+  catch_flag = 0;
+  _run_trap_internal (SIGINT, "interrupt trap");
+}
+
+/* Free all the allocated strings in the list of traps and reset the trap
+   values to the default.  Intended to be called from subshells that want
+   to complete work done by reset_signal_handlers upon execution of a
+   subsequent `trap' command that changes a signal's disposition.  We need
+   to make sure that we duplicate the behavior of
+   reset_or_restore_signal_handlers and not change the disposition of signals
+   that are set to be ignored. */
+void
+free_trap_strings ()
+{
+  register int i;
+
+  for (i = 0; i < NSIG; i++)
+    {
+      if (trap_list[i] != (char *)IGNORE_SIG)
+	free_trap_string (i);
+    }
+  for (i = NSIG; i < BASH_NSIG; i++)
+    {
+      /* Don't free the trap string if the subshell inherited the trap */
+      if ((sigmodes[i] & SIG_TRAPPED) == 0)
+	{
+	  free_trap_string (i);
+	  trap_list[i] = (char *)NULL;
+	}
+    }
+}
+
+/* Free a trap command string associated with SIG without changing signal
+   disposition.  Intended to be called from free_trap_strings()  */
+static void
+free_trap_string (sig)
+     int sig;
+{
+  change_signal (sig, (char *)DEFAULT_SIG);
+  sigmodes[sig] &= ~SIG_TRAPPED;		/* XXX - SIG_INPROGRESS? */
+}
+
+/* Reset the handler for SIG to the original value but leave the trap string
+   in place. */
+static void
+reset_signal (sig)
+     int sig;
+{
+  set_signal_handler (sig, original_signals[sig]);
+  sigmodes[sig] &= ~SIG_TRAPPED;		/* XXX - SIG_INPROGRESS? */
+}
+
+/* Set the handler signal SIG to the original and free any trap
+   command associated with it. */
+static void
+restore_signal (sig)
+     int sig;
+{
+  set_signal_handler (sig, original_signals[sig]);
+  change_signal (sig, (char *)DEFAULT_SIG);
+  sigmodes[sig] &= ~SIG_TRAPPED;
+}
+
+static void
+reset_or_restore_signal_handlers (reset)
+     sh_resetsig_func_t *reset;
+{
+  register int i;
+
+  /* Take care of the exit trap first */
+  if (sigmodes[EXIT_TRAP] & SIG_TRAPPED)
+    {
+      sigmodes[EXIT_TRAP] &= ~SIG_TRAPPED;	/* XXX - SIG_INPROGRESS? */
+      if (reset != reset_signal)
+	{
+	  free_trap_command (EXIT_TRAP);
+	  trap_list[EXIT_TRAP] = (char *)NULL;
+	}
+    }
+
+  for (i = 1; i < NSIG; i++)
+    {
+      if (sigmodes[i] & SIG_TRAPPED)
+	{
+	  if (trap_list[i] == (char *)IGNORE_SIG)
+	    set_signal_handler (i, SIG_IGN);
+	  else
+	    (*reset) (i);
+	}
+      else if (sigmodes[i] & SIG_SPECIAL)
+	(*reset) (i);
+      pending_traps[i] = 0;	/* XXX */
+    }
+
+  /* Command substitution and other child processes don't inherit the
+     debug, error, or return traps.  If we're in the debugger, and the
+     `functrace' or `errtrace' options have been set, then let command
+     substitutions inherit them.  Let command substitution inherit the
+     RETURN trap if we're in the debugger and tracing functions. */
+  if (function_trace_mode == 0)
+    {
+      sigmodes[DEBUG_TRAP] &= ~SIG_TRAPPED;
+      sigmodes[RETURN_TRAP] &= ~SIG_TRAPPED;
+    }
+  if (error_trace_mode == 0)
+    sigmodes[ERROR_TRAP] &= ~SIG_TRAPPED;
+}
+
+/* Reset trapped signals to their original values, but don't free the
+   trap strings.  Called by the command substitution code and other places
+   that create a "subshell environment". */
+void
+reset_signal_handlers ()
+{
+  reset_or_restore_signal_handlers (reset_signal);
+}
+
+/* Reset all trapped signals to their original values.  Signals set to be
+   ignored with trap '' SIGNAL should be ignored, so we make sure that they
+   are.  Called by child processes after they are forked. */
+void
+restore_original_signals ()
+{
+  reset_or_restore_signal_handlers (restore_signal);
+}
+
+/* Change the flags associated with signal SIG without changing the trap
+   string. The string is TRAP_LIST[SIG] if we need it. */
+static void
+reinit_trap (sig)
+     int sig;
+{
+  sigmodes[sig] |= SIG_TRAPPED;
+  if (trap_list[sig] == (char *)IGNORE_SIG)
+    sigmodes[sig] |= SIG_IGNORED;
+  else
+    sigmodes[sig] &= ~SIG_IGNORED;
+  if (sigmodes[sig] & SIG_INPROGRESS)
+    sigmodes[sig] |= SIG_CHANGED;
+}
+
+/* Undo the effects of reset_signal_handlers(), which unsets the traps but
+   leaves the trap strings in place. This understands how reset_signal_handlers
+   works. */
+void
+restore_traps ()
+{
+  char *trapstr;
+  int i;
+
+  /* Take care of the exit trap first. If TRAP_LIST[0] is non-null, the trap
+     has been set. */
+  trapstr = trap_list[EXIT_TRAP];
+  if (trapstr)
+    reinit_trap (EXIT_TRAP);
+
+  /* Then DEBUG, RETURN, and ERROR. TRAP_LIST[N] == 0 if these signals are
+     not trapped. This knows what reset_signal_handlers does for these traps */
+  trapstr = trap_list[DEBUG_TRAP];
+  if (trapstr && function_trace_mode == 0)
+    reinit_trap (DEBUG_TRAP);
+  trapstr = trap_list[RETURN_TRAP];
+  if (trapstr && function_trace_mode == 0)
+    reinit_trap (RETURN_TRAP);
+  trapstr = trap_list[ERROR_TRAP];
+  if (trapstr && error_trace_mode == 0)
+    reinit_trap (ERROR_TRAP);
+
+  /* And finally all the `real' signals. reset_signal_handlers just changes the
+     signal handler for these signals, leaving the trap value in place. We
+     intuit what to do based on that value. We assume that signals marked as
+     SIG_SPECIAL are reinitialized by initialize_signals (), so we don't
+     change the signal handler unless the signal is supposed to be ignored. */
+  for (i = 1; i < NSIG; i++)
+    {
+      trapstr = trap_list[i];
+      if (sigmodes[i] & SIG_SPECIAL)
+	{
+	  if (trapstr && trapstr != (char *)DEFAULT_SIG)
+	    reinit_trap (i);
+	  if (trapstr == (char *)IGNORE_SIG && (sigmodes[i] & SIG_NO_TRAP) == 0)
+	    set_signal_handler (i, SIG_IGN);
+	}
+      else if (trapstr == (char *)IGNORE_SIG)
+	{
+	  reinit_trap (i);
+	  if ((sigmodes[i] & SIG_NO_TRAP) == 0)
+	    set_signal_handler (i, SIG_IGN);
+	}
+      else if (trapstr != (char *)DEFAULT_SIG)
+        /* set_signal duplicates the string argument before freeing it. */
+	set_signal (i, trapstr);
+
+      pending_traps[i] = 0;	/* XXX */
+    }
+}
+
+/* If a trap handler exists for signal SIG, then call it; otherwise just
+   return failure.  Returns 1 if it called the trap handler. */
+int
+maybe_call_trap_handler (sig)
+     int sig;
+{
+  /* Call the trap handler for SIG if the signal is trapped and not ignored. */
+  if ((sigmodes[sig] & SIG_TRAPPED) && ((sigmodes[sig] & SIG_IGNORED) == 0))
+    {
+      switch (sig)
+	{
+	case SIGINT:
+	  run_interrupt_trap (0);
+	  break;
+	case EXIT_TRAP:
+	  run_exit_trap ();
+	  break;
+	case DEBUG_TRAP:
+	  run_debug_trap ();
+	  break;
+	case ERROR_TRAP:
+	  run_error_trap ();
+	  break;
+	default:
+	  trap_handler (sig);
+	  break;
+	}
+      return (1);
+    }
+  else
+    return (0);
+}
+
+int
+signal_is_trapped (sig)
+     int sig;
+{
+  return (sigmodes[sig] & SIG_TRAPPED);
+}
+
+int
+signal_is_pending (sig)
+     int sig;
+{
+  return (pending_traps[sig]);
+}
+
+int
+signal_is_special (sig)
+     int sig;
+{
+  return (sigmodes[sig] & SIG_SPECIAL);
+}
+
+int
+signal_is_ignored (sig)
+     int sig;
+{
+  return (sigmodes[sig] & SIG_IGNORED);
+}
+
+int
+signal_is_hard_ignored (sig)
+     int sig;
+{
+  return (sigmodes[sig] & SIG_HARD_IGNORE);
+}
+
+void
+set_signal_hard_ignored (sig)
+     int sig;
+{
+  sigmodes[sig] |= SIG_HARD_IGNORE;
+  original_signals[sig] = SIG_IGN;
+}
+
+void
+set_signal_ignored (sig)
+     int sig;
+{
+  original_signals[sig] = SIG_IGN;
+}
+
+int
+signal_in_progress (sig)
+     int sig;
+{
+  return (sigmodes[sig] & SIG_INPROGRESS);
+}
+
+#if 0 /* unused */
+int
+block_trapped_signals (maskp, omaskp)
+     sigset_t *maskp;
+     sigset_t *omaskp;
+{
+  int i;
+
+  sigemptyset (maskp);
+  for (i = 1; i < NSIG; i++)
+    if (sigmodes[i] & SIG_TRAPPED)
+      sigaddset (maskp, i);
+  return (sigprocmask (SIG_BLOCK, maskp, omaskp));
+}
+
+int
+unblock_trapped_signals (maskp)
+     sigset_t *maskp;
+{
+  return (sigprocmask (SIG_SETMASK, maskp, 0));
+}
+#endif