jobs.cc

/* jobs.cc - functions that make children, remember them, and handle their
 * termination. */

/* This file works with both POSIX and BSD systems.  It implements job
   control. */

/* Copyright (C) 1989-2022 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_SYS_FILE_H)
#include <sys/file.h>
#endif

#include <sys/ioctl.h>
#if defined(HAVE_SYS_PARAM_H)
#include <sys/param.h>
#endif

#if defined(BUFFERED_INPUT)
#include "input.hh"
#endif

/* Need to include this up here for *_TTY_DRIVER definitions. */
#include "shtty.hh"

#include "shell.hh"

#include "builtext.hh"
#include "builtins/common.hh"

#if defined(READLINE)
#include "readline.hh"
#endif

#if !defined(DEFAULT_CHILD_MAX)
#define DEFAULT_CHILD_MAX 4096
#endif

#if !defined(MAX_CHILD_MAX)
#define MAX_CHILD_MAX 32768
#endif

namespace bash
{

/* Flag values for second argument to delete_job */
enum delete_job_flags
{
  DEL_WARNSTOPPED = 1, /* warn about deleting stopped jobs */
  DEL_NOBGPID = 2      /* don't add pgrp leader to bgpids */
};

/* Take care of system dependencies that must be handled when waiting for
   children.  The arguments to the WAITPID macro match those to the Posix.1
   waitpid() function. NOTE: wait3() is obsolete, so only the waitpid()
   path remains. If you'd like to run bashcpp on a system with only wait3(),
   feel free to add back the alternative macro definition. */
#if defined(_POSIX_VERSION) || defined(HAVE_WAITPID)
#define WAITPID(pid, statusp, options)                                        \
  waitpid (static_cast<pid_t> (pid), statusp, options)
#else
#error You must define an alternative WAITPID() macro, e.g. using wait3().
#endif /* !_POSIX_VERSION && !HAVE_WAITPID*/

/* getpgrp () varies between systems.  Even systems that claim to be
   Posix.1 compatible lie sometimes (Ultrix, SunOS4, apollo). */
#if defined(GETPGRP_VOID)
#define getpgid(p) getpgrp ()
#else
#define getpgid(p) getpgrp (p)
#endif /* !GETPGRP_VOID */

/* Some systems let waitpid(2) tell callers about stopped children. */
#if !defined(WCONTINUED) || defined(WCONTINUED_BROKEN)
#undef WCONTINUED
#define WCONTINUED 0
#endif

#if !defined(WIFCONTINUED)
#define WIFCONTINUED(s) (0)
#endif

#define QUEUE_SIGCHLD(os) (os) = sigchld, queue_sigchld++

/* We set queue_sigchld around the call to waitchld to protect data structures
   from a SIGCHLD arriving while waitchld is executing. */
#define UNQUEUE_SIGCHLD(os)                                                   \
  do                                                                          \
    {                                                                         \
      queue_sigchld--;                                                        \
      if (queue_sigchld == 0 && os != sigchld)                                \
        {                                                                     \
          queue_sigchld = 1;                                                  \
          waitchld (-1, 0);                                                   \
          queue_sigchld = 0;                                                  \
        }                                                                     \
    }                                                                         \
  while (0)

#if 0
static SigHandler *old_tstp, *old_ttou, *old_ttin;
static SigHandler *old_cont = (SigHandler *)SIG_DFL;

/* A place to temporarily save the current pipeline. */
static struct pipeline_saver *saved_pipeline;
static bool saved_already_making_children;

/* Set this to non-zero whenever you don't want the jobs list to change at
   all: no jobs deleted and no status change notifications.  This is used,
   for example, when executing SIGCHLD traps, which may run arbitrary
   commands. */
static int jobs_list_frozen;

static char retcode_name_buffer[64];
#endif

#if !defined(_POSIX_VERSION)

/* These are definitions to map POSIX 1003.1 functions onto existing BSD
   library functions and system calls. */
#define setpgid(pid, pgrp) setpgrp (pid, pgrp)
#define tcsetpgrp(fd, pgrp) ioctl ((fd), TIOCSPGRP, &(pgrp))

pid_t
tcgetpgrp (int fd)
{
  pid_t pgrp;

  /* ioctl will handle setting errno correctly. */
  if (ioctl (fd, TIOCGPGRP, &pgrp) < 0)
    return -1;
  return pgrp;
}

#endif /* !_POSIX_VERSION */

/* Return the working directory for the current process.  Unlike
   job_working_directory, this does not call malloc/new, nor do any
   of the functions it calls.  This is so that it can safely be called
   from a signal handler. */
const char *
Shell::current_working_directory ()
{
  static char d[PATH_MAX]; // Static cache var (safe to leave here)

  const char *dir = get_string_value ("PWD");

  if (dir == nullptr && the_current_working_directory && no_symbolic_links)
    dir = the_current_working_directory;

  if (dir == 0)
    {
      dir = getcwd (d, sizeof (d));
      if (dir)
        dir = d;
    }

  return (dir == nullptr) ? "<unknown>" : dir;
}

// Return the working directory for the current process. This returns a new
// string that the caller must delete.
char *
Shell::job_working_directory ()
{
  const char *pwd_dir = get_string_value ("PWD");
  if (pwd_dir)
    return savestring (pwd_dir);

  char *dir = get_working_directory ("job-working-directory");
  if (dir)
    return dir;

  return savestring ("<unknown>");
}

void
Shell::save_pipeline (bool clear)
{
  sigset_t set, oset;
  struct pipeline_saver *saver;

  BLOCK_CHILD (set, oset);
  saver = alloc_pipeline_saver ();
  saver->pipeline = the_pipeline;
  saver->next = saved_pipeline;
  saved_pipeline = saver;
  if (clear)
    the_pipeline = nullptr;
  saved_already_making_children = already_making_children;
  UNBLOCK_CHILD (oset);
}

PROCESS *
Shell::restore_pipeline (bool discard)
{
  PROCESS *old_pipeline;
  sigset_t set, oset;
  struct pipeline_saver *saver;

  BLOCK_CHILD (set, oset);
  old_pipeline = the_pipeline;
  the_pipeline = saved_pipeline->pipeline;
  saver = saved_pipeline;
  saved_pipeline = saved_pipeline->next;
  free (saver);
  already_making_children = saved_already_making_children;
  UNBLOCK_CHILD (oset);

  if (discard && old_pipeline)
    {
      discard_pipeline (old_pipeline);
      return nullptr;
    }
  return old_pipeline;
}

/* Start building a pipeline.  */
void
Shell::start_pipeline ()
{
  if (the_pipeline)
    {
      cleanup_the_pipeline ();
      /* If job_control == 0, pipeline_pgrp will always be equal to shell_pgrp;
         if job_control != 0, pipeline_pgrp == shell_pgrp for command and
         process substitution, in which case we want it to be the same as
         shell_pgrp for the lifetime of this shell instance. */
      if (pipeline_pgrp != shell_pgrp)
        pipeline_pgrp = 0;
#if defined(PGRP_PIPE)
      sh_closepipe (pgrp_pipe);
#endif
    }

#if defined(PGRP_PIPE)
  if (job_control)
    {
      if (pipe (pgrp_pipe) == -1)
        sys_error (_ ("start_pipeline: pgrp pipe"));
    }
#endif
}

/* Stop building a pipeline.  Install the process list in the job array.
   This returns the index of the newly installed job.
   DEFERRED is a command structure to be executed upon satisfactory
   execution exit of this pipeline. */
int
Shell::stop_pipeline (bool async, COMMAND *deferred)
{
  JOB *newjob;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);

#if defined(PGRP_PIPE)
  /* The parent closes the process group synchronization pipe. */
  sh_closepipe (pgrp_pipe);
#endif

  cleanup_dead_jobs ();

  if (js.j_jobslots == 0)
    {
      js.j_jobslots = JOB_SLOTS;
      jobs = (JOB **)xmalloc (js.j_jobslots * sizeof (JOB *));

      /* Now blank out these new entries. */
      for (int i = 0; i < js.j_jobslots; i++)
        jobs[i] = nullptr;

      js.j_firstj = js.j_lastj = js.j_njobs = 0;
    }

  /* Scan from the last slot backward, looking for the next free one. */
  /* XXX - revisit this interactive assumption */
  /* XXX - this way for now */
  int i;
  if (interactive)
    {
      for (i = js.j_jobslots; i; i--)
        if (jobs[i - 1])
          break;
    }
  else
    {
#if 0
      /* This wraps around, but makes it inconvenient to extend the array */
      for (i = js.j_lastj+1; i != js.j_lastj; i++)
	{
	  if (i >= js.j_jobslots)
	    i = 0;
	  if (jobs[i] == 0)
	    break;
	}
      if (i == js.j_lastj)
        i = js.j_jobslots;
#else
      /* This doesn't wrap around yet. */
      for (i = js.j_lastj ? js.j_lastj + 1 : js.j_lastj; i < js.j_jobslots;
           i++)
        if (jobs[i] == 0)
          break;
#endif
    }

  /* Do we need more room? */

  /* First try compaction */
  if ((!interactive_shell || subshell_environment) && i == js.j_jobslots
      && js.j_jobslots >= MAX_JOBS_IN_ARRAY)
    {
      i = compact_jobs_list (0);
    }

  /* If we can't compact, reallocate */
  if (i == js.j_jobslots)
    {
      js.j_jobslots += JOB_SLOTS;
      jobs = (JOB **)xrealloc (jobs, (js.j_jobslots * sizeof (JOB *)));

      for (int j = i; j < js.j_jobslots; j++)
        jobs[j] = nullptr;
    }

  /* Add the current pipeline to the job list. */
  if (the_pipeline)
    {
      PROCESS *p;
      int any_running, any_stopped, n;

      newjob = new JOB ();

      for (n = 1, p = the_pipeline; p->next != the_pipeline; n++, p = p->next)
        ;
      p->next = nullptr;
      newjob->pipe = REVERSE_LIST (the_pipeline, PROCESS *);
      for (p = newjob->pipe; p->next; p = p->next)
        ;
      p->next = newjob->pipe;

      the_pipeline = nullptr;
      newjob->pgrp = pipeline_pgrp;

      /* Invariant: if the shell is executing a command substitution,
         pipeline_pgrp == shell_pgrp. Other parts of the shell assume this. */
      if (pipeline_pgrp != shell_pgrp)
        pipeline_pgrp = 0;

      newjob->flags = 0;
      if (pipefail_opt)
        newjob->flags |= J_PIPEFAIL;

      /* Flag to see if in another pgrp. */
      if (job_control)
        newjob->flags |= J_JOBCONTROL;

      /* Set the state of this pipeline. */
      p = newjob->pipe;
      any_running = any_stopped = 0;
      do
        {
          any_running |= PRUNNING (p);
          any_stopped |= PSTOPPED (p);
          p = p->next;
        }
      while (p != newjob->pipe);

      newjob->state
          = any_running ? JRUNNING : (any_stopped ? JSTOPPED : JDEAD);
      newjob->wd = job_working_directory ();
      newjob->deferred = deferred;

      newjob->j_cleanup = nullptr;
      newjob->cleanarg = nullptr;

      jobs[i] = newjob;
      if (newjob->state == JDEAD && (newjob->flags & J_FOREGROUND))
        setjstatus (i);
      if (newjob->state == JDEAD)
        {
          js.c_reaped += n; /* wouldn't have been done since this was not part
                               of a job */
          js.j_ndead++;
        }
      js.c_injobs += n;

      js.j_lastj = i;
      js.j_njobs++;
    }
  else
    newjob = nullptr;

  if (newjob)
    js.j_lastmade = newjob;

  if (async)
    {
      if (newjob)
        {
          newjob->flags &= ~J_FOREGROUND;
          newjob->flags |= J_ASYNC;
          js.j_lastasync = newjob;
        }
      reset_current ();
    }
  else
    {
      if (newjob)
        {
          newjob->flags |= J_FOREGROUND;
          /*
           *		!!!!! NOTE !!!!!  (chet@po.cwru.edu)
           *
           * The currently-accepted job control wisdom says to set the
           * terminal's process group n+1 times in an n-step pipeline:
           * once in the parent and once in each child.  This is where
           * the parent gives it away.
           *
           * Don't give the terminal away if this shell is an asynchronous
           * subshell or if we're a (presumably non-interactive) shell running
           * in the background.
           *
           */
          if (job_control && newjob->pgrp
              && (subshell_environment & SUBSHELL_ASYNC) == 0
              && !running_in_background)
            maybe_give_terminal_to (shell_pgrp, newjob->pgrp, 0);
        }
    }

  stop_making_children ();
  UNBLOCK_CHILD (oset);
  return newjob ? i : js.j_current;
}

/* Functions to manage the list of exited background pids whose status has
   been saved.

   pidstat_table:

   The current implementation is a hash table using a single (separate) arena
   for storage that can be allocated and freed as a unit.  The size of the hash
   table is a multiple of PIDSTAT_TABLE_SZ (4096) and multiple PIDs that hash
   to the same value are chained through the bucket_next and bucket_prev
   pointers (basically coalesced hashing for collision resolution).

   bgpids.storage:

   All pid/status storage is done using the circular buffer bgpids.storage.
   This must contain at least js.c_childmax entries.  The circular buffer is
   used to supply the ordered list Posix requires ("the last CHILD_MAX
   processes").  To avoid searching the entire storage table for a given PID,
   the hash table (pidstat_table) holds pointers into the storage arena and
   uses a doubly-linked list of cells (bucket_next/bucket_prev, also pointers
   into the arena) to implement collision resolution. */

/* The number of elements in bgpids.storage always has to be > js.c_childmax
   for the circular buffer to work right. */
void
Shell::bgp_resize ()
{
  ps_index_t nsize, nsize_cur, nsize_max;
  ps_index_t psi;

  if (bgpids.nalloc == 0)
    {
      /* invalidate hash table when bgpids table is reallocated */
      for (psi = 0; psi < PIDSTAT_TABLE_SZ; psi++)
        pidstat_table[psi] = NO_PIDSTAT;
      nsize = BGPIDS_TABLE_SZ; /* should be power of 2 */
      bgpids.head = 0;
    }
  else
    nsize = bgpids.nalloc;

  nsize_max = TYPE_MAXIMUM (ps_index_t);
  nsize_cur = (ps_index_t)js.c_childmax;
  if (nsize_cur < 0) /* overflow */
    nsize_cur = MAX_CHILD_MAX;

  while (nsize > 0 && nsize < nsize_cur) /* > 0 should catch overflow */
    nsize <<= 1;
  if (nsize > nsize_max || nsize <= 0) /* overflow? */
    nsize = nsize_max;
  if (nsize > MAX_CHILD_MAX)
    nsize = nsize_max = MAX_CHILD_MAX; /* hard cap */

  if (bgpids.nalloc < nsize_cur && bgpids.nalloc < nsize_max)
    {
      bgpids.storage = (struct pidstat *)xrealloc (
          bgpids.storage, nsize * sizeof (struct pidstat));

      for (psi = bgpids.nalloc; psi < nsize; psi++)
        bgpids.storage[psi].pid = NO_PID;

      bgpids.nalloc = nsize;
    }
  else if (bgpids.head >= bgpids.nalloc) /* wrap around */
    bgpids.head = 0;
}

ps_index_t
Shell::bgp_getindex ()
{
  if (bgpids.nalloc < (ps_index_t)js.c_childmax
      || bgpids.head >= bgpids.nalloc)
    bgp_resize ();

  pshash_delindex (bgpids.head); /* XXX - clear before reusing */
  return bgpids.head++;
}

ps_index_t *
Shell::pshash_getbucket (pid_t pid)
{
  unsigned long hash; /* XXX - u_bits32_t */

  hash = pid * 0x9e370001UL;
  return &pidstat_table[hash % PIDSTAT_TABLE_SZ];
}

struct pidstat *
Shell::bgp_add (pid_t pid, int status)
{
  ps_index_t *bucket, psi;
  struct pidstat *ps;

  /* bucket == existing chain of pids hashing to same value
     psi = where were going to put this pid/status */

  bucket = pshash_getbucket (pid); /* index into pidstat_table */
  psi = bgp_getindex ();           /* bgpids.head, index into storage */

  /* XXX - what if psi == *bucket? */
  if (psi == *bucket)
    {
      internal_debug (
          "hashed pid %d (pid %d) collides with bgpids.head, skipping", psi,
          pid);
      bgpids.storage[psi].pid = NO_PID; /* make sure */
      psi = bgp_getindex ();            /* skip to next one */
    }

  ps = &bgpids.storage[psi];

  ps->pid = pid;
  ps->status = status;
  ps->bucket_next = *bucket;
  ps->bucket_prev = NO_PIDSTAT;

  bgpids.npid++;

#if 0
  if (bgpids.npid > js.c_childmax)
    bgp_prune ();
#endif

  if (ps->bucket_next != NO_PIDSTAT)
    bgpids.storage[ps->bucket_next].bucket_prev = psi;

  *bucket = psi; /* set chain head in hash table */

  return ps;
}

void
Shell::pshash_delindex (ps_index_t psi)
{
  struct pidstat *ps;
  ps_index_t *bucket;

  ps = &bgpids.storage[psi];
  if (ps->pid == NO_PID)
    return;

  if (ps->bucket_next != NO_PIDSTAT)
    bgpids.storage[ps->bucket_next].bucket_prev = ps->bucket_prev;
  if (ps->bucket_prev != NO_PIDSTAT)
    bgpids.storage[ps->bucket_prev].bucket_next = ps->bucket_next;
  else
    {
      bucket = pshash_getbucket (ps->pid);
      *bucket = ps->bucket_next; /* deleting chain head in hash table */
    }

  /* clear out this cell, in case it gets reused. */
  ps->pid = NO_PID;
  ps->bucket_next = ps->bucket_prev = NO_PIDSTAT;
}

int
Shell::bgp_delete (pid_t pid)
{
  ps_index_t psi, orig_psi;

  if (bgpids.storage == 0 || bgpids.nalloc == 0 || bgpids.npid == 0)
    return 0;

  /* Search chain using hash to find bucket in pidstat_table */
  for (orig_psi = psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT;
       psi = bgpids.storage[psi].bucket_next)
    {
      if (bgpids.storage[psi].pid == pid)
        break;
      if (orig_psi == bgpids.storage[psi].bucket_next) /* catch reported bug */
        {
          internal_warning (
              _ ("bgp_delete: LOOP: psi (%d) == storage[psi].bucket_next"),
              psi);
          return 0;
        }
    }

  if (psi == NO_PIDSTAT)
    return 0; /* not found */

#if 0
  itrace("bgp_delete: deleting %d", pid);
#endif

  pshash_delindex (psi); /* hash table management */

  bgpids.npid--;
  return 1;
}

/* Clear out the list of saved statuses */
void
Shell::bgp_clear ()
{
  if (bgpids.storage == 0 || bgpids.nalloc == 0)
    return;

  free (bgpids.storage);

  bgpids.storage = 0;
  bgpids.nalloc = 0;
  bgpids.head = 0;

  bgpids.npid = 0;
}

/* Search for PID in the list of saved background pids; return its status if
   found.  If not found, return -1.  We hash to the right spot in pidstat_table
   and follow the bucket chain to the end. */
int
Shell::bgp_search (pid_t pid)
{
  ps_index_t psi, orig_psi;

  if (bgpids.storage == 0 || bgpids.nalloc == 0 || bgpids.npid == 0)
    return -1;

  /* Search chain using hash to find bucket in pidstat_table */
  for (orig_psi = psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT;
       psi = bgpids.storage[psi].bucket_next)
    {
      if (bgpids.storage[psi].pid == pid)
        return bgpids.storage[psi].status;
      if (orig_psi == bgpids.storage[psi].bucket_next) /* catch reported bug */
        {
          internal_warning (
              _ ("bgp_search: LOOP: psi (%d) == storage[psi].bucket_next"),
              psi);
          return -1;
        }
    }

  return -1;
}

/* External interface to bgp_add; takes care of blocking and unblocking
   SIGCHLD. Not really used. */
void
Shell::save_proc_status (pid_t pid, int status)
{
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);
  bgp_add (pid, status);
  UNBLOCK_CHILD (oset);
}

#if defined(PROCESS_SUBSTITUTION)
/* Functions to add and remove PROCESS * children from the list of running
   asynchronous process substitutions. The list is currently a simple singly
   linked list of PROCESS *, so it works with the set of callers that want
   a child. subst.c:process_substitute adds to the list, the various wait*
   functions manipulate child->running and child->status, and processes are
   eventually removed from the list and added to the bgpids table. */

PROCESS *
procsub_add (PROCESS *p)
{
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);
  if (procsubs.head == 0)
    {
      procsubs.head = procsubs.end = p;
      procsubs.nproc = 0;
    }
  else
    {
      procsubs.end->next = p;
      procsubs.end = p;
    }
  procsubs.nproc++;
  UNBLOCK_CHILD (oset);

  return p;
}

PROCESS *
procsub_search (pid_t pid)
{
  PROCESS *p;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);
  for (p = procsubs.head; p; p = p->next)
    if (p->pid == pid)
      break;
  UNBLOCK_CHILD (oset);

  return p;
}

PROCESS *
procsub_delete (pid_t pid)
{
  PROCESS *p, *prev;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);
  for (p = prev = procsubs.head; p; prev = p, p = p->next)
    if (p->pid == pid)
      {
        prev->next = p->next;
        break;
      }

  if (p == 0)
    {
      UNBLOCK_CHILD (oset);
      return p;
    }

  if (p == procsubs.head)
    procsubs.head = procsubs.head->next;
  else if (p == procsubs.end)
    procsubs.end = prev;

  procsubs.nproc--;
  if (procsubs.nproc == 0)
    procsubs.head = procsubs.end = 0;
  else if (procsubs.nproc == 1) /* XXX */
    procsubs.end = procsubs.head;

  /* this can't be called anywhere in a signal handling path */
  bgp_add (p->pid, process_exit_status (p->status));
  UNBLOCK_CHILD (oset);
  return p;
}

int
procsub_waitpid (pid_t pid)
{
  PROCESS *p;
  int r;

  p = procsub_search (pid);
  if (p == 0)
    return -1;
  if (p->running == PS_DONE)
    return p->status;
  r = wait_for (p->pid, 0);
  return r; /* defer removing until later */
}

void
procsub_waitall ()
{
  PROCESS *p;
  int r;

  for (p = procsubs.head; p; p = p->next)
    {
      if (p->running == PS_DONE)
        continue;
      r = wait_for (p->pid, 0);
    }
}

void
procsub_clear ()
{
  PROCESS *p, *ps;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);

  for (ps = procsubs.head; ps;)
    {
      p = ps;
      ps = ps->next;
      procsub_free (p);
    }
  procsubs.head = procsubs.end = 0;
  procsubs.nproc = 0;
  UNBLOCK_CHILD (oset);
}

/* Must be called with SIGCHLD blocked. */
void
procsub_prune ()
{
  PROCESS *ohead, *oend, *ps, *p;
  int onproc;

  if (procsubs.nproc == 0)
    return;

  ohead = procsubs.head;
  oend = procsubs.end;
  onproc = procsubs.nproc;

  procsubs.head = procsubs.end = 0;
  procsubs.nproc = 0;

  for (p = ohead; p;)
    {
      ps = p->next;
      p->next = 0;
      if (p->running == PS_DONE)
        {
          bgp_add (p->pid, process_exit_status (p->status));
          procsub_free (p);
        }
      else
        procsub_add (p);
      p = ps;
    }
}
#endif

/* Reset the values of js.j_lastj and js.j_firstj after one or both have
   been deleted.  The caller should check whether js.j_njobs is 0 before
   calling this.  This wraps around, but the rest of the code does not.  At
   this point, it should not matter. */
static void
reset_job_indices ()
{
  int old;

  if (jobs[js.j_firstj] == 0)
    {
      old = js.j_firstj++;
      if (old >= js.j_jobslots)
        old = js.j_jobslots - 1;
      while (js.j_firstj != old)
        {
          if (js.j_firstj >= js.j_jobslots)
            js.j_firstj = 0;
          if (jobs[js.j_firstj] || js.j_firstj == old) /* needed if old == 0 */
            break;
          js.j_firstj++;
        }
      if (js.j_firstj == old)
        js.j_firstj = js.j_lastj = js.j_njobs = 0;
    }
  if (jobs[js.j_lastj] == 0)
    {
      old = js.j_lastj--;
      if (old < 0)
        old = 0;
      while (js.j_lastj != old)
        {
          if (js.j_lastj < 0)
            js.j_lastj = js.j_jobslots - 1;
          if (jobs[js.j_lastj]
              || js.j_lastj == old) /* needed if old == js.j_jobslots */
            break;
          js.j_lastj--;
        }
      if (js.j_lastj == old)
        js.j_firstj = js.j_lastj = js.j_njobs = 0;
    }
}

/* Delete all DEAD jobs that the user had received notification about. */
static void
cleanup_dead_jobs ()
{
  int i;
  int os;
  PROCESS *discard;

  if (js.j_jobslots == 0 || jobs_list_frozen)
    return;

  QUEUE_SIGCHLD (os);

  /* XXX could use js.j_firstj and js.j_lastj here */
  for (i = 0; i < js.j_jobslots; i++)
    {
      if (i < js.j_firstj && jobs[i])
        INTERNAL_DEBUG (
            ("cleanup_dead_jobs: job %d non-null before js.j_firstj (%d)", i,
             js.j_firstj));
      if (i > js.j_lastj && jobs[i])
        INTERNAL_DEBUG (
            ("cleanup_dead_jobs: job %d non-null after js.j_lastj (%d)", i,
             js.j_lastj));

      if (jobs[i] && DEADJOB (i) && IS_NOTIFIED (i))
        delete_job (i, 0);
    }

#if defined(PROCESS_SUBSTITUTION)
  procsub_prune ();
  last_procsub_child = nullptr;
#endif

#if defined(COPROCESS_SUPPORT)
  coproc_reap ();
#endif

  UNQUEUE_SIGCHLD (os);
}

static int
processes_in_job (int job)
{
  int nproc;
  PROCESS *p;

  nproc = 0;
  p = jobs[job]->pipe;
  do
    {
      p = p->next;
      nproc++;
    }
  while (p != jobs[job]->pipe);

  return nproc;
}

static void
delete_old_job (pid_t pid)
{
  PROCESS *p;
  int job;

  job = find_job (pid, 0, &p);
  if (job != NO_JOB)
    {
      INTERNAL_DEBUG (("delete_old_job: found pid %d in job %d with state %d",
                       pid, job, jobs[job]->state));
      if (JOBSTATE (job) == JDEAD)
        delete_job (job, DEL_NOBGPID);
      else
        {
          internal_debug (_ ("forked pid %d appears in running job %d"), pid,
                          job + 1);
          if (p)
            p->pid = 0;
        }
    }
}

/* Reallocate and compress the jobs list.  This returns with a jobs array
   whose size is a multiple of JOB_SLOTS and can hold the current number of
   jobs.  Heuristics are used to minimize the number of new reallocs. */
static void
realloc_jobs_list ()
{
  sigset_t set, oset;
  int nsize, i, j, ncur, nprev;
  JOB **nlist;

  ncur = nprev = NO_JOB;
  nsize = ((js.j_njobs + JOB_SLOTS - 1) / JOB_SLOTS);
  nsize *= JOB_SLOTS;
  i = js.j_njobs % JOB_SLOTS;
  if (i == 0 || i > (JOB_SLOTS >> 1))
    nsize += JOB_SLOTS;

  BLOCK_CHILD (set, oset);
  nlist = (js.j_jobslots == nsize) ? jobs
                                   : (JOB **)xmalloc (nsize * sizeof (JOB *));

  js.c_reaped = js.j_ndead = 0;
  for (i = j = 0; i < js.j_jobslots; i++)
    if (jobs[i])
      {
        if (i == js.j_current)
          ncur = j;
        if (i == js.j_previous)
          nprev = j;
        nlist[j++] = jobs[i];
        if (jobs[i]->state == JDEAD)
          {
            js.j_ndead++;
            js.c_reaped += processes_in_job (i);
          }
      }

#if 0
  itrace ("realloc_jobs_list: resize jobs list from %d to %d", js.j_jobslots, nsize);
  itrace ("realloc_jobs_list: j_lastj changed from %d to %d", js.j_lastj, (j > 0) ? j - 1 : 0);
  itrace ("realloc_jobs_list: j_njobs changed from %d to %d", js.j_njobs, j);
  itrace ("realloc_jobs_list: js.j_ndead %d js.c_reaped %d", js.j_ndead, js.c_reaped);
#endif

  js.j_firstj = 0;
  js.j_lastj = (j > 0) ? j - 1 : 0;
  js.j_njobs = j;
  js.j_jobslots = nsize;

  /* Zero out remaining slots in new jobs list */
  for (; j < nsize; j++)
    nlist[j] = nullptr;

  if (jobs != nlist)
    {
      free (jobs);
      jobs = nlist;
    }

  if (ncur != NO_JOB)
    js.j_current = ncur;
  if (nprev != NO_JOB)
    js.j_previous = nprev;

  /* Need to reset these */
  if (js.j_current == NO_JOB || js.j_previous == NO_JOB
      || js.j_current > js.j_lastj || js.j_previous > js.j_lastj)
    reset_current ();

#if 0
  itrace ("realloc_jobs_list: reset js.j_current (%d) and js.j_previous (%d)", js.j_current, js.j_previous);
#endif

  UNBLOCK_CHILD (oset);
}

/* Compact the jobs list by removing dead jobs.  Assume that we have filled
   the jobs array to some predefined maximum.  Called when the shell is not
   the foreground process (subshell_environment != 0).  Returns the first
   available slot in the compacted list.  If that value is js.j_jobslots, then
   the list needs to be reallocated.  The jobs array may be in new memory if
   this returns > 0 and < js.j_jobslots.  FLAGS is reserved for future use. */
static int
compact_jobs_list (int flags)
{
  if (js.j_jobslots == 0 || jobs_list_frozen)
    return js.j_jobslots;

  reap_dead_jobs ();
  realloc_jobs_list ();

#if 0
  itrace("compact_jobs_list: returning %d", (js.j_lastj || jobs[js.j_lastj]) ? js.j_lastj + 1 : 0);
#endif

  return (js.j_lastj || jobs[js.j_lastj]) ? js.j_lastj + 1 : 0;
}

/* Delete the job at INDEX from the job list.  Must be called
   with SIGCHLD blocked. */
void
delete_job (int job_index, int dflags)
{
  JOB *temp;
  PROCESS *proc;
  int ndel;

  if (js.j_jobslots == 0 || jobs_list_frozen)
    return;

  if ((dflags & DEL_WARNSTOPPED) && subshell_environment == 0
      && STOPPED (job_index))
    internal_warning (_ ("deleting stopped job %d with process group %ld"),
                      job_index + 1, (long)jobs[job_index]->pgrp);

  temp = jobs[job_index];
  if (temp == 0)
    return;

  if ((dflags & DEL_NOBGPID) == 0
      && (temp->flags & (J_ASYNC | J_FOREGROUND)) == J_ASYNC)
    {
      proc = find_last_proc (job_index, 0);
      if (proc)
        bgp_add (proc->pid, process_exit_status (proc->status));
    }

  jobs[job_index] = nullptr;
  if (temp == js.j_lastmade)
    js.j_lastmade = 0;
  else if (temp == js.j_lastasync)
    js.j_lastasync = 0;

  free (temp->wd);
  ndel = discard_pipeline (temp->pipe);

  js.c_injobs -= ndel;
  if (temp->state == JDEAD)
    {
      /* XXX - save_pipeline and restore_pipeline (e.g., for DEBUG trap) can
         mess with this total. */
      js.c_reaped -= ndel; /* assumes proc hadn't been reaped earlier */
      js.j_ndead--;

      if (js.c_reaped < 0)
        {
          INTERNAL_DEBUG (("delete_job (%d pgrp %d): js.c_reaped (%d) < 0 "
                           "ndel = %d js.j_ndead = %d",
                           job_index, temp->pgrp, js.c_reaped, ndel,
                           js.j_ndead));
          js.c_reaped = 0;
        }
    }

  if (temp->deferred)
    dispose_command (temp->deferred);

  free (temp);

  js.j_njobs--;
  if (js.j_njobs == 0)
    js.j_firstj = js.j_lastj = 0;
  else if (jobs[js.j_firstj] == 0 || jobs[js.j_lastj] == 0)
    reset_job_indices ();

  if (job_index == js.j_current || job_index == js.j_previous)
    reset_current ();
}

/* Must be called with SIGCHLD blocked. */
void
nohup_job (int job_index)
{
  JOB *temp;

  if (js.j_jobslots == 0)
    return;

  if ((temp = jobs[job_index]))
    temp->flags |= J_NOHUP;
}

/* Get rid of the data structure associated with a process chain. */
int
discard_pipeline (PROCESS *chain)
{
  PROCESS *this_, *next;
  int n;

  this_ = chain;
  n = 0;
  do
    {
      next = this_->next;
      FREE (this_->command);
      free (this_);
      n++;
      this_ = next;
    }
  while (this_ != chain);

  return n;
}

/* Add this process to the chain being built in the_pipeline.
   NAME is the command string that will be exec'ed later.
   PID is the process id of the child. */
static void
add_process (char *name, pid_t pid)
{
  PROCESS *t, *p;

#if defined(RECYCLES_PIDS)
  int j;
  p = find_process (pid, 0, &j);
  if (p)
    {
      if (j == NO_JOB)
        internal_debug ("add_process: process %5ld (%s) in the_pipeline",
                        (long)p->pid, p->command);
      if (PALIVE (p))
        internal_warning (
            _ ("add_process: pid %5ld (%s) marked as still alive"),
            (long)p->pid, p->command);
      p->running = PS_RECYCLED; /* mark as recycled */
    }
#endif

  t = (PROCESS *)xmalloc (sizeof (PROCESS));
  t->next = the_pipeline;
  t->pid = pid;
  WSTATUS (t->status) = 0;
  t->running = PS_RUNNING;
  t->command = name;
  the_pipeline = t;

  if (t->next == 0)
    t->next = t;
  else
    {
      p = t->next;
      while (p->next != t->next)
        p = p->next;
      p->next = t;
    }
}

/* Create a (dummy) PROCESS with NAME, PID, and STATUS, and make it the last
   process in jobs[JID]->pipe.  Used by the lastpipe code. */
void
append_process (char *name, pid_t pid, int status, int jid)
{
  PROCESS *t, *p;

  t = (PROCESS *)xmalloc (sizeof (PROCESS));
  t->next = nullptr;
  t->pid = pid;
  /* set process exit status using offset discovered by configure */
  t->status = (status & 0xff) << WEXITSTATUS_OFFSET;
  t->running = PS_DONE;
  t->command = name;

  js.c_reaped++; /* XXX */

  for (p = jobs[jid]->pipe; p->next != jobs[jid]->pipe; p = p->next)
    ;
  p->next = t;
  t->next = jobs[jid]->pipe;
}

#if 0
/* Take the last job and make it the first job.  Must be called with
   SIGCHLD blocked. */
int
rotate_the_pipeline ()
{
  PROCESS *p;

  if (the_pipeline->next == the_pipeline)
    return;
  for (p = the_pipeline; p->next != the_pipeline; p = p->next)
    ;
  the_pipeline = p;
}

/* Reverse the order of the processes in the_pipeline.  Must be called with
   SIGCHLD blocked. */
int
reverse_the_pipeline ()
{
  PROCESS *p, *n;

  if (the_pipeline->next == the_pipeline)
    return;

  for (p = the_pipeline; p->next != the_pipeline; p = p->next)
    ;
  p->next = nullptr;

  n = REVERSE_LIST (the_pipeline, PROCESS *);

  the_pipeline = n;
  for (p = the_pipeline; p->next; p = p->next)
    ;
  p->next = the_pipeline;
}
#endif

/* Map FUNC over the list of jobs.  If FUNC returns non-zero,
   then it is time to stop mapping, and that is the return value
   for map_over_jobs.  FUNC is called with a JOB, arg1, arg2,
   and INDEX. */
int
Shell::map_over_jobs (sh_job_map_func_t *func, int arg1, int arg2)
{
  int i;
  int result;
  sigset_t set, oset;

  if (js.j_jobslots == 0)
    return 0;

  BLOCK_CHILD (set, oset);

  /* XXX could use js.j_firstj here */
  for (i = result = 0; i < js.j_jobslots; i++)
    {
      if (i < js.j_firstj && jobs[i])
        INTERNAL_DEBUG (
            ("map_over_jobs: job %d non-null before js.j_firstj (%d)", i,
             js.j_firstj));
      if (i > js.j_lastj && jobs[i])
        INTERNAL_DEBUG (
            ("map_over_jobs: job %d non-null after js.j_lastj (%d)", i,
             js.j_lastj));

      if (jobs[i])
        {
          result = (*func) (jobs[i], arg1, arg2, i);
          if (result)
            break;
        }
    }

  UNBLOCK_CHILD (oset);

  return result;
}

/* Cause all the jobs in the current pipeline to exit. */
void
terminate_current_pipeline ()
{
  if (pipeline_pgrp && pipeline_pgrp != shell_pgrp)
    {
      killpg (pipeline_pgrp, SIGTERM);
      killpg (pipeline_pgrp, SIGCONT);
    }
}

/* Cause all stopped jobs to exit. */
void
terminate_stopped_jobs ()
{
  int i;

  /* XXX could use js.j_firstj here */
  for (i = 0; i < js.j_jobslots; i++)
    {
      if (jobs[i] && STOPPED (i))
        {
          killpg (jobs[i]->pgrp, SIGTERM);
          killpg (jobs[i]->pgrp, SIGCONT);
        }
    }
}

/* Cause all jobs, running or stopped, to receive a hangup signal.  If
   a job is marked J_NOHUP, don't send the SIGHUP. */
void
hangup_all_jobs ()
{
  int i;

  /* XXX could use js.j_firstj here */
  for (i = 0; i < js.j_jobslots; i++)
    {
      if (jobs[i])
        {
          if (jobs[i]->flags & J_NOHUP)
            continue;
          killpg (jobs[i]->pgrp, SIGHUP);
          if (STOPPED (i))
            killpg (jobs[i]->pgrp, SIGCONT);
        }
    }
}

void
kill_current_pipeline ()
{
  stop_making_children ();
  start_pipeline ();
}

static PROCESS *
find_pid_in_pipeline (pid_t pid, PROCESS *pipeline, int alive_only)
{
  PROCESS *p;

  p = pipeline;
  do
    {
      /* Return it if we found it.  Don't ever return a recycled pid. */
      if (p->pid == pid
          && ((alive_only == 0 && PRECYCLED (p) == 0) || PALIVE (p)))
        return p;

      p = p->next;
    }
  while (p != pipeline);
  return nullptr;
}

/* Return the pipeline that PID belongs to.  Note that the pipeline
   doesn't have to belong to a job.  Must be called with SIGCHLD blocked.
   If JOBP is non-null, return the index of the job containing PID.  */
static PROCESS *
find_pipeline (pid_t pid, int alive_only, int *jobp)
{
  int job;
  PROCESS *p;
  struct pipeline_saver *save;

  /* See if this process is in the pipeline that we are building. */
  p = nullptr;
  if (jobp)
    *jobp = NO_JOB;

  if (the_pipeline
      && (p = find_pid_in_pipeline (pid, the_pipeline, alive_only)))
    return p;

  /* Is this process in a saved pipeline? */
  for (save = saved_pipeline; save; save = save->next)
    if (save->pipeline
        && (p = find_pid_in_pipeline (pid, save->pipeline, alive_only)))
      return p;

#if defined(PROCESS_SUBSTITUTION)
  if (procsubs.nproc > 0 && (p = procsub_search (pid))
      && ((alive_only == 0 && PRECYCLED (p) == 0) || PALIVE (p)))
    return p;
#endif

  job = find_job (pid, alive_only, &p);
  if (jobp)
    *jobp = job;
  return (job == NO_JOB) ? nullptr : jobs[job]->pipe;
}

/* Return the PROCESS * describing PID.  If JOBP is non-null return the index
   into the jobs array of the job containing PID.  Must be called with
   SIGCHLD blocked. */
static PROCESS *
find_process (pid_t pid, int alive_only, int *jobp)
{
  PROCESS *p;

  p = find_pipeline (pid, alive_only, jobp);
  while (p && p->pid != pid)
    p = p->next;
  return p;
}

/* Return the job index that PID belongs to, or NO_JOB if it doesn't
   belong to any job.  Must be called with SIGCHLD blocked. */
static int
find_job (pid_t pid, int alive_only, PROCESS **procp)
{
  int i;
  PROCESS *p;

  /* XXX could use js.j_firstj here, and should check js.j_lastj */
  for (i = 0; i < js.j_jobslots; i++)
    {
      if (i < js.j_firstj && jobs[i])
        INTERNAL_DEBUG (("find_job: job %d non-null before js.j_firstj (%d)",
                         i, js.j_firstj));
      if (i > js.j_lastj && jobs[i])
        INTERNAL_DEBUG (("find_job: job %d non-null after js.j_lastj (%d)", i,
                         js.j_lastj));

      if (jobs[i])
        {
          p = jobs[i]->pipe;

          do
            {
              if (p->pid == pid
                  && ((alive_only == 0 && PRECYCLED (p) == 0) || PALIVE (p)))
                {
                  if (procp)
                    *procp = p;
                  return i;
                }

              p = p->next;
            }
          while (p != jobs[i]->pipe);
        }
    }

  return NO_JOB;
}

/* Find a job given a PID.  If BLOCK is non-zero, block SIGCHLD as
   required by find_job. */
int
get_job_by_pid (pid_t pid, int block, PROCESS **procp)
{
  int job;
  sigset_t set, oset;

  if (block)
    BLOCK_CHILD (set, oset);

  job = find_job (pid, 0, procp);

  if (block)
    UNBLOCK_CHILD (oset);

  return job;
}

/* Print descriptive information about the job with leader pid PID. */
void
describe_pid (pid_t pid)
{
  int job;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);

  job = find_job (pid, 0, NULL);

  if (job != NO_JOB)
    fprintf (stderr, "[%d] %ld\n", job + 1, (long)pid);
  else
    programming_error (_ ("describe_pid: %ld: no such pid"), (long)pid);

  UNBLOCK_CHILD (oset);
}

static char *
j_strsignal (int s)
{
  char *x;

  x = strsignal (s);
  if (x == 0)
    {
      x = retcode_name_buffer;
      snprintf (x, sizeof (retcode_name_buffer), _ ("Signal %d"), s);
    }
  return x;
}

static const char *
printable_job_status (int j, PROCESS *p, int format)
{
  char *temp;
  int es;

  temp = (char *)_ ("Done");

  if (STOPPED (j) && format == 0)
    {
      if (posixly_correct == 0 || p == 0 || (WIFSTOPPED (p->status) == 0))
        temp = (char *)_ ("Stopped");
      else
        {
          temp = retcode_name_buffer;
          snprintf (temp, sizeof (retcode_name_buffer), _ ("Stopped(%s)"),
                    signal_name (WSTOPSIG (p->status)));
        }
    }
  else if (RUNNING (j))
    temp = (char *)_ ("Running");
  else
    {
      if (WIFSTOPPED (p->status))
        temp = j_strsignal (WSTOPSIG (p->status));
      else if (WIFSIGNALED (p->status))
        temp = j_strsignal (WTERMSIG (p->status));
      else if (WIFEXITED (p->status))
        {
          temp = retcode_name_buffer;
          es = WEXITSTATUS (p->status);
          if (es == 0)
            {
              strncpy (temp, _ ("Done"), sizeof (retcode_name_buffer) - 1);
              temp[sizeof (retcode_name_buffer) - 1] = '\0';
            }
          else if (posixly_correct)
            snprintf (temp, sizeof (retcode_name_buffer), _ ("Done(%d)"), es);
          else
            snprintf (temp, sizeof (retcode_name_buffer), _ ("Exit %d"), es);
        }
      else
        temp = (char *)_ ("Unknown status");
    }

  return temp;
}

/* This is the way to print out information on a job if you
   know the index.  FORMAT is:

    JLIST_NORMAL)   [1]+ Running	   emacs
    JLIST_LONG  )   [1]+ 2378 Running      emacs
    -1	  )   [1]+ 2378	      emacs

    JLIST_NORMAL)   [1]+ Stopped	   ls | more
    JLIST_LONG  )   [1]+ 2369 Stopped      ls
                         2367	    | more
    JLIST_PID_ONLY)
        Just list the pid of the process group leader (really
        the process group).
    JLIST_CHANGED_ONLY)
        Use format JLIST_NORMAL, but list only jobs about which
        the user has not been notified. */

/* Print status for pipeline P.  If JOB_INDEX is >= 0, it is the index into
   the JOBS array corresponding to this pipeline.  FORMAT is as described
   above.  Must be called with SIGCHLD blocked.

   If you're printing a pipeline that's not in the jobs array, like the
   current pipeline as it's being created, pass -1 for JOB_INDEX */
static void
print_pipeline (PROCESS *p, int job_index, int format, FILE *stream)
{
  PROCESS *first, *last, *show;
  int es, name_padding;
  const char *temp;

  if (p == 0)
    return;

  first = last = p;
  while (last->next != first)
    last = last->next;

  for (;;)
    {
      if (p != first)
        fprintf (stream, format ? "     " : " |");

      if (format != JLIST_STANDARD)
        fprintf (stream, "%5ld", (long)p->pid);

      fprintf (stream, " ");

      if (format > -1 && job_index >= 0)
        {
          show = format ? p : last;
          temp = printable_job_status (job_index, show, format);

          if (p != first)
            {
              if (format)
                {
                  if (show->running == first->running
                      && WSTATUS (show->status) == WSTATUS (first->status))
                    temp = "";
                }
              else
                temp = (char *)NULL;
            }

          if (temp)
            {
              fprintf (stream, "%s", temp);

              es = STRLEN (temp);
              if (es == 0)
                es = 2; /* strlen ("| ") */
              name_padding = LONGEST_SIGNAL_DESC - es;

              fprintf (stream, "%*s", name_padding, "");

              if ((WIFSTOPPED (show->status) == 0)
                  && (WIFCONTINUED (show->status) == 0)
                  && WIFCORED (show->status))
                fprintf (stream, _ ("(core dumped) "));
            }
        }

      if (p != first && format)
        fprintf (stream, "| ");

      if (p->command)
        fprintf (stream, "%s", p->command);

      if (p == last && job_index >= 0)
        {
          temp = current_working_directory ();

          if (RUNNING (job_index) && (IS_FOREGROUND (job_index) == 0))
            fprintf (stream, " &");

          if (strcmp (temp, jobs[job_index]->wd) != 0)
            fprintf (stream, _ ("  (wd: %s)"),
                     polite_directory_format (jobs[job_index]->wd));
        }

      if (format || (p == last))
        {
          /* We need to add a CR only if this is an interactive shell, and
             we're reporting the status of a completed job asynchronously.
             We can't really check whether this particular job is being
             reported asynchronously, so just add the CR if the shell is
             currently interactive and asynchronous notification is enabled. */
          if (asynchronous_notification && interactive)
            putc ('\r', stream);
          fprintf (stream, "\n");
        }

      if (p == last)
        break;
      p = p->next;
    }
  fflush (stream);
}

/* Print information to STREAM about jobs[JOB_INDEX] according to FORMAT.
   Must be called with SIGCHLD blocked or queued with queue_sigchld */
static void
pretty_print_job (int job_index, int format, FILE *stream)
{
  PROCESS *p;

  /* Format only pid information about the process group leader? */
  if (format == JLIST_PID_ONLY)
    {
      fprintf (stream, "%ld\n", (long)jobs[job_index]->pipe->pid);
      return;
    }

  if (format == JLIST_CHANGED_ONLY)
    {
      if (IS_NOTIFIED (job_index))
        return;
      format = JLIST_STANDARD;
    }

  if (format != JLIST_NONINTERACTIVE)
    fprintf (stream, "[%d]%c ", job_index + 1,
             (job_index == js.j_current)    ? '+'
             : (job_index == js.j_previous) ? '-'
                                            : ' ');

  if (format == JLIST_NONINTERACTIVE)
    format = JLIST_LONG;

  p = jobs[job_index]->pipe;

  print_pipeline (p, job_index, format, stream);

  /* We have printed information about this job.  When the job's
     status changes, waitchld () sets the notification flag to 0. */
  jobs[job_index]->flags |= J_NOTIFIED;
}

static int
print_job (JOB *job, int format, int state, int job_index)
{
  if (state == -1 || (JOB_STATE)state == job->state)
    pretty_print_job (job_index, format, stdout);
  return 0;
}

void
list_one_job (JOB *job, int format, int ignore, int job_index)
{
  pretty_print_job (job_index, format, stdout);
  cleanup_dead_jobs ();
}

void
list_stopped_jobs (int format)
{
  cleanup_dead_jobs ();
  map_over_jobs (print_job, format, (int)JSTOPPED);
}

void
list_running_jobs (int format)
{
  cleanup_dead_jobs ();
  map_over_jobs (print_job, format, (int)JRUNNING);
}

/* List jobs.  If FORMAT is non-zero, then the long form of the information
   is printed, else just a short version. */
void
list_all_jobs (int format)
{
  cleanup_dead_jobs ();
  map_over_jobs (print_job, format, -1);
}

/* Fork, handling errors.  Returns the pid of the newly made child, or 0.
   COMMAND is just for remembering the name of the command; we don't do
   anything else with it.  ASYNC_P says what to do with the tty.  If
   non-zero, then don't give it away. */
pid_t
Shell::make_child (string_view command, make_child_flags flags)
{
  int async_p, forksleep;
  sigset_t set, oset, termset, chldset, oset_copy;
  pid_t pid;
  SigHandler *oterm;

  sigemptyset (&oset_copy);
  sigprocmask (SIG_BLOCK, nullptr, &oset_copy);
  sigaddset (&oset_copy, SIGTERM);

  /* Block SIGTERM here and unblock in child after fork resets the
     set of pending signals. */
  sigemptyset (&set);
  sigaddset (&set, SIGCHLD);
  sigaddset (&set, SIGINT);
  sigaddset (&set, SIGTERM);

  sigemptyset (&oset);
  sigprocmask (SIG_BLOCK, &set, &oset);

  /* Blocked in the parent, child will receive it after unblocking SIGTERM */
  if (interactive_shell)
    oterm = set_signal_handler (SIGTERM, SIG_DFL);

  making_children ();

  async_p = (flags & FORK_ASYNC);
  forksleep = 1;

#if defined(BUFFERED_INPUT)
  /* If default_buffered_input is active, we are reading a script.  If
     the command is asynchronous, we have already duplicated /dev/null
     as fd 0, but have not changed the buffered stream corresponding to
     the old fd 0.  We don't want to sync the stream in this case. */
  if (default_buffered_input != -1 && (!async_p || default_buffered_input > 0))
    sync_buffered_stream (default_buffered_input);
#endif /* BUFFERED_INPUT */

  /* Create the child, handle severe errors.  Retry on EAGAIN. */
  while ((pid = fork ()) < 0 && errno == EAGAIN && forksleep < FORKSLEEP_MAX)
    {
      /* bash-4.2 */
      /* keep SIGTERM blocked until we reset the handler to SIG_IGN */
      sigprocmask (SIG_SETMASK, &oset_copy, nullptr);
      /* If we can't create any children, try to reap some dead ones. */
      waitchld (-1, 0);

      errno = EAGAIN; /* restore errno */
      sys_error ("fork: retry");

      if (sleep (forksleep) != 0)
        break;
      forksleep <<= 1;

      if (interrupt_state)
        break;
      sigprocmask (SIG_SETMASK, &set, nullptr);
    }

  if (pid != 0)
    if (interactive_shell)
      set_signal_handler (SIGTERM, oterm);

  if (pid < 0)
    {
      sys_error ("fork");

      /* Kill all of the processes in the current pipeline. */
      terminate_current_pipeline ();

      /* Discard the current pipeline, if any. */
      if (the_pipeline)
        kill_current_pipeline ();

      set_exit_status (EX_NOEXEC);
      throw_to_top_level (); /* Reset signals, etc. */
    }

  if (pid == 0)
    {
      /* In the child.  Give this child the right process group, set the
         signals to the default state for a new process. */
      pid_t mypid;

      subshell_environment |= SUBSHELL_IGNTRAP;

      /* If this ends up being changed to modify or use `command' in the
         child process, go back and change callers who free `command' in
         the child process when this returns. */
      mypid = getpid ();
#if defined(BUFFERED_INPUT)
      /* Close default_buffered_input if it's > 0.  We don't close it if it's
         0 because that's the file descriptor used when redirecting input,
         and it's wrong to close the file in that case. */
      unset_bash_input (0);
#endif /* BUFFERED_INPUT */

      CLRINTERRUPT; /* XXX - children have their own interrupt state */

      /* Restore top-level signal mask, including unblocking SIGTERM */
      restore_sigmask ();

      if (job_control)
        {
          /* All processes in this pipeline belong in the same
             process group. */

          if (pipeline_pgrp == 0) /* This is the first child. */
            pipeline_pgrp = mypid;

          /* Check for running command in backquotes. */
          if (pipeline_pgrp == shell_pgrp)
            ignore_tty_job_signals ();
          else
            default_tty_job_signals ();

          /* Set the process group before trying to mess with the terminal's
             process group.  This is mandated by POSIX. */
          /* This is in accordance with the Posix 1003.1 standard,
             section B.7.2.4, which says that trying to set the terminal
             process group with tcsetpgrp() to an unused pgrp value (like
             this would have for the first child) is an error.  Section
             B.4.3.3, p. 237 also covers this, in the context of job control
             shells. */
          if (setpgid (mypid, pipeline_pgrp) < 0)
            sys_error (_ ("child setpgid (%ld to %ld)"), (long)mypid,
                       (long)pipeline_pgrp);

          /* By convention (and assumption above), if
             pipeline_pgrp == shell_pgrp, we are making a child for
             command substitution.
             In this case, we don't want to give the terminal to the
             shell's process group (we could be in the middle of a
             pipeline, for example). */
          if ((flags & FORK_NOTERM) == 0 && async_p == 0
              && pipeline_pgrp != shell_pgrp
              && ((subshell_environment & (SUBSHELL_ASYNC | SUBSHELL_PIPE))
                  == 0)
              && running_in_background == 0)
            give_terminal_to (pipeline_pgrp, 0);

#if defined(PGRP_PIPE)
          if (pipeline_pgrp == mypid)
            pipe_read (pgrp_pipe);
#endif
        }
      else /* Without job control... */
        {
          if (pipeline_pgrp == 0)
            pipeline_pgrp = shell_pgrp;

          /* If these signals are set to SIG_DFL, we encounter the curious
             situation of an interactive ^Z to a running process *working*
             and stopping the process, but being unable to do anything with
             that process to change its state.  On the other hand, if they
             are set to SIG_IGN, jobs started from scripts do not stop when
             the shell running the script gets a SIGTSTP and stops. */

          default_tty_job_signals ();
        }

#if defined(PGRP_PIPE)
      /* Release the process group pipe, since our call to setpgid ()
         is done.  The last call to sh_closepipe is done in stop_pipeline. */
      sh_closepipe (pgrp_pipe);
#endif /* PGRP_PIPE */

      /* Don't set last_asynchronous_pid in the child */

#if defined(RECYCLES_PIDS)
      if (last_asynchronous_pid == mypid)
        /* Avoid pid aliasing.  1 seems like a safe, unusual pid value. */
        last_asynchronous_pid = 1;
#endif
    }
  else
    {
      /* In the parent.  Remember the pid of the child just created
         as the proper pgrp if this is the first child. */

      if (job_control)
        {
          if (pipeline_pgrp == 0)
            {
              pipeline_pgrp = pid;
              /* Don't twiddle terminal pgrps in the parent!  This is the bug,
                 not the good thing of twiddling them in the child! */
              /* give_terminal_to (pipeline_pgrp, 0); */
            }
          /* This is done on the recommendation of the Rationale section of
             the POSIX 1003.1 standard, where it discusses job control and
             shells.  It is done to avoid possible race conditions. (Ref.
             1003.1 Rationale, section B.4.3.3, page 236). */
          setpgid (pid, pipeline_pgrp);
        }
      else
        {
          if (pipeline_pgrp == 0)
            pipeline_pgrp = shell_pgrp;
        }

      /* Place all processes into the jobs array regardless of the
         state of job_control. */
      add_process (command, pid);

      if (async_p)
        last_asynchronous_pid = pid;
#if defined(RECYCLES_PIDS)
      else if (last_asynchronous_pid == pid)
        /* Avoid pid aliasing.  1 seems like a safe, unusual pid value. */
        last_asynchronous_pid = 1;
#endif

      /* Delete the saved status for any job containing this PID in case it's
         been reused. */
      delete_old_job (pid);

      /* Perform the check for pid reuse unconditionally.  Some systems reuse
         PIDs before giving a process CHILD_MAX/_SC_CHILD_MAX unique ones. */
      bgp_delete (pid); /* new process, discard any saved status */

      last_made_pid = pid;

      /* keep stats */
      js.c_totforked++;
      js.c_living++;

      /* Unblock SIGTERM, SIGINT, and SIGCHLD unless creating a pipeline, in
         which case SIGCHLD remains blocked until all commands in the pipeline
         have been created (execute_cmd.c:execute_pipeline()). */
      sigprocmask (SIG_SETMASK, &oset, nullptr);
    }

  return pid;
}

/* These two functions are called only in child processes. */
void
ignore_tty_job_signals ()
{
  set_signal_handler (SIGTSTP, SIG_IGN);
  set_signal_handler (SIGTTIN, SIG_IGN);
  set_signal_handler (SIGTTOU, SIG_IGN);
}

/* Reset the tty-generated job control signals to SIG_DFL unless that signal
   was ignored at entry to the shell, in which case we need to set it to
   SIG_IGN in the child.  We can't rely on resetting traps, since the hard
   ignored signals can't be trapped. */
void
default_tty_job_signals ()
{
  if (signal_is_trapped (SIGTSTP) == 0 && signal_is_hard_ignored (SIGTSTP))
    set_signal_handler (SIGTSTP, SIG_IGN);
  else
    set_signal_handler (SIGTSTP, SIG_DFL);

  if (signal_is_trapped (SIGTTIN) == 0 && signal_is_hard_ignored (SIGTTIN))
    set_signal_handler (SIGTTIN, SIG_IGN);
  else
    set_signal_handler (SIGTTIN, SIG_DFL);

  if (signal_is_trapped (SIGTTOU) == 0 && signal_is_hard_ignored (SIGTTOU))
    set_signal_handler (SIGTTOU, SIG_IGN);
  else
    set_signal_handler (SIGTTOU, SIG_DFL);
}

/* Called once in a parent process. */
void
get_original_tty_job_signals ()
{
  static int fetched = 0;

  if (fetched == 0)
    {
      if (interactive_shell)
        {
          set_original_signal (SIGTSTP, SIG_DFL);
          set_original_signal (SIGTTIN, SIG_DFL);
          set_original_signal (SIGTTOU, SIG_DFL);
        }
      else
        {
          get_original_signal (SIGTSTP);
          get_original_signal (SIGTTIN);
          get_original_signal (SIGTTOU);
        }
      fetched = 1;
    }
}

/* When we end a job abnormally, or if we stop a job, we set the tty to the
   state kept in here.  When a job ends normally, we set the state in here
   to the state of the tty. */

static TTYSTRUCT shell_tty_info;

/* Return the fd from which we are actually getting input. */
#define input_tty() (shell_tty != -1) ? shell_tty : fileno (stderr)

/* Fill the contents of shell_tty_info with the current tty info. */
int
get_tty_state ()
{
  int tty;

  tty = input_tty ();
  if (tty != -1)
    {
#if defined(TERMIOS_TTY_DRIVER)
      if (tcgetattr (tty, &shell_tty_info) < 0)
        {
#if 0
	  /* Only print an error message if we're really interactive at
	     this time. */
	  if (interactive)
	    sys_error ("[%ld: %d (%d)] tcgetattr", (long)getpid (), shell_level, tty);
#endif
          return -1;
        }
#endif /* TERMIOS_TTY_DRIVER */
      if (check_window_size)
        get_new_window_size (nullptr, nullptr);
    }
  return 0;
}

/* Make the current tty use the state in shell_tty_info. */
int
set_tty_state ()
{
  int tty;

  tty = input_tty ();
  if (tty != -1)
    {
#if defined(TERMIOS_TTY_DRIVER)
      if (tcsetattr (tty, TCSADRAIN, &shell_tty_info) < 0)
        {
          /* Only print an error message if we're really interactive at
             this time. */
          if (interactive)
            sys_error ("[%ld: %d (%d)] tcsetattr", (long)getpid (),
                       shell_level, tty);
          return -1;
        }
#endif /* TERMIOS_TTY_DRIVER */
    }
  return 0;
}

/* Given an index into the jobs array JOB, return the PROCESS struct of the
   last process in that job's pipeline.  This is the one whose exit status
   counts.  Must be called with SIGCHLD blocked or queued. */
static PROCESS *
find_last_proc (int job, int block)
{
  PROCESS *p;
  sigset_t set, oset;

  if (block)
    BLOCK_CHILD (set, oset);

  p = jobs[job]->pipe;
  while (p && p->next != jobs[job]->pipe)
    p = p->next;

  if (block)
    UNBLOCK_CHILD (oset);

  return p;
}

static pid_t
find_last_pid (int job, int block)
{
  PROCESS *p;

  p = find_last_proc (job, block);
  /* Possible race condition here. */
  return p->pid;
}

/* Wait for a particular child of the shell to finish executing.
   This low-level function prints an error message if PID is not
   a child of this shell.  It returns -1 if it fails, or whatever
   wait_for returns otherwise.  If the child is not found in the
   jobs table, it returns 127.  If FLAGS doesn't include JWAIT_PERROR,
   we suppress the error message if PID isn't found. */

int
wait_for_single_pid (pid_t pid, int flags)
{
  PROCESS *child;
  sigset_t set, oset;
  int r, job, alive;

  BLOCK_CHILD (set, oset);
  child = find_pipeline (pid, 0, (int *)NULL);
  UNBLOCK_CHILD (oset);

  if (child == 0)
    {
      r = bgp_search (pid);
      if (r >= 0)
        return r;
    }

  if (child == 0)
    {
      if (flags & JWAIT_PERROR)
        internal_error (_ ("wait: pid %ld is not a child of this shell"),
                        (long)pid);
      return (257);
    }

  alive = 0;
  do
    {
      r = wait_for (pid, 0);
      if ((flags & JWAIT_FORCE) == 0)
        break;

      BLOCK_CHILD (set, oset);
      alive = PALIVE (child);
      UNBLOCK_CHILD (oset);
    }
  while (alive);

  /* POSIX.2: if we just waited for a job, we can remove it from the jobs
     table. */
  BLOCK_CHILD (set, oset);
  job = find_job (pid, 0, NULL);
  if (job != NO_JOB && jobs[job] && DEADJOB (job))
    jobs[job]->flags |= J_NOTIFIED;
  UNBLOCK_CHILD (oset);

  /* If running in posix mode, remove the job from the jobs table immediately
   */
  if (posixly_correct)
    {
      cleanup_dead_jobs ();
      bgp_delete (pid);
    }

  /* Check for a trapped signal interrupting the wait builtin and jump out */
  CHECK_WAIT_INTR;

  return r;
}

/* Wait for all of the background processes started by this shell to finish. */
int
wait_for_background_pids (struct procstat *ps)
{
  register int i, r;
  int any_stopped, check_async, njobs;
  sigset_t set, oset;
  pid_t pid;

  for (njobs = any_stopped = 0, check_async = 1;;)
    {
      BLOCK_CHILD (set, oset);

      /* find first running job; if none running in foreground, break */
      /* XXX could use js.j_firstj and js.j_lastj here */
      int i;
      for (i = 0; i < js.j_jobslots; i++)
        {
          if (i < js.j_firstj && jobs[i])
            INTERNAL_DEBUG (("wait_for_background_pids: job %d non-null "
                             "before js.j_firstj (%d)",
                             i, js.j_firstj));
          if (i > js.j_lastj && jobs[i])
            INTERNAL_DEBUG (("wait_for_background_pids: job %d non-null after "
                             "js.j_lastj (%d)",
                             i, js.j_lastj));

          if (jobs[i] && STOPPED (i))
            {
              builtin_warning ("job %d[%d] stopped", i + 1,
                               find_last_pid (i, 0));
              any_stopped = 1;
            }

          if (jobs[i] && RUNNING (i) && IS_FOREGROUND (i) == 0)
            break;
        }
      if (i == js.j_jobslots)
        {
          UNBLOCK_CHILD (oset);
          break;
        }

      /* now wait for the last pid in that job. */
      pid = find_last_pid (i, 0);
      UNBLOCK_CHILD (oset);
      QUIT;
      errno = 0; /* XXX */
      int r = wait_for_single_pid (pid, JWAIT_PERROR);
      if (ps)
        {
          ps->pid = pid;
          ps->status = (r < 0 || r > 256) ? 127 : r;
        }
      if (r == -1 && errno == ECHILD)
        {
          /* If we're mistaken about job state, compensate. */
          check_async = 0;
          mark_all_jobs_as_dead ();
        }
      njobs++;
    }

#if defined(PROCESS_SUBSTITUTION)
  procsub_waitall ();
#endif

  /* POSIX.2 says the shell can discard the statuses of all completed jobs if
     `wait' is called with no arguments. */
  mark_dead_jobs_as_notified (1);
  cleanup_dead_jobs ();
  bgp_clear ();

  return njobs;
}

/* Make OLD_SIGINT_HANDLER the SIGINT signal handler. */
#define INVALID_SIGNAL_HANDLER (SigHandler *)wait_for_background_pids
static SigHandler *old_sigint_handler = INVALID_SIGNAL_HANDLER;

static bool wait_sigint_received;
static bool child_caught_sigint;

bool waiting_for_child;

/* Clean up state after longjmp to wait_intr_buf */
void
wait_sigint_cleanup ()
{
  queue_sigchld = 0;
  waiting_for_child = 0;
  restore_sigint_handler ();
}

static void
restore_sigint_handler ()
{
  if (old_sigint_handler != INVALID_SIGNAL_HANDLER)
    {
      set_signal_handler (SIGINT, old_sigint_handler);
      old_sigint_handler = INVALID_SIGNAL_HANDLER;
      waiting_for_child = 0;
    }
}

/* Handle SIGINT while we are waiting for children in a script to exit.
   The `wait' builtin should be interruptible, but all others should be
   effectively ignored (i.e. not cause the shell to exit). */
static sighandler
wait_sigint_handler (int sig)
{
  SigHandler *sigint_handler;

  if (this_shell_builtin && this_shell_builtin == wait_builtin)
    {
      set_exit_status (128 + SIGINT);
      restore_sigint_handler ();
      /* If we got a SIGINT while in `wait', and SIGINT is trapped, do
         what POSIX.2 says (see builtins/wait.def for more info). */
      if (this_shell_builtin && this_shell_builtin == wait_builtin
          && signal_is_trapped (SIGINT)
          && ((sigint_handler = trap_to_sighandler (SIGINT)) == trap_handler))
        {
          trap_handler (SIGINT); /* set pending_traps[SIGINT] */
          wait_signal_received = SIGINT;
          if (wait_intr_flag)
            sh_longjmp (wait_intr_buf, 1);
          else
            /* Let CHECK_WAIT_INTR handle it in wait_for/waitchld */
            return;
        }
      else /* wait_builtin but signal not trapped, treat as interrupt */
        kill (getpid (), SIGINT);
    }

  /* XXX - should this be interrupt_state?  If it is, the shell will act
     as if it got the SIGINT interrupt. */
  if (waiting_for_child)
    wait_sigint_received = 1;
  else
    {
      set_exit_status (128 + SIGINT);
      restore_sigint_handler ();
      kill (getpid (), SIGINT);
    }

  /* Otherwise effectively ignore the SIGINT and allow the running job to
     be killed. */
}

static int
process_exit_signal (WAIT status)
{
  return WIFSIGNALED (status) ? WTERMSIG (status) : 0;
}

static int
process_exit_status (WAIT status)
{
  if (WIFSIGNALED (status))
    return 128 + WTERMSIG (status);
  else if (WIFSTOPPED (status) == 0)
    return WEXITSTATUS (status);
  else
    return EXECUTION_SUCCESS;
}

static WAIT
job_signal_status (int job)
{
  PROCESS *p;
  WAIT s;

  p = jobs[job]->pipe;
  do
    {
      s = p->status;
      if (WIFSIGNALED (s) || WIFSTOPPED (s))
        break;
      p = p->next;
    }
  while (p != jobs[job]->pipe);

  return s;
}

/* Return the exit status of the last process in the pipeline for job JOB.
   This is the exit status of the entire job. */
static WAIT
raw_job_exit_status (int job)
{
  PROCESS *p;
  int fail;
  WAIT ret;

  if (jobs[job]->flags & J_PIPEFAIL)
    {
      fail = 0;
      p = jobs[job]->pipe;
      do
        {
          if (WSTATUS (p->status) != EXECUTION_SUCCESS)
            fail = WSTATUS (p->status);
          p = p->next;
        }
      while (p != jobs[job]->pipe);
      WSTATUS (ret) = fail;
      return ret;
    }

  for (p = jobs[job]->pipe; p->next != jobs[job]->pipe; p = p->next)
    ;
  return p->status;
}

/* Return the exit status of job JOB.  This is the exit status of the last
   (rightmost) process in the job's pipeline, modified if the job was killed
   by a signal or stopped. */
int
job_exit_status (int job)
{
  return process_exit_status (raw_job_exit_status (job));
}

int
job_exit_signal (int job)
{
  return process_exit_signal (raw_job_exit_status (job));
}

#define FIND_CHILD(pid, child)                                                \
  do                                                                          \
    {                                                                         \
      child = find_pipeline (pid, 0, (int *)NULL);                            \
      if (child == 0)                                                         \
        {                                                                     \
          give_terminal_to (shell_pgrp, 0);                                   \
          UNBLOCK_CHILD (oset);                                               \
          internal_error (_ ("wait_for: No record of process %ld"),           \
                          (long)pid);                                         \
          restore_sigint_handler ();                                          \
          return termination_state = 127;                                     \
        }                                                                     \
    }                                                                         \
  while (0)

/* Wait for pid (one of our children) to terminate, then
   return the termination state.  Returns 127 if PID is not found in
   the jobs table.  Returns -1 if waitchld() returns -1, indicating
   that there are no unwaited-for child processes. */
int
wait_for (pid_t pid, int flags)
{
  int job, termination_state, r;
  WAIT s;
  PROCESS *child;
  sigset_t set, oset;

  /* In the case that this code is interrupted, and we longjmp () out of it,
     we are relying on the code in throw_to_top_level () to restore the
     top-level signal mask. */
  child = 0;
  BLOCK_CHILD (set, oset);

  /* Ignore interrupts while waiting for a job run without job control
     to finish.  We don't want the shell to exit if an interrupt is
     received, only if one of the jobs run is killed via SIGINT.  If
     job control is not set, the job will be run in the same pgrp as
     the shell, and the shell will see any signals the job gets.  In
     fact, we want this set every time the waiting shell and the waited-
     for process are in the same process group, including command
     substitution. */

  /* This is possibly a race condition -- should it go in stop_pipeline? */
  wait_sigint_received = child_caught_sigint = 0;
  if (job_control == 0 || (subshell_environment & SUBSHELL_COMSUB))
    {
      SigHandler *temp_sigint_handler;

      temp_sigint_handler = set_signal_handler (SIGINT, wait_sigint_handler);
      if (temp_sigint_handler == wait_sigint_handler)
        internal_debug ("wait_for: recursively setting old_sigint_handler to "
                        "wait_sigint_handler: running_trap = %d",
                        running_trap);
      else
        old_sigint_handler = temp_sigint_handler;
      waiting_for_child = 0;
      if (old_sigint_handler == SIG_IGN)
        set_signal_handler (SIGINT, old_sigint_handler);
    }

  termination_state = last_command_exit_value;

  if (interactive && job_control == 0)
    QUIT;
  /* Check for terminating signals and exit the shell if we receive one */
  CHECK_TERMSIG;

  /* Check for a trapped signal interrupting the wait builtin and jump out */
  CHECK_WAIT_INTR;

  /* If we say wait_for (), then we have a record of this child somewhere.
     If it and none of its peers are running, don't call waitchld(). */

  job = NO_JOB;
  do
    {
      if (pid != ANY_PID)
        FIND_CHILD (pid, child);

      /* If this child is part of a job, then we are really waiting for the
         job to finish.  Otherwise, we are waiting for the child to finish.
         We check for JDEAD in case the job state has been set by waitchld
         after receipt of a SIGCHLD. */
      if (job == NO_JOB && pid != ANY_PID) /* XXX -- && pid != ANY_PID ? */
        job = find_job (pid, 0, NULL);

      /* waitchld() takes care of setting the state of the job.  If the job
         has already exited before this is called, sigchld_handler will have
         called waitchld and the state will be set to JDEAD. */

      if (pid == ANY_PID || PRUNNING (child)
          || (job != NO_JOB && RUNNING (job)))
        {
          int old_waiting;

          queue_sigchld = 1;
          old_waiting = waiting_for_child;
          waiting_for_child = 1;
          /* XXX - probably not strictly necessary but we want to catch
             everything that happened before we switch the behavior of
             trap_handler to longjmp on a trapped signal (waiting_for_child) */
          CHECK_WAIT_INTR;
          r = waitchld (pid, 1); /* XXX */
          waiting_for_child = old_waiting;
#if 0
itrace("wait_for: blocking wait for %d returns %d child = %p", (int)pid, r, child);
#endif
          queue_sigchld = 0;
          if (r == -1 && errno == ECHILD && this_shell_builtin == wait_builtin)
            {
              termination_state = -1;
              /* XXX - restore sigint handler here */
              restore_sigint_handler ();
              goto wait_for_return;
            }

          /* If child is marked as running, but waitpid() returns -1/ECHILD,
             there is something wrong.  Somewhere, wait should have returned
             that child's pid.  Mark the child as not running and the job,
             if it exists, as JDEAD. */
          if (r == -1 && errno == ECHILD)
            {
              if (child)
                {
                  child->running = PS_DONE;
                  WSTATUS (child->status)
                      = 0; /* XXX -- can't find true status */
                }
              js.c_living = 0; /* no living child processes */
              if (job != NO_JOB)
                {
                  jobs[job]->state = JDEAD;
                  js.c_reaped++;
                  js.j_ndead++;
                }
              if (pid == ANY_PID)
                {
                  termination_state = -1;
                  break;
                }
            }
        }

      /* If the shell is interactive, and job control is disabled, see
         if the foreground process has died due to SIGINT and jump out
         of the wait loop if it has.  waitchld has already restored the
         old SIGINT signal handler. */
      if (interactive && job_control == 0)
        QUIT;
      /* Check for terminating signals and exit the shell if we receive one */
      CHECK_TERMSIG;

      /* Check for a trapped signal interrupting the wait builtin and jump out
       */
      CHECK_WAIT_INTR;

      if (pid == ANY_PID)
        {
          /* XXX - could set child but we don't have a handle on what waitchld
            reaps.  Leave termination_state alone. */
          restore_sigint_handler ();
          goto wait_for_return;
        }
    }
  while (PRUNNING (child) || (job != NO_JOB && RUNNING (job)));

  /* Restore the original SIGINT signal handler before we return. */
  restore_sigint_handler ();

  /* The exit state of the command is either the termination state of the
     child, or the termination state of the job.  If a job, the status
     of the last child in the pipeline is the significant one.  If the command
     or job was terminated by a signal, note that value also. */
  termination_state = (job != NO_JOB)
                          ? job_exit_status (job)
                          : (child ? process_exit_status (child->status)
                                   : EXECUTION_SUCCESS);
  last_command_exit_signal
      = (job != NO_JOB) ? job_exit_signal (job)
                        : (child ? process_exit_signal (child->status) : 0);

  /* XXX */
  if ((job != NO_JOB && JOBSTATE (job) == JSTOPPED)
      || (child && WIFSTOPPED (child->status)))
    termination_state = 128 + WSTOPSIG (child->status);

  if (job == NO_JOB || IS_JOBCONTROL (job))
    {
      /* XXX - under what circumstances is a job not present in the jobs
         table (job == NO_JOB)?
                1.  command substitution

         In the case of command substitution, at least, it's probably not
         the right thing to give the terminal to the shell's process group,
         even though there is code in subst.c:command_substitute to work
         around it.

         Things that don't:
                $PROMPT_COMMAND execution
                process substitution
       */
#if 0
if (job == NO_JOB)
  itrace("wait_for: job == NO_JOB, giving the terminal to shell_pgrp (%ld)", (long)shell_pgrp);
#endif
      /* Don't modify terminal pgrp if we are running in background or a
         subshell.  Make sure subst.c:command_substitute uses the same
         conditions to determine whether or not it should undo this and
         give the terminal to pipeline_pgrp. */

      if ((flags & JWAIT_NOTERM) == 0 && running_in_background == 0
          && (subshell_environment & (SUBSHELL_ASYNC | SUBSHELL_PIPE)) == 0)
        give_terminal_to (shell_pgrp, 0);
    }

  /* If the command did not exit cleanly, or the job is just
     being stopped, then reset the tty state back to what it
     was before this command.  Reset the tty state and notify
     the user of the job termination only if the shell is
     interactive.  Clean up any dead jobs in either case. */
  if (job != NO_JOB)
    {
      if (interactive_shell && subshell_environment == 0)
        {
          /* This used to use `child->status'.  That's wrong, however, for
             pipelines.  `child' is the first process in the pipeline.  It's
             likely that the process we want to check for abnormal termination
             or stopping is the last process in the pipeline, especially if
             it's long-lived and the first process is short-lived.  Since we
             know we have a job here, we can check all the processes in this
             job's pipeline and see if one of them stopped or terminated due
             to a signal.  We might want to change this later to just check
             the last process in the pipeline.  If no process exits due to a
             signal, S is left as the status of the last job in the pipeline.
           */
          s = job_signal_status (job);

          if (WIFSIGNALED (s) || WIFSTOPPED (s))
            {
              set_tty_state ();

              /* If the current job was stopped or killed by a signal, and
                 the user has requested it, get a possibly new window size */
              if (check_window_size
                  && (job == js.j_current || IS_FOREGROUND (job)))
                get_new_window_size (nullptr, nullptr);
            }
          else
#if defined(READLINE)
            /* We don't want to do this if we are running a process during
               programmable completion or a command bound to `bind -x'. */
            if (RL_ISSTATE (RL_STATE_COMPLETING | RL_STATE_DISPATCHING
                            | RL_STATE_TERMPREPPED)
                == 0)
#endif
              get_tty_state ();

          /* If job control is enabled, the job was started with job
             control, the job was the foreground job, and it was killed
             by SIGINT, then print a newline to compensate for the kernel
             printing the ^C without a trailing newline. */
          if (job_control && IS_JOBCONTROL (job) && IS_FOREGROUND (job)
              && WIFSIGNALED (s) && WTERMSIG (s) == SIGINT)
            {
              /* If SIGINT is not trapped and the shell is in a for, while,
                 or until loop, act as if the shell received SIGINT as
                 well, so the loop can be broken.  This doesn't call the
                 SIGINT signal handler; maybe it should. */
              if (signal_is_trapped (SIGINT) == 0
                  && (loop_level
                      || (shell_compatibility_level > 32 && executing_list)))
                ADDINTERRUPT;
              /* Call any SIGINT trap handler if the shell is running a loop,
                 so the loop can be broken.  This seems more useful and matches
                 the behavior when the shell is running a builtin command in a
                 loop when it is interrupted.  Change ADDINTERRUPT to
                 trap_handler (SIGINT) to run the trap without interrupting the
                 loop. */
              else if (signal_is_trapped (SIGINT) && loop_level)
                ADDINTERRUPT;
              /* If an interactive shell with job control enabled is sourcing
                 a file, allow the interrupt to terminate the file sourcing. */
              else if (interactive_shell && signal_is_trapped (SIGINT) == 0
                       && sourcelevel)
                ADDINTERRUPT;
              else
                {
                  putchar ('\n');
                  fflush (stdout);
                }
            }
        }
      else if ((subshell_environment & (SUBSHELL_COMSUB | SUBSHELL_PIPE))
               && wait_sigint_received)
        {
          /* If waiting for a job in a subshell started to do command
             substitution or to run a pipeline element that consists of
             something like a while loop or a for loop, simulate getting
             and being killed by the SIGINT to pass the status back to our
             parent. */
          if (child_caught_sigint == 0 && signal_is_trapped (SIGINT) == 0)
            {
              UNBLOCK_CHILD (oset);
              old_sigint_handler = set_signal_handler (SIGINT, SIG_DFL);
              if (old_sigint_handler == SIG_IGN)
                restore_sigint_handler ();
              else
                kill (getpid (), SIGINT);
            }
        }
      else if (interactive_shell == 0 && subshell_environment == 0
               && IS_FOREGROUND (job))
        {
          s = job_signal_status (job);

          /* If we are non-interactive, but job control is enabled, and the job
             died due to SIGINT, pretend we got the SIGINT */
          if (job_control && IS_JOBCONTROL (job) && WIFSIGNALED (s)
              && WTERMSIG (s) == SIGINT)
            {
              ADDINTERRUPT; /* For now */
            }

          if (check_window_size)
            get_new_window_size (nullptr, nullptr);
        }

      /* Moved here from set_job_status_and_cleanup, which is in the SIGCHLD
         signal handler path */
      if (DEADJOB (job)
          && IS_FOREGROUND (job) /*&& subshell_environment == 0*/)
        setjstatus (job);

      /* If this job is dead, notify the user of the status.  If the shell
         is interactive, this will display a message on the terminal.  If
         the shell is not interactive, make sure we turn on the notify bit
         so we don't get an unwanted message about the job's termination,
         and so delete_job really clears the slot in the jobs table. */
      notify_and_cleanup ();
    }

wait_for_return:

  UNBLOCK_CHILD (oset);

  return termination_state;
}

/* Wait for the last process in the pipeline for JOB.  Returns whatever
   wait_for returns: the last process's termination state or -1 if there
   are no unwaited-for child processes or an error occurs.  If FLAGS
   includes JWAIT_FORCE, we wait for the job to terminate, no just change
   state */
int
wait_for_job (int job, int flags, struct procstat *ps)
{
  pid_t pid;
  int r, state;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);
  state = JOBSTATE (job);
  if (state == JSTOPPED)
    internal_warning (_ ("wait_for_job: job %d is stopped"), job + 1);

  pid = find_last_pid (job, 0);
  UNBLOCK_CHILD (oset);

  do
    {
      r = wait_for (pid, 0);
      if (r == -1 && errno == ECHILD)
        mark_all_jobs_as_dead ();

      CHECK_WAIT_INTR;

      if ((flags & JWAIT_FORCE) == 0)
        break;

      BLOCK_CHILD (set, oset);
      state = (job != NO_JOB && jobs[job]) ? JOBSTATE (job) : JDEAD;
      UNBLOCK_CHILD (oset);
    }
  while (state != JDEAD);

  /* POSIX.2: we can remove the job from the jobs table if we just waited
     for it. */
  BLOCK_CHILD (set, oset);
  if (job != NO_JOB && jobs[job] && DEADJOB (job))
    jobs[job]->flags |= J_NOTIFIED;
  UNBLOCK_CHILD (oset);

  if (ps)
    {
      ps->pid = pid;
      ps->status = (r < 0) ? 127 : r;
    }
  return r;
}

/* Wait for any background job started by this shell to finish.  Very
   similar to wait_for_background_pids().  Returns the exit status of
   the next exiting job, -1 if there are no background jobs.  The caller
   is responsible for translating -1 into the right return value. RPID,
   if non-null, gets the pid of the job's process leader. */
int
wait_for_any_job (int flags, struct procstat *ps)
{
  pid_t pid;
  int i, r;
  sigset_t set, oset;

  if (jobs_list_frozen)
    return -1;

  /* First see if there are any unnotified dead jobs that we can report on */
  BLOCK_CHILD (set, oset);
  for (i = 0; i < js.j_jobslots; i++)
    {
      if ((flags & JWAIT_WAITING) && jobs[i] && IS_WAITING (i) == 0)
        continue; /* if we don't want it, skip it */
      if (jobs[i] && DEADJOB (i) && IS_NOTIFIED (i) == 0)
        {
        return_job:
          r = job_exit_status (i);
          pid = find_last_pid (i, 0);
          if (ps)
            {
              ps->pid = pid;
              ps->status = r;
            }
          notify_of_job_status (); /* XXX */
          delete_job (i, 0);
#if defined(COPROCESS_SUPPORT)
          coproc_reap ();
#endif
          UNBLOCK_CHILD (oset);
          return r;
        }
    }
  UNBLOCK_CHILD (oset);

  /* At this point, we have no dead jobs in the jobs table.  Wait until we
     get one, even if it takes multiple pids exiting. */
  for (;;)
    {
      /* Make sure there is a background job to wait for */
      BLOCK_CHILD (set, oset);
      for (i = 0; i < js.j_jobslots; i++)
        if (jobs[i] && RUNNING (i) && IS_FOREGROUND (i) == 0)
          break;
      if (i == js.j_jobslots)
        {
          UNBLOCK_CHILD (oset);
          return -1;
        }

      UNBLOCK_CHILD (oset);

      QUIT;
      CHECK_TERMSIG;
      CHECK_WAIT_INTR;

      errno = 0;
      r = wait_for (ANY_PID, 0); /* special sentinel value for wait_for */
      if (r == -1 && errno == ECHILD)
        mark_all_jobs_as_dead ();

      /* Now we see if we have any dead jobs and return the first one */
      BLOCK_CHILD (set, oset);
      for (i = 0; i < js.j_jobslots; i++)
        {
          if ((flags & JWAIT_WAITING) && jobs[i] && IS_WAITING (i) == 0)
            continue; /* if we don't want it, skip it */
          if (jobs[i] && DEADJOB (i))
            goto return_job;
        }
      UNBLOCK_CHILD (oset);
    }

  return -1;
}

/* Print info about dead jobs, and then delete them from the list
   of known jobs.  This does not actually delete jobs when the
   shell is not interactive, because the dead jobs are not marked
   as notified. */
void
notify_and_cleanup ()
{
  if (jobs_list_frozen)
    return;

  if (interactive || interactive_shell == 0 || sourcelevel)
    notify_of_job_status ();

  cleanup_dead_jobs ();
}

/* Make dead jobs disappear from the jobs array without notification.
   This is used when the shell is not interactive. */
void
reap_dead_jobs ()
{
  mark_dead_jobs_as_notified (0);
  cleanup_dead_jobs ();
}

/* Return the next closest (chronologically) job to JOB which is in
   STATE.  STATE can be JSTOPPED, JRUNNING.  NO_JOB is returned if
   there is no next recent job. */
static int
most_recent_job_in_state (int job, JOB_STATE state)
{
  int i, result;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);

  for (result = NO_JOB, i = job - 1; i >= 0; i--)
    {
      if (jobs[i] && (JOBSTATE (i) == state))
        {
          result = i;
          break;
        }
    }

  UNBLOCK_CHILD (oset);

  return result;
}

/* Return the newest *stopped* job older than JOB, or NO_JOB if not
   found. */
static int
job_last_stopped (int job)
{
  return most_recent_job_in_state (job, JSTOPPED);
}

/* Return the newest *running* job older than JOB, or NO_JOB if not
   found. */
static int
job_last_running (int job)
{
  return most_recent_job_in_state (job, JRUNNING);
}

/* Make JOB be the current job, and make previous be useful.  Must be
   called with SIGCHLD blocked. */
static void
set_current_job (int job)
{
  int candidate;

  if (js.j_current != job)
    {
      js.j_previous = js.j_current;
      js.j_current = job;
    }

  /* First choice for previous job is the old current job. */
  if (js.j_previous != js.j_current && js.j_previous != NO_JOB
      && jobs[js.j_previous] && STOPPED (js.j_previous))
    return;

  /* Second choice:  Newest stopped job that is older than
     the current job. */
  candidate = NO_JOB;
  if (STOPPED (js.j_current))
    {
      candidate = job_last_stopped (js.j_current);

      if (candidate != NO_JOB)
        {
          js.j_previous = candidate;
          return;
        }
    }

  /* If we get here, there is either only one stopped job, in which case it is
     the current job and the previous job should be set to the newest running
     job, or there are only running jobs and the previous job should be set to
     the newest running job older than the current job.  We decide on which
     alternative to use based on whether or not JOBSTATE(js.j_current) is
     JSTOPPED. */

  candidate = RUNNING (js.j_current) ? job_last_running (js.j_current)
                                     : job_last_running (js.j_jobslots);

  if (candidate != NO_JOB)
    {
      js.j_previous = candidate;
      return;
    }

  /* There is only a single job, and it is both `+' and `-'. */
  js.j_previous = js.j_current;
}

/* Make current_job be something useful, if it isn't already. */

/* Here's the deal:  The newest non-running job should be `+', and the
   next-newest non-running job should be `-'.  If there is only a single
   stopped job, the js.j_previous is the newest non-running job.  If there
   are only running jobs, the newest running job is `+' and the
   next-newest running job is `-'.  Must be called with SIGCHLD blocked. */

static void
reset_current ()
{
  int candidate;

  if (js.j_jobslots && js.j_current != NO_JOB && jobs[js.j_current]
      && STOPPED (js.j_current))
    candidate = js.j_current;
  else
    {
      candidate = NO_JOB;

      /* First choice: the previous job. */
      if (js.j_previous != NO_JOB && jobs[js.j_previous]
          && STOPPED (js.j_previous))
        candidate = js.j_previous;

      /* Second choice: the most recently stopped job. */
      if (candidate == NO_JOB)
        candidate = job_last_stopped (js.j_jobslots);

      /* Third choice: the newest running job. */
      if (candidate == NO_JOB)
        candidate = job_last_running (js.j_jobslots);
    }

  /* If we found a job to use, then use it.  Otherwise, there
     are no jobs period. */
  if (candidate != NO_JOB)
    set_current_job (candidate);
  else
    js.j_current = js.j_previous = NO_JOB;
}

/* Set up the job structures so we know the job and its processes are
   all running. */
static void
set_job_running (int job)
{
  PROCESS *p;

  /* Each member of the pipeline is now running. */
  p = jobs[job]->pipe;

  do
    {
      if (WIFSTOPPED (p->status))
        p->running = PS_RUNNING; /* XXX - could be PS_STOPPED */
      p = p->next;
    }
  while (p != jobs[job]->pipe);

  /* This means that the job is running. */
  JOBSTATE (job) = JRUNNING;
}

/* Start a job.  FOREGROUND if non-zero says to do that.  Otherwise,
   start the job in the background.  JOB is a zero-based index into
   JOBS.  Returns -1 if it is unable to start a job, and the return
   status of the job otherwise. */
int
start_job (int job, bool foreground)
{
  sigset_t set, oset;
  static TTYSTRUCT save_stty;

  BLOCK_CHILD (set, oset);

  if ((subshell_environment & SUBSHELL_COMSUB)
      && (pipeline_pgrp == shell_pgrp))
    {
      internal_error (_ ("%s: no current jobs"), this_command_name);
      UNBLOCK_CHILD (oset);
      return -1;
    }

  if (DEADJOB (job))
    {
      internal_error (_ ("%s: job has terminated"), this_command_name);
      UNBLOCK_CHILD (oset);
      return -1;
    }

  bool already_running = RUNNING (job);

  if (!foreground && already_running)
    {
      internal_error (_ ("%s: job %d already in background"),
                      this_command_name, job + 1);
      UNBLOCK_CHILD (oset);
      return 0; /* XPG6/SUSv3 says this is not an error */
    }

  const char *wd = current_working_directory ();

  /* You don't know about the state of this job.  Do you? */
  jobs[job]->flags &= ~J_NOTIFIED;

  if (foreground)
    {
      set_current_job (job);
      jobs[job]->flags |= J_FOREGROUND;
    }

  /* Tell the outside world what we're doing. */
  PROCESS *p = jobs[job]->pipe;
  const char *s;

  if (!foreground)
    {
      /* POSIX.2 says `bg' doesn't give any indication about current or
         previous job. */
      if (posixly_correct == 0)
        s = (job == js.j_current) ? "+ "
                                  : ((job == js.j_previous) ? "- " : " ");
      else
        s = " ";
      printf ("[%d]%s", job + 1, s);
    }

  do
    {
      printf ("%s%s", p->command ? p->command : "",
              p->next != jobs[job]->pipe ? " | " : "");
      p = p->next;
    }
  while (p != jobs[job]->pipe);

  if (!foreground)
    printf (" &");

  if (strcmp (wd, jobs[job]->wd) != 0)
    printf ("	(wd: %s)", polite_directory_format (jobs[job]->wd));

  printf ("\n");

  /* Run the job. */
  if (already_running == 0)
    set_job_running (job);

  /* Save the tty settings before we start the job in the foreground. */
  if (foreground)
    {
      get_tty_state ();
      save_stty = shell_tty_info;
      /* Give the terminal to this job. */
      if (IS_JOBCONTROL (job))
        give_terminal_to (jobs[job]->pgrp, 0);
    }
  else
    jobs[job]->flags &= ~J_FOREGROUND;

  /* If the job is already running, then don't bother jump-starting it. */
  if (already_running == 0)
    {
      jobs[job]->flags |= J_NOTIFIED;
      killpg (jobs[job]->pgrp, SIGCONT);
    }

  if (foreground)
    {
      pid_t pid;
      int st;

      pid = find_last_pid (job, 0);
      UNBLOCK_CHILD (oset);
      st = wait_for (pid, 0);
      shell_tty_info = save_stty;
      set_tty_state ();
      return st;
    }
  else
    {
      reset_current ();
      UNBLOCK_CHILD (oset);
      return 0;
    }
}

/* Give PID SIGNAL.  This determines what job the pid belongs to (if any).
   If PID does belong to a job, and the job is stopped, then CONTinue the
   job after giving it SIGNAL.  Returns -1 on failure.  If GROUP is non-null,
   then kill the process group associated with PID. */
int
kill_pid (pid_t pid, int sig, int group)
{
  PROCESS *p;
  int job, result, negative;
  sigset_t set, oset;

  if (pid < -1)
    {
      pid = -pid;
      group = negative = 1;
    }
  else
    negative = 0;

  result = EXECUTION_SUCCESS;
  if (group)
    {
      BLOCK_CHILD (set, oset);
      p = find_pipeline (pid, 0, &job);

      if (job != NO_JOB)
        {
          jobs[job]->flags &= ~J_NOTIFIED;

          /* Kill process in backquotes or one started without job control? */

          /* If we're passed a pid < -1, just call killpg and see what happens
           */
          if (negative && jobs[job]->pgrp == shell_pgrp)
            result = killpg (pid, sig);
          /* If we're killing using job control notification, for example,
             without job control active, we have to do things ourselves. */
          else if (jobs[job]->pgrp
                   == shell_pgrp) /* XXX - IS_JOBCONTROL(job) == 0? */
            {
              p = jobs[job]->pipe;
              do
                {
                  if (PALIVE (p) == 0)
                    continue; /* avoid pid recycling problem */
                  kill (p->pid, sig);
                  if (PEXITED (p) && (sig == SIGTERM || sig == SIGHUP))
                    kill (p->pid, SIGCONT);
                  p = p->next;
                }
              while (p != jobs[job]->pipe);
            }
          else
            {
              result = killpg (jobs[job]->pgrp, sig);
              if (p && STOPPED (job) && (sig == SIGTERM || sig == SIGHUP))
                killpg (jobs[job]->pgrp, SIGCONT);
              /* If we're continuing a stopped job via kill rather than bg or
                 fg, emulate the `bg' behavior. */
              if (p && STOPPED (job) && (sig == SIGCONT))
                {
                  set_job_running (job);
                  jobs[job]->flags &= ~J_FOREGROUND;
                  jobs[job]->flags |= J_NOTIFIED;
                }
            }
        }
      else
        result = killpg (pid, sig);

      UNBLOCK_CHILD (oset);
    }
  else
    result = kill (pid, sig);

  return result;
}

/* sigchld_handler () flushes at least one of the children that we are
   waiting for.  It gets run when we have gotten a SIGCHLD signal. */
static sighandler
sigchld_handler (int sig)
{
  int n, oerrno;

  oerrno = errno;
  REINSTALL_SIGCHLD_HANDLER;
  sigchld++;
  n = 0;
  if (queue_sigchld == 0)
    n = waitchld (-1, 0);
  errno = oerrno;
}

/* waitchld() reaps dead or stopped children.  It's called by wait_for and
   sigchld_handler, and runs until there aren't any children terminating any
   more.
   If BLOCK is 1, this is to be a blocking wait for a single child, although
   an arriving SIGCHLD could cause the wait to be non-blocking.  It returns
   the number of children reaped, or -1 if there are no unwaited-for child
   processes. */
static int
waitchld (pid_t wpid, int block)
{
  WAIT status;
  PROCESS *child;
  pid_t pid;
  int ind;

  int call_set_current, last_stopped_job, job, children_exited, waitpid_flags;
  static int wcontinued = WCONTINUED; /* run-time fix for glibc problem */

  call_set_current = children_exited = 0;
  last_stopped_job = NO_JOB;

  do
    {
      /* We don't want to be notified about jobs stopping if job control
         is not active.  XXX - was interactive_shell instead of job_control */
      waitpid_flags = (job_control && subshell_environment == 0)
                          ? (WUNTRACED | wcontinued)
                          : 0;
      if (sigchld || block == 0)
        waitpid_flags |= WNOHANG;

      /* Check for terminating signals and exit the shell if we receive one */
      CHECK_TERMSIG;
      /* Check for a trapped signal interrupting the wait builtin and jump out
       */
      CHECK_WAIT_INTR;

      if (block == 1 && queue_sigchld == 0 && (waitpid_flags & WNOHANG) == 0)
        {
          internal_warning (
              _ ("waitchld: turning on WNOHANG to avoid indefinite block"));
          waitpid_flags |= WNOHANG;
        }

      pid = WAITPID (-1, &status, waitpid_flags);

#if 0
if (wpid != -1 && block)
  itrace("waitchld: blocking waitpid returns %d", pid);
#endif
#if 0
if (wpid != -1)
  itrace("waitchld: %s waitpid returns %d", block?"blocking":"non-blocking", pid);
#endif
      /* WCONTINUED may be rejected by waitpid as invalid even when defined */
      if (wcontinued && pid < 0 && errno == EINVAL)
        {
          wcontinued = 0;
          continue; /* jump back to the test and retry without WCONTINUED */
        }

      /* The check for WNOHANG is to make sure we decrement sigchld only
         if it was non-zero before we called waitpid. */
      if (sigchld > 0 && (waitpid_flags & WNOHANG))
        sigchld--;

      /* If waitpid returns -1 with errno == ECHILD, there are no more
         unwaited-for child processes of this shell. */
      if (pid < 0 && errno == ECHILD)
        {
          if (children_exited == 0)
            return -1;
          else
            break;
        }

#if 0
itrace("waitchld: waitpid returns %d block = %d children_exited = %d", pid, block, children_exited);
#endif
      /* If waitpid returns 0, there are running children.  If it returns -1,
         the only other error POSIX says it can return is EINTR. */
      CHECK_TERMSIG;
      CHECK_WAIT_INTR;

      /* If waitpid returns -1/EINTR and the shell saw a SIGINT, then we
         assume the child has blocked or handled SIGINT.  In that case, we
         require the child to actually die due to SIGINT to act on the
         SIGINT we received; otherwise we assume the child handled it and
         let it go. */
      if (pid < 0 && errno == EINTR && wait_sigint_received)
        child_caught_sigint = 1;

      if (pid <= 0)
        continue; /* jumps right to the test */

      /* Linux kernels appear to signal the parent but not interrupt the
         waitpid() (or restart it even without SA_RESTART) on SIGINT, so if
         we saw a SIGINT and the process exited or died due to some other
         signal, assume the child caught the SIGINT. */
      if (wait_sigint_received
          && (WIFSIGNALED (status) == 0 || WTERMSIG (status) != SIGINT))
        child_caught_sigint = 1;

      /* If the child process did die due to SIGINT, forget our assumption
         that it caught or otherwise handled it. */
      if (WIFSIGNALED (status) && WTERMSIG (status) == SIGINT)
        child_caught_sigint = 0;

      /* children_exited is used to run traps on SIGCHLD.  We don't want to
         run the trap if a process is just being continued. */
      if (WIFCONTINUED (status) == 0)
        {
          children_exited++;
          js.c_living--;
        }

      /* Locate our PROCESS for this pid. */
      child = find_process (pid, 1, &job); /* want living procs only */

#if defined(COPROCESS_SUPPORT)
      coproc_pidchk (pid, WSTATUS (status));
#endif

#if defined(PROCESS_SUBSTITUTION)
      /* Only manipulate the list of process substitutions while SIGCHLD
         is blocked. We only use this as a hint that we can remove FIFOs
         or close file descriptors corresponding to terminated process
         substitutions. */
      if ((ind = find_procsub_child (pid)) >= 0)
        set_procsub_status (ind, pid, WSTATUS (status));
#endif

      /* It is not an error to have a child terminate that we did
         not have a record of.  This child could have been part of
         a pipeline in backquote substitution.  Even so, I'm not
         sure child is ever non-zero. */
      if (child == 0)
        {
          if (WIFEXITED (status) || WIFSIGNALED (status))
            js.c_reaped++;
          continue;
        }

      /* Remember status, and whether or not the process is running. */
      child->status = status;
      child->running = WIFCONTINUED (status) ? PS_RUNNING : PS_DONE;

      if (PEXITED (child))
        {
          js.c_totreaped++;
          if (job != NO_JOB)
            js.c_reaped++;
        }

      if (job == NO_JOB)
        continue;

      call_set_current += set_job_status_and_cleanup (job);

      if (STOPPED (job))
        last_stopped_job = job;
      else if (DEADJOB (job) && last_stopped_job == job)
        last_stopped_job = NO_JOB;
    }
  while ((sigchld || block == 0) && pid > (pid_t)0);

  /* If a job was running and became stopped, then set the current
     job.  Otherwise, don't change a thing. */
  if (call_set_current)
    {
      if (last_stopped_job != NO_JOB)
        set_current_job (last_stopped_job);
      else
        reset_current ();
    }

  /* Call a SIGCHLD trap handler for each child that exits, if one is set. */
  if (children_exited
      && (signal_is_trapped (SIGCHLD)
          || trap_list[SIGCHLD] == (char *)IMPOSSIBLE_TRAP_HANDLER)
      && trap_list[SIGCHLD] != (char *)IGNORE_SIG)
    {
      if (posixly_correct && this_shell_builtin
          && this_shell_builtin == wait_builtin)
        {
          /* This was trap_handler (SIGCHLD) but that can lose traps if
             children_exited > 1 */
          queue_sigchld_trap (children_exited);
          wait_signal_received = SIGCHLD;
          /* If we're in a signal handler, let CHECK_WAIT_INTR pick it up;
             run_pending_traps will call run_sigchld_trap later  */
          if (sigchld == 0 && wait_intr_flag)
            sh_longjmp (wait_intr_buf, 1);
        }
      /* If not in posix mode and not executing the wait builtin, queue the
         signal for later handling.  Run the trap immediately if we are
         executing the wait builtin, but don't break out of `wait'. */
      else if (sigchld) /* called from signal handler */
        queue_sigchld_trap (children_exited);
      else if (signal_in_progress (SIGCHLD))
        queue_sigchld_trap (children_exited);
      else if (trap_list[SIGCHLD] == (char *)IMPOSSIBLE_TRAP_HANDLER)
        queue_sigchld_trap (children_exited);
      else if (running_trap)
        queue_sigchld_trap (children_exited);
      else if (this_shell_builtin == wait_builtin)
        run_sigchld_trap (children_exited); /* XXX */
      else
        queue_sigchld_trap (children_exited);
    }

  /* We have successfully recorded the useful information about this process
     that has just changed state.  If we notify asynchronously, and the job
     that this process belongs to is no longer running, then notify the user
     of that fact now. */
  if (asynchronous_notification && interactive && executing_builtin == 0)
    notify_of_job_status ();

  return children_exited;
}

/* Set the status of JOB and perform any necessary cleanup if the job is
   marked as JDEAD.

   Currently, the cleanup activity is restricted to handling any SIGINT
   received while waiting for a foreground job to finish. */
static int
set_job_status_and_cleanup (int job)
{
  PROCESS *child;
  int tstatus, job_state, any_stopped, any_tstped, call_set_current;
  SigHandler *temp_handler;

  child = jobs[job]->pipe;
  jobs[job]->flags &= ~J_NOTIFIED;

  call_set_current = 0;

  /*
   * COMPUTE JOB STATUS
   */

  /* If all children are not running, but any of them is  stopped, then
     the job is stopped, not dead. */
  job_state = any_stopped = any_tstped = 0;
  do
    {
      job_state |= PRUNNING (child);
#if 0
      if (PEXITED (child) && (WIFSTOPPED (child->status)))
#else
      /* Only checking for WIFSTOPPED now, not for PS_DONE */
      if (PSTOPPED (child))
#endif
      {
        any_stopped = 1;
        any_tstped |= job_control && (WSTOPSIG (child->status) == SIGTSTP);
      }
      child = child->next;
    }
  while (child != jobs[job]->pipe);

  /* If job_state != 0, the job is still running, so don't bother with
     setting the process exit status and job state unless we're
     transitioning from stopped to running. */
  if (job_state != 0 && JOBSTATE (job) != JSTOPPED)
    return 0;

  /*
   * SET JOB STATUS
   */

  /* The job is either stopped or dead.  Set the state of the job accordingly.
   */
  if (any_stopped)
    {
      jobs[job]->state = JSTOPPED;
      jobs[job]->flags &= ~J_FOREGROUND;
      call_set_current++;
      /* Suspending a job with SIGTSTP breaks all active loops. */
      if (any_tstped && loop_level)
        breaking = loop_level;
    }
  else if (job_state != 0) /* was stopped, now running */
    {
      jobs[job]->state = JRUNNING;
      call_set_current++;
    }
  else
    {
      jobs[job]->state = JDEAD;
      js.j_ndead++;

#if 0
      if (IS_FOREGROUND (job))
	setjstatus (job);
#endif

      /* If this job has a cleanup function associated with it, call it
         with `cleanarg' as the single argument, then set the function
         pointer to NULL so it is not inadvertently called twice.  The
         cleanup function is responsible for deallocating cleanarg. */
      if (jobs[job]->j_cleanup)
        {
          (*jobs[job]->j_cleanup) (jobs[job]->cleanarg);
          jobs[job]->j_cleanup = (sh_vptrfunc_t *)NULL;
        }
    }

  /*
   * CLEANUP
   *
   * Currently, we just do special things if we got a SIGINT while waiting
   * for a foreground job to complete
   */

  if (JOBSTATE (job) == JDEAD)
    {
      /* If we're running a shell script and we get a SIGINT with a
         SIGINT trap handler, but the foreground job handles it and
         does not exit due to SIGINT, run the trap handler but do not
         otherwise act as if we got the interrupt. */
      if (wait_sigint_received && interactive_shell == 0 && child_caught_sigint
          && IS_FOREGROUND (job) && signal_is_trapped (SIGINT))
        {
          int old_frozen;
          wait_sigint_received = 0;
          last_command_exit_value = process_exit_status (child->status);

          old_frozen = jobs_list_frozen;
          jobs_list_frozen = 1;
          tstatus = maybe_call_trap_handler (SIGINT);
          jobs_list_frozen = old_frozen;
        }

      /* If the foreground job is killed by SIGINT when job control is not
         active, we need to perform some special handling.

         The check of wait_sigint_received is a way to determine if the
         SIGINT came from the keyboard (in which case the shell has already
         seen it, and wait_sigint_received is non-zero, because keyboard
         signals are sent to process groups) or via kill(2) to the foreground
         process by another process (or itself).  If the shell did receive the
         SIGINT, it needs to perform normal SIGINT processing.  XXX - should
         this change its behavior depending on whether the last command in an
         pipeline exited due to SIGINT, or any process in the pipeline?  Right
         now it does this if any process in the pipeline exits due to SIGINT.
       */
      else if (wait_sigint_received && child_caught_sigint == 0
               && IS_FOREGROUND (job) && IS_JOBCONTROL (job) == 0)
        {
          int old_frozen;

          wait_sigint_received = 0;

          /* If SIGINT is trapped, set the exit status so that the trap
             handler can see it. */
          if (signal_is_trapped (SIGINT))
            last_command_exit_value = process_exit_status (child->status);

          /* If the signal is trapped, let the trap handler get it no matter
             what and simply return if the trap handler returns.
             maybe_call_trap_handler() may cause dead jobs to be removed from
             the job table because of a call to execute_command.  We work
             around this by setting JOBS_LIST_FROZEN. */
          old_frozen = jobs_list_frozen;
          jobs_list_frozen = 1;
          tstatus = maybe_call_trap_handler (SIGINT);
          jobs_list_frozen = old_frozen;
          if (tstatus == 0 && old_sigint_handler != INVALID_SIGNAL_HANDLER)
            {
              /* wait_sigint_handler () has already seen SIGINT and
                 allowed the wait builtin to jump out.  We need to
                 call the original SIGINT handler, if necessary.  If
                 the original handler is SIG_DFL, we need to resend
                 the signal to ourselves. */

              temp_handler = old_sigint_handler;

              /* Bogus.  If we've reset the signal handler as the result
                 of a trap caught on SIGINT, then old_sigint_handler
                 will point to trap_handler, which now knows nothing about
                 SIGINT (if we reset the sighandler to the default).
                 In this case, we have to fix things up.  What a crock. */
              if (temp_handler == trap_handler
                  && signal_is_trapped (SIGINT) == 0)
                temp_handler = trap_to_sighandler (SIGINT);
              restore_sigint_handler ();
              if (temp_handler == SIG_DFL)
                termsig_handler (SIGINT); /* XXX */
              else if (temp_handler != SIG_IGN)
                (*temp_handler) (SIGINT);
            }
        }
    }

  return call_set_current;
}

/* Build the array of values for the $PIPESTATUS variable from the set of
   exit statuses of all processes in the job J. */
static void
setjstatus (int j)
{
#if defined(ARRAY_VARS)
  int i;
  PROCESS *p;

  for (i = 1, p = jobs[j]->pipe; p->next != jobs[j]->pipe; p = p->next, i++)
    ;
  i++;
  if (statsize < i)
    {
      pstatuses = (int *)xrealloc (pstatuses, i * sizeof (int));
      statsize = i;
    }
  i = 0;
  p = jobs[j]->pipe;
  do
    {
      pstatuses[i++] = process_exit_status (p->status);
      p = p->next;
    }
  while (p != jobs[j]->pipe);

  pstatuses[i] = -1; /* sentinel */
  set_pipestatus_array (pstatuses, i);
#endif
}

void
run_sigchld_trap (int nchild)
{
  char *trap_command;
  int i;

  /* Turn off the trap list during the call to parse_and_execute ()
     to avoid potentially infinite recursive calls.  Preserve the
     values of last_command_exit_value, last_made_pid, and the_pipeline
     around the execution of the trap commands. */
  trap_command = savestring (trap_list[SIGCHLD]);

  begin_unwind_frame ("SIGCHLD trap");
  unwind_protect_var (last_command_exit_value);
  unwind_protect_var (last_command_exit_signal);
  unwind_protect_var (last_made_pid);
  unwind_protect_var (jobs_list_frozen);
  unwind_protect_var (the_pipeline);
  unwind_protect_var (subst_assign_varlist);
  unwind_protect_var (this_shell_builtin);
  unwind_protect_var (temporary_env);

  /* We have to add the commands this way because they will be run
     in reverse order of adding.  We don't want maybe_set_sigchld_trap ()
     to reference freed memory. */
  add_unwind_protect_ptr (xfree, trap_command);
  add_unwind_protect_ptr (maybe_set_sigchld_trap, trap_command);

  subst_assign_varlist = nullptr;
  the_pipeline = nullptr;
  temporary_env = 0; /* traps should not run with temporary env */

  running_trap = SIGCHLD + 1;

  set_impossible_sigchld_trap ();
  jobs_list_frozen = 1;
  for (i = 0; i < nchild; i++)
    {
      parse_and_execute (savestring (trap_command), "trap",
                         SEVAL_NOHIST | SEVAL_RESETLINE);
    }

  run_unwind_frame ("SIGCHLD trap");
  running_trap = 0;
}

/* Function to call when you want to notify people of changes
   in job status.  This prints out all jobs which are pending
   notification to stderr, and marks those printed as already
   notified, thus making them candidates for cleanup. */
static void
notify_of_job_status ()
{
  int job, termsig;
  const char *dir;
  sigset_t set, oset;
  WAIT s;

  if (jobs == 0 || js.j_jobslots == 0)
    return;

  if (old_ttou != 0)
    {
      sigemptyset (&set);
      sigaddset (&set, SIGCHLD);
      sigaddset (&set, SIGTTOU);
      sigemptyset (&oset);
      sigprocmask (SIG_BLOCK, &set, &oset);
    }
  else
    queue_sigchld++;

  /* XXX could use js.j_firstj here */
  for (job = 0, dir = (char *)NULL; job < js.j_jobslots; job++)
    {
      if (jobs[job] && IS_NOTIFIED (job) == 0)
        {
          s = raw_job_exit_status (job);
          termsig = WTERMSIG (s);

          /* POSIX.2 says we have to hang onto the statuses of at most the
             last CHILD_MAX background processes if the shell is running a
             script.  If the shell is running a script, either from a file
             or standard input, don't print anything unless the job was
             killed by a signal. */
          if (startup_state == 0 && WIFSIGNALED (s) == 0
              && ((DEADJOB (job) && IS_FOREGROUND (job) == 0)
                  || STOPPED (job)))
            continue;

          /* If job control is disabled, don't print the status messages.
             Mark dead jobs as notified so that they get cleaned up.  If
             startup_state == 2 and subshell_environment has the
             SUBSHELL_COMSUB bit turned on, we were started to run a command
             substitution, so don't print anything.
             Otherwise, if the shell is not interactive, POSIX says that `jobs'
             is the only way to notify of job status. */
          if ((job_control == 0 && interactive_shell)
              || (startup_state == 2
                  && (subshell_environment & SUBSHELL_COMSUB))
              || (startup_state == 2 && posixly_correct
                  && (subshell_environment & SUBSHELL_COMSUB) == 0))
            {
              /* POSIX.2 compatibility:  if the shell is not interactive,
                 hang onto the job corresponding to the last asynchronous
                 pid until the user has been notified of its status or does
                 a `wait'. */
              if (DEADJOB (job)
                  && (interactive_shell
                      || (find_last_pid (job, 0) != last_asynchronous_pid)))
                jobs[job]->flags |= J_NOTIFIED;
              continue;
            }

          /* Print info on jobs that are running in the background,
             and on foreground jobs that were killed by anything
             except SIGINT (and possibly SIGPIPE). */
          switch (JOBSTATE (job))
            {
            case JDEAD:
              if (interactive_shell == 0 && termsig && WIFSIGNALED (s)
                  && termsig != SIGINT &&
#if defined(DONT_REPORT_SIGTERM)
                  termsig != SIGTERM &&
#endif
#if defined(DONT_REPORT_SIGPIPE)
                  termsig != SIGPIPE &&
#endif
                  signal_is_trapped (termsig) == 0)
                {
                  /* Don't print `0' for a line number. */
                  fprintf (stderr, _ ("%s: line %d: "), get_name_for_error (),
                           (line_number == 0) ? 1 : line_number);
                  pretty_print_job (job, JLIST_NONINTERACTIVE, stderr);
                }
              else if (IS_FOREGROUND (job))
                {
#if !defined(DONT_REPORT_SIGPIPE)
                  if (termsig && WIFSIGNALED (s) && termsig != SIGINT)
#else
                  if (termsig && WIFSIGNALED (s) && termsig != SIGINT
                      && termsig != SIGPIPE)
#endif
                    {
                      fprintf (stderr, "%s", j_strsignal (termsig));

                      if (WIFCORED (s))
                        fprintf (stderr, _ (" (core dumped)"));

                      fprintf (stderr, "\n");
                    }
                }
              else if (job_control) /* XXX job control test added */
                {
                  if (dir == 0)
                    dir = current_working_directory ();
                  pretty_print_job (job, JLIST_STANDARD, stderr);
                  if (dir && strcmp (dir, jobs[job]->wd) != 0)
                    fprintf (stderr, _ ("(wd now: %s)\n"),
                             polite_directory_format (dir));
                }

              jobs[job]->flags |= J_NOTIFIED;
              break;

            case JSTOPPED:
              fprintf (stderr, "\n");
              if (dir == 0)
                dir = current_working_directory ();
              pretty_print_job (job, JLIST_STANDARD, stderr);
              if (dir && (strcmp (dir, jobs[job]->wd) != 0))
                fprintf (stderr, _ ("(wd now: %s)\n"),
                         polite_directory_format (dir));
              jobs[job]->flags |= J_NOTIFIED;
              break;

            case JRUNNING:
            case JMIXED:
              break;

            default:
              programming_error ("notify_of_job_status");
            }
        }
    }
  if (old_ttou != 0)
    sigprocmask (SIG_SETMASK, &oset, nullptr);
  else
    queue_sigchld--;
}

/* Initialize the job control mechanism, and set up the tty stuff. */
bool
initialize_job_control (bool force)
{
  pid_t t;
  int t_errno, tty_sigs;

  t_errno = -1;
  shell_pgrp = getpgid (0);

  if (shell_pgrp == -1)
    {
      sys_error (_ ("initialize_job_control: getpgrp failed"));
      exit (1);
    }

  /* We can only have job control if we are interactive unless we force it. */
  if (!interactive && !force)
    {
      job_control = false;
      original_pgrp = NO_PID;
      shell_tty = fileno (stderr);
      terminal_pgrp = tcgetpgrp (shell_tty); /* for checking later */
    }
  else
    {
      shell_tty = -1;

      /* If forced_interactive is set, we skip the normal check that stderr
         is attached to a tty, so we need to check here.  If it's not, we
         need to see whether we have a controlling tty by opening /dev/tty,
         since trying to use job control tty pgrp manipulations on a non-tty
         is going to fail. */
      if (forced_interactive && isatty (fileno (stderr)) == 0)
        shell_tty = open ("/dev/tty", O_RDWR | O_NONBLOCK);

      /* Get our controlling terminal.  If job_control is set, or
         interactive is set, then this is an interactive shell no
         matter where fd 2 is directed. */
      if (shell_tty == -1)
        shell_tty = dup (fileno (stderr)); /* fd 2 */

      if (shell_tty != -1)
        shell_tty = move_to_high_fd (shell_tty, 1, -1);

      /* Compensate for a bug in systems that compiled the BSD
         rlogind with DEBUG defined, like NeXT and Alliant. */
      if (shell_pgrp == 0)
        {
          shell_pgrp = getpid ();
          setpgid (0, shell_pgrp);
          if (shell_tty != -1)
            tcsetpgrp (shell_tty, shell_pgrp);
        }

      tty_sigs = 0;
      while ((terminal_pgrp = tcgetpgrp (shell_tty)) != -1)
        {
          if (shell_pgrp != terminal_pgrp)
            {
              SigHandler *ottin;

              CHECK_TERMSIG;
              ottin = set_signal_handler (SIGTTIN, SIG_DFL);
              kill (0, SIGTTIN);
              set_signal_handler (SIGTTIN, ottin);
              if (tty_sigs++ > 16)
                {
                  sys_error (_ (
                      "initialize_job_control: no job control in background"));
                  job_control = false;
                  original_pgrp
                      = terminal_pgrp; /* for eventual give_terminal_to */
                  goto just_bail;
                }
              continue;
            }
          break;
        }

      if (terminal_pgrp == -1)
        t_errno = errno;

      /* Make sure that we are using the new line discipline. */
      if (set_new_line_discipline (shell_tty) < 0)
        {
          sys_error (_ ("initialize_job_control: line discipline"));
          job_control = false;
        }
      else
        {
          original_pgrp = shell_pgrp;
          shell_pgrp = getpid ();

          if ((original_pgrp != shell_pgrp) && (setpgid (0, shell_pgrp) < 0))
            {
              sys_error (_ ("initialize_job_control: setpgid"));
              shell_pgrp = original_pgrp;
            }

          job_control = true;

          /* If (and only if) we just set our process group to our pid,
             thereby becoming a process group leader, and the terminal
             is not in the same process group as our (new) process group,
             then set the terminal's process group to our (new) process
             group.  If that fails, set our process group back to what it
             was originally (so we can still read from the terminal) and
             turn off job control.  */
          if (shell_pgrp != original_pgrp && shell_pgrp != terminal_pgrp)
            {
              if (give_terminal_to (shell_pgrp, 0) < 0)
                {
                  t_errno = errno;
                  setpgid (0, original_pgrp);
                  shell_pgrp = original_pgrp;
                  errno = t_errno;
                  sys_error (_ ("cannot set terminal process group (%d)"),
                             shell_pgrp);
                  job_control = false;
                }
            }

          if (job_control
              && ((t = tcgetpgrp (shell_tty)) == -1 || t != shell_pgrp))
            {
              if (t_errno != -1)
                errno = t_errno;
              sys_error (_ ("cannot set terminal process group (%d)"), t);
              job_control = false;
            }
        }
      if (!job_control)
        internal_error (_ ("no job control in this shell"));
    }

just_bail:
  running_in_background = terminal_pgrp != shell_pgrp;

  if (shell_tty != fileno (stderr))
    SET_CLOSE_ON_EXEC (shell_tty);

  set_signal_handler (SIGCHLD, &sigchld_handler);

  change_flag ('m', job_control ? '-' : '+');

  if (interactive)
    get_tty_state ();

  set_maxchild (0);

  return job_control;
}

#ifdef DEBUG
void
debug_print_pgrps ()
{
  itrace ("original_pgrp = %ld shell_pgrp = %ld terminal_pgrp = %ld",
          (long)original_pgrp, (long)shell_pgrp, (long)terminal_pgrp);
  itrace ("tcgetpgrp(%d) -> %ld, getpgid(0) -> %ld", shell_tty,
          (long)tcgetpgrp (shell_tty), (long)getpgid (0));
  itrace ("pipeline_pgrp -> %ld", (long)pipeline_pgrp);
}
#endif

/* Set the line discipline to the best this system has to offer.
   Return -1 if this is not possible. */
static int
set_new_line_discipline (int tty)
{
#if defined(TERMIOS_TTY_DRIVER)
#if defined(TERMIOS_LDISC) && defined(NTTYDISC)
  if (tcgetattr (tty, &shell_tty_info) < 0)
    return -1;

  if (shell_tty_info.c_line != NTTYDISC)
    {
      shell_tty_info.c_line = NTTYDISC;
      if (tcsetattr (tty, TCSADRAIN, &shell_tty_info) < 0)
        return -1;
    }
#endif /* TERMIOS_LDISC && NTTYDISC */
  return 0;
#endif /* TERMIOS_TTY_DRIVER */

#if !defined(TERMIOS_TTY_DRIVER)
  return -1;
#endif
}

/* Setup this shell to handle C-C, etc. */
void
initialize_job_signals ()
{
  if (interactive)
    {
      set_signal_handler (SIGINT, sigint_sighandler);
      set_signal_handler (SIGTSTP, SIG_IGN);
      set_signal_handler (SIGTTOU, SIG_IGN);
      set_signal_handler (SIGTTIN, SIG_IGN);
    }
  else if (job_control)
    {
      old_tstp = set_signal_handler (SIGTSTP, &sigstop_sighandler);
      old_ttin = set_signal_handler (SIGTTIN, &sigstop_sighandler);
      old_ttou = set_signal_handler (SIGTTOU, &sigstop_sighandler);
    }
  /* Leave disposition unmodified for non-interactive shells without job
     control. */
}

/* Here we handle CONT signals. */
static sighandler
sigcont_sighandler (int sig)
{
  initialize_job_signals ();
  set_signal_handler (SIGCONT, old_cont);
  kill (getpid (), SIGCONT);
}

/* Here we handle stop signals while we are running not as a login shell. */
static sighandler
sigstop_sighandler (int sig)
{
  set_signal_handler (SIGTSTP, old_tstp);
  set_signal_handler (SIGTTOU, old_ttou);
  set_signal_handler (SIGTTIN, old_ttin);

  old_cont = set_signal_handler (SIGCONT, sigcont_sighandler);

  give_terminal_to (shell_pgrp, 0);

  kill (getpid (), sig);
}

/* Give the terminal to PGRP.  */
int
give_terminal_to (pid_t pgrp, int force)
{
  sigset_t set, oset;
  int r, e;

  r = 0;
  if (job_control || force)
    {
      sigemptyset (&set);
      sigaddset (&set, SIGTTOU);
      sigaddset (&set, SIGTTIN);
      sigaddset (&set, SIGTSTP);
      sigaddset (&set, SIGCHLD);
      sigemptyset (&oset);
      sigprocmask (SIG_BLOCK, &set, &oset);

      if (tcsetpgrp (shell_tty, pgrp) < 0)
        {
          /* Maybe we should print an error message? */
#if 0
	  sys_error ("tcsetpgrp(%d) failed: pid %ld to pgrp %ld",
	    shell_tty, (long)getpid(), (long)pgrp);
#endif
          r = -1;
          e = errno;
        }
      else
        terminal_pgrp = pgrp;
      sigprocmask (SIG_SETMASK, &oset, nullptr);
    }

  if (r == -1)
    errno = e;

  return r;
}

/* Give terminal to NPGRP iff it's currently owned by OPGRP.  FLAGS are the
   flags to pass to give_terminal_to(). */
static int
maybe_give_terminal_to (pid_t opgrp, pid_t npgrp, int flags)
{
  int tpgrp;

  tpgrp = tcgetpgrp (shell_tty);
  if (tpgrp < 0 && errno == ENOTTY)
    return -1;
  if (tpgrp == npgrp)
    {
      terminal_pgrp = npgrp;
      return 0;
    }
  else if (tpgrp != opgrp)
    {
      internal_debug ("%d: maybe_give_terminal_to: terminal pgrp == %d shell "
                      "pgrp = %d new pgrp = %d in_background = %d",
                      (int)getpid (), tpgrp, opgrp, npgrp,
                      running_in_background);
      return -1;
    }
  else
    return give_terminal_to (npgrp, flags);
}

/* Clear out any jobs in the job array.  This is intended to be used by
   children of the shell, who should not have any job structures as baggage
   when they start executing (forking subshells for parenthesized execution
   and functions with pipes are the two that spring to mind).  If RUNNING_ONLY
   is nonzero, only running jobs are removed from the table. */
void
delete_all_jobs (int running_only)
{
  int i;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);

  /* XXX - need to set j_lastj, j_firstj appropriately if running_only != 0. */
  if (js.j_jobslots)
    {
      js.j_current = js.j_previous = NO_JOB;

      /* XXX could use js.j_firstj here */
      for (i = 0; i < js.j_jobslots; i++)
        {
          if (i < js.j_firstj && jobs[i])
            INTERNAL_DEBUG (
                ("delete_all_jobs: job %d non-null before js.j_firstj (%d)", i,
                 js.j_firstj));
          if (i > js.j_lastj && jobs[i])
            INTERNAL_DEBUG (
                ("delete_all_jobs: job %d non-null after js.j_lastj (%d)", i,
                 js.j_lastj));

          if (jobs[i] && (running_only == 0 || (running_only && RUNNING (i))))
            /* We don't want to add any of these pids to bgpids.  If
               running_only is non-zero, we don't want to add running jobs to
               the list. If we are interested in all jobs, not just running
               jobs, and we are going to clear the bgpids list below
               (bgp_clear()), we don't need to bother. */
            delete_job (i, DEL_WARNSTOPPED | DEL_NOBGPID);
        }
      if (running_only == 0)
        {
          free ((char *)jobs);
          js.j_jobslots = 0;
          js.j_firstj = js.j_lastj = js.j_njobs = 0;
        }
    }

  if (running_only == 0)
    bgp_clear ();

  UNBLOCK_CHILD (oset);
}

/* Mark all jobs in the job array so that they don't get a SIGHUP when the
   shell gets one.  If RUNNING_ONLY is nonzero, mark only running jobs. */
void
nohup_all_jobs (int running_only)
{
  int i;
  sigset_t set, oset;

  BLOCK_CHILD (set, oset);

  if (js.j_jobslots)
    {
      /* XXX could use js.j_firstj here */
      for (i = 0; i < js.j_jobslots; i++)
        if (jobs[i] && (running_only == 0 || (running_only && RUNNING (i))))
          nohup_job (i);
    }

  UNBLOCK_CHILD (oset);
}

int
count_all_jobs ()
{
  int i, n;
  sigset_t set, oset;

  /* This really counts all non-dead jobs. */
  BLOCK_CHILD (set, oset);
  /* XXX could use js.j_firstj here */
  for (i = n = 0; i < js.j_jobslots; i++)
    {
      if (i < js.j_firstj && jobs[i])
        INTERNAL_DEBUG (
            ("count_all_jobs: job %d non-null before js.j_firstj (%d)", i,
             js.j_firstj));
      if (i > js.j_lastj && jobs[i])
        INTERNAL_DEBUG (
            ("count_all_jobs: job %d non-null after js.j_lastj (%d)", i,
             js.j_lastj));

      if (jobs[i] && DEADJOB (i) == 0)
        n++;
    }
  UNBLOCK_CHILD (oset);
  return n;
}

static void
mark_all_jobs_as_dead ()
{
  int i;
  sigset_t set, oset;

  if (js.j_jobslots == 0)
    return;

  BLOCK_CHILD (set, oset);

  /* XXX could use js.j_firstj here */
  for (i = 0; i < js.j_jobslots; i++)
    if (jobs[i])
      {
        jobs[i]->state = JDEAD;
        js.j_ndead++;
      }

  UNBLOCK_CHILD (oset);
}

/* Mark all dead jobs as notified, so delete_job () cleans them out
   of the job table properly.  POSIX.2 says we need to save the
   status of the last CHILD_MAX jobs, so we count the number of dead
   jobs and mark only enough as notified to save CHILD_MAX statuses. */
static void
mark_dead_jobs_as_notified (int force)
{
  int i, ndead, ndeadproc;
  sigset_t set, oset;

  if (js.j_jobslots == 0)
    return;

  BLOCK_CHILD (set, oset);

  /* If FORCE is non-zero, we don't have to keep CHILD_MAX statuses
     around; just run through the array. */
  if (force)
    {
      /* XXX could use js.j_firstj here */
      for (i = 0; i < js.j_jobslots; i++)
        {
          if (jobs[i] && DEADJOB (i)
              && (interactive_shell
                  || (find_last_pid (i, 0) != last_asynchronous_pid)))
            jobs[i]->flags |= J_NOTIFIED;
        }
      UNBLOCK_CHILD (oset);
      return;
    }

  /* Mark enough dead jobs as notified to keep CHILD_MAX processes left in the
     array with the corresponding not marked as notified.  This is a better
     way to avoid pid aliasing and reuse problems than keeping the POSIX-
     mandated CHILD_MAX jobs around.  delete_job() takes care of keeping the
     bgpids list regulated. */

  /* Count the number of dead jobs */
  /* XXX could use js.j_firstj here */
  for (i = ndead = ndeadproc = 0; i < js.j_jobslots; i++)
    {
      if (i < js.j_firstj && jobs[i])
        INTERNAL_DEBUG (("mark_dead_jobs_as_notified: job %d non-null before "
                         "js.j_firstj (%d)",
                         i, js.j_firstj));
      if (i > js.j_lastj && jobs[i])
        INTERNAL_DEBUG (("mark_dead_jobs_as_notified: job %d non-null after "
                         "js.j_lastj (%d)",
                         i, js.j_lastj));

      if (jobs[i] && DEADJOB (i))
        {
          ndead++;
          ndeadproc += processes_in_job (i);
        }
    }

#if 0
  if (ndeadproc != js.c_reaped)
    itrace("mark_dead_jobs_as_notified: ndeadproc (%d) != js.c_reaped (%d)", ndeadproc, js.c_reaped);
#endif
  if (ndead != js.j_ndead)
    INTERNAL_DEBUG (
        ("mark_dead_jobs_as_notified: ndead (%d) != js.j_ndead (%d)", ndead,
         js.j_ndead));

  if (js.c_childmax < 0)
    set_maxchild (0);

  /* Don't do anything if the number of dead processes is less than CHILD_MAX
     and we're not forcing a cleanup. */
  if (ndeadproc <= js.c_childmax)
    {
      UNBLOCK_CHILD (oset);
      return;
    }

#if 0
itrace("mark_dead_jobs_as_notified: child_max = %d ndead = %d ndeadproc = %d", js.c_childmax, ndead, ndeadproc);
#endif

  /* Mark enough dead jobs as notified that we keep CHILD_MAX jobs in
     the list.  This isn't exactly right yet; changes need to be made
     to stop_pipeline so we don't mark the newer jobs after we've
     created CHILD_MAX slots in the jobs array.  This needs to be
     integrated with a way to keep the jobs array from growing without
     bound.  Maybe we wrap back around to 0 after we reach some max
     limit, and there are sufficient job slots free (keep track of total
     size of jobs array (js.j_jobslots) and running count of number of jobs
     in jobs array.  Then keep a job index corresponding to the `oldest job'
     and start this loop there, wrapping around as necessary.  In effect,
     we turn the list into a circular buffer. */
  /* XXX could use js.j_firstj here */
  for (i = 0; i < js.j_jobslots; i++)
    {
      if (jobs[i] && DEADJOB (i)
          && (interactive_shell
              || (find_last_pid (i, 0) != last_asynchronous_pid)))
        {
          if (i < js.j_firstj && jobs[i])
            INTERNAL_DEBUG (("mark_dead_jobs_as_notified: job %d non-null "
                             "before js.j_firstj (%d)",
                             i, js.j_firstj));
          if (i > js.j_lastj && jobs[i])
            INTERNAL_DEBUG (("mark_dead_jobs_as_notified: job %d non-null "
                             "after js.j_lastj (%d)",
                             i, js.j_lastj));

          /* If marking this job as notified would drop us down below
             child_max, don't mark it so we can keep at least child_max
             statuses.  XXX -- need to check what Posix actually says
             about keeping statuses. */
          if ((ndeadproc -= processes_in_job (i)) <= js.c_childmax)
            break;
          jobs[i]->flags |= J_NOTIFIED;
        }
    }

  UNBLOCK_CHILD (oset);
}

/* Here to allow other parts of the shell (like the trap stuff) to
   freeze and unfreeze the jobs list. */
int
freeze_jobs_list ()
{
  int o;

  o = jobs_list_frozen;
  jobs_list_frozen = 1;
  return o;
}

void
unfreeze_jobs_list ()
{
  jobs_list_frozen = 0;
}

void
set_jobs_list_frozen (int s)
{
  jobs_list_frozen = s;
}

/* Allow or disallow job control to take place.  Returns the old value
   of job_control. */
bool
set_job_control (bool arg)
{
  bool old;

  old = job_control;
  job_control = arg;

  if (terminal_pgrp == NO_PID && shell_tty >= 0)
    terminal_pgrp = tcgetpgrp (shell_tty);

  /* If we're turning on job control we're going to want to know the shell's
     process group. */
  if (job_control != old && job_control)
    shell_pgrp = getpgid (0);

  running_in_background = (terminal_pgrp != shell_pgrp);

#if 0
  if (interactive_shell == 0 && running_in_background == 0 && job_control != old)
    {
      if (job_control)
	initialize_job_signals ();
      else
	default_tty_job_signals ();
    }
#endif

  /* If we're turning on job control, reset pipeline_pgrp so make_child will
     put new child processes into the right pgrp */
  if (job_control != old && job_control)
    pipeline_pgrp = 0;

  return old;
}

/* Turn off all traces of job control.  This is run by children of the shell
   which are going to do shellsy things, like wait (), etc. */
void
without_job_control ()
{
  stop_making_children ();
  start_pipeline ();
#if defined(PGRP_PIPE)
  sh_closepipe (pgrp_pipe);
#endif
  delete_all_jobs (0);
  set_job_control (0);
}

/* If this shell is interactive, terminate all stopped jobs and
   restore the original terminal process group.  This is done
   before the `exec' builtin calls shell_execve. */
void
end_job_control ()
{
  if (job_control)
    terminate_stopped_jobs ();

  if (original_pgrp >= 0 && terminal_pgrp != original_pgrp)
    give_terminal_to (original_pgrp, 1);

  if (original_pgrp >= 0 && setpgid (0, original_pgrp) == 0)
    shell_pgrp = original_pgrp;
}

/* Restart job control by closing shell tty and reinitializing.  This is
   called after an exec fails in an interactive shell and we do not exit. */
void
restart_job_control ()
{
  if (shell_tty != -1)
    close (shell_tty);
  initialize_job_control (0);
}

/* Set the maximum number of background children we keep track of to NCHILD.
   If the caller passes NCHILD as 0 or -1, this ends up setting it to
   LMAXCHILD, which is initialized the first time through. */
void
set_maxchild (int nchild)
{
  static int lmaxchild = -1;

  /* Initialize once. */
  if (lmaxchild < 0)
    {
      errno = 0;
      lmaxchild = getmaxchild ();
      if (lmaxchild < 0 && errno == 0)
        lmaxchild = MAX_CHILD_MAX; /* assume unlimited */
    }
  if (lmaxchild < 0)
    lmaxchild = DEFAULT_CHILD_MAX;

  /* Clamp value we set.  Minimum is what Posix requires, maximum is defined
     above as MAX_CHILD_MAX. */
  if (nchild < lmaxchild)
    nchild = lmaxchild;
  else if (nchild > MAX_CHILD_MAX)
    nchild = MAX_CHILD_MAX;

  js.c_childmax = nchild;
}

/* Set the handler to run when the shell receives a SIGCHLD signal. */
void
set_sigchld_handler ()
{
  set_signal_handler (SIGCHLD, sigchld_handler);
}

#if defined(PGRP_PIPE)
/* Read from the read end of a pipe.  This is how the process group leader
   blocks until all of the processes in a pipeline have been made. */
static void
pipe_read (int *pp)
{
  char ch;

  if (pp[1] >= 0)
    {
      close (pp[1]);
      pp[1] = -1;
    }

  if (pp[0] >= 0)
    {
      while (read (pp[0], &ch, 1) == -1 && errno == EINTR)
        ;
    }
}

/* Functional interface closes our local-to-job-control pipes. */
void
close_pgrp_pipe ()
{
  sh_closepipe (pgrp_pipe);
}

void
save_pgrp_pipe (int *p, int clear)
{
  p[0] = pgrp_pipe[0];
  p[1] = pgrp_pipe[1];
  if (clear)
    pgrp_pipe[0] = pgrp_pipe[1] = -1;
}

void
restore_pgrp_pipe (int *p)
{
  pgrp_pipe[0] = p[0];
  pgrp_pipe[1] = p[1];
}

#endif /* PGRP_PIPE */

}