text: /* Job execution and handling for GNU Make.
  Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
  1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
  Foundation, Inc.
  This file is part of GNU Make.
  
  GNU Make is free software; you can redistribute it and/or modify it under the
  terms of the GNU General Public License as published by the Free Software
  Foundation; either version 2, or (at your option) any later version.
  
  GNU Make 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
  GNU Make; see the file COPYING.  If not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.  */
  
  #include "make.h"
  
  #include <assert.h>
  
  #include "job.h"
  #include "debug.h"
  #include "filedef.h"
  #include "commands.h"
  #include "variable.h"
  #include "debug.h"
  
  #include <string.h>
  
  /* Default shell to use.  */
  #ifdef WINDOWS32
  #include <windows.h>
  
  char *default_shell = "sh.exe";
  int no_default_sh_exe = 1;
  int batch_mode_shell = 1;
  HANDLE main_thread;
  
  #elif defined (_AMIGA)
  
  char default_shell[] = "";
  extern int MyExecute (char **);
  int batch_mode_shell = 0;
  
  #elif defined (__MSDOS__)
  
  /* The default shell is a pointer so we can change it if Makefile
     says so.  It is without an explicit path so we get a chance
     to search the $PATH for it (since MSDOS doesn't have standard
     directories we could trust).  */
  char *default_shell = "command.com";
  int batch_mode_shell = 0;
  
  #elif defined (__EMX__)
  
  char *default_shell = "/bin/sh";
  int batch_mode_shell = 0;
  
  #elif defined (VMS)
  
  # include <descrip.h>
  char default_shell[] = "";
  int batch_mode_shell = 0;
  
  #elif defined (__riscos__)
  
  char default_shell[] = "";
  int batch_mode_shell = 0;
  
  #else
  
  char default_shell[] = "/bin/sh";
  int batch_mode_shell = 0;
  
  #endif
  
  #ifdef __MSDOS__
  # include <process.h>
  static int execute_by_shell;
  static int dos_pid = 123;
  int dos_status;
  int dos_command_running;
  #endif /* __MSDOS__ */
  
  #ifdef _AMIGA
  # include <proto/dos.h>
  static int amiga_pid = 123;
  static int amiga_status;
  static char amiga_bname[32];
  static int amiga_batch_file;
  #endif /* Amiga.  */
  
  #ifdef VMS
  # ifndef __GNUC__
  #   include <processes.h>
  # endif
  # include <starlet.h>
  # include <lib$routines.h>
  static void vmsWaitForChildren PARAMS ((int *));
  #endif
  
  #ifdef WINDOWS32
  # include <windows.h>
  # include <io.h>
  # include <process.h>
  # include "sub_proc.h"
  # include "w32err.h"
  # include "pathstuff.h"
  #endif /* WINDOWS32 */
  
  #ifdef __EMX__
  # include <process.h>
  #endif
  
  #if defined (HAVE_SYS_WAIT_H) || defined (HAVE_UNION_WAIT)
  # include <sys/wait.h>
  #endif
  
  #ifdef HAVE_WAITPID
  # define WAIT_NOHANG(status)	waitpid (-1, (status), WNOHANG)
  #else	/* Don't have waitpid.  */
  # ifdef HAVE_WAIT3
  #  ifndef wait3
  extern int wait3 ();
  #  endif
  #  define WAIT_NOHANG(status)	wait3 ((status), WNOHANG, (struct rusage *) 0)
  # endif /* Have wait3.  */
  #endif /* Have waitpid.  */
  
  #if !defined (wait) && !defined (POSIX)
  extern int wait ();
  #endif
  
  #ifndef	HAVE_UNION_WAIT
  
  # define WAIT_T int
  
  # ifndef WTERMSIG
  #  define WTERMSIG(x) ((x) & 0x7f)
  # endif
  # ifndef WCOREDUMP
  #  define WCOREDUMP(x) ((x) & 0x80)
  # endif
  # ifndef WEXITSTATUS
  #  define WEXITSTATUS(x) (((x) >> 8) & 0xff)
  # endif
  # ifndef WIFSIGNALED
  #  define WIFSIGNALED(x) (WTERMSIG (x) != 0)
  # endif
  # ifndef WIFEXITED
  #  define WIFEXITED(x) (WTERMSIG (x) == 0)
  # endif
  
  #else	/* Have `union wait'.  */
  
  # define WAIT_T union wait
  # ifndef WTERMSIG
  #  define WTERMSIG(x) ((x).w_termsig)
  # endif
  # ifndef WCOREDUMP
  #  define WCOREDUMP(x) ((x).w_coredump)
  # endif
  # ifndef WEXITSTATUS
  #  define WEXITSTATUS(x) ((x).w_retcode)
  # endif
  # ifndef WIFSIGNALED
  #  define WIFSIGNALED(x) (WTERMSIG(x) != 0)
  # endif
  # ifndef WIFEXITED
  #  define WIFEXITED(x) (WTERMSIG(x) == 0)
  # endif
  
  #endif	/* Don't have `union wait'.  */
  
  #ifndef	HAVE_UNISTD_H
  extern int dup2 ();
  extern int execve ();
  extern void _exit ();
  # ifndef VMS
  extern int geteuid ();
  extern int getegid ();
  extern int setgid ();
  extern int getgid ();
  # endif
  #endif
  
  extern char *allocated_variable_expand_for_file PARAMS ((char *line, struct file *file));
  
  extern int getloadavg PARAMS ((double loadavg[], int nelem));
  extern int start_remote_job PARAMS ((char **argv, char **envp, int stdin_fd,
  		int *is_remote, int *id_ptr, int *used_stdin));
  extern int start_remote_job_p PARAMS ((int));
  extern int remote_status PARAMS ((int *exit_code_ptr, int *signal_ptr,
  		int *coredump_ptr, int block));
  
  RETSIGTYPE child_handler PARAMS ((int));
  static void free_child PARAMS ((struct child *));
  static void start_job_command PARAMS ((struct child *child));
  static int load_too_high PARAMS ((void));
  static int job_next_command PARAMS ((struct child *));
  static int start_waiting_job PARAMS ((struct child *));
  
  /* Chain of all live (or recently deceased) children.  */
  
  struct child *children = 0;
  
  /* Number of children currently running.  */
  
  unsigned int job_slots_used = 0;
  
  /* Nonzero if the `good' standard input is in use.  */
  
  static int good_stdin_used = 0;
  
  /* Chain of children waiting to run until the load average goes down.  */
  
  static struct child *waiting_jobs = 0;
  
  /* Non-zero if we use a *real* shell (always so on Unix).  */
  
  int unixy_shell = 1;
  
  /* Number of jobs started in the current second.  */
  
  unsigned long job_counter = 0;
  
  /* Number of jobserver tokens this instance is currently using.  */
  
  unsigned int jobserver_tokens = 0;
  
  #ifdef WINDOWS32
  /*
   * The macro which references this function is defined in make.h.
   */
  int
  w32_kill(int pid, int sig)
  {
    return ((process_kill((HANDLE)pid, sig) == TRUE) ? 0 : -1);
  }
  
  /* This function creates a temporary file name with an extension specified
   * by the unixy arg.
   * Return an xmalloc'ed string of a newly created temp file and its
   * file descriptor, or die.  */
  static char *
  create_batch_file (char const *base, int unixy, int *fd)
  {
    const char *const ext = unixy ? "sh" : "bat";
    const char *error = NULL;
    char temp_path[MAXPATHLEN]; /* need to know its length */
    unsigned path_size = GetTempPath(sizeof temp_path, temp_path);
    int path_is_dot = 0;
    unsigned uniq = 1;
    const unsigned sizemax = strlen (base) + strlen (ext) + 10;
  
    if (path_size == 0)
      {
        path_size = GetCurrentDirectory (sizeof temp_path, temp_path);
        path_is_dot = 1;
      }
  
    while (path_size > 0 &&
           path_size + sizemax < sizeof temp_path &&
           uniq < 0x10000)
      {
        unsigned size = sprintf (temp_path + path_size,
                                 "%s%s-%x.%s",
                                 temp_path[path_size - 1] == '\\' ? "" : "\\",
                                 base, uniq, ext);
        HANDLE h = CreateFile (temp_path,  /* file name */
                               GENERIC_READ | GENERIC_WRITE, /* desired access */
                               0,                            /* no share mode */
                               NULL,                         /* default security attributes */
                               CREATE_NEW,                   /* creation disposition */
                               FILE_ATTRIBUTE_NORMAL |       /* flags and attributes */
                               FILE_ATTRIBUTE_TEMPORARY,     /* we'll delete it */
                               NULL);                        /* no template file */
  
        if (h == INVALID_HANDLE_VALUE)
          {
            const DWORD er = GetLastError();
  
            if (er == ERROR_FILE_EXISTS || er == ERROR_ALREADY_EXISTS)
              ++uniq;
  
            /* the temporary path is not guaranteed to exist */
            else if (path_is_dot == 0)
              {
                path_size = GetCurrentDirectory (sizeof temp_path, temp_path);
                path_is_dot = 1;
              }
  
            else
              {
                error = map_windows32_error_to_string (er);
                break;
              }
          }
        else
          {
            const unsigned final_size = path_size + size + 1;
            char *const path = (char *) xmalloc (final_size);
            memcpy (path, temp_path, final_size);
            *fd = _open_osfhandle ((long)h, 0);
            if (unixy)
              {
                char *p;
                int ch;
                for (p = path; (ch = *p) != 0; ++p)
                  if (ch == '\\')
                    *p = '/';
              }
            return path; /* good return */
          }
      }
  
    *fd = -1;
    if (error == NULL)
      error = _("Cannot create a temporary file\n");
    fatal (NILF, error);
  
    /* not reached */
    return NULL;
  }
  #endif /* WINDOWS32 */
  
  #ifdef __EMX__
  /* returns whether path is assumed to be a unix like shell. */
  int
  _is_unixy_shell (const char *path)
  {
    /* list of non unix shells */
    const char *known_os2shells[] = {
      "cmd.exe",
      "cmd",
      "4os2.exe",
      "4os2",
      "4dos.exe",
      "4dos",
      "command.com",
      "command",
      NULL
    };
  
    /* find the rightmost '/' or '\\' */
    const char *name = strrchr (path, '/');
    const char *p = strrchr (path, '\\');
    unsigned i;
  
    if (name && p)    /* take the max */
      name = (name > p) ? name : p;
    else if (p)       /* name must be 0 */
      name = p;
    else if (!name)   /* name and p must be 0 */
      name = path;
  
    if (*name == '/' || *name == '\\') name++;
  
    i = 0;
    while (known_os2shells[i] != NULL) {
      if (stricmp (name, known_os2shells[i]) == 0) /* strcasecmp() */
        return 0; /* not a unix shell */
      i++;
    }
  
    /* in doubt assume a unix like shell */
    return 1;
  }
  #endif /* __EMX__ */
  
  
  /* Write an error message describing the exit status given in
     EXIT_CODE, EXIT_SIG, and COREDUMP, for the target TARGET_NAME.
     Append "(ignored)" if IGNORED is nonzero.  */
  
  static void
  child_error (char *target_name, int exit_code, int exit_sig, int coredump,
               int ignored)
  {
    if (ignored && silent_flag)
      return;
  
  #ifdef VMS
    if (!(exit_code & 1))
        error (NILF,
               (ignored ? _("*** [%s] Error 0x%x (ignored)")
                : _("*** [%s] Error 0x%x")),
               target_name, exit_code);
  #else
    if (exit_sig == 0)
      error (NILF, ignored ? _("[%s] Error %d (ignored)") :
  	   _("*** [%s] Error %d"),
  	   target_name, exit_code);
    else
      error (NILF, "*** [%s] %s%s",
  	   target_name, strsignal (exit_sig),
  	   coredump ? _(" (core dumped)") : "");
  #endif /* VMS */
  }
  
  
  /* Handle a dead child.  This handler may or may not ever be installed.
  
     If we're using the jobserver feature, we need it.  First, installing it
     ensures the read will interrupt on SIGCHLD.  Second, we close the dup'd
     read FD to ensure we don't enter another blocking read without reaping all
     the dead children.  In this case we don't need the dead_children count.
  
     If we don't have either waitpid or wait3, then make is unreliable, but we
     use the dead_children count to reap children as best we can.  */
  
  static unsigned int dead_children = 0;
  
  RETSIGTYPE
  child_handler (int sig UNUSED)
  {
    ++dead_children;
  
    if (job_rfd >= 0)
      {
        close (job_rfd);
        job_rfd = -1;
      }
  
  #ifdef __EMX__
    /* The signal handler must called only once! */
    signal (SIGCHLD, SIG_DFL);
  #endif
  
    /* This causes problems if the SIGCHLD interrupts a printf().
    DB (DB_JOBS, (_("Got a SIGCHLD; %u unreaped children.\n"), dead_children));
    */
  }
  
  extern int shell_function_pid, shell_function_completed;
  
  /* Reap all dead children, storing the returned status and the new command
     state (`cs_finished') in the `file' member of the `struct child' for the
     dead child, and removing the child from the chain.  In addition, if BLOCK
     nonzero, we block in this function until we've reaped at least one
     complete child, waiting for it to die if necessary.  If ERR is nonzero,
     print an error message first.  */
  
  void
  reap_children (int block, int err)
  {
  #ifndef WINDOWS32
    WAIT_T status;
    /* Initially, assume we have some.  */
    int reap_more = 1;
  #endif
  
  #ifdef WAIT_NOHANG
  # define REAP_MORE reap_more
  #else
  # define REAP_MORE dead_children
  #endif
  
    /* As long as:
  
         We have at least one child outstanding OR a shell function in progress,
           AND
         We're blocking for a complete child OR there are more children to reap
  
       we'll keep reaping children.  */
  
    while ((children != 0 || shell_function_pid != 0)
           && (block || REAP_MORE))
      {
        int remote = 0;
        pid_t pid;
        int exit_code, exit_sig, coredump;
        register struct child *lastc, *c;
        int child_failed;
        int any_remote, any_local;
        int dontcare;
  
        if (err && block)
  	{
            static int printed = 0;
  
  	  /* We might block for a while, so let the user know why.
               Only print this message once no matter how many jobs are left.  */
  	  fflush (stdout);
            if (!printed)
              error (NILF, _("*** Waiting for unfinished jobs...."));
            printed = 1;
  	}
  
        /* We have one less dead child to reap.  As noted in
  	 child_handler() above, this count is completely unimportant for
  	 all modern, POSIX-y systems that support wait3() or waitpid().
  	 The rest of this comment below applies only to early, broken
  	 pre-POSIX systems.  We keep the count only because... it's there...
  
  	 The test and decrement are not atomic; if it is compiled into:
  	 	register = dead_children - 1;
  		dead_children = register;
  	 a SIGCHLD could come between the two instructions.
  	 child_handler increments dead_children.
  	 The second instruction here would lose that increment.  But the
  	 only effect of dead_children being wrong is that we might wait
  	 longer than necessary to reap a child, and lose some parallelism;
  	 and we might print the "Waiting for unfinished jobs" message above
  	 when not necessary.  */
  
        if (dead_children > 0)
  	--dead_children;
  
        any_remote = 0;
        any_local = shell_function_pid != 0;
        for (c = children; c != 0; c = c->next)
  	{
  	  any_remote |= c->remote;
  	  any_local |= ! c->remote;
  	  DB (DB_JOBS, (_("Live child 0x%08lx (%s) PID %ld %s\n"),
                          (unsigned long int) c, c->file->name,
                          (long) c->pid, c->remote ? _(" (remote)") : ""));
  #ifdef VMS
  	  break;
  #endif
  	}
  
        /* First, check for remote children.  */
        if (any_remote)
  	pid = remote_status (&exit_code, &exit_sig, &coredump, 0);
        else
  	pid = 0;
  
        if (pid > 0)
  	/* We got a remote child.  */
  	remote = 1;
        else if (pid < 0)
  	{
            /* A remote status command failed miserably.  Punt.  */
  	remote_status_lose:
  	  pfatal_with_name ("remote_status");
  	}
        else
  	{
  	  /* No remote children.  Check for local children.  */
  #if !defined(__MSDOS__) && !defined(_AMIGA) && !defined(WINDOWS32)
  	  if (any_local)
  	    {
  #ifdef VMS
  	      vmsWaitForChildren (&status);
  	      pid = c->pid;
  #else
  #ifdef WAIT_NOHANG
  	      if (!block)
  		pid = WAIT_NOHANG (&status);
  	      else
  #endif
  		pid = wait (&status);
  #endif /* !VMS */
  	    }
  	  else
  	    pid = 0;
  
  	  if (pid < 0)
  	    {
                /* The wait*() failed miserably.  Punt.  */
  	      pfatal_with_name ("wait");
  	    }
  	  else if (pid > 0)
  	    {
  	      /* We got a child exit; chop the status word up.  */
  	      exit_code = WEXITSTATUS (status);
  	      exit_sig = WIFSIGNALED (status) ? WTERMSIG (status) : 0;
  	      coredump = WCOREDUMP (status);
  
                /* If we have started jobs in this second, remove one.  */
                if (job_counter)
                  --job_counter;
  	    }
  	  else
  	    {
  	      /* No local children are dead.  */
                reap_more = 0;
  
  	      if (!block || !any_remote)
                  break;
  
                /* Now try a blocking wait for a remote child.  */
                pid = remote_status (&exit_code, &exit_sig, &coredump, 1);
                if (pid < 0)
                  goto remote_status_lose;
                else if (pid == 0)
                  /* No remote children either.  Finally give up.  */
                  break;
  
                /* We got a remote child.  */
                remote = 1;
  	    }
  #endif /* !__MSDOS__, !Amiga, !WINDOWS32.  */
  
  #ifdef __MSDOS__
  	  /* Life is very different on MSDOS.  */
  	  pid = dos_pid - 1;
  	  status = dos_status;
  	  exit_code = WEXITSTATUS (status);
  	  if (exit_code == 0xff)
  	    exit_code = -1;
  	  exit_sig = WIFSIGNALED (status) ? WTERMSIG (status) : 0;
  	  coredump = 0;
  #endif /* __MSDOS__ */
  #ifdef _AMIGA
  	  /* Same on Amiga */
  	  pid = amiga_pid - 1;
  	  status = amiga_status;
  	  exit_code = amiga_status;
  	  exit_sig = 0;
  	  coredump = 0;
  #endif /* _AMIGA */
  #ifdef WINDOWS32
            {
              HANDLE hPID;
              int werr;
              HANDLE hcTID, hcPID;
              exit_code = 0;
              exit_sig = 0;
              coredump = 0;
  
              /* Record the thread ID of the main process, so that we
                 could suspend it in the signal handler.  */
              if (!main_thread)
                {
                  hcTID = GetCurrentThread ();
                  hcPID = GetCurrentProcess ();
                  if (!DuplicateHandle (hcPID, hcTID, hcPID, &main_thread, 0,
                                        FALSE, DUPLICATE_SAME_ACCESS))
                    {
                      DWORD e = GetLastError ();
                      fprintf (stderr,
                               "Determine main thread ID (Error %ld: %s)\n",
                               e, map_windows32_error_to_string(e));
                    }
                  else
                    DB (DB_VERBOSE, ("Main thread handle = 0x%08lx\n",
                                     (unsigned long)main_thread));
                }
  
              /* wait for anything to finish */
              hPID = process_wait_for_any();
              if (hPID)
                {
  
                  /* was an error found on this process? */
                  werr = process_last_err(hPID);
  
                  /* get exit data */
                  exit_code = process_exit_code(hPID);
  
                  if (werr)
                    fprintf(stderr, "make (e=%d): %s",
                            exit_code, map_windows32_error_to_string(exit_code));
  
                  /* signal */
                  exit_sig = process_signal(hPID);
  
                  /* cleanup process */
                  process_cleanup(hPID);
  
                  coredump = 0;
                }
              pid = (pid_t) hPID;
            }
  #endif /* WINDOWS32 */
  	}
  
        /* Check if this is the child of the `shell' function.  */
        if (!remote && pid == shell_function_pid)
  	{
  	  /* It is.  Leave an indicator for the `shell' function.  */
  	  if (exit_sig == 0 && exit_code == 127)
  	    shell_function_completed = -1;
  	  else
  	    shell_function_completed = 1;
  	  break;
  	}
  
        child_failed = exit_sig != 0 || exit_code != 0;
  
        /* Search for a child matching the deceased one.  */
        lastc = 0;
        for (c = children; c != 0; lastc = c, c = c->next)
  	if (c->remote == remote && c->pid == pid)
  	  break;
  
        if (c == 0)
          /* An unknown child died.
             Ignore it; it was inherited from our invoker.  */
          continue;
  
        DB (DB_JOBS, (child_failed
                      ? _("Reaping losing child 0x%08lx PID %ld %s\n")
                      : _("Reaping winning child 0x%08lx PID %ld %s\n"),
                      (unsigned long int) c, (long) c->pid,
                      c->remote ? _(" (remote)") : ""));
  
        if (c->sh_batch_file) {
          DB (DB_JOBS, (_("Cleaning up temp batch file %s\n"),
                        c->sh_batch_file));
  
          /* just try and remove, don't care if this fails */
          remove (c->sh_batch_file);
  
          /* all done with memory */
          free (c->sh_batch_file);
          c->sh_batch_file = NULL;
        }
  
        /* If this child had the good stdin, say it is now free.  */
        if (c->good_stdin)
          good_stdin_used = 0;
  
        dontcare = c->dontcare;
  
        if (child_failed && !c->noerror && !ignore_errors_flag)
          {
            /* The commands failed.  Write an error message,
               delete non-precious targets, and abort.  */
            static int delete_on_error = -1;
  
            if (!dontcare)
              child_error (c->file->name, exit_code, exit_sig, coredump, 0);
  
            c->file->update_status = 2;
            if (delete_on_error == -1)
              {
                struct file *f = lookup_file (".DELETE_ON_ERROR");
                delete_on_error = f != 0 && f->is_target;
              }
            if (exit_sig != 0 || delete_on_error)
              delete_child_targets (c);
          }
        else
          {
            if (child_failed)
              {
                /* The commands failed, but we don't care.  */
                child_error (c->file->name,
                             exit_code, exit_sig, coredump, 1);
                child_failed = 0;
              }
  
            /* If there are more commands to run, try to start them.  */
            if (job_next_command (c))
              {
                if (handling_fatal_signal)
                  {
                    /* Never start new commands while we are dying.
                       Since there are more commands that wanted to be run,
                       the target was not completely remade.  So we treat
                       this as if a command had failed.  */
                    c->file->update_status = 2;
                  }
                else
                  {
                    /* Check again whether to start remotely.
                       Whether or not we want to changes over time.
                       Also, start_remote_job may need state set up
                       by start_remote_job_p.  */
                    c->remote = start_remote_job_p (0);
                    start_job_command (c);
                    /* Fatal signals are left blocked in case we were
                       about to put that child on the chain.  But it is
                       already there, so it is safe for a fatal signal to
                       arrive now; it will clean up this child's targets.  */
                    unblock_sigs ();
                    if (c->file->command_state == cs_running)
                      /* We successfully started the new command.
                         Loop to reap more children.  */
                      continue;
                  }
  
                if (c->file->update_status != 0)
                  /* We failed to start the commands.  */
                  delete_child_targets (c);
              }
            else
              /* There are no more commands.  We got through them all
                 without an unignored error.  Now the target has been
                 successfully updated.  */
              c->file->update_status = 0;
          }
  
        /* When we get here, all the commands for C->file are finished
           (or aborted) and C->file->update_status contains 0 or 2.  But
           C->file->command_state is still cs_running if all the commands
           ran; notice_finish_file looks for cs_running to tell it that
           it's interesting to check the file's modtime again now.  */
  
        if (! handling_fatal_signal)
          /* Notice if the target of the commands has been changed.
             This also propagates its values for command_state and
             update_status to its also_make files.  */
          notice_finished_file (c->file);
  
        DB (DB_JOBS, (_("Removing child 0x%08lx PID %ld%s from chain.\n"),
                      (unsigned long int) c, (long) c->pid,
                      c->remote ? _(" (remote)") : ""));
  
        /* Block fatal signals while frobnicating the list, so that
           children and job_slots_used are always consistent.  Otherwise
           a fatal signal arriving after the child is off the chain and
           before job_slots_used is decremented would believe a child was
           live and call reap_children again.  */
        block_sigs ();
  
        /* There is now another slot open.  */
        if (job_slots_used > 0)
          --job_slots_used;
  
        /* Remove the child from the chain and free it.  */
        if (lastc == 0)
          children = c->next;
        else
          lastc->next = c->next;
  
        free_child (c);
  
        unblock_sigs ();
  
        /* If the job failed, and the -k flag was not given, die,
           unless we are already in the process of dying.  */
        if (!err && child_failed && !dontcare && !keep_going_flag &&
            /* fatal_error_signal will die with the right signal.  */
            !handling_fatal_signal)
          die (2);
  
        /* Only block for one child.  */
        block = 0;
      }
  
    return;
  }
  
  /* Free the storage allocated for CHILD.  */
  
  static void
  free_child (struct child *child)
  {
    if (!jobserver_tokens)
      fatal (NILF, "INTERNAL: Freeing child 0x%08lx (%s) but no tokens left!\n",
             (unsigned long int) child, child->file->name);
  
    /* If we're using the jobserver and this child is not the only outstanding
       job, put a token back into the pipe for it.  */
  
    if (job_fds[1] >= 0 && jobserver_tokens > 1)
      {
        char token = '+';
        int r;
  
        /* Write a job token back to the pipe.  */
  
        EINTRLOOP (r, write (job_fds[1], &token, 1));
        if (r != 1)
  	pfatal_with_name (_("write jobserver"));
  
        DB (DB_JOBS, (_("Released token for child 0x%08lx (%s).\n"),
                      (unsigned long int) child, child->file->name));
      }
  
    --jobserver_tokens;
  
    if (handling_fatal_signal) /* Don't bother free'ing if about to die.  */
      return;
  
    if (child->command_lines != 0)
      {
        register unsigned int i;
        for (i = 0; i < child->file->cmds->ncommand_lines; ++i)
  	free (child->command_lines[i]);
        free ((char *) child->command_lines);
      }
  
    if (child->environment != 0)
      {
        register char **ep = child->environment;
        while (*ep != 0)
  	free (*ep++);
        free ((char *) child->environment);
      }
  
    free ((char *) child);
  }
  
  #ifdef POSIX
  extern sigset_t fatal_signal_set;
  #endif
  
  void
  block_sigs (void)
  {
  #ifdef POSIX
    (void) sigprocmask (SIG_BLOCK, &fatal_signal_set, (sigset_t *) 0);
  #else
  # ifdef HAVE_SIGSETMASK
    (void) sigblock (fatal_signal_mask);
  # endif
  #endif
  }
  
  #ifdef POSIX
  void
  unblock_sigs (void)
  {
    sigset_t empty;
    sigemptyset (&empty);
    sigprocmask (SIG_SETMASK, &empty, (sigset_t *) 0);
  }
  #endif
  
  #ifdef MAKE_JOBSERVER
  RETSIGTYPE
  job_noop (int sig UNUSED)
  {
  }
  /* Set the child handler action flags to FLAGS.  */
  static void
  set_child_handler_action_flags (int set_handler, int set_alarm)
  {
    struct sigaction sa;
  
  #ifdef __EMX__
    /* The child handler must be turned off here.  */
    signal (SIGCHLD, SIG_DFL);
  #endif
  
    bzero ((char *) &sa, sizeof sa);
    sa.sa_handler = child_handler;
    sa.sa_flags = set_handler ? 0 : SA_RESTART;
  #if defined SIGCHLD
    sigaction (SIGCHLD, &sa, NULL);
  #endif
  #if defined SIGCLD && SIGCLD != SIGCHLD
    sigaction (SIGCLD, &sa, NULL);
  #endif
  #if defined SIGALRM
    if (set_alarm)
      {
        /* If we're about to enter the read(), set an alarm to wake up in a
           second so we can check if the load has dropped and we can start more
           work.  On the way out, turn off the alarm and set SIG_DFL.  */
        alarm (set_handler ? 1 : 0);
        sa.sa_handler = set_handler ? job_noop : SIG_DFL;
        sa.sa_flags = 0;
        sigaction (SIGALRM, &sa, NULL);
      }
  #endif
  }
  #endif
  
  
  /* Start a job to run the commands specified in CHILD.
     CHILD is updated to reflect the commands and ID of the child process.
  
     NOTE: On return fatal signals are blocked!  The caller is responsible
     for calling `unblock_sigs', once the new child is safely on the chain so
     it can be cleaned up in the event of a fatal signal.  */
  
  static void
  start_job_command (struct child *child)
  {
  #if !defined(_AMIGA) && !defined(WINDOWS32)
    static int bad_stdin = -1;
  #endif
    register char *p;
    int flags;
  #ifdef VMS
    char *argv;
  #else
    char **argv;
  #endif
  
    /* If we have a completely empty commandset, stop now.  */
    if (!child->command_ptr)
      goto next_command;
  
    /* Combine the flags parsed for the line itself with
       the flags specified globally for this target.  */
    flags = (child->file->command_flags
  	   | child->file->cmds->lines_flags[child->command_line - 1]);
  
    p = child->command_ptr;
    child->noerror = ((flags & COMMANDS_NOERROR) != 0);
  
    while (*p != '\0')
      {
        if (*p == '@')
  	flags |= COMMANDS_SILENT;
        else if (*p == '+')
  	flags |= COMMANDS_RECURSE;
        else if (*p == '-')
  	child->noerror = 1;
        else if (!isblank ((unsigned char)*p))
  	break;
        ++p;
      }
  
    /* Update the file's command flags with any new ones we found.  We only
       keep the COMMANDS_RECURSE setting.  Even this isn't 100% correct; we are
       now marking more commands recursive than should be in the case of
       multiline define/endef scripts where only one line is marked "+".  In
       order to really fix this, we'll have to keep a lines_flags for every
       actual line, after expansion.  */
    child->file->cmds->lines_flags[child->command_line - 1]
      |= flags & COMMANDS_RECURSE;
  
    /* Figure out an argument list from this command line.  */
  
    {
      char *end = 0;
  #ifdef VMS
      argv = p;
  #else
      argv = construct_command_argv (p, &end, child->file, &child->sh_batch_file);
  #endif
      if (end == NULL)
        child->command_ptr = NULL;
      else
        {
  	*end++ = '\0';
  	child->command_ptr = end;
        }
    }
  
    /* If -q was given, say that updating `failed' if there was any text on the
       command line, or `succeeded' otherwise.  The exit status of 1 tells the
       user that -q is saying `something to do'; the exit status for a random
       error is 2.  */
    if (argv != 0 && question_flag && !(flags & COMMANDS_RECURSE))
      {
  #ifndef VMS
        free (argv[0]);
        free ((char *) argv);
  #endif
        child->file->update_status = 1;
        notice_finished_file (child->file);
        return;
      }
  
    if (touch_flag && !(flags & COMMANDS_RECURSE))
      {
        /* Go on to the next command.  It might be the recursive one.
  	 We construct ARGV only to find the end of the command line.  */
  #ifndef VMS
        if (argv)
          {
            free (argv[0]);
            free ((char *) argv);
          }
  #endif
        argv = 0;
      }
  
    if (argv == 0)
      {
      next_command:
  #ifdef __MSDOS__
        execute_by_shell = 0;   /* in case construct_command_argv sets it */
  #endif
        /* This line has no commands.  Go to the next.  */
        if (job_next_command (child))
  	start_job_command (child);
        else
  	{
  	  /* No more commands.  Make sure we're "running"; we might not be if
               (e.g.) all commands were skipped due to -n.  */
            set_command_state (child->file, cs_running);
  	  child->file->update_status = 0;
  	  notice_finished_file (child->file);
  	}
        return;
      }
  
    /* Print out the command.  If silent, we call `message' with null so it
       can log the working directory before the command's own error messages
       appear.  */
  
    message (0, (just_print_flag || (!(flags & COMMANDS_SILENT) && !silent_flag))
  	   ? "%s" : (char *) 0, p);
  
    /* Tell update_goal_chain that a command has been started on behalf of
       this target.  It is important that this happens here and not in
       reap_children (where we used to do it), because reap_children might be
       reaping children from a different target.  We want this increment to
       guaranteedly indicate that a command was started for the dependency
       chain (i.e., update_file recursion chain) we are processing.  */
  
    ++commands_started;
  
    /* Optimize an empty command.  People use this for timestamp rules,
       so avoid forking a useless shell.  Do this after we increment
       commands_started so make still treats this special case as if it
       performed some action (makes a difference as to what messages are
       printed, etc.  */
  
  #if !defined(VMS) && !defined(_AMIGA)
    if (
  #if defined __MSDOS__ || defined (__EMX__)
        unixy_shell	/* the test is complicated and we already did it */
  #else
        (argv[0] && !strcmp (argv[0], "/bin/sh"))
  #endif
        && (argv[1]
            && argv[1][0] == '-' && argv[1][1] == 'c' && argv[1][2] == '\0')
        && (argv[2] && argv[2][0] == ':' && argv[2][1] == '\0')
        && argv[3] == NULL)
      {
        free (argv[0]);
        free ((char *) argv);
        goto next_command;
      }
  #endif  /* !VMS && !_AMIGA */
  
    /* If -n was given, recurse to get the next line in the sequence.  */
  
    if (just_print_flag && !(flags & COMMANDS_RECURSE))
      {
  #ifndef VMS
        free (argv[0]);
        free ((char *) argv);
  #endif
        goto next_command;
      }
  
    /* Flush the output streams so they won't have things written twice.  */
  
    fflush (stdout);
    fflush (stderr);
  
  #ifndef VMS
  #if !defined(WINDOWS32) && !defined(_AMIGA) && !defined(__MSDOS__)
  
    /* Set up a bad standard input that reads from a broken pipe.  */
  
    if (bad_stdin == -1)
      {
        /* Make a file descriptor that is the read end of a broken pipe.
  	 This will be used for some children's standard inputs.  */
        int pd[2];
        if (pipe (pd) == 0)
  	{
  	  /* Close the write side.  */
  	  (void) close (pd[1]);
  	  /* Save the read side.  */
  	  bad_stdin = pd[0];
  
  	  /* Set the descriptor to close on exec, so it does not litter any
  	     child's descriptor table.  When it is dup2'd onto descriptor 0,
  	     that descriptor will not close on exec.  */
  	  CLOSE_ON_EXEC (bad_stdin);
  	}
      }
  
  #endif /* !WINDOWS32 && !_AMIGA && !__MSDOS__ */
  
    /* Decide whether to give this child the `good' standard input
       (one that points to the terminal or whatever), or the `bad' one
       that points to the read side of a broken pipe.  */
  
    child->good_stdin = !good_stdin_used;
    if (child->good_stdin)
      good_stdin_used = 1;
  
  #endif /* !VMS */
  
    child->deleted = 0;
  
  #ifndef _AMIGA
    /* Set up the environment for the child.  */
    if (child->environment == 0)
      child->environment = target_environment (child->file);
  #endif
  
  #if !defined(__MSDOS__) && !defined(_AMIGA) && !defined(WINDOWS32)
  
  #ifndef VMS
    /* start_waiting_job has set CHILD->remote if we can start a remote job.  */
    if (child->remote)
      {
        int is_remote, id, used_stdin;
        if (start_remote_job (argv, child->environment,
  			    child->good_stdin ? 0 : bad_stdin,
  			    &is_remote, &id, &used_stdin))
          /* Don't give up; remote execution may fail for various reasons.  If
             so, simply run the job locally.  */
  	goto run_local;
        else
  	{
  	  if (child->good_stdin && !used_stdin)
  	    {
  	      child->good_stdin = 0;
  	      good_stdin_used = 0;
  	    }
  	  child->remote = is_remote;
  	  child->pid = id;
  	}
      }
    else
  #endif /* !VMS */
      {
        /* Fork the child process.  */
  
        char **parent_environ;
  
      run_local:
        block_sigs ();
  
        child->remote = 0;
  
  #ifdef VMS
        if (!child_execute_job (argv, child)) {
          /* Fork failed!  */
          perror_with_name ("vfork", "");
          goto error;
        }
  
  #else
  
        parent_environ = environ;
  
  # ifdef __EMX__
        /* If we aren't running a recursive command and we have a jobserver
           pipe, close it before exec'ing.  */
        if (!(flags & COMMANDS_RECURSE) && job_fds[0] >= 0)
  	{
  	  CLOSE_ON_EXEC (job_fds[0]);
  	  CLOSE_ON_EXEC (job_fds[1]);
  	}
        if (job_rfd >= 0)
  	CLOSE_ON_EXEC (job_rfd);
  
        /* Never use fork()/exec() here! Use spawn() instead in exec_command() */
        child->pid = child_execute_job (child->good_stdin ? 0 : bad_stdin, 1,
                                        argv, child->environment);
        if (child->pid < 0)
  	{
  	  /* spawn failed!  */
  	  unblock_sigs ();
  	  perror_with_name ("spawn", "");
  	  goto error;
  	}
  
        /* undo CLOSE_ON_EXEC() after the child process has been started */
        if (!(flags & COMMANDS_RECURSE) && job_fds[0] >= 0)
  	{
  	  fcntl (job_fds[0], F_SETFD, 0);
  	  fcntl (job_fds[1], F_SETFD, 0);
  	}
        if (job_rfd >= 0)
  	fcntl (job_rfd, F_SETFD, 0);
  
  #else  /* !__EMX__ */
  
        child->pid = vfork ();
        environ = parent_environ;	/* Restore value child may have clobbered.  */
        if (child->pid == 0)
  	{
  	  /* We are the child side.  */
  	  unblock_sigs ();
  
            /* If we aren't running a recursive command and we have a jobserver
               pipe, close it before exec'ing.  */
            if (!(flags & COMMANDS_RECURSE) && job_fds[0] >= 0)
              {
                close (job_fds[0]);
                close (job_fds[1]);
              }
            if (job_rfd >= 0)
              close (job_rfd);
  
  	  child_execute_job (child->good_stdin ? 0 : bad_stdin, 1,
                               argv, child->environment);
  	}
        else if (child->pid < 0)
  	{
  	  /* Fork failed!  */
  	  unblock_sigs ();
  	  perror_with_name ("vfork", "");
  	  goto error;
  	}
  # endif  /* !__EMX__ */
  #endif /* !VMS */
      }
  
  #else	/* __MSDOS__ or Amiga or WINDOWS32 */
  #ifdef __MSDOS__
    {
      int proc_return;
  
      block_sigs ();
      dos_status = 0;
  
      /* We call `system' to do the job of the SHELL, since stock DOS
         shell is too dumb.  Our `system' knows how to handle long
         command lines even if pipes/redirection is needed; it will only
         call COMMAND.COM when its internal commands are used.  */
      if (execute_by_shell)
        {
  	char *cmdline = argv[0];
  	/* We don't have a way to pass environment to `system',
  	   so we need to save and restore ours, sigh...  */
  	char **parent_environ = environ;
  
  	environ = child->environment;
  
  	/* If we have a *real* shell, tell `system' to call
  	   it to do everything for us.  */
  	if (unixy_shell)
  	  {
  	    /* A *real* shell on MSDOS may not support long
  	       command lines the DJGPP way, so we must use `system'.  */
  	    cmdline = argv[2];	/* get past "shell -c" */
  	  }
  
  	dos_command_running = 1;
  	proc_return = system (cmdline);
  	environ = parent_environ;
  	execute_by_shell = 0;	/* for the next time */
        }
      else
        {
  	dos_command_running = 1;
  	proc_return = spawnvpe (P_WAIT, argv[0], argv, child->environment);
        }
  
      /* Need to unblock signals before turning off
         dos_command_running, so that child's signals
         will be treated as such (see fatal_error_signal).  */
      unblock_sigs ();
      dos_command_running = 0;
  
      /* If the child got a signal, dos_status has its
         high 8 bits set, so be careful not to alter them.  */
      if (proc_return == -1)
        dos_status |= 0xff;
      else
        dos_status |= (proc_return & 0xff);
      ++dead_children;
      child->pid = dos_pid++;
    }
  #endif /* __MSDOS__ */
  #ifdef _AMIGA
    amiga_status = MyExecute (argv);
  
    ++dead_children;
    child->pid = amiga_pid++;
    if (amiga_batch_file)
    {
       amiga_batch_file = 0;
       DeleteFile (amiga_bname);        /* Ignore errors.  */
    }
  #endif	/* Amiga */
  #ifdef WINDOWS32
    {
        HANDLE hPID;
        char* arg0;
  
        /* make UNC paths safe for CreateProcess -- backslash format */
        arg0 = argv[0];
        if (arg0 && arg0[0] == '/' && arg0[1] == '/')
          for ( ; arg0 && *arg0; arg0++)
            if (*arg0 == '/')
              *arg0 = '\\';
  
        /* make sure CreateProcess() has Path it needs */
        sync_Path_environment();
  
        hPID = process_easy(argv, child->environment);
  
        if (hPID != INVALID_HANDLE_VALUE)
          child->pid = (int) hPID;
        else {
          int i;
          unblock_sigs();
          fprintf(stderr,
                  _("process_easy() failed to launch process (e=%ld)\n"),
                  process_last_err(hPID));
          for (i = 0; argv[i]; i++)
            fprintf(stderr, "%s ", argv[i]);
          fprintf(stderr, _("\nCounted %d args in failed launch\n"), i);
          goto error;
        }
    }
  #endif /* WINDOWS32 */
  #endif	/* __MSDOS__ or Amiga or WINDOWS32 */
  
    /* Bump the number of jobs started in this second.  */
    ++job_counter;
  
    /* We are the parent side.  Set the state to
       say the commands are running and return.  */
  
    set_command_state (child->file, cs_running);
  
    /* Free the storage used by the child's argument list.  */
  #ifndef VMS
    free (argv[0]);
    free ((char *) argv);
  #endif
  
    return;
  
   error:
    child->file->update_status = 2;
    notice_finished_file (child->file);
    return;
  }
  
  /* Try to start a child running.
     Returns nonzero if the child was started (and maybe finished), or zero if
     the load was too high and the child was put on the `waiting_jobs' chain.  */
  
  static int
  start_waiting_job (struct child *c)
  {
    struct file *f = c->file;
  
    /* If we can start a job remotely, we always want to, and don't care about
       the local load average.  We record that the job should be started
       remotely in C->remote for start_job_command to test.  */
  
    c->remote = start_remote_job_p (1);
  
    /* If we are running at least one job already and the load average
       is too high, make this one wait.  */
    if (!c->remote
        && ((job_slots_used > 0 && load_too_high ())
  #ifdef WINDOWS32
  	  || (process_used_slots () >= MAXIMUM_WAIT_OBJECTS)
  #endif
  	  ))
      {
        /* Put this child on the chain of children waiting for the load average
           to go down.  */
        set_command_state (f, cs_running);
        c->next = waiting_jobs;
        waiting_jobs = c;
        return 0;
      }
  
    /* Start the first command; reap_children will run later command lines.  */
    start_job_command (c);
  
    switch (f->command_state)
      {
      case cs_running:
        c->next = children;
        DB (DB_JOBS, (_("Putting child 0x%08lx (%s) PID %ld%s on the chain.\n"),
                      (unsigned long int) c, c->file->name,
                      (long) c->pid, c->remote ? _(" (remote)") : ""));
        children = c;
        /* One more job slot is in use.  */
        ++job_slots_used;
        unblock_sigs ();
        break;
  
      case cs_not_started:
        /* All the command lines turned out to be empty.  */
        f->update_status = 0;
        /* FALLTHROUGH */
  
      case cs_finished:
        notice_finished_file (f);
        free_child (c);
        break;
  
      default:
        assert (f->command_state == cs_finished);
        break;
      }
  
    return 1;
  }
  
  /* Create a `struct child' for FILE and start its commands running.  */
  
  void
  new_job (struct file *file)
  {
    register struct commands *cmds = file->cmds;
    register struct child *c;
    char **lines;
    register unsigned int i;
  
    /* Let any previously decided-upon jobs that are waiting
       for the load to go down start before this new one.  */
    start_waiting_jobs ();
  
    /* Reap any children that might have finished recently.  */
    reap_children (0, 0);
  
    /* Chop the commands up into lines if they aren't already.  */
    chop_commands (cmds);
  
    /* Expand the command lines and store the results in LINES.  */
    lines = (char **) xmalloc (cmds->ncommand_lines * sizeof (char *));
    for (i = 0; i < cmds->ncommand_lines; ++i)
      {
        /* Collapse backslash-newline combinations that are inside variable
  	 or function references.  These are left alone by the parser so
  	 that they will appear in the echoing of commands (where they look
  	 nice); and collapsed by construct_command_argv when it tokenizes.
  	 But letting them survive inside function invocations loses because
  	 we don't want the functions to see them as part of the text.  */
  
        char *in, *out, *ref;
  
        /* IN points to where in the line we are scanning.
  	 OUT points to where in the line we are writing.
  	 When we collapse a backslash-newline combination,
  	 IN gets ahead of OUT.  */
  
        in = out = cmds->command_lines[i];
        while ((ref = strchr (in, '$')) != 0)
  	{
  	  ++ref;		/* Move past the $.  */
  
  	  if (out != in)
  	    /* Copy the text between the end of the last chunk
  	       we processed (where IN points) and the new chunk
  	       we are about to process (where REF points).  */
  	    bcopy (in, out, ref - in);
  
  	  /* Move both pointers past the boring stuff.  */
  	  out += ref - in;
  	  in = ref;
  
  	  if (*ref == '(' || *ref == '{')
  	    {
  	      char openparen = *ref;
  	      char closeparen = openparen == '(' ? ')' : '}';
  	      int count;
  	      char *p;
  
  	      *out++ = *in++;	/* Copy OPENPAREN.  */
  	      /* IN now points past the opening paren or brace.
  		 Count parens or braces until it is matched.  */
  	      count = 0;
  	      while (*in != '\0')
  		{
  		  if (*in == closeparen && --count < 0)
  		    break;
  		  else if (*in == '\\' && in[1] == '\n')
  		    {
  		      /* We have found a backslash-newline inside a
  			 variable or function reference.  Eat it and
  			 any following whitespace.  */
  
  		      int quoted = 0;
  		      for (p = in - 1; p > ref && *p == '\\'; --p)
  			quoted = !quoted;
  
  		      if (quoted)
  			/* There were two or more backslashes, so this is
  			   not really a continuation line.  We don't collapse
  			   the quoting backslashes here as is done in
  			   collapse_continuations, because the line will
  			   be collapsed again after expansion.  */
  			*out++ = *in++;
  		      else
  			{
  			  /* Skip the backslash, newline and
  			     any following whitespace.  */
  			  in = next_token (in + 2);
  
  			  /* Discard any preceding whitespace that has
  			     already been written to the output.  */
  			  while (out > ref
  				 && isblank ((unsigned char)out[-1]))
  			    --out;
  
  			  /* Replace it all with a single space.  */
  			  *out++ = ' ';
  			}
  		    }
  		  else
  		    {
  		      if (*in == openparen)
  			++count;
  
  		      *out++ = *in++;
  		    }
  		}
  	    }
  	}
  
        /* There are no more references in this line to worry about.
  	 Copy the remaining uninteresting text to the output.  */
        if (out != in)
  	strcpy (out, in);
  
        /* Finally, expand the line.  */
        lines[i] = allocated_variable_expand_for_file (cmds->command_lines[i],
  						     file);
      }
  
    /* Start the command sequence, record it in a new
       `struct child', and add that to the chain.  */
  
    c = (struct child *) xmalloc (sizeof (struct child));
    bzero ((char *)c, sizeof (struct child));
    c->file = file;
    c->command_lines = lines;
    c->sh_batch_file = NULL;
  
    /* Cache dontcare flag because file->dontcare can be changed once we
       return. Check dontcare inheritance mechanism for details.  */
    c->dontcare = file->dontcare;
  
    /* Fetch the first command line to be run.  */
    job_next_command (c);
  
    /* Wait for a job slot to be freed up.  If we allow an infinite number
       don't bother; also job_slots will == 0 if we're using the jobserver.  */
  
    if (job_slots != 0)
      while (job_slots_used == job_slots)
        reap_children (1, 0);
  
  #ifdef MAKE_JOBSERVER
    /* If we are controlling multiple jobs make sure we have a token before
       starting the child. */
  
    /* This can be inefficient.  There's a decent chance that this job won't
       actually have to run any subprocesses: the command script may be empty
       or otherwise optimized away.  It would be nice if we could defer
       obtaining a token until just before we need it, in start_job_command.
       To do that we'd need to keep track of whether we'd already obtained a
       token (since start_job_command is called for each line of the job, not
       just once).  Also more thought needs to go into the entire algorithm;
       this is where the old parallel job code waits, so...  */
  
    else if (job_fds[0] >= 0)
      while (1)
        {
          char token;
  	int got_token;
  	int saved_errno;
  
          DB (DB_JOBS, ("Need a job token; we %shave children\n",
                        children ? "" : "don't "));
  
          /* If we don't already have a job started, use our "free" token.  */
          if (!jobserver_tokens)
            break;
  
          /* Read a token.  As long as there's no token available we'll block.
             We enable interruptible system calls before the read(2) so that if
             we get a SIGCHLD while we're waiting, we'll return with EINTR and
             we can process the death(s) and return tokens to the free pool.
  
             Once we return from the read, we immediately reinstate restartable
             system calls.  This allows us to not worry about checking for
             EINTR on all the other system calls in the program.
  
             There is one other twist: there is a span between the time
             reap_children() does its last check for dead children and the time
             the read(2) call is entered, below, where if a child dies we won't
             notice.  This is extremely serious as it could cause us to
             deadlock, given the right set of events.
  
             To avoid this, we do the following: before we reap_children(), we
             dup(2) the read FD on the jobserver pipe.  The read(2) call below
             uses that new FD.  In the signal handler, we close that FD.  That
             way, if a child dies during the section mentioned above, the
             read(2) will be invoked with an invalid FD and will return
             immediately with EBADF.  */
  
          /* Make sure we have a dup'd FD.  */
          if (job_rfd < 0)
            {
              DB (DB_JOBS, ("Duplicate the job FD\n"));
              job_rfd = dup (job_fds[0]);
            }
  
          /* Reap anything that's currently waiting.  */
          reap_children (0, 0);
  
          /* Kick off any jobs we have waiting for an opportunity that
             can run now (ie waiting for load). */
          start_waiting_jobs ();
  
          /* If our "free" slot has become available, use it; we don't need an
             actual token.  */
          if (!jobserver_tokens)
            break;
  
          /* There must be at least one child already, or we have no business
             waiting for a token. */
          if (!children)
            fatal (NILF, "INTERNAL: no children as we go to sleep on read\n");
  
          /* Set interruptible system calls, and read() for a job token.  */
  	set_child_handler_action_flags (1, waiting_jobs != NULL);
  	got_token = read (job_rfd, &token, 1);
  	saved_errno = errno;
  	set_child_handler_action_flags (0, waiting_jobs != NULL);
  
          /* If we got one, we're done here.  */
  	if (got_token == 1)
            {
              DB (DB_JOBS, (_("Obtained token for child 0x%08lx (%s).\n"),
                            (unsigned long int) c, c->file->name));
              break;
            }
  
          /* If the error _wasn't_ expected (EINTR or EBADF), punt.  Otherwise,
             go back and reap_children(), and try again.  */
  	errno = saved_errno;
          if (errno != EINTR && errno != EBADF)
            pfatal_with_name (_("read jobs pipe"));
          if (errno == EBADF)
            DB (DB_JOBS, ("Read returned EBADF.\n"));
        }
  #endif
  
    ++jobserver_tokens;
  
    /* The job is now primed.  Start it running.
       (This will notice if there are in fact no commands.)  */
    (void) start_waiting_job (c);
  
    if (job_slots == 1 || not_parallel)
      /* Since there is only one job slot, make things run linearly.
         Wait for the child to die, setting the state to `cs_finished'.  */
      while (file->command_state == cs_running)
        reap_children (1, 0);
  
    return;
  }
  
  /* Move CHILD's pointers to the next command for it to execute.
     Returns nonzero if there is another command.  */
  
  static int
  job_next_command (struct child *child)
  {
    while (child->command_ptr == 0 || *child->command_ptr == '\0')
      {
        /* There are no more lines in the expansion of this line.  */
        if (child->command_line == child->file->cmds->ncommand_lines)
  	{
  	  /* There are no more lines to be expanded.  */
  	  child->command_ptr = 0;
  	  return 0;
  	}
        else
  	/* Get the next line to run.  */
  	child->command_ptr = child->command_lines[child->command_line++];
      }
    return 1;
  }
  
  /* Determine if the load average on the system is too high to start a new job.
     The real system load average is only recomputed once a second.  However, a
     very parallel make can easily start tens or even hundreds of jobs in a
     second, which brings the system to its knees for a while until that first
     batch of jobs clears out.
  
     To avoid this we use a weighted algorithm to try to account for jobs which
     have been started since the last second, and guess what the load average
     would be now if it were computed.
  
     This algorithm was provided by Thomas Riedl <thomas.riedl@siemens.com>,
     who writes:
  
  !      calculate something load-oid and add to the observed sys.load,
  !      so that latter can catch up:
  !      - every job started increases jobctr;
  !      - every dying job decreases a positive jobctr;
  !      - the jobctr value gets zeroed every change of seconds,
  !        after its value*weight_b is stored into the 'backlog' value last_sec
  !      - weight_a times the sum of jobctr and last_sec gets
  !        added to the observed sys.load.
  !
  !      The two weights have been tried out on 24 and 48 proc. Sun Solaris-9
  !      machines, using a several-thousand-jobs-mix of cpp, cc, cxx and smallish
  !      sub-shelled commands (rm, echo, sed...) for tests.
  !      lowering the 'direct influence' factor weight_a (e.g. to 0.1)
  !      resulted in significant excession of the load limit, raising it
  !      (e.g. to 0.5) took bad to small, fast-executing jobs and didn't
  !      reach the limit in most test cases.
  !
  !      lowering the 'history influence' weight_b (e.g. to 0.1) resulted in
  !      exceeding the limit for longer-running stuff (compile jobs in
  !      the .5 to 1.5 sec. range),raising it (e.g. to 0.5) overrepresented
  !      small jobs' effects.
  
   */
  
  #define LOAD_WEIGHT_A           0.25
  #define LOAD_WEIGHT_B           0.25
  
  static int
  load_too_high (void)
  {
  #if defined(__MSDOS__) || defined(VMS) || defined(_AMIGA) || defined(__riscos__)
    return 1;
  #else
    static double last_sec;
    static time_t last_now;
    double load, guess;
    time_t now;
  
  #ifdef WINDOWS32
    /* sub_proc.c cannot wait for more than MAXIMUM_WAIT_OBJECTS children */
    if (process_used_slots () >= MAXIMUM_WAIT_OBJECTS)
      return 1;
  #endif
  
    if (max_load_average < 0)
      return 0;
  
    /* Find the real system load average.  */
    make_access ();
    if (getloadavg (&load, 1) != 1)
      {
        static int lossage = -1;
        /* Complain only once for the same error.  */
        if (lossage == -1 || errno != lossage)
  	{
  	  if (errno == 0)
  	    /* An errno value of zero means getloadavg is just unsupported.  */
  	    error (NILF,
                     _("cannot enforce load limits on this operating system"));
  	  else
  	    perror_with_name (_("cannot enforce load limit: "), "getloadavg");
  	}
        lossage = errno;
        load = 0;
      }
    user_access ();
  
    /* If we're in a new second zero the counter and correct the backlog
       value.  Only keep the backlog for one extra second; after that it's 0.  */
    now = time (NULL);
    if (last_now < now)
      {
        if (last_now == now - 1)
          last_sec = LOAD_WEIGHT_B * job_counter;
        else
          last_sec = 0.0;
  
        job_counter = 0;
        last_now = now;
      }
  
    /* Try to guess what the load would be right now.  */
    guess = load + (LOAD_WEIGHT_A * (job_counter + last_sec));
  
    DB (DB_JOBS, ("Estimated system load = %f (actual = %f) (max requested = %f)\n",
                  guess, load, max_load_average));
  
    return guess >= max_load_average;
  #endif
  }
  
  /* Start jobs that are waiting for the load to be lower.  */
  
  void
  start_waiting_jobs (void)
  {
    struct child *job;
  
    if (waiting_jobs == 0)
      return;
  
    do
      {
        /* Check for recently deceased descendants.  */
        reap_children (0, 0);
  
        /* Take a job off the waiting list.  */
        job = waiting_jobs;
        waiting_jobs = job->next;
  
        /* Try to start that job.  We break out of the loop as soon
  	 as start_waiting_job puts one back on the waiting list.  */
      }
    while (start_waiting_job (job) && waiting_jobs != 0);
  
    return;
  }
  
  #ifndef WINDOWS32
  
  /* EMX: Start a child process. This function returns the new pid.  */
  # if defined __MSDOS__ || defined __EMX__
  int
  child_execute_job (int stdin_fd, int stdout_fd, char **argv, char **envp)
  {
    int pid;
    /* stdin_fd == 0 means: nothing to do for stdin;
       stdout_fd == 1 means: nothing to do for stdout */
    int save_stdin = (stdin_fd != 0) ? dup (0) : 0;
    int save_stdout = (stdout_fd != 1) ? dup (1): 1;
  
    /* < 0 only if dup() failed */
    if (save_stdin < 0)
      fatal (NILF, _("no more file handles: could not duplicate stdin\n"));
    if (save_stdout < 0)
      fatal (NILF, _("no more file handles: could not duplicate stdout\n"));
  
    /* Close unnecessary file handles for the child.  */
    if (save_stdin != 0)
      CLOSE_ON_EXEC (save_stdin);
    if (save_stdout != 1)
      CLOSE_ON_EXEC (save_stdout);
  
    /* Connect the pipes to the child process.  */
    if (stdin_fd != 0)
      (void) dup2 (stdin_fd, 0);
    if (stdout_fd != 1)
      (void) dup2 (stdout_fd, 1);
  
    /* stdin_fd and stdout_fd must be closed on exit because we are
       still in the parent process */
    if (stdin_fd != 0)
      CLOSE_ON_EXEC (stdin_fd);
    if (stdout_fd != 1)
      CLOSE_ON_EXEC (stdout_fd);
  
    /* Run the command.  */
    pid = exec_command (argv, envp);
  
    /* Restore stdout/stdin of the parent and close temporary FDs.  */
    if (stdin_fd != 0)
      {
        if (dup2 (save_stdin, 0) != 0)
          fatal (NILF, _("Could not restore stdin\n"));
        else
          close (save_stdin);
      }
  
    if (stdout_fd != 1)
      {
        if (dup2 (save_stdout, 1) != 1)
          fatal (NILF, _("Could not restore stdout\n"));
        else
          close (save_stdout);
      }
  
    return pid;
  }
  
  #elif !defined (_AMIGA) && !defined (__MSDOS__) && !defined (VMS)
  
  /* UNIX:
     Replace the current process with one executing the command in ARGV.
     STDIN_FD and STDOUT_FD are used as the process's stdin and stdout; ENVP is
     the environment of the new program.  This function does not return.  */
  void
  child_execute_job (int stdin_fd, int stdout_fd, char **argv, char **envp)
  {
    if (stdin_fd != 0)
      (void) dup2 (stdin_fd, 0);
    if (stdout_fd != 1)
      (void) dup2 (stdout_fd, 1);
    if (stdin_fd != 0)
      (void) close (stdin_fd);
    if (stdout_fd != 1)
      (void) close (stdout_fd);
  
    /* Run the command.  */
    exec_command (argv, envp);
  }
  #endif /* !AMIGA && !__MSDOS__ && !VMS */
  #endif /* !WINDOWS32 */
  
  #ifndef _AMIGA
  /* Replace the current process with one running the command in ARGV,
     with environment ENVP.  This function does not return.  */
  
  /* EMX: This function returns the pid of the child process.  */
  # ifdef __EMX__
  int
  # else
  void
  # endif
  exec_command (char **argv, char **envp)
  {
  #ifdef VMS
    /* to work around a problem with signals and execve: ignore them */
  #ifdef SIGCHLD
    signal (SIGCHLD,SIG_IGN);
  #endif
    /* Run the program.  */
    execve (argv[0], argv, envp);
    perror_with_name ("execve: ", argv[0]);
    _exit (EXIT_FAILURE);
  #else
  #ifdef WINDOWS32
    HANDLE hPID;
    HANDLE hWaitPID;
    int err = 0;
    int exit_code = EXIT_FAILURE;
  
    /* make sure CreateProcess() has Path it needs */
    sync_Path_environment();
  
    /* launch command */
    hPID = process_easy(argv, envp);
  
    /* make sure launch ok */
    if (hPID == INVALID_HANDLE_VALUE)
      {
        int i;
        fprintf(stderr,
                _("process_easy() failed failed to launch process (e=%ld)\n"),
                process_last_err(hPID));
        for (i = 0; argv[i]; i++)
            fprintf(stderr, "%s ", argv[i]);
        fprintf(stderr, _("\nCounted %d args in failed launch\n"), i);
        exit(EXIT_FAILURE);
      }
  
    /* wait and reap last child */
    hWaitPID = process_wait_for_any();
    while (hWaitPID)
      {
        /* was an error found on this process? */
        err = process_last_err(hWaitPID);
  
        /* get exit data */
        exit_code = process_exit_code(hWaitPID);
  
        if (err)
            fprintf(stderr, "make (e=%d, rc=%d): %s",
                    err, exit_code, map_windows32_error_to_string(err));
  
        /* cleanup process */
        process_cleanup(hWaitPID);
  
        /* expect to find only last pid, warn about other pids reaped */
        if (hWaitPID == hPID)
            break;
        else
            fprintf(stderr,
                    _("make reaped child pid %ld, still waiting for pid %ld\n"),
                    (DWORD)hWaitPID, (DWORD)hPID);
      }
  
    /* return child's exit code as our exit code */
    exit(exit_code);
  
  #else  /* !WINDOWS32 */
  
  # ifdef __EMX__
    int pid;
  # endif
  
    /* Be the user, permanently.  */
    child_access ();
  
  # ifdef __EMX__
  
    /* Run the program.  */
    pid = spawnvpe (P_NOWAIT, argv[0], argv, envp);
  
    if (pid >= 0)
      return pid;
  
    /* the file might have a strange shell extension */
    if (errno == ENOENT)
      errno = ENOEXEC;
  
  # else
  
    /* Run the program.  */
    environ = envp;
    execvp (argv[0], argv);
  
  # endif /* !__EMX__ */
  
    switch (errno)
      {
      case ENOENT:
        error (NILF, _("%s: Command not found"), argv[0]);
        break;
      case ENOEXEC:
        {
  	/* The file is not executable.  Try it as a shell script.  */
  	extern char *getenv ();
  	char *shell;
  	char **new_argv;
  	int argc;
          int i=1;
  
  # ifdef __EMX__
          /* Do not use $SHELL from the environment */
  	struct variable *p = lookup_variable ("SHELL", 5);
  	if (p)
  	  shell = p->value;
          else
            shell = 0;
  # else
  	shell = getenv ("SHELL");
  # endif
  	if (shell == 0)
  	  shell = default_shell;
  
  	argc = 1;
  	while (argv[argc] != 0)
  	  ++argc;
  
  # ifdef __EMX__
          if (!unixy_shell)
            ++argc;
  # endif
  
  	new_argv = (char **) alloca ((1 + argc + 1) * sizeof (char *));
  	new_argv[0] = shell;
  
  # ifdef __EMX__
          if (!unixy_shell)
            {
              new_argv[1] = "/c";
              ++i;
              --argc;
            }
  # endif
  
          new_argv[i] = argv[0];
  	while (argc > 0)
  	  {
  	    new_argv[i + argc] = argv[argc];
  	    --argc;
  	  }
  
  # ifdef __EMX__
  	pid = spawnvpe (P_NOWAIT, shell, new_argv, envp);
  	if (pid >= 0)
            break;
  # else
  	execvp (shell, new_argv);
  # endif
  	if (errno == ENOENT)
  	  error (NILF, _("%s: Shell program not found"), shell);
  	else
  	  perror_with_name ("execvp: ", shell);
  	break;
        }
  
  # ifdef __EMX__
      case EINVAL:
        /* this nasty error was driving me nuts :-( */
        error (NILF, _("spawnvpe: environment space might be exhausted"));
        /* FALLTHROUGH */
  # endif
  
      default:
        perror_with_name ("execvp: ", argv[0]);
        break;
      }
  
  # ifdef __EMX__
    return pid;
  # else
    _exit (127);
  # endif
  #endif /* !WINDOWS32 */
  #endif /* !VMS */
  }
  #else /* On Amiga */
  void exec_command (char **argv)
  {
    MyExecute (argv);
  }
  
  void clean_tmp (void)
  {
    DeleteFile (amiga_bname);
  }
  
  #endif /* On Amiga */
  
  #ifndef VMS
  /* Figure out the argument list necessary to run LINE as a command.  Try to
     avoid using a shell.  This routine handles only ' quoting, and " quoting
     when no backslash, $ or ` characters are seen in the quotes.  Starting
     quotes may be escaped with a backslash.  If any of the characters in
     sh_chars[] is seen, or any of the builtin commands listed in sh_cmds[]
     is the first word of a line, the shell is used.
  
     If RESTP is not NULL, *RESTP is set to point to the first newline in LINE.
     If *RESTP is NULL, newlines will be ignored.
  
     SHELL is the shell to use, or nil to use the default shell.
     IFS is the value of $IFS, or nil (meaning the default).  */
  
  static char **
  construct_command_argv_internal (char *line, char **restp, char *shell,
                                   char *ifs, char **batch_filename_ptr)
  {
  #ifdef __MSDOS__
    /* MSDOS supports both the stock DOS shell and ports of Unixy shells.
       We call `system' for anything that requires ``slow'' processing,
       because DOS shells are too dumb.  When $SHELL points to a real
       (unix-style) shell, `system' just calls it to do everything.  When
       $SHELL points to a DOS shell, `system' does most of the work
       internally, calling the shell only for its internal commands.
       However, it looks on the $PATH first, so you can e.g. have an
       external command named `mkdir'.
  
       Since we call `system', certain characters and commands below are
       actually not specific to COMMAND.COM, but to the DJGPP implementation
       of `system'.  In particular:
  
         The shell wildcard characters are in DOS_CHARS because they will
         not be expanded if we call the child via `spawnXX'.
  
         The `;' is in DOS_CHARS, because our `system' knows how to run
         multiple commands on a single line.
  
         DOS_CHARS also include characters special to 4DOS/NDOS, so we
         won't have to tell one from another and have one more set of
         commands and special characters.  */
    static char sh_chars_dos[] = "*?[];|<>%^&()";
    static char *sh_cmds_dos[] = { "break", "call", "cd", "chcp", "chdir", "cls",
  				 "copy", "ctty", "date", "del", "dir", "echo",
  				 "erase", "exit", "for", "goto", "if", "md",
  				 "mkdir", "path", "pause", "prompt", "rd",
  				 "rmdir", "rem", "ren", "rename", "set",
  				 "shift", "time", "type", "ver", "verify",
  				 "vol", ":", 0 };
  
    static char sh_chars_sh[]  = "#;\"*?[]&|<>(){}$`^";
    static char *sh_cmds_sh[]  = { "cd", "echo", "eval", "exec", "exit", "login",
  				 "logout", "set", "umask", "wait", "while",
  				 "for", "case", "if", ":", ".", "break",
  				 "continue", "export", "read", "readonly",
  				 "shift", "times", "trap", "switch", "unset",
                                   0 };
  
    char *sh_chars;
    char **sh_cmds;
  #elif defined (__EMX__)
    static char sh_chars_dos[] = "*?[];|<>%^&()";
    static char *sh_cmds_dos[] = { "break", "call", "cd", "chcp", "chdir", "cls",
  				 "copy", "ctty", "date", "del", "dir", "echo",
  				 "erase", "exit", "for", "goto", "if", "md",
  				 "mkdir", "path", "pause", "prompt", "rd",
  				 "rmdir", "rem", "ren", "rename", "set",
  				 "shift", "time", "type", "ver", "verify",
  				 "vol", ":", 0 };
  
    static char sh_chars_os2[] = "*?[];|<>%^()\"'&";
    static char *sh_cmds_os2[] = { "call", "cd", "chcp", "chdir", "cls", "copy",
  			     "date", "del", "detach", "dir", "echo",
  			     "endlocal", "erase", "exit", "for", "goto", "if",
  			     "keys", "md", "mkdir", "move", "path", "pause",
  			     "prompt", "rd", "rem", "ren", "rename", "rmdir",
  			     "set", "setlocal", "shift", "start", "time",
                               "type", "ver", "verify", "vol", ":", 0 };
  
    static char sh_chars_sh[]  = "#;\"*?[]&|<>(){}$`^~'";
    static char *sh_cmds_sh[]  = { "echo", "cd", "eval", "exec", "exit", "login",
  				 "logout", "set", "umask", "wait", "while",
  				 "for", "case", "if", ":", ".", "break",
  				 "continue", "export", "read", "readonly",
  				 "shift", "times", "trap", "switch", "unset",
                                   0 };
    char *sh_chars;
    char **sh_cmds;
  
  #elif defined (_AMIGA)
    static char sh_chars[] = "#;\"|<>()?*$`";
    static char *sh_cmds[] = { "cd", "eval", "if", "delete", "echo", "copy",
  			     "rename", "set", "setenv", "date", "makedir",
  			     "skip", "else", "endif", "path", "prompt",
  			     "unset", "unsetenv", "version",
  			     0 };
  #elif defined (WINDOWS32)
    static char sh_chars_dos[] = "\"|&<>";
    static char *sh_cmds_dos[] = { "break", "call", "cd", "chcp", "chdir", "cls",
  			     "copy", "ctty", "date", "del", "dir", "echo",
  			     "erase", "exit", "for", "goto", "if", "if", "md",
  			     "mkdir", "path", "pause", "prompt", "rd", "rem",
                               "ren", "rename", "rmdir", "set", "shift", "time",
                               "type", "ver", "verify", "vol", ":", 0 };
    static char sh_chars_sh[] = "#;\"*?[]&|<>(){}$`^";
    static char *sh_cmds_sh[] = { "cd", "eval", "exec", "exit", "login",
  			     "logout", "set", "umask", "wait", "while", "for",
  			     "case", "if", ":", ".", "break", "continue",
  			     "export", "read", "readonly", "shift", "times",
  			     "trap", "switch", "test",
  #ifdef BATCH_MODE_ONLY_SHELL
                   "echo",
  #endif
                   0 };
    char*  sh_chars;
    char** sh_cmds;
  #elif defined(__riscos__)
    static char sh_chars[] = "";
    static char *sh_cmds[] = { 0 };
  #else  /* must be UNIX-ish */
    static char sh_chars[] = "#;\"*?[]&|<>(){}$`^~!";
    static char *sh_cmds[] = { ".", ":", "break", "case", "cd", "continue",
                               "eval", "exec", "exit", "export", "for", "if",
                               "login", "logout", "read", "readonly", "set",
                               "shift", "switch", "test", "times", "trap",
                               "umask", "wait", "while", 0 };
  #endif
    register int i;
    register char *p;
    register char *ap;
    char *end;
    int instring, word_has_equals, seen_nonequals, last_argument_was_empty;
    char **new_argv = 0;
    char *argstr = 0;
  #ifdef WINDOWS32
    int slow_flag = 0;
  
    if (!unixy_shell) {
      sh_cmds = sh_cmds_dos;
      sh_chars = sh_chars_dos;
    } else {
      sh_cmds = sh_cmds_sh;
      sh_chars = sh_chars_sh;
    }
  #endif /* WINDOWS32 */
  
    if (restp != NULL)
      *restp = NULL;
  
    /* Make sure not to bother processing an empty line.  */
    while (isblank ((unsigned char)*line))
      ++line;
    if (*line == '\0')
      return 0;
  
    /* See if it is safe to parse commands internally.  */
    if (shell == 0)
      shell = default_shell;
  #ifdef WINDOWS32
    else if (strcmp (shell, default_shell))
    {
      char *s1 = _fullpath(NULL, shell, 0);
      char *s2 = _fullpath(NULL, default_shell, 0);
  
      slow_flag = strcmp((s1 ? s1 : ""), (s2 ? s2 : ""));
  
      if (s1)
        free (s1);
      if (s2)
        free (s2);
    }
    if (slow_flag)
      goto slow;
  #else  /* not WINDOWS32 */
  #if defined (__MSDOS__) || defined (__EMX__)
    else if (stricmp (shell, default_shell))
      {
        extern int _is_unixy_shell (const char *_path);
  
        DB (DB_BASIC, (_("$SHELL changed (was `%s', now `%s')\n"),
                       default_shell, shell));
        unixy_shell = _is_unixy_shell (shell);
        /* we must allocate a copy of shell: construct_command_argv() will free
         * shell after this function returns.  */
        default_shell = xstrdup (shell);
      }
    if (unixy_shell)
      {
        sh_chars = sh_chars_sh;
        sh_cmds  = sh_cmds_sh;
      }
    else
      {
        sh_chars = sh_chars_dos;
        sh_cmds  = sh_cmds_dos;
  # ifdef __EMX__
        if (_osmode == OS2_MODE)
          {
            sh_chars = sh_chars_os2;
            sh_cmds = sh_cmds_os2;
          }
  # endif
      }
  #else  /* !__MSDOS__ */
    else if (strcmp (shell, default_shell))
      goto slow;
  #endif /* !__MSDOS__ && !__EMX__ */
  #endif /* not WINDOWS32 */
  
    if (ifs != 0)
      for (ap = ifs; *ap != '\0'; ++ap)
        if (*ap != ' ' && *ap != '\t' && *ap != '\n')
  	goto slow;
  
    i = strlen (line) + 1;
  
    /* More than 1 arg per character is impossible.  */
    new_argv = (char **) xmalloc (i * sizeof (char *));
  
    /* All the args can fit in a buffer as big as LINE is.   */
    ap = new_argv[0] = argstr = (char *) xmalloc (i);
    end = ap + i;
  
    /* I is how many complete arguments have been found.  */
    i = 0;
    instring = word_has_equals = seen_nonequals = last_argument_was_empty = 0;
    for (p = line; *p != '\0'; ++p)
      {
        assert (ap <= end);
  
        if (instring)
  	{
  	  /* Inside a string, just copy any char except a closing quote
  	     or a backslash-newline combination.  */
  	  if (*p == instring)
  	    {
  	      instring = 0;
  	      if (ap == new_argv[0] || *(ap-1) == '\0')
  		last_argument_was_empty = 1;
  	    }
  	  else if (*p == '\\' && p[1] == '\n')
              {
                /* Backslash-newline is handled differently depending on what
                   kind of string we're in: inside single-quoted strings you
                   keep them; in double-quoted strings they disappear.
  	         For DOS/Windows/OS2, if we don't have a POSIX shell,
  		 we keep the pre-POSIX behavior of removing the
  		 backslash-newline.  */
                if (instring == '"'
  #if defined (__MSDOS__) || defined (__EMX__) || defined (WINDOWS32)
  		  || !unixy_shell
  #endif
  		  )
                  ++p;
                else
                  {
                    *(ap++) = *(p++);
                    *(ap++) = *p;
                  }
                /* If there's a TAB here, skip it.  */
                if (p[1] == '\t')
                  ++p;
              }
  	  else if (*p == '\n' && restp != NULL)
  	    {
  	      /* End of the command line.  */
  	      *restp = p;
  	      goto end_of_line;
  	    }
  	  /* Backslash, $, and ` are special inside double quotes.
  	     If we see any of those, punt.
  	     But on MSDOS, if we use COMMAND.COM, double and single
  	     quotes have the same effect.  */
  	  else if (instring == '"' && strchr ("\\$`", *p) != 0 && unixy_shell)
  	    goto slow;
  	  else
  	    *ap++ = *p;
  	}
        else if (strchr (sh_chars, *p) != 0)
  	/* Not inside a string, but it's a special char.  */
  	goto slow;
  #ifdef  __MSDOS__
        else if (*p == '.' && p[1] == '.' && p[2] == '.' && p[3] != '.')
  	/* `...' is a wildcard in DJGPP.  */
  	goto slow;
  #endif
        else
  	/* Not a special char.  */
  	switch (*p)
  	  {
  	  case '=':
  	    /* Equals is a special character in leading words before the
  	       first word with no equals sign in it.  This is not the case
  	       with sh -k, but we never get here when using nonstandard
  	       shell flags.  */
  	    if (! seen_nonequals && unixy_shell)
  	      goto slow;
  	    word_has_equals = 1;
  	    *ap++ = '=';
  	    break;
  
  	  case '\\':
  	    /* Backslash-newline has special case handling, ref POSIX.
                 We're in the fastpath, so emulate what the shell would do.  */
  	    if (p[1] == '\n')
  	      {
  		/* Throw out the backslash and newline.  */
                  ++p;
  
  		/* If there is a tab after a backslash-newline, remove it.  */
  		if (p[1] == '\t')
                    ++p;
  
                  /* If there's nothing in this argument yet, skip any
                     whitespace before the start of the next word.  */
                  if (ap == new_argv[i])
                    p = next_token (p + 1) - 1;
  	      }
  	    else if (p[1] != '\0')
                {
  #ifdef HAVE_DOS_PATHS
                  /* Only remove backslashes before characters special to Unixy
                     shells.  All other backslashes are copied verbatim, since
                     they are probably DOS-style directory separators.  This
                     still leaves a small window for problems, but at least it
                     should work for the vast majority of naive users.  */
  
  #ifdef __MSDOS__
                  /* A dot is only special as part of the "..."
                     wildcard.  */
                  if (strneq (p + 1, ".\\.\\.", 5))
                    {
                      *ap++ = '.';
                      *ap++ = '.';
                      p += 4;
                    }
                  else
  #endif
                    if (p[1] != '\\' && p[1] != '\''
                        && !isspace ((unsigned char)p[1])
                        && strchr (sh_chars_sh, p[1]) == 0)
                      /* back up one notch, to copy the backslash */
                      --p;
  #endif  /* HAVE_DOS_PATHS */
  
                  /* Copy and skip the following char.  */
                  *ap++ = *++p;
                }
  	    break;
  
  	  case '\'':
  	  case '"':
  	    instring = *p;
  	    break;
  
  	  case '\n':
  	    if (restp != NULL)
  	      {
  		/* End of the command line.  */
  		*restp = p;
  		goto end_of_line;
  	      }
  	    else
  	      /* Newlines are not special.  */
  	      *ap++ = '\n';
  	    break;
  
  	  case ' ':
  	  case '\t':
  	    /* We have the end of an argument.
  	       Terminate the text of the argument.  */
  	    *ap++ = '\0';
  	    new_argv[++i] = ap;
  	    last_argument_was_empty = 0;
  
  	    /* Update SEEN_NONEQUALS, which tells us if every word
  	       heretofore has contained an `='.  */
  	    seen_nonequals |= ! word_has_equals;
  	    if (word_has_equals && ! seen_nonequals)
  	      /* An `=' in a word before the first
  		 word without one is magical.  */
  	      goto slow;
  	    word_has_equals = 0; /* Prepare for the next word.  */
  
  	    /* If this argument is the command name,
  	       see if it is a built-in shell command.
  	       If so, have the shell handle it.  */
  	    if (i == 1)
  	      {
  		register int j;
  		for (j = 0; sh_cmds[j] != 0; ++j)
                    {
                      if (streq (sh_cmds[j], new_argv[0]))
                        goto slow;
  # ifdef __EMX__
                      /* Non-Unix shells are case insensitive.  */
                      if (!unixy_shell
                          && strcasecmp (sh_cmds[j], new_argv[0]) == 0)
                        goto slow;
  # endif
                    }
  	      }
  
  	    /* Ignore multiple whitespace chars.  */
  	    p = next_token (p) - 1;
  	    break;
  
  	  default:
  	    *ap++ = *p;
  	    break;
  	  }
      }
   end_of_line:
  
    if (instring)
      /* Let the shell deal with an unterminated quote.  */
      goto slow;
  
    /* Terminate the last argument and the argument list.  */
  
    *ap = '\0';
    if (new_argv[i][0] != '\0' || last_argument_was_empty)
      ++i;
    new_argv[i] = 0;
  
    if (i == 1)
      {
        register int j;
        for (j = 0; sh_cmds[j] != 0; ++j)
  	if (streq (sh_cmds[j], new_argv[0]))
  	  goto slow;
      }
  
    if (new_argv[0] == 0)
      {
        /* Line was empty.  */
        free (argstr);
        free ((char *)new_argv);
        return 0;
      }
  
    return new_argv;
  
   slow:;
    /* We must use the shell.  */
  
    if (new_argv != 0)
      {
        /* Free the old argument list we were working on.  */
        free (argstr);
        free ((char *)new_argv);
      }
  
  #ifdef __MSDOS__
    execute_by_shell = 1;	/* actually, call `system' if shell isn't unixy */
  #endif
  
  #ifdef _AMIGA
    {
      char *ptr;
      char *buffer;
      char *dptr;
  
      buffer = (char *)xmalloc (strlen (line)+1);
  
      ptr = line;
      for (dptr=buffer; *ptr; )
      {
        if (*ptr == '\\' && ptr[1] == '\n')
  	ptr += 2;
        else if (*ptr == '@') /* Kludge: multiline commands */
        {
  	ptr += 2;
  	*dptr++ = '\n';
        }
        else
  	*dptr++ = *ptr++;
      }
      *dptr = 0;
  
      new_argv = (char **) xmalloc (2 * sizeof (char *));
      new_argv[0] = buffer;
      new_argv[1] = 0;
    }
  #else	/* Not Amiga  */
  #ifdef WINDOWS32
    /*
     * Not eating this whitespace caused things like
     *
     *    sh -c "\n"
     *
     * which gave the shell fits. I think we have to eat
     * whitespace here, but this code should be considered
     * suspicious if things start failing....
     */
  
    /* Make sure not to bother processing an empty line.  */
    while (isspace ((unsigned char)*line))
      ++line;
    if (*line == '\0')
      return 0;
  #endif /* WINDOWS32 */
    {
      /* SHELL may be a multi-word command.  Construct a command line
         "SHELL -c LINE", with all special chars in LINE escaped.
         Then recurse, expanding this command line to get the final
         argument list.  */
  
      unsigned int shell_len = strlen (shell);
  #ifndef VMS
      static char minus_c[] = " -c ";
  #else
      static char minus_c[] = "";
  #endif
      unsigned int line_len = strlen (line);
  
      char *new_line = (char *) alloca (shell_len + (sizeof (minus_c) - 1)
  				      + (line_len * 2) + 1);
      char *command_ptr = NULL; /* used for batch_mode_shell mode */
  
  # ifdef __EMX__ /* is this necessary? */
      if (!unixy_shell)
        minus_c[1] = '/'; /* " /c " */
  # endif
  
      ap = new_line;
      bcopy (shell, ap, shell_len);
      ap += shell_len;
      bcopy (minus_c, ap, sizeof (minus_c) - 1);
      ap += sizeof (minus_c) - 1;
      command_ptr = ap;
      for (p = line; *p != '\0'; ++p)
        {
  	if (restp != NULL && *p == '\n')
  	  {
  	    *restp = p;
  	    break;
  	  }
  	else if (*p == '\\' && p[1] == '\n')
  	  {
  	    /* POSIX says we keep the backslash-newline, but throw out
                 the next char if it's a TAB.  If we don't have a POSIX
                 shell on DOS/Windows/OS2, mimic the pre-POSIX behavior
                 and remove the backslash/newline.  */
  #if defined (__MSDOS__) || defined (__EMX__) || defined (WINDOWS32)
  # define PRESERVE_BSNL  unixy_shell
  #else
  # define PRESERVE_BSNL  1
  #endif
  	    if (PRESERVE_BSNL)
  	      {
  		*(ap++) = '\\';
  		*(ap++) = '\\';
  		*(ap++) = '\n';
  	      }
  
  	    ++p;
  	    if (p[1] == '\t')
  	      ++p;
  
  	    continue;
  	  }
  
          /* DOS shells don't know about backslash-escaping.  */
  	if (unixy_shell && !batch_mode_shell &&
              (*p == '\\' || *p == '\'' || *p == '"'
               || isspace ((unsigned char)*p)
               || strchr (sh_chars, *p) != 0))
  	  *ap++ = '\\';
  #ifdef __MSDOS__
          else if (unixy_shell && strneq (p, "...", 3))
            {
              /* The case of `...' wildcard again.  */
              strcpy (ap, "\\.\\.\\");
              ap += 5;
              p  += 2;
            }
  #endif
  	*ap++ = *p;
        }
      if (ap == new_line + shell_len + sizeof (minus_c) - 1)
        /* Line was empty.  */
        return 0;
      *ap = '\0';
  
  #ifdef WINDOWS32
      /* Some shells do not work well when invoked as 'sh -c xxx' to run a
         command line (e.g. Cygnus GNUWIN32 sh.exe on WIN32 systems).  In these
         cases, run commands via a script file.  */
      if (just_print_flag) {
        /* Need to allocate new_argv, although it's unused, because
          start_job_command will want to free it and its 0'th element.  */
        new_argv = (char **) xmalloc(2 * sizeof (char *));
        new_argv[0] = xstrdup ("");
        new_argv[1] = NULL;
      } else if ((no_default_sh_exe || batch_mode_shell) && batch_filename_ptr) {
        int temp_fd;
        FILE* batch = NULL;
        int id = GetCurrentProcessId();
        PATH_VAR(fbuf);
  
        /* create a file name */
        sprintf(fbuf, "make%d", id);
        *batch_filename_ptr = create_batch_file (fbuf, unixy_shell, &temp_fd);
  
        DB (DB_JOBS, (_("Creating temporary batch file %s\n"),
                      *batch_filename_ptr));
  
        /* Create a FILE object for the batch file, and write to it the
  	 commands to be executed.  Put the batch file in TEXT mode.  */
        _setmode (temp_fd, _O_TEXT);
        batch = _fdopen (temp_fd, "wt");
        if (!unixy_shell)
          fputs ("@echo off\n", batch);
        fputs (command_ptr, batch);
        fputc ('\n', batch);
        fclose (batch);
  
        /* create argv */
        new_argv = (char **) xmalloc(3 * sizeof (char *));
        if (unixy_shell) {
          new_argv[0] = xstrdup (shell);
          new_argv[1] = *batch_filename_ptr; /* only argv[0] gets freed later */
        } else {
          new_argv[0] = xstrdup (*batch_filename_ptr);
          new_argv[1] = NULL;
        }
        new_argv[2] = NULL;
      } else
  #endif /* WINDOWS32 */
      if (unixy_shell)
        new_argv = construct_command_argv_internal (new_line, (char **) NULL,
                                                    (char *) 0, (char *) 0,
                                                    (char **) 0);
  #ifdef __EMX__
      else if (!unixy_shell)
        {
  	/* new_line is local, must not be freed therefore
             We use line here instead of new_line because we run the shell
             manually.  */
          size_t line_len = strlen (line);
          char *p = new_line;
          char *q = new_line;
          memcpy (new_line, line, line_len + 1);
          /* replace all backslash-newline combination and also following tabs */
          while (*q != '\0')
            {
              if (q[0] == '\\' && q[1] == '\n')
                {
                  q += 2; /* remove '\\' and '\n' */
                  if (q[0] == '\t')
                    q++; /* remove 1st tab in the next line */
                }
              else
                *p++ = *q++;
            }
          *p = '\0';
  
  # ifndef NO_CMD_DEFAULT
          if (strnicmp (new_line, "echo", 4) == 0
              && (new_line[4] == ' ' || new_line[4] == '\t'))
            {
              /* the builtin echo command: handle it separately */
              size_t echo_len = line_len - 5;
              char *echo_line = new_line + 5;
  
              /* special case: echo 'x="y"'
                 cmd works this way: a string is printed as is, i.e., no quotes
                 are removed. But autoconf uses a command like echo 'x="y"' to
                 determine whether make works. autoconf expects the output x="y"
                 so we will do exactly that.
                 Note: if we do not allow cmd to be the default shell
                 we do not need this kind of voodoo */
              if (echo_line[0] == '\''
                  && echo_line[echo_len - 1] == '\''
                  && strncmp (echo_line + 1, "ac_maketemp=",
                              strlen ("ac_maketemp=")) == 0)
                {
                  /* remove the enclosing quotes */
                  memmove (echo_line, echo_line + 1, echo_len - 2);
                  echo_line[echo_len - 2] = '\0';
                }
            }
  # endif
  
          {
            /* Let the shell decide what to do. Put the command line into the
               2nd command line argument and hope for the best ;-)  */
            size_t sh_len = strlen (shell);
  
            /* exactly 3 arguments + NULL */
            new_argv = (char **) xmalloc (4 * sizeof (char *));
            /* Exactly strlen(shell) + strlen("/c") + strlen(line) + 3 times
               the trailing '\0' */
            new_argv[0] = (char *) malloc (sh_len + line_len + 5);
            memcpy (new_argv[0], shell, sh_len + 1);
            new_argv[1] = new_argv[0] + sh_len + 1;
            memcpy (new_argv[1], "/c", 3);
            new_argv[2] = new_argv[1] + 3;
            memcpy (new_argv[2], new_line, line_len + 1);
            new_argv[3] = NULL;
          }
        }
  #elif defined(__MSDOS__)
      else
        {
          /* With MSDOS shells, we must construct the command line here
             instead of recursively calling ourselves, because we
             cannot backslash-escape the special characters (see above).  */
          new_argv = (char **) xmalloc (sizeof (char *));
          line_len = strlen (new_line) - shell_len - sizeof (minus_c) + 1;
          new_argv[0] = xmalloc (line_len + 1);
          strncpy (new_argv[0],
                   new_line + shell_len + sizeof (minus_c) - 1, line_len);
          new_argv[0][line_len] = '\0';
        }
  #else
      else
        fatal (NILF, _("%s (line %d) Bad shell context (!unixy && !batch_mode_shell)\n"),
              __FILE__, __LINE__);
  #endif
    }
  #endif	/* ! AMIGA */
  
    return new_argv;
  }
  #endif /* !VMS */
  
  /* Figure out the argument list necessary to run LINE as a command.  Try to
     avoid using a shell.  This routine handles only ' quoting, and " quoting
     when no backslash, $ or ` characters are seen in the quotes.  Starting
     quotes may be escaped with a backslash.  If any of the characters in
     sh_chars[] is seen, or any of the builtin commands listed in sh_cmds[]
     is the first word of a line, the shell is used.
  
     If RESTP is not NULL, *RESTP is set to point to the first newline in LINE.
     If *RESTP is NULL, newlines will be ignored.
  
     FILE is the target whose commands these are.  It is used for
     variable expansion for $(SHELL) and $(IFS).  */
  
  char **
  construct_command_argv (char *line, char **restp, struct file *file,
                          char **batch_filename_ptr)
  {
    char *shell, *ifs;
    char **argv;
  
  #ifdef VMS
    char *cptr;
    int argc;
  
    argc = 0;
    cptr = line;
    for (;;)
      {
        while ((*cptr != 0)
  	     && (isspace ((unsigned char)*cptr)))
  	cptr++;
        if (*cptr == 0)
  	break;
        while ((*cptr != 0)
  	     && (!isspace((unsigned char)*cptr)))
  	cptr++;
        argc++;
      }
  
    argv = (char **)malloc (argc * sizeof (char *));
    if (argv == 0)
      abort ();
  
    cptr = line;
    argc = 0;
    for (;;)
      {
        while ((*cptr != 0)
  	     && (isspace ((unsigned char)*cptr)))
  	cptr++;
        if (*cptr == 0)
  	break;
        DB (DB_JOBS, ("argv[%d] = [%s]\n", argc, cptr));
        argv[argc++] = cptr;
        while ((*cptr != 0)
  	     && (!isspace((unsigned char)*cptr)))
  	cptr++;
        if (*cptr != 0)
  	*cptr++ = 0;
      }
  #else
    {
      /* Turn off --warn-undefined-variables while we expand SHELL and IFS.  */
      int save = warn_undefined_variables_flag;
      warn_undefined_variables_flag = 0;
  
      shell = allocated_variable_expand_for_file ("$(SHELL)", file);
  #ifdef WINDOWS32
      /*
       * Convert to forward slashes so that construct_command_argv_internal()
       * is not confused.
       */
      if (shell) {
        char *p = w32ify (shell, 0);
        strcpy (shell, p);
      }
  #endif
  #ifdef __EMX__
      {
        static const char *unixroot = NULL;
        static const char *last_shell = "";
        static int init = 0;
        if (init == 0)
  	{
  	  unixroot = getenv ("UNIXROOT");
  	  /* unixroot must be NULL or not empty */
  	  if (unixroot && unixroot[0] == '\0') unixroot = NULL;
  	  init = 1;
  	}
  
        /* if we have an unixroot drive and if shell is not default_shell
           (which means it's either cmd.exe or the test has already been
           performed) and if shell is an absolute path without drive letter,
           try whether it exists e.g.: if "/bin/sh" does not exist use
           "$UNIXROOT/bin/sh" instead.  */
        if (unixroot && shell && strcmp (shell, last_shell) != 0
  	  && (shell[0] == '/' || shell[0] == '\\'))
  	{
  	  /* trying a new shell, check whether it exists */
  	  size_t size = strlen (shell);
  	  char *buf = xmalloc (size + 7);
  	  memcpy (buf, shell, size);
  	  memcpy (buf + size, ".exe", 5); /* including the trailing '\0' */
            if (access (shell, F_OK) != 0 && access (buf, F_OK) != 0)
  	    {
  	      /* try the same for the unixroot drive */
  	      memmove (buf + 2, buf, size + 5);
  	      buf[0] = unixroot[0];
  	      buf[1] = unixroot[1];
  	      if (access (buf, F_OK) == 0)
  		/* we have found a shell! */
  		/* free(shell); */
  		shell = buf;
  	      else
  		free (buf);
  	    }
  	  else
              free (buf);
  	}
      }
  #endif /* __EMX__ */
  
      ifs = allocated_variable_expand_for_file ("$(IFS)", file);
  
      warn_undefined_variables_flag = save;
    }
  
    argv = construct_command_argv_internal (line, restp, shell, ifs, batch_filename_ptr);
  
    free (shell);
    free (ifs);
  #endif /* !VMS */
    return argv;
  }
  
  #if !defined(HAVE_DUP2) && !defined(_AMIGA)
  int
  dup2 (int old, int new)
  {
    int fd;
  
    (void) close (new);
    fd = dup (old);
    if (fd != new)
      {
        (void) close (fd);
        errno = EMFILE;
        return -1;
      }
  
    return fd;
  }
  #endif /* !HAPE_DUP2 && !_AMIGA */
  
  /* On VMS systems, include special VMS functions.  */
  
  #ifdef VMS
  #include "vmsjobs.c"
  #endif
  