sysdep.c

/* Interfaces to system-dependent kernel and library entries.
   Copyright (C) 1985, 86,87,88,93,94,95, 1999, 2000, 2001
   Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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 Emacs 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 Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


#include "config.h"
#include <signal.h>
#include <setjmp.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "lisp.h"
/* Including stdlib.h isn't necessarily enough to get srandom
   declared, e.g. without __USE_XOPEN_EXTENDED with glibc 2.  */
#ifdef HAVE_RANDOM
#if 0 /* It turns out that defining _OSF_SOURCE in osf5-0.h gets
	 random prototyped as returning `int'.  It looks to me as
	 though the best way to DTRT is to prefer the rand48 functions
	 (per libc.info).  -- fx */
extern long int random P_ ((void));
#endif
#if 0 /* Don't prototype srandom; it takes an unsigned argument on
	 some systems, and an unsigned long on others, like FreeBSD
	 4.1.  */
extern void srandom P_ ((unsigned int));
#endif
#endif

#include "blockinput.h"
#undef NULL

#ifdef macintosh
/* It is essential to include stdlib.h so that this file picks up
   the correct definitions of rand, srand, and RAND_MAX.
   Otherwise random numbers will not work correctly.  */
#include <stdlib.h>

#ifndef subprocesses
/* Nonzero means delete a process right away if it exits (process.c).  */
static int delete_exited_processes;
#endif
#endif  /* macintosh */

#ifdef WINDOWSNT
#define read sys_read
#define write sys_write
#include <windows.h>
#ifndef NULL
#define NULL 0
#endif
#endif /* not WINDOWSNT */

/* Does anyone other than VMS need this? */
#ifndef fwrite
#define sys_fwrite fwrite
#else
#undef fwrite
#endif

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>

/* Get _POSIX_VDISABLE, if it is available.  */
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif

#ifdef HAVE_SETPGID
#if !defined (USG) || defined (BSD_PGRPS)
#undef setpgrp
#define setpgrp setpgid
#endif
#endif

/* Get SI_SRPC_DOMAIN, if it is available.  */
#ifdef HAVE_SYS_SYSTEMINFO_H
#include <sys/systeminfo.h>
#endif

#ifdef MSDOS	/* Demacs 1.1.2 91/10/20 Manabu Higashida, MW Aug 1993 */
#include <dos.h>
#include "dosfns.h"
#include "msdos.h"
#include <sys/param.h>

#if __DJGPP__ > 1
extern int etext;
extern unsigned start __asm__ ("start");
#endif
#endif

#ifndef USE_CRT_DLL
#ifndef errno
extern int errno;
#endif
#endif

#ifdef VMS
#include <rms.h>
#include <ttdef.h>
#include <tt2def.h>
#include <iodef.h>
#include <ssdef.h>
#include <descrip.h>
#include <fibdef.h>
#include <atrdef.h>
#include <ctype.h>
#include <string.h>
#ifdef __GNUC__
#include <sys/file.h>
#else
#include <file.h>
#endif
#undef F_SETFL
#ifndef RAB$C_BID
#include <rab.h>
#endif
#define MAXIOSIZE (32 * PAGESIZE) /* Don't I/O more than 32 blocks at a time */
#endif /* VMS */

#ifndef BSD4_1
#ifdef BSD_SYSTEM /* avoid writing defined (BSD_SYSTEM) || defined (USG)
	      because the vms compiler doesn't grok `defined' */
#include <fcntl.h>
#endif
#ifdef USG
#ifndef USG5
#include <fcntl.h>
#endif
#endif
#endif /* not 4.1 bsd */

#ifndef MSDOS
#include <sys/ioctl.h>
#endif

#include "systty.h"
#include "syswait.h"

#ifdef BROKEN_TIOCGWINSZ
#undef TIOCGWINSZ
#undef TIOCSWINSZ
#endif

#if defined (USG) || defined (DGUX)
#include <sys/utsname.h>
#ifndef MEMORY_IN_STRING_H
#include <memory.h>
#endif
#if defined (TIOCGWINSZ) || defined (ISC4_0)
#ifdef NEED_SIOCTL
#include <sys/sioctl.h>
#endif
#ifdef NEED_PTEM_H
#include <sys/stream.h>
#include <sys/ptem.h>
#endif
#endif /* TIOCGWINSZ or ISC4_0 */
#endif /* USG or DGUX */

extern int quit_char;

#include "keyboard.h"
#include "frame.h"
#include "window.h"
#include "termhooks.h"
#include "termchar.h"
#include "termopts.h"
#include "dispextern.h"
#include "process.h"

#ifdef WINDOWSNT
#include <direct.h>
/* In process.h which conflicts with the local copy.  */
#define _P_WAIT 0
int _CRTAPI1 _spawnlp (int, const char *, const char *, ...);
int _CRTAPI1 _getpid (void);
#endif

#ifdef NONSYSTEM_DIR_LIBRARY
#include "ndir.h"
#endif /* NONSYSTEM_DIR_LIBRARY */

#include "syssignal.h"
#include "systime.h"
#ifdef HAVE_UTIME_H
#include <utime.h>
#endif

#ifndef HAVE_UTIMES
#ifndef HAVE_STRUCT_UTIMBUF
/* We want to use utime rather than utimes, but we couldn't find the
   structure declaration.  We'll use the traditional one.  */
struct utimbuf {
  long actime;
  long modtime;
};
#endif
#endif

/* LPASS8 is new in 4.3, and makes cbreak mode provide all 8 bits.  */
#ifndef LPASS8
#define LPASS8 0
#endif

#ifdef BSD4_1
#define LNOFLSH 0100000
#endif

static int baud_convert[] =
#ifdef BAUD_CONVERT
  BAUD_CONVERT;
#else
  {
    0, 50, 75, 110, 135, 150, 200, 300, 600, 1200,
    1800, 2400, 4800, 9600, 19200, 38400
  };
#endif

#ifdef HAVE_SPEED_T
#include <termios.h>
#else
#if defined (HAVE_LIBNCURSES) && ! defined (NCURSES_OSPEED_T)
#else
#if defined (HAVE_TERMIOS_H) && defined (LINUX)
#include <termios.h>
#endif
#endif
#endif

int emacs_ospeed;

/* The file descriptor for Emacs's input terminal.
   Under Unix, this is normally zero except when using X;
   under VMS, we place the input channel number here.  */
int input_fd;

void croak P_ ((char *));

#ifdef AIXHFT
void hft_init ();
void hft_reset ();
#endif

/* Temporary used by `sigblock' when defined in terms of signprocmask.  */

SIGMASKTYPE sigprocmask_set;


/* Specify a different file descriptor for further input operations.  */

void
change_input_fd (fd)
     int fd;
{
  input_fd = fd;
}

/* Discard pending input on descriptor input_fd.  */

void
discard_tty_input ()
{
#ifndef WINDOWSNT
  struct emacs_tty buf;

  if (noninteractive)
    return;

  /* Discarding input is not safe when the input could contain
     replies from the X server.  So don't do it.  */
  if (read_socket_hook)
    return;

#ifdef VMS
  end_kbd_input ();
  SYS$QIOW (0, input_fd, IO$_READVBLK|IO$M_PURGE, input_iosb, 0, 0,
	    &buf.main, 0, 0, terminator_mask, 0, 0);
  queue_kbd_input ();
#else /* not VMS */
#ifdef APOLLO
  {
    int zero = 0;
    ioctl (input_fd, TIOCFLUSH, &zero);
  }
#else /* not Apollo */
#ifdef MSDOS    /* Demacs 1.1.1 91/10/16 HIRANO Satoshi */
  while (dos_keyread () != -1)
    ;
#else /* not MSDOS */
  EMACS_GET_TTY (input_fd, &buf);
  EMACS_SET_TTY (input_fd, &buf, 0);
#endif /* not MSDOS */
#endif /* not Apollo */
#endif /* not VMS */
#endif /* not WINDOWSNT */
}

#ifdef SIGTSTP

/* Arrange for character C to be read as the next input from
   the terminal.  */

void
stuff_char (c)
     char c;
{
  if (read_socket_hook)
    return;

/* Should perhaps error if in batch mode */
#ifdef TIOCSTI
  ioctl (input_fd, TIOCSTI, &c);
#else /* no TIOCSTI */
  error ("Cannot stuff terminal input characters in this version of Unix");
#endif /* no TIOCSTI */
}

#endif /* SIGTSTP */

void
init_baud_rate ()
{
  if (noninteractive)
    emacs_ospeed = 0;
  else
    {
#ifdef INIT_BAUD_RATE
      INIT_BAUD_RATE ();
#else
#ifdef DOS_NT
    emacs_ospeed = 15;
#else  /* not DOS_NT */
#ifdef VMS
      struct sensemode sg;

      SYS$QIOW (0, input_fd, IO$_SENSEMODE, &sg, 0, 0,
		&sg.class, 12, 0, 0, 0, 0 );
      emacs_ospeed = sg.xmit_baud;
#else /* not VMS */
#ifdef HAVE_TERMIOS
      struct termios sg;

      sg.c_cflag = B9600;
      tcgetattr (input_fd, &sg);
      emacs_ospeed = cfgetospeed (&sg);
#if defined (USE_GETOBAUD) && defined (getobaud)
      /* m88k-motorola-sysv3 needs this (ghazi@noc.rutgers.edu) 9/1/94. */
      if (emacs_ospeed == 0)
        emacs_ospeed = getobaud (sg.c_cflag);
#endif
#else /* neither VMS nor TERMIOS */
#ifdef HAVE_TERMIO
      struct termio sg;

      sg.c_cflag = B9600;
#ifdef HAVE_TCATTR
      tcgetattr (input_fd, &sg);
#else
      ioctl (input_fd, TCGETA, &sg);
#endif
      emacs_ospeed = sg.c_cflag & CBAUD;
#else /* neither VMS nor TERMIOS nor TERMIO */
      struct sgttyb sg;
      
      sg.sg_ospeed = B9600;
      if (ioctl (input_fd, TIOCGETP, &sg) < 0)
	abort ();
      emacs_ospeed = sg.sg_ospeed;
#endif /* not HAVE_TERMIO */
#endif /* not HAVE_TERMIOS */
#endif /* not VMS */
#endif /* not DOS_NT */
#endif /* not INIT_BAUD_RATE */
    }
   
  baud_rate = (emacs_ospeed < sizeof baud_convert / sizeof baud_convert[0]
	       ? baud_convert[emacs_ospeed] : 9600);
  if (baud_rate == 0)
    baud_rate = 1200;
}

/*ARGSUSED*/
void
set_exclusive_use (fd)
     int fd;
{
#ifdef FIOCLEX
  ioctl (fd, FIOCLEX, 0);
#endif
  /* Ok to do nothing if this feature does not exist */
}

#ifndef subprocesses

wait_without_blocking ()
{
#ifdef BSD_SYSTEM
  wait3 (0, WNOHANG | WUNTRACED, 0);
#else
  croak ("wait_without_blocking");
#endif
  synch_process_alive = 0;
}

#endif /* not subprocesses */

int wait_debugging;   /* Set nonzero to make following function work under dbx
			 (at least for bsd).  */

SIGTYPE
wait_for_termination_signal ()
{}

/* Wait for subprocess with process id `pid' to terminate and
   make sure it will get eliminated (not remain forever as a zombie) */

void
wait_for_termination (pid)
     int pid;
{
  while (1)
    {
#ifdef subprocesses
#ifdef VMS
      int status;

      status = SYS$FORCEX (&pid, 0, 0);
      break;
#else /* not VMS */
#if defined (BSD_SYSTEM) || (defined (HPUX) && !defined (HPUX_5))
      /* Note that kill returns -1 even if the process is just a zombie now.
	 But inevitably a SIGCHLD interrupt should be generated
	 and child_sig will do wait3 and make the process go away. */
      /* There is some indication that there is a bug involved with
	 termination of subprocesses, perhaps involving a kernel bug too,
	 but no idea what it is.  Just as a hunch we signal SIGCHLD to see
	 if that causes the problem to go away or get worse.  */
      sigsetmask (sigmask (SIGCHLD));
      if (0 > kill (pid, 0))
	{
	  sigsetmask (SIGEMPTYMASK);
	  kill (getpid (), SIGCHLD);
	  break;
	}
      if (wait_debugging)
	sleep (1);
      else
	sigpause (SIGEMPTYMASK);
#else /* not BSD_SYSTEM, and not HPUX version >= 6 */
#if defined (UNIPLUS)
      if (0 > kill (pid, 0))
	break;
      wait (0);
#else /* neither BSD_SYSTEM nor UNIPLUS: random sysV */
#ifdef POSIX_SIGNALS    /* would this work for LINUX as well? */
      sigblock (sigmask (SIGCHLD));
      errno = 0;
      if (kill (pid, 0) == -1 && errno == ESRCH)
	{
	  sigunblock (sigmask (SIGCHLD));
	  break;
	}

      /* FIXME: Since sigpause is not POSIX and its use is deprecated,
	 this should probably be `sigsuspend (&empty_mask)', which is
	 POSIX.  I'm not making that change right away because the
	 release is nearing.  2001-09-20 gerd.  */
      sigpause (SIGEMPTYMASK);
#else /* not POSIX_SIGNALS */
#ifdef HAVE_SYSV_SIGPAUSE
      sighold (SIGCHLD);
      if (0 > kill (pid, 0))
	{
	  sigrelse (SIGCHLD);
	  break;
	}
      sigpause (SIGCHLD);
#else /* not HAVE_SYSV_SIGPAUSE */
#ifdef WINDOWSNT
      wait (0);
      break;
#else /* not WINDOWSNT */
      if (0 > kill (pid, 0))
	break;
      /* Using sleep instead of pause avoids timing error.
	 If the inferior dies just before the sleep,
	 we lose just one second.  */
      sleep (1);
#endif /* not WINDOWSNT */
#endif /* not HAVE_SYSV_SIGPAUSE */
#endif /* not POSIX_SIGNALS */
#endif /* not UNIPLUS */
#endif /* not BSD_SYSTEM, and not HPUX version >= 6 */
#endif /* not VMS */
#else /* not subprocesses */
#if __DJGPP__ > 1
      break;
#else /* not __DJGPP__ > 1 */
#ifndef BSD4_1
      if (kill (pid, 0) < 0)
	break;
      wait (0);
#else /* BSD4_1 */
      int status;
      status = wait (0);
      if (status == pid || status == -1)
	break;
#endif /* BSD4_1 */
#endif /* not __DJGPP__ > 1*/
#endif /* not subprocesses */
    }
}

#ifdef subprocesses

/*
 *	flush any pending output
 *      (may flush input as well; it does not matter the way we use it)
 */
 
void
flush_pending_output (channel)
     int channel;
{
#ifdef HAVE_TERMIOS
  /* If we try this, we get hit with SIGTTIN, because
     the child's tty belongs to the child's pgrp. */
#else
#ifdef TCFLSH
  ioctl (channel, TCFLSH, 1);
#else
#ifdef TIOCFLUSH
  int zero = 0;
  /* 3rd arg should be ignored
     but some 4.2 kernels actually want the address of an int
     and nonzero means something different.  */
  ioctl (channel, TIOCFLUSH, &zero);
#endif
#endif
#endif
}

#ifndef VMS
/*  Set up the terminal at the other end of a pseudo-terminal that
    we will be controlling an inferior through.
    It should not echo or do line-editing, since that is done
    in Emacs.  No padding needed for insertion into an Emacs buffer.  */

void
child_setup_tty (out)
     int out;
{
#ifndef DOS_NT
  struct emacs_tty s;

  EMACS_GET_TTY (out, &s);

#if defined (HAVE_TERMIO) || defined (HAVE_TERMIOS)
  s.main.c_oflag |= OPOST;	/* Enable output postprocessing */
  s.main.c_oflag &= ~ONLCR;	/* Disable map of NL to CR-NL on output */
#ifdef NLDLY
  s.main.c_oflag &= ~(NLDLY|CRDLY|TABDLY|BSDLY|VTDLY|FFDLY);
  				/* No output delays */
#endif
  s.main.c_lflag &= ~ECHO;	/* Disable echo */
  s.main.c_lflag |= ISIG;	/* Enable signals */
#if 0
  s.main.c_iflag &= ~ICRNL;	/* Disable map of CR to NL on input */
#ifdef INLCR  /* Just being cautious, since I can't check how
		 widespread INLCR is--rms.  */
  s.main.c_iflag &= ~INLCR;	/* Disable map of NL to CR on input */
#endif
#endif
#ifdef IUCLC
  s.main.c_iflag &= ~IUCLC;	/* Disable downcasing on input.  */
#endif
#ifdef ISTRIP
  s.main.c_iflag &= ~ISTRIP;	/* don't strip 8th bit on input */
#endif
#ifdef OLCUC
  s.main.c_oflag &= ~OLCUC;	/* Disable upcasing on output.  */
#endif
  s.main.c_oflag &= ~TAB3;	/* Disable tab expansion */
  s.main.c_cflag = (s.main.c_cflag & ~CSIZE) | CS8; /* Don't strip 8th bit */
#if 0
  /* Said to be unnecessary:  */
  s.main.c_cc[VMIN] = 1;	/* minimum number of characters to accept  */
  s.main.c_cc[VTIME] = 0;	/* wait forever for at least 1 character  */
#endif

  s.main.c_lflag |= ICANON;	/* Enable erase/kill and eof processing */
  s.main.c_cc[VEOF] = 04;	/* insure that EOF is Control-D */
  s.main.c_cc[VERASE] = CDISABLE;	/* disable erase processing */
  s.main.c_cc[VKILL] = CDISABLE;	/* disable kill processing */

#ifdef HPUX
  s.main.c_cflag = (s.main.c_cflag & ~CBAUD) | B9600; /* baud rate sanity */
#endif /* HPUX */

#ifdef AIX
/* AIX enhanced edit loses NULs, so disable it */
#ifndef IBMR2AIX
  s.main.c_line = 0;
  s.main.c_iflag &= ~ASCEDIT;
#endif
  /* Also, PTY overloads NUL and BREAK.
     don't ignore break, but don't signal either, so it looks like NUL.  */
  s.main.c_iflag &= ~IGNBRK;
  s.main.c_iflag &= ~BRKINT;
  /* QUIT and INTR work better as signals, so disable character forms */
  s.main.c_cc[VINTR] = 0377;
#ifdef SIGNALS_VIA_CHARACTERS
  /* the QUIT and INTR character are used in process_send_signal
     so set them here to something useful.  */
  if (s.main.c_cc[VQUIT] == 0377)
    s.main.c_cc[VQUIT] = '\\'&037;	/* Control-\ */
  if (s.main.c_cc[VINTR] == 0377)
    s.main.c_cc[VINTR] = 'C'&037;	/* Control-C */
#else /* no TIOCGPGRP or no TIOCGLTC or no TIOCGETC */
  /* QUIT and INTR work better as signals, so disable character forms */
  s.main.c_cc[VQUIT] = 0377;
  s.main.c_cc[VINTR] = 0377;
  s.main.c_lflag &= ~ISIG;
#endif /* no TIOCGPGRP or no TIOCGLTC or no TIOCGETC */
  s.main.c_cc[VEOL] = 0377;
  s.main.c_cflag = (s.main.c_cflag & ~CBAUD) | B9600; /* baud rate sanity */
#endif /* AIX */

#else /* not HAVE_TERMIO */

  s.main.sg_flags &= ~(ECHO | CRMOD | ANYP | ALLDELAY | RAW | LCASE
		       | CBREAK | TANDEM);
  s.main.sg_flags |= LPASS8;
  s.main.sg_erase = 0377;
  s.main.sg_kill = 0377;
  s.lmode = LLITOUT | s.lmode;        /* Don't strip 8th bit */

#endif /* not HAVE_TERMIO */

  EMACS_SET_TTY (out, &s, 0);

#ifdef BSD4_1
  if (interrupt_input)
    reset_sigio ();
#endif /* BSD4_1 */
#ifdef RTU
  {
    int zero = 0;
    ioctl (out, FIOASYNC, &zero);
  }
#endif /* RTU */
#endif /* not DOS_NT */
}
#endif /* not VMS */

#endif /* subprocesses */

/* Record a signal code and the handler for it.  */
struct save_signal
{
  int code;
  SIGTYPE (*handler) P_ ((int));
};

static void save_signal_handlers P_ ((struct save_signal *));
static void restore_signal_handlers P_ ((struct save_signal *));

/* Suspend the Emacs process; give terminal to its superior.  */

void
sys_suspend ()
{
#ifdef VMS
  /* "Foster" parentage allows emacs to return to a subprocess that attached
     to the current emacs as a cheaper than starting a whole new process.  This
     is set up by KEPTEDITOR.COM.  */
  unsigned long parent_id, foster_parent_id;
  char *fpid_string;

  fpid_string = getenv ("EMACS_PARENT_PID");
  if (fpid_string != NULL)
    {
      sscanf (fpid_string, "%x", &foster_parent_id);
      if (foster_parent_id != 0)
	parent_id = foster_parent_id;
      else
	parent_id = getppid ();
    }
  else
    parent_id = getppid ();

  xfree (fpid_string);		/* On VMS, this was malloc'd */

  if (parent_id && parent_id != 0xffffffff)
    {
      SIGTYPE (*oldsig)() = (int) signal (SIGINT, SIG_IGN);
      int status = LIB$ATTACH (&parent_id) & 1;
      signal (SIGINT, oldsig);
      return status;
    }
  else
    {
      struct {
	int	l;
	char	*a;
      } d_prompt;
      d_prompt.l = sizeof ("Emacs: ");		/* Our special prompt */
      d_prompt.a = "Emacs: ";			/* Just a reminder */
      LIB$SPAWN (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, &d_prompt, 0);
      return 1;
    }
  return -1;
#else
#if defined (SIGTSTP) && !defined (MSDOS)

  {
    int pgrp = EMACS_GETPGRP (0);
    EMACS_KILLPG (pgrp, SIGTSTP);
  }

#else /* No SIGTSTP */
#ifdef USG_JOBCTRL /* If you don't know what this is don't mess with it */
  ptrace (0, 0, 0, 0);		/* set for ptrace - caught by csh */
  kill (getpid (), SIGQUIT);

#else /* No SIGTSTP or USG_JOBCTRL */

/* On a system where suspending is not implemented,
   instead fork a subshell and let it talk directly to the terminal
   while we wait.  */
  sys_subshell ();

#endif /* no USG_JOBCTRL */
#endif /* no SIGTSTP */
#endif /* not VMS */
}

/* Fork a subshell.  */

#ifndef macintosh
void
sys_subshell ()
{
#ifndef VMS
#ifdef DOS_NT	/* Demacs 1.1.2 91/10/20 Manabu Higashida */
  int st;
  char oldwd[MAXPATHLEN+1]; /* Fixed length is safe on MSDOS.  */
#endif
  int pid;
  struct save_signal saved_handlers[5];
  Lisp_Object dir;
  unsigned char *str = 0;
  int len;

  saved_handlers[0].code = SIGINT;
  saved_handlers[1].code = SIGQUIT;
  saved_handlers[2].code = SIGTERM;
#ifdef SIGIO
  saved_handlers[3].code = SIGIO;
  saved_handlers[4].code = 0;
#else
  saved_handlers[3].code = 0;
#endif

  /* Mentioning current_buffer->buffer would mean including buffer.h,
     which somehow wedges the hp compiler.  So instead...  */

  dir = intern ("default-directory");
  if (NILP (Fboundp (dir)))
    goto xyzzy;
  dir = Fsymbol_value (dir);
  if (!STRINGP (dir))
    goto xyzzy;

  dir = expand_and_dir_to_file (Funhandled_file_name_directory (dir), Qnil);
  str = (unsigned char *) alloca (XSTRING (dir)->size + 2);
  len = XSTRING (dir)->size;
  bcopy (XSTRING (dir)->data, str, len);
  if (str[len - 1] != '/') str[len++] = '/';
  str[len] = 0;
 xyzzy:

#ifdef DOS_NT
  pid = 0;
#if __DJGPP__ > 1
  save_signal_handlers (saved_handlers);
  synch_process_alive = 1;
#endif /* __DJGPP__ > 1 */
#else  
  pid = vfork ();
  if (pid == -1)
    error ("Can't spawn subshell");
#endif

  if (pid == 0)
    {
      char *sh = 0;

#ifdef DOS_NT    /* MW, Aug 1993 */
      getwd (oldwd);
      if (sh == 0)
	sh = (char *) egetenv ("SUSPEND");	/* KFS, 1994-12-14 */
#endif
      if (sh == 0)
	sh = (char *) egetenv ("SHELL");
      if (sh == 0)
	sh = "sh";

      /* Use our buffer's default directory for the subshell.  */
      if (str)
	chdir ((char *) str);

#ifdef subprocesses
      close_process_descs ();	/* Close Emacs's pipes/ptys */
#endif

#ifdef SET_EMACS_PRIORITY
      {
	extern int emacs_priority;

	if (emacs_priority < 0)
	  nice (-emacs_priority);
      }
#endif

#ifdef MSDOS    /* Demacs 1.1.2 91/10/20 Manabu Higashida */
      st = system (sh);
      chdir (oldwd);
#if 0	/* This is also reported if last command executed in subshell failed, KFS */
      if (st)
	report_file_error ("Can't execute subshell", Fcons (build_string (sh), Qnil));
#endif
#else /* not MSDOS */
#ifdef  WINDOWSNT
      /* Waits for process completion */
      pid = _spawnlp (_P_WAIT, sh, sh, NULL);
      chdir (oldwd);
      if (pid == -1)
	write (1, "Can't execute subshell", 22);
#else   /* not WINDOWSNT */
      execlp (sh, sh, 0);
      write (1, "Can't execute subshell", 22);
      _exit (1);
#endif  /* not WINDOWSNT */
#endif /* not MSDOS */
    }

  /* Do this now if we did not do it before.  */
#if !defined (MSDOS) || __DJGPP__ == 1
  save_signal_handlers (saved_handlers);
  synch_process_alive = 1;
#endif

#ifndef DOS_NT
  wait_for_termination (pid);
#endif
  restore_signal_handlers (saved_handlers);
  synch_process_alive = 0;
#endif /* !VMS */
}
#endif /* !macintosh */

static void
save_signal_handlers (saved_handlers)
     struct save_signal *saved_handlers;
{
  while (saved_handlers->code)
    {
      saved_handlers->handler
	= (SIGTYPE (*) P_ ((int))) signal (saved_handlers->code, SIG_IGN);
      saved_handlers++;
    }
}

static void
restore_signal_handlers (saved_handlers)
     struct save_signal *saved_handlers;
{
  while (saved_handlers->code)
    {
      signal (saved_handlers->code, saved_handlers->handler);
      saved_handlers++;
    }
}

#ifdef F_SETFL

int old_fcntl_flags;

void
init_sigio (fd)
     int fd;
{
#ifdef FASYNC
  old_fcntl_flags = fcntl (fd, F_GETFL, 0) & ~FASYNC;
  fcntl (fd, F_SETFL, old_fcntl_flags | FASYNC);
#endif
  interrupts_deferred = 0;
}

void
reset_sigio ()
{
  unrequest_sigio ();
}

#ifdef FASYNC		/* F_SETFL does not imply existence of FASYNC */

void
request_sigio ()
{
  if (read_socket_hook)
    return;

#ifdef SIGWINCH
  sigunblock (sigmask (SIGWINCH));
#endif
  fcntl (input_fd, F_SETFL, old_fcntl_flags | FASYNC);

  interrupts_deferred = 0;
}

void
unrequest_sigio ()
{
  if (read_socket_hook)
    return;

#ifdef SIGWINCH
  sigblock (sigmask (SIGWINCH));
#endif
  fcntl (input_fd, F_SETFL, old_fcntl_flags);
  interrupts_deferred = 1;
}

#else /* no FASYNC */
#ifdef STRIDE		/* Stride doesn't have FASYNC - use FIOASYNC */

void
request_sigio ()
{
  int on = 1;

  if (read_socket_hook)
    return;

  ioctl (input_fd, FIOASYNC, &on);
  interrupts_deferred = 0;
}

void
unrequest_sigio ()
{
  int off = 0;