sysdep.c

/* Interfaces to system-dependent kernel and library entries.
   Copyright (C) 1985, 86, 87, 88, 93, 94, 95 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 <signal.h>
#include <setjmp.h>

#include <config.h>
#include "lisp.h"
#include "blockinput.h"
#undef NULL

#define min(x,y) ((x) > (y) ? (y) : (x))

/* In this file, open, read and write refer to the system calls,
   not our sugared interfaces  sys_open, sys_read and sys_write.
   Contrariwise, for systems where we use the system calls directly,
   define sys_read, etc. here as aliases for them.  */
#ifndef read
#define sys_read read
#define sys_write write
#endif /* `read' is not a macro */

#undef read
#undef write

#ifdef WINDOWSNT
#define read _read
#define write _write
#include <windows.h>
extern int errno;
#endif /* not WINDOWSNT */

#ifndef close
#define sys_close close
#else 
#undef close
#endif

#ifndef open
#define sys_open open
#else /* `open' is a macro */
#undef open
#endif /* `open' is a macro */

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

#ifndef HAVE_H_ERRNO
extern int h_errno;
#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

/* 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

extern int errno;

#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>
#include <string.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 "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

#ifndef VFORK_RETURN_TYPE
#define VFORK_RETURN_TYPE int
#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

#if defined (HAVE_LIBNCURSES) && ! defined (NCURSES_OSPEED_T)
extern short ospeed;
#else
#if defined (HAVE_TERMIOS_H) && defined (LINUX)
#include <termios.h>
/* HJL's version of libc is said to need this on the Alpha.
   On the other hand, DEC OSF1 on the Alpha needs ospeed to be a short.  */
extern speed_t ospeed;
#else
extern short ospeed;
#endif
#endif

/* 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 *));



/* 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)
    ospeed = 0;
  else
    {
#ifdef INIT_BAUD_RATE
      INIT_BAUD_RATE ();
#else
#ifdef DOS_NT
    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 );
      ospeed = sg.xmit_baud;
#else /* not VMS */
#ifdef HAVE_TERMIOS
      struct termios sg;

      sg.c_cflag = B9600;
      tcgetattr (input_fd, &sg);
      ospeed = cfgetospeed (&sg);
#if defined (USE_GETOBAUD) && defined (getobaud)
      /* m88k-motorola-sysv3 needs this (ghazi@noc.rutgers.edu) 9/1/94. */
      if (ospeed == 0)
        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
      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 ();
      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 = (ospeed < sizeof baud_convert / sizeof baud_convert[0]
	       ? baud_convert[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));
      if (0 > kill (pid, 0))
	{
	  sigunblock (sigmask (SIGCHLD));
	  break;
	}
      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 */
#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.  */

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 */
}

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;

  if (read_socket_hook)
    return;

  ioctl (input_fd, FIOASYNC, &off);
  interrupts_deferred = 1;
}

#else /* not FASYNC, not STRIDE */
 
#ifdef _CX_UX

#include <termios.h>

void
request_sigio ()
{
  int on = 1;
  sigset_t st;

  if (read_socket_hook)
    return;

  sigemptyset(&st);
  sigaddset(&st, SIGIO);
  ioctl (input_fd, FIOASYNC, &on);
  interrupts_deferred = 0;
  sigprocmask(SIG_UNBLOCK, &st, (sigset_t *)0);
}

void
unrequest_sigio ()
{
  int off = 0;

  if (read_socket_hook)
    return;

  ioctl (input_fd, FIOASYNC, &off);
  interrupts_deferred = 1;
}

#else /* ! _CX_UX */

void
request_sigio ()
{
  if (read_socket_hook)
    return;

  croak ("request_sigio");
}
 
void
unrequest_sigio ()
{
  if (read_socket_hook)
    return;

  croak ("unrequest_sigio");
}
 
#endif /* _CX_UX */
#endif /* STRIDE */
#endif /* FASYNC */
#endif /* F_SETFL */

/* Saving and restoring the process group of Emacs's terminal.  */

#ifdef BSD_PGRPS

/* The process group of which Emacs was a member when it initially
   started.

   If Emacs was in its own process group (i.e. inherited_pgroup ==
   getpid ()), then we know we're running under a shell with job
   control (Emacs would never be run as part of a pipeline).
   Everything is fine.

   If Emacs was not in its own process group, then we know we're
   running under a shell (or a caller) that doesn't know how to
   separate itself from Emacs (like sh).  Emacs must be in its own
   process group in order to receive SIGIO correctly.  In this
   situation, we put ourselves in our own pgroup, forcibly set the
   tty's pgroup to our pgroup, and make sure to restore and reinstate
   the tty's pgroup just like any other terminal setting.  If
   inherited_group was not the tty's pgroup, then we'll get a
   SIGTTmumble when we try to change the tty's pgroup, and a CONT if
   it goes foreground in the future, which is what should happen.  */
int inherited_pgroup;

/* Split off the foreground process group to Emacs alone.
   When we are in the foreground, but not started in our own process
   group, redirect the TTY to point to our own process group.  We need
   to be in our own process group to receive SIGIO properly.  */
void
narrow_foreground_group ()
{
  int me = getpid ();

  setpgrp (0, inherited_pgroup);
  if (inherited_pgroup != me)
    EMACS_SET_TTY_PGRP (input_fd, &me);