newlib-cygwin/winsup/cygwin/spawn.cc

/* spawn.cc

   Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.

This file is part of Cygwin.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <process.h>
#include <sys/wait.h>
#include <errno.h>
#include <limits.h>
#include <wingdi.h>
#include <winuser.h>
#include <ctype.h>
#include "cygerrno.h"
#include <sys/cygwin.h>
#include "security.h"
#include "fhandler.h"
#include "path.h"
#include "dtable.h"
#include "sigproc.h"
#include "cygheap.h"
#include "child_info.h"
#include "shared_info.h"
#include "pinfo.h"
#define NEED_VFORK
#include "perthread.h"
#include "registry.h"
#include "environ.h"
#include "cygthread.h"

#define LINE_BUF_CHUNK (MAX_PATH * 2)

static suffix_info std_suffixes[] =
{
  suffix_info (".exe", 1), suffix_info ("", 1),
  suffix_info (".com"), suffix_info (".cmd"),
  suffix_info (".bat"), suffix_info (".dll"),
  suffix_info (NULL)
};

HANDLE hExeced;
DWORD dwExeced;

/* Add .exe to PROG if not already present and see if that exists.
   If not, return PROG (converted from posix to win32 rules if necessary).
   The result is always BUF.

   Returns (possibly NULL) suffix */

static const char *
perhaps_suffix (const char *prog, path_conv& buf)
{
  char *ext;

  debug_printf ("prog '%s'", prog);
  buf.check (prog, PC_SYM_FOLLOW | PC_FULL, std_suffixes);

  if (!buf.exists () || buf.isdir ())
    ext = NULL;
  else if (buf.known_suffix)
    ext = (char *) buf + (buf.known_suffix - buf.get_win32 ());
  else
    ext = strchr (buf, '\0');

  debug_printf ("buf %s, suffix found '%s'", (char *) buf, ext);
  return ext;
}

/* Find an executable name, possibly by appending known executable
   suffixes to it.  The win32-translated name is placed in 'buf'.
   Any found suffix is returned in known_suffix.

   If the file is not found and !null_if_not_found then the win32 version
   of name is placed in buf and returned.  Otherwise the contents of buf
   is undefined and NULL is returned.  */

const char * __stdcall
find_exec (const char *name, path_conv& buf, const char *mywinenv,
	   unsigned opt, const char **known_suffix)
{
  const char *suffix = "";
  debug_printf ("find_exec (%s)", name);
  const char *retval = buf;
  char tmp[MAX_PATH];
  const char *posix = (opt & FE_NATIVE) ? NULL : name;
  bool has_slash = strchr (name, '/');

  /* Check to see if file can be opened as is first.
     Win32 systems always check . first, but PATH may not be set up to
     do this. */
  if ((has_slash || opt & FE_CWD)
      && (suffix = perhaps_suffix (name, buf)) != NULL)
    {
      if (posix && !has_slash)
	{
	  tmp[0] = '.';
	  tmp[1] = '/';
	  strcpy (tmp + 2, name);
	  posix = tmp;
	}
      goto out;
    }

  win_env *winpath;
  const char *path;
  const char *posix_path;

  /* Return the error condition if this is an absolute path or if there
     is no PATH to search. */
  if (strchr (name, '/') || strchr (name, '\\') ||
      isdrive (name) ||
      !(winpath = getwinenv (mywinenv)) ||
      !(path = winpath->get_native ()) ||
      *path == '\0')
    goto errout;

  debug_printf ("%s%s", mywinenv, path);

  posix = (opt & FE_NATIVE) ? NULL : tmp;
  posix_path = winpath->get_posix () - 1;
  /* Iterate over the specified path, looking for the file with and
     without executable extensions. */
  do
    {
      posix_path++;
      char *eotmp = strccpy (tmp, &path, ';');
      /* An empty path or '.' means the current directory, but we've
	 already tried that.  */
      if (opt & FE_CWD && (tmp[0] == '\0' || (tmp[0] == '.' && tmp[1] == '\0')))
	continue;

      *eotmp++ = '\\';
      strcpy (eotmp, name);

      debug_printf ("trying %s", tmp);

      if ((suffix = perhaps_suffix (tmp, buf)) != NULL)
	{
	  if (posix == tmp)
	    {
	      eotmp = strccpy (tmp, &posix_path, ':');
	      if (eotmp == tmp)
		*eotmp++ = '.';
	      *eotmp++ = '/';
	      strcpy (eotmp, name);
	    }
	  goto out;
	}
    }
  while (*path && *++path && (posix_path = strchr (posix_path, ':')));

 errout:
  posix = NULL;
  /* Couldn't find anything in the given path.
     Take the appropriate action based on null_if_not_found. */
  if (opt & FE_NNF)
    retval = NULL;
  else if (opt & FE_NATIVE)
    buf.check (name);
  else
    retval = name;

 out:
  if (posix)
    buf.set_path (posix);
  debug_printf ("%s = find_exec (%s)", (char *) buf, name);
  if (known_suffix)
    *known_suffix = suffix ?: strchr (buf, '\0');
  return retval;
}

/* Utility for spawn_guts.  */

static HANDLE
handle (int n, int direction)
{
  fhandler_base *fh = cygheap->fdtab[n];

  if (!fh)
    return INVALID_HANDLE_VALUE;
  if (fh->get_close_on_exec ())
    return INVALID_HANDLE_VALUE;
  if (direction == 0)
    return fh->get_handle ();
  return fh->get_output_handle ();
}

int
iscmd (const char *argv0, const char *what)
{
  int n;
  n = strlen (argv0) - strlen (what);
  if (n >= 2 && argv0[1] != ':')
    return 0;
  return n >= 0 && strcasematch (argv0 + n, what) &&
	 (n == 0 || isdirsep (argv0[n - 1]));
}

class linebuf
{
 public:
  size_t ix;
  char *buf;
  size_t alloced;
  linebuf () : ix (0), buf (NULL), alloced (0) {}
  ~linebuf () {if (buf) free (buf);}
  void add (const char *what, int len);
  void add (const char *what) {add (what, strlen (what));}
  void prepend (const char *what, int len);
};

void
linebuf::add (const char *what, int len)
{
  size_t newix;
  if ((newix = ix + len) >= alloced || !buf)
    {
      alloced += LINE_BUF_CHUNK + newix;
      buf = (char *) realloc (buf, alloced + 1);
    }
  memcpy (buf + ix, what, len);
  ix = newix;
  buf[ix] = '\0';
}

void
linebuf::prepend (const char *what, int len)
{
  int buflen;
  size_t newix;
  if ((newix = ix + len) >= alloced)
    {
      alloced += LINE_BUF_CHUNK + newix;
      buf = (char *) realloc (buf, alloced + 1);
      buf[ix] = '\0';
    }
  if ((buflen = strlen (buf)))
      memmove (buf + len, buf, buflen + 1);
  else
      buf[newix] = '\0';
  memcpy (buf, what, len);
  ix = newix;
}

class av
{
  char **argv;
  int calloced;
 public:
  int error;
  int argc;
  av (int ac, const char * const *av) : calloced (0), error (false), argc (ac)
  {
    argv = (char **) cmalloc (HEAP_1_ARGV, (argc + 5) * sizeof (char *));
    memcpy (argv, av, (argc + 1) * sizeof (char *));
  }
  ~av ()
  {
    if (argv)
      {
	for (int i = 0; i < calloced; i++)
	  if (argv[i])
	    cfree (argv[i]);
	cfree (argv);
      }
  }
  int unshift (const char *what, int conv = 0);
  operator char **() {return argv;}
  void all_calloced () {calloced = argc;}
  void replace0_maybe (const char *arg0)
  {
    /* Note: Assumes that argv array has not yet been "unshifted" */
    if (!calloced
	&& (argv[0] = cstrdup1 (arg0)))
      calloced = true;
    else
      error = errno;
  }
  void dup_maybe (int i)
  {
    if (i >= calloced
	&& !(argv[i] = cstrdup1 (argv[i])))
      error = errno;
  }
  void dup_all ()
  {
    for (int i = calloced; i < argc; i++)
      if (!(argv[i] = cstrdup1 (argv[i])))
	error = errno;
  }
};

int
av::unshift (const char *what, int conv)
{
  char **av;
  av = (char **) crealloc (argv, (argc + 2) * sizeof (char *));
  if (!av)
    return 0;

  argv = av;
  memmove (argv + 1, argv, (argc + 1) * sizeof (char *));
  char buf[MAX_PATH + 1];
  if (conv)
    {
      cygwin_conv_to_posix_path (what, buf);
      char *p = strchr (buf, '\0') - 4;
      if (p > buf && strcasematch (p, ".exe"))
	*p = '\0';
      what = buf;
    }
  if (!(*argv = cstrdup1 (what)))
    error = errno;
  argc++;
  calloced++;
  return 1;
}

static int __stdcall
spawn_guts (const char * prog_arg, const char *const *argv,
	    const char *const envp[], int mode)
{
  BOOL rc;
  pid_t cygpid;
  sigframe thisframe (mainthread);

  MALLOC_CHECK;

  if (prog_arg == NULL)
    {
      syscall_printf ("prog_arg is NULL");
      set_errno (EINVAL);
      return -1;
    }

  syscall_printf ("spawn_guts (%d, %.9500s)", mode, prog_arg);

  if (argv == NULL)
    {
      syscall_printf ("argv is NULL");
      set_errno (EINVAL);
      return -1;
    }

  path_conv real_path;

  linebuf one_line;

  STARTUPINFO si = {0, NULL, NULL, NULL, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, NULL, NULL, NULL, NULL};

  child_info_spawn ciresrv;
  si.lpReserved2 = (LPBYTE) &ciresrv;
  si.cbReserved2 = sizeof (ciresrv);

  DWORD chtype;
  if (mode != _P_OVERLAY)
    chtype = PROC_SPAWN;
  else
    chtype = PROC_EXEC;

  HANDLE subproc_ready;
  if (chtype != PROC_EXEC)
    subproc_ready = NULL;
  else
    {
      subproc_ready = CreateEvent (&sec_all, TRUE, FALSE, NULL);
      ProtectHandleINH (subproc_ready);
    }

  init_child_info (chtype, &ciresrv, (mode == _P_OVERLAY) ? myself->pid : 1,
		   subproc_ready);
  if (!DuplicateHandle (hMainProc, hMainProc, hMainProc, &ciresrv.parent, 0, 1,
			DUPLICATE_SAME_ACCESS))
     {
       system_printf ("couldn't create handle to myself for child, %E");
       return -1;
     }

  ciresrv.moreinfo = (cygheap_exec_info *) ccalloc (HEAP_1_EXEC, 1, sizeof (cygheap_exec_info));
  ciresrv.moreinfo->old_title = NULL;

  /* CreateProcess takes one long string that is the command line (sigh).
     We need to quote any argument that has whitespace or embedded "'s.  */

  int ac;
  for (ac = 0; argv[ac]; ac++)
    /* nothing */;

  av newargv (ac, argv);

  int null_app_name = 0;
  if (ac == 3 && argv[1][0] == '/' && argv[1][1] == 'c' &&
      (iscmd (argv[0], "command.com") || iscmd (argv[0], "cmd.exe")))
    {
      real_path.check (prog_arg);
      one_line.add ("\"");
      if (!real_path.error)
	one_line.add (real_path);
      else
	one_line.add (argv[0]);
      one_line.add ("\"");
      one_line.add (" ");
      one_line.add (argv[1]);
      one_line.add (" ");
      one_line.add (argv[2]);
      strcpy (real_path, argv[0]);
      null_app_name = 1;
      goto skip_arg_parsing;
    }

  const char *ext;
  if ((ext = perhaps_suffix (prog_arg, real_path)) == NULL)
    {
      set_errno (ENOENT);
      return -1;
    }

  MALLOC_CHECK;

  /* If the file name ends in either .exe, .com, .bat, or .cmd we assume
     that it is NOT a script file */
  while (*ext == '\0')
    {
      HANDLE hnd = CreateFile (real_path, GENERIC_READ,
			       FILE_SHARE_READ | FILE_SHARE_WRITE,
			       &sec_none_nih, OPEN_EXISTING,
			       FILE_ATTRIBUTE_NORMAL, 0);
      if (hnd == INVALID_HANDLE_VALUE)
	{
	  __seterrno ();
	  return -1;
	}

      DWORD done;

      char buf[2 * MAX_PATH + 1];
      buf[0] = buf[1] = buf[2] = buf[sizeof (buf) - 1] = '\0';
      if (!ReadFile (hnd, buf, sizeof (buf) - 1, &done, 0))
	{
	  CloseHandle (hnd);
	  __seterrno ();
	  return -1;
	}

      CloseHandle (hnd);

      if (buf[0] == 'M' && buf[1] == 'Z')
	break;

      debug_printf ("%s is a script", (char *) real_path);

      char *pgm, *arg1;

      if (buf[0] != '#' || buf[1] != '!')
	{
	  pgm = (char *) "/bin/sh";
	  arg1 = NULL;
	}
      else
	{
	  char *ptr;
	  pgm = buf + 2;
	  pgm += strspn (pgm, " \t");
	  for (ptr = pgm, arg1 = NULL;
	       *ptr && *ptr != '\r' && *ptr != '\n';
	       ptr++)
	    if (!arg1 && (*ptr == ' ' || *ptr == '\t'))
	      {
		/* Null terminate the initial command and step over
		   any additional white space.  If we've hit the
		   end of the line, exit the loop.  Otherwise, we've
		   found the first argument. Position the current
		   pointer on the last known white space. */
		*ptr = '\0';
		char *newptr = ptr + 1;
		newptr += strspn (newptr, " \t");
		if (!*newptr || *newptr == '\r' || *newptr == '\n')
		  break;
		arg1 = newptr;
		ptr = newptr - 1;
	      }

	  *ptr = '\0';
	}

      /* Replace argv[0] with the full path to the script if this is the
	 first time through the loop. */
      newargv.replace0_maybe (prog_arg);

      /* pointers:
       * pgm	interpreter name
       * arg1	optional string
       */
      if (arg1)
	newargv.unshift (arg1);

      /* FIXME: This should not be using FE_NATIVE.  It should be putting
	 the posix path on the argv list. */
      find_exec (pgm, real_path, "PATH=", FE_NATIVE, &ext);
      newargv.unshift (real_path, 1);
    }

  if (real_path.iscygexec ())
    newargv.dup_all ();
  else
    {
      for (int i = 0; i < newargv.argc; i++)
	{
	  char *p = NULL;
	  const char *a;

	  newargv.dup_maybe (i);
	  a = i ? newargv[i] : (char *) real_path;
	  int len = strlen (a);
	  if (len != 0 && !strpbrk (a, " \t\n\r\""))
	    one_line.add (a, len);
	  else
	    {
	      one_line.add ("\"", 1);
	      /* Handle embedded special characters " and \.
		 A " is always preceded by a \.
		 A \ is not special unless it precedes a ".  If it does,
		 then all preceding \'s must be doubled to avoid having
		 the Windows command line parser interpret the \ as quoting
		 the ".  This rule applies to a string of \'s before the end
		 of the string, since cygwin/windows uses a " to delimit the
		 argument. */
	      for (; (p = strpbrk (a, "\"\\")); a = ++p)
		{
		  one_line.add (a, p - a);
		  /* Find length of string of backslashes */
		  int n = strspn (p, "\\");
		  if (!n)
		    one_line.add ("\\\"", 2);	/* No backslashes, so it must be a ".
						   The " has to be protected with a backslash. */
		  else
		    {
		      one_line.add (p, n);	/* Add the run of backslashes */
		      /* Need to double up all of the preceding
			 backslashes if they precede a quote or EOS. */
		      if (!p[n] || p[n] == '"')
			one_line.add (p, n);
		      p += n - 1;		/* Point to last backslash */
		    }
		}
	      if (*a)
		one_line.add (a);
	      one_line.add ("\"", 1);
	    }
	  MALLOC_CHECK;
	  one_line.add (" ", 1);
	  MALLOC_CHECK;
	}

      MALLOC_CHECK;
      if (one_line.ix)
	one_line.buf[one_line.ix - 1] = '\0';
      else
	one_line.add ("", 1);
      MALLOC_CHECK;
    }

  char *envblock;
  newargv.all_calloced ();
  if (newargv.error)
    {
      set_errno (newargv.error);
      return -1;
    }

  ciresrv.moreinfo->argc = newargv.argc;
  ciresrv.moreinfo->argv = newargv;
  ciresrv.hexec_proc = hexec_proc;

  if (mode != _P_OVERLAY ||
      !DuplicateHandle (hMainProc, myself.shared_handle (), hMainProc,
			&ciresrv.moreinfo->myself_pinfo, 0,
			TRUE, DUPLICATE_SAME_ACCESS))
    ciresrv.moreinfo->myself_pinfo = NULL;

 skip_arg_parsing:
  PROCESS_INFORMATION pi = {NULL, 0, 0, 0};
  si.lpReserved = NULL;
  si.lpDesktop = NULL;
  si.dwFlags = STARTF_USESTDHANDLES;
  si.hStdInput = handle (0, 0); /* Get input handle */
  si.hStdOutput = handle (1, 1); /* Get output handle */
  si.hStdError = handle (2, 1); /* Get output handle */
  si.cb = sizeof (si);

  int flags = CREATE_DEFAULT_ERROR_MODE | GetPriorityClass (hMainProc);

  if (mode == _P_DETACH || !set_console_state_for_spawn ())
    flags |= DETACHED_PROCESS;
  if (mode != _P_OVERLAY)
    flags |= CREATE_SUSPENDED;

  /* Some file types (currently only sockets) need extra effort in the
     parent after CreateProcess and before copying the datastructures
     to the child. So we have to start the child in suspend state,
     unfortunately, to avoid a race condition. */
  if (cygheap->fdtab.need_fixup_before ())
    flags |= CREATE_SUSPENDED;


  const char *runpath = null_app_name ? NULL : (const char *) real_path;

  syscall_printf ("null_app_name %d (%s, %.9500s)", null_app_name, runpath, one_line.buf);

  void *newheap;
  /* Preallocated buffer for `sec_user' call */
  char sa_buf[1024];

  cygbench ("spawn-guts");

  cygheap->fdtab.set_file_pointers_for_exec ();
  if (cygheap->user.issetuid ())
    RevertToSelf ();
  /* When ruid != euid we create the new process under the current original
     account and impersonate in child, this way maintaining the different
     effective vs. real ids.
     FIXME: If ruid != euid and ruid != orig_uid we currently give
     up on ruid. The new process will have ruid == euid. */
  if (!cygheap->user.issetuid ()
      || (cygheap->user.orig_uid == cygheap->user.real_uid
	  && cygheap->user.orig_gid == cygheap->user.real_gid
	  && !cygheap->user.groups.issetgroups ()))
    {
      PSECURITY_ATTRIBUTES sec_attribs = sec_user_nih (sa_buf);
      ciresrv.moreinfo->envp = build_env (envp, envblock, ciresrv.moreinfo->envc,
					  real_path.iscygexec ());
      newheap = cygheap_setup_for_child (&ciresrv, cygheap->fdtab.need_fixup_before ());
      rc = CreateProcess (runpath,	/* image name - with full path */
			  one_line.buf,	/* what was passed to exec */
			  sec_attribs,	/* process security attrs */
			  sec_attribs,	/* thread security attrs */
			  TRUE,		/* inherit handles from parent */
			  flags,
			  envblock,	/* environment */
			  0,		/* use current drive/directory */
			  &si,
			  &pi);
    }
  else
    {
      PSID sid = cygheap->user.sid ();

      /* Set security attributes with sid */
      PSECURITY_ATTRIBUTES sec_attribs = sec_user_nih (sa_buf, sid);

      /* Load users registry hive. */
      load_registry_hive (sid);

      /* allow the child to interact with our window station/desktop */
      HANDLE hwst, hdsk;
      SECURITY_INFORMATION dsi = DACL_SECURITY_INFORMATION;
      DWORD n;
      char wstname[1024];
      char dskname[1024];

      hwst = GetProcessWindowStation ();
      SetUserObjectSecurity (hwst, &dsi, get_null_sd ());
      GetUserObjectInformation (hwst, UOI_NAME, wstname, 1024, &n);
      hdsk = GetThreadDesktop (GetCurrentThreadId ());
      SetUserObjectSecurity (hdsk, &dsi, get_null_sd ());
      GetUserObjectInformation (hdsk, UOI_NAME, dskname, 1024, &n);
      strcat (wstname, "\\");
      strcat (wstname, dskname);
      si.lpDesktop = wstname;

      ciresrv.moreinfo->envp = build_env (envp, envblock, ciresrv.moreinfo->envc,
					  real_path.iscygexec ());
      newheap = cygheap_setup_for_child (&ciresrv, cygheap->fdtab.need_fixup_before ());
      rc = CreateProcessAsUser (cygheap->user.token,
		       runpath,		/* image name - with full path */
		       one_line.buf,	/* what was passed to exec */
		       sec_attribs,     /* process security attrs */
		       sec_attribs,     /* thread security attrs */
		       TRUE,		/* inherit handles from parent */
		       flags,
		       envblock,	/* environment */
		       0,		/* use current drive/directory */
		       &si,
		       &pi);
    }
  /* Restore impersonation. In case of _P_OVERLAY this isn't
     allowed since it would overwrite child data. */
  if (mode != _P_OVERLAY && cygheap->user.issetuid ())
    ImpersonateLoggedOnUser (cygheap->user.token);

  MALLOC_CHECK;
  if (envblock)
    free (envblock);
  MALLOC_CHECK;

  /* Set errno now so that debugging messages from it appear before our
     final debugging message [this is a general rule for debugging
     messages].  */
  if (!rc)
    {
      __seterrno ();
      syscall_printf ("CreateProcess failed, %E");
      if (subproc_ready)
	ForceCloseHandle (subproc_ready);
      cygheap_setup_for_child_cleanup (newheap, &ciresrv, 0);
      return -1;
    }

  /* Fixup the parent datastructure if needed and resume the child's
     main thread. */
  if (!cygheap->fdtab.need_fixup_before ())
    cygheap_setup_for_child_cleanup (newheap, &ciresrv, 0);
  else
    {
      cygheap->fdtab.fixup_before_exec (pi.dwProcessId);
      cygheap_setup_for_child_cleanup (newheap, &ciresrv, 1);
      if (mode == _P_OVERLAY)
	{
	  ResumeThread (pi.hThread);
	  cygthread::terminate ();
	}
    }

  if (mode != _P_OVERLAY)
    cygpid = cygwin_pid (pi.dwProcessId);
  else
    cygpid = myself->pid;

  /* We print the original program name here so the user can see that too.  */
  syscall_printf ("%d = spawn_guts (%s, %.9500s)",
		  rc ? cygpid : (unsigned int) -1, prog_arg, one_line.buf);

  /* Name the handle similarly to proc_subproc. */
  ProtectHandle1 (pi.hProcess, childhProc);

  if (mode == _P_OVERLAY)
    {
      /* These are both duplicated in the child code.  We do this here,
	 primarily for strace. */
      strace.execing = 1;
      hExeced = pi.hProcess;
      dwExeced = pi.dwProcessId;
      strcpy (myself->progname, real_path);
      close_all_files ();
    }
  else
    {
      myself->set_has_pgid_children ();
      ProtectHandle (pi.hThread);
      pinfo child (cygpid, 1);
      if (!child)
	{
	  set_errno (EAGAIN);
	  syscall_printf ("-1 = spawnve (), process table full");
	  return -1;
	}
      child->dwProcessId = pi.dwProcessId;
      child->hProcess = pi.hProcess;
      child.remember ();
      strcpy (child->progname, real_path);
      /* FIXME: This introduces an unreferenced, open handle into the child.
	 The purpose is to keep the pid shared memory open so that all of
	 the fields filled out by child.remember do not disappear and so there
	 is not a brief period during which the pid is not available.
	 However, we should try to find another way to do this eventually. */
      (void) DuplicateHandle (hMainProc, child.shared_handle (), pi.hProcess,
			      NULL, 0, 0, DUPLICATE_SAME_ACCESS);
      /* Start the child running */
      ResumeThread (pi.hThread);
    }

  ForceCloseHandle (pi.hThread);

  sigproc_printf ("spawned windows pid %d", pi.dwProcessId);

  DWORD res;
  BOOL exited;

  res = 0;
  exited = FALSE;
  MALLOC_CHECK;
  if (mode == _P_OVERLAY)
    {
      int nwait = 3;
      HANDLE waitbuf[3] = {pi.hProcess, signal_arrived, subproc_ready};
      for (int i = 0; i < 100; i++)
	{
	  switch (WaitForMultipleObjects (nwait, waitbuf, FALSE, INFINITE))
	    {
	    case WAIT_OBJECT_0:
	      sigproc_printf ("subprocess exited");
	      DWORD exitcode;
	      if (!GetExitCodeProcess (pi.hProcess, &exitcode))
		exitcode = 1;
	      res |= exitcode;
	      exited = TRUE;
	      break;
	    case WAIT_OBJECT_0 + 1:
	      sigproc_printf ("signal arrived");
	      reset_signal_arrived ();
	      continue;
	    case WAIT_OBJECT_0 + 2:
	      if (my_parent_is_alive ())
		res |= EXIT_REPARENTING;
	      else if (!myself->ppid_handle)
		{
		  nwait = 2;
		  sigproc_terminate ();
		  continue;
		}
	      break;
	    case WAIT_FAILED:
	      system_printf ("wait failed: nwait %d, pid %d, winpid %d, %E",
			     nwait, myself->pid, myself->dwProcessId);
	      system_printf ("waitbuf[0] %p %d", waitbuf[0],
			     WaitForSingleObject (waitbuf[0], 0));
	      system_printf ("waitbuf[1] %p = %d", waitbuf[1],
			     WaitForSingleObject (waitbuf[1], 0));
	      system_printf ("waitbuf[w] %p = %d", waitbuf[2],
			     WaitForSingleObject (waitbuf[2], 0));
	      set_errno (ECHILD);
	      try_to_debug ();
	      return -1;
	    }
	  break;
	}

      ForceCloseHandle (subproc_ready);

      sigproc_printf ("res = %x", res);

      if (res & EXIT_REPARENTING)
	{
	  /* Try to reparent child process.
	   * Make handles to child available to parent process and exit with
	   * EXIT_REPARENTING status. Wait() syscall in parent will then wait
	   * for newly created child.
	   */
	  HANDLE oldh = myself->hProcess;
	  HANDLE h = myself->ppid_handle;
	  sigproc_printf ("parent handle %p", h);
	  int rc = DuplicateHandle (hMainProc, pi.hProcess, h, &myself->hProcess,
				    0, FALSE, DUPLICATE_SAME_ACCESS);
	  sigproc_printf ("%d = DuplicateHandle, oldh %p, newh %p",
			  rc, oldh, myself->hProcess);
	  if (!rc && my_parent_is_alive ())
	    {
	      system_printf ("Reparent failed, parent handle %p, %E", h);
	      system_printf ("my dwProcessId %d, myself->dwProcessId %d",
			     GetCurrentProcessId (), myself->dwProcessId);
	      system_printf ("old hProcess %p, hProcess %p", oldh, myself->hProcess);
	    }
	}

    }

  MALLOC_CHECK;

  switch (mode)
    {
    case _P_OVERLAY:
      ForceCloseHandle1 (pi.hProcess, childhProc);
      proc_terminate ();
      myself->exit (res, 1);
      break;
    case _P_WAIT:
      waitpid (cygpid, (int *) &res, 0);
      break;
    case _P_DETACH:
      res = 0;	/* Lose all memory of this child. */
      break;
    case _P_NOWAIT:
    case _P_NOWAITO:
    case _P_VFORK:
      res = cygpid;
      break;
    default:
      break;
    }

  return (int) res;
}

extern "C" int
cwait (int *result, int pid, int)
{
  return waitpid (pid, result, 0);
}

/*
 * Helper function for spawn runtime calls.
 * Doesn't search the path.
 */

extern "C" int
spawnve (int mode, const char *path, const char *const *argv,
	 const char *const *envp)
{
  int ret;
  vfork_save *vf = vfork_storage.val ();

  if (vf != NULL && (vf->pid < 0) && mode == _P_OVERLAY)
    mode = _P_NOWAIT;
  else
    vf = NULL;

  syscall_printf ("spawnve (%s, %s, %x)", path, argv[0], envp);

  switch (mode)
    {
    case _P_OVERLAY:
      /* We do not pass _P_SEARCH_PATH here. execve doesn't search PATH.*/
      /* Just act as an exec if _P_OVERLAY set. */
      spawn_guts (path, argv, envp, mode);
      /* Errno should be set by spawn_guts.  */
      ret = -1;
      break;
    case _P_VFORK:
    case _P_NOWAIT:
    case _P_NOWAITO:
    case _P_WAIT:
    case _P_DETACH:
      subproc_init ();
      ret = spawn_guts (path, argv, envp, mode);
      if (vf)
	{
	  debug_printf ("longjmping due to vfork");
	  if (ret < 0)
	    vf->restore_exit (ret);
	  else
	    vf->restore_pid (ret);
	}
      break;
    default:
      set_errno (EINVAL);
      ret = -1;
      break;
    }
  return ret;
}

/*
 * spawn functions as implemented in the MS runtime library.
 * Most of these based on (and copied from) newlib/libc/posix/execXX.c
 */

extern "C" int
spawnl (int mode, const char *path, const char *arg0, ...)
{
  int i;
  va_list args;
  const char *argv[256];

  va_start (args, arg0);
  argv[0] = arg0;
  i = 1;

  do
      argv[i] = va_arg (args, const char *);
  while (argv[i++] != NULL);

  va_end (args);

  return spawnve (mode, path, (char * const  *) argv, cur_environ ());
}

extern "C" int
spawnle (int mode, const char *path, const char *arg0, ...)
{
  int i;
  va_list args;
  const char * const *envp;
  const char *argv[256];

  va_start (args, arg0);
  argv[0] = arg0;
  i = 1;

  do
    argv[i] = va_arg (args, const char *);
  while (argv[i++] != NULL);

  envp = va_arg (args, const char * const *);
  va_end (args);

  return spawnve (mode, path, (char * const *) argv, (char * const *) envp);
}

extern "C" int
spawnlp (int mode, const char *path, const char *arg0, ...)
{
  int i;
  va_list args;
  const char *argv[256];

  va_start (args, arg0);
  argv[0] = arg0;
  i = 1;

  do
      argv[i] = va_arg (args, const char *);
  while (argv[i++] != NULL);

  va_end (args);

  return spawnvpe (mode, path, (char * const *) argv, cur_environ ());
}

extern "C" int
spawnlpe (int mode, const char *path, const char *arg0, ...)
{
  int i;
  va_list args;
  const char * const *envp;
  const char *argv[256];

  va_start (args, arg0);
  argv[0] = arg0;
  i = 1;

  do
    argv[i] = va_arg (args, const char *);
  while (argv[i++] != NULL);

  envp = va_arg (args, const char * const *);
  va_end (args);

  return spawnvpe (mode, path, (char * const *) argv, envp);
}

extern "C" int
spawnv (int mode, const char *path, const char * const *argv)
{
  return spawnve (mode, path, argv, cur_environ ());
}

extern "C" int
spawnvp (int mode, const char *path, const char * const *argv)
{
  return spawnvpe (mode, path, argv, cur_environ ());
}

extern "C" int
spawnvpe (int mode, const char *file, const char * const *argv,
					     const char * const *envp)
{
  path_conv buf;
  return spawnve (mode, find_exec (file, buf), argv, envp);
}