newlib-cygwin/winsup/cygwin/dtable.cc

/* dtable.cc: file descriptor support.

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. */

#define  __INSIDE_CYGWIN_NET__

#include "winsup.h"
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <wchar.h>

#define USE_SYS_TYPES_FD_SET
#include <winsock.h>
#include "pinfo.h"
#include "cygerrno.h"
#include "perprocess.h"
#include "path.h"
#include "fhandler.h"
#include "select.h"
#include "dtable.h"
#include "cygheap.h"
#include "tls_pbuf.h"
#include "ntdll.h"
#include "shared_info.h"

static const DWORD std_consts[] = {STD_INPUT_HANDLE, STD_OUTPUT_HANDLE,
				   STD_ERROR_HANDLE};

static bool handle_to_fn (HANDLE, char *);

#define WCLEN(x) ((sizeof (x) / sizeof (WCHAR)) - 1)
static const char unknown_file[] = "some disk file";
static const WCHAR DEV_NULL[] = L"\\Device\\Null";
static const WCHAR DEV_SOCKET[] = L"\\Device\\Afd";

static const WCHAR DEVICE_PREFIX[] = L"\\device\\";
static const size_t DEVICE_PREFIX_LEN WCLEN (DEVICE_PREFIX);

static const WCHAR DEV_NAMED_PIPE[] = L"\\Device\\NamedPipe\\";
static const size_t DEV_NAMED_PIPE_LEN = WCLEN (DEV_NAMED_PIPE);

static const WCHAR DEV_REMOTE[] = L"\\Device\\LanmanRedirector\\";
static const size_t DEV_REMOTE_LEN = WCLEN (DEV_REMOTE);

static const WCHAR DEV_REMOTE1[] = L"\\Device\\WinDfs\\Root\\";
static const size_t DEV_REMOTE1_LEN = WCLEN (DEV_REMOTE1);

/* Set aside space for the table of fds */
void
dtable_init ()
{
  if (!cygheap->fdtab.size)
    cygheap->fdtab.extend (NOFILE_INCR, 0);
}

void
set_std_handle (int fd)
{
  fhandler_base *fh = cygheap->fdtab[fd];
  if (fd == 0)
    SetStdHandle (std_consts[fd], fh ? fh->get_handle () : NULL);
  else if (fd <= 2)
    SetStdHandle (std_consts[fd], fh ? fh->get_output_handle () : NULL);
}

int
dtable::extend (size_t howmuch, size_t min)
{
  size_t new_size = size + howmuch;
  fhandler_base **newfds;

  if (new_size <= OPEN_MAX)
    /* ok */;
  else if (size < OPEN_MAX && min < OPEN_MAX)
    new_size = OPEN_MAX;
  else
    {
      set_errno (EMFILE);
      return 0;
    }

  /* Try to allocate more space for fd table. We can't call realloc ()
     here to preserve old table if memory allocation fails */

  if (!(newfds = (fhandler_base **) ccalloc (HEAP_ARGV, new_size, sizeof newfds[0])))
    {
      debug_printf ("calloc failed");
      set_errno (ENOMEM);
      return 0;
    }
  if (fds)
    {
      memcpy (newfds, fds, size * sizeof (fds[0]));
      cfree (fds);
    }

  size = new_size;
  fds = newfds;
  debug_printf ("size %ld, fds %p", size, fds);
  return 1;
}

void
dtable::get_debugger_info ()
{
  extern bool jit_debug;
  if (!jit_debug && being_debugged ())
    {
      char std[3][sizeof ("/dev/ptyNNNN")];
      std[0][0] = std[1][0] = std [2][0] = '\0';
      char buf[sizeof ("cYgstd %x") + 64];
      sprintf (buf, "cYgstd %p %zx %x", &std, sizeof (std[0]), 3);
      OutputDebugString (buf);
      for (int i = 0; i < 3; i++)
	if (std[i][0])
	  {
	    HANDLE h = GetStdHandle (std_consts[i]);
	    fhandler_base *fh = build_fh_name (std[i]);
	    if (!fh)
	      continue;
	    fds[i] = fh;
	    if (!fh->open ((i ? (i == 2 ? O_RDWR : O_WRONLY) : O_RDONLY)
			   | O_BINARY, 0777))
	      release (i);
	    else
	      {
		CloseHandle (h);
		/* Copy to Windows' idea of a standard handle, otherwise
		   we have invalid standard handles when calling Windows
		   functions (small_printf and strace might suffer, too). */
		SetStdHandle (std_consts[i], i ? fh->get_output_handle ()
					       : fh->get_handle ());
	      }
	  }
    }
}

/* Initialize the file descriptor/handle mapping table.
   This function should only be called when a cygwin function is invoked
   by a non-cygwin function, i.e., it should only happen very rarely. */

void
dtable::stdio_init ()
{
  if (myself->cygstarted || ISSTATE (myself, PID_CYGPARENT))
    {
      tty_min *t = cygwin_shared->tty.get_cttyp ();
      if (t && t->is_console)
	init_console_handler (true);
      return;
    }

  HANDLE in = GetStdHandle (STD_INPUT_HANDLE);
  HANDLE out = GetStdHandle (STD_OUTPUT_HANDLE);
  HANDLE err = GetStdHandle (STD_ERROR_HANDLE);

  init_std_file_from_handle (0, in);

  /* STD_ERROR_HANDLE has been observed to be the same as
     STD_OUTPUT_HANDLE.  We need separate handles (e.g. using pipes
     to pass data from child to parent).  */
  /* CV 2008-10-17: Under debugger control, std fd's have been potentially
     initialized in dtable::get_debugger_info ().  In this case
     init_std_file_from_handle is a no-op, so, even if out == err we don't
     want to duplicate the handle since it will be unused. */
  if (out == err && (!being_debugged () || not_open (2)))
    {
      /* Since this code is not invoked for forked tasks, we don't have
	 to worry about the close-on-exec flag here.  */
      if (!DuplicateHandle (GetCurrentProcess (), out,
			    GetCurrentProcess (), &err,
			    0, TRUE, DUPLICATE_SAME_ACCESS))
	{
	  /* If that fails, do this as a fall back.  */
	  err = out;
	  system_printf ("couldn't make stderr distinct from stdout, %E");
	}
    }

  init_std_file_from_handle (1, out);
  init_std_file_from_handle (2, err);
}

const int dtable::initial_archetype_size;

fhandler_base *
dtable::find_archetype (device& dev)
{
  for (unsigned i = 0; i < farchetype; i++)
    if (archetypes[i]->get_device () == (dev_t) dev)
      return archetypes[i];
  return NULL;
}

fhandler_base **
dtable::add_archetype ()
{
  if (farchetype++ >= narchetypes)
    archetypes = (fhandler_base **) crealloc_abort (archetypes, (narchetypes += initial_archetype_size) * sizeof archetypes[0]);
  return archetypes + farchetype - 1;
}

void
dtable::delete_archetype (fhandler_base *fh)
{
  for (unsigned i = 0; i < farchetype; i++)
    if (fh == archetypes[i])
      {
	debug_printf ("deleting element %d for %s(%d/%d)", i, fh->get_name (),
		      fh->dev ().get_major (), fh->dev ().get_minor ());
	if (i < --farchetype)
	  archetypes[i] = archetypes[farchetype];
	break;
      }

  delete fh;
}

int
dtable::find_unused_handle (size_t start)
{
  /* When extending, try to allocate a NOFILE_INCR chunk
     following the empty fd.  */
  size_t extendby = NOFILE_INCR + ((start >= size) ? 1 + start - size : 0);

  /* This do loop should only ever execute twice. */
  int res = -1;
  do
    {
      for (size_t i = start; i < size; i++)
	if (fds[i] == NULL)
	  {
	    res = (int) i;
	    goto out;
	  }
    }
  while (extend (extendby, start));
out:
  return res;
}

void
dtable::release (int fd)
{
  if (fds[fd]->need_fixup_before ())
    dec_need_fixup_before ();
  fds[fd]->dec_refcnt ();
  fds[fd] = NULL;
  if (fd <= 2)
    set_std_handle (fd);
}

extern "C" int
cygwin_attach_handle_to_fd (char *name, int fd, HANDLE handle, mode_t bin,
			    DWORD myaccess)
{
  cygheap->fdtab.lock ();
  if (fd == -1)
    fd = cygheap->fdtab.find_unused_handle ();
  fhandler_base *fh = build_fh_name (name);
  if (!fh)
    fd = -1;
  else
    {
      cygheap->fdtab[fd] = fh;
      cygheap->fdtab[fd]->inc_refcnt ();
      fh->init (handle, myaccess, bin ?: fh->pc_binmode ());
    }
  cygheap->fdtab.unlock ();
  return fd;
}

void
dtable::init_std_file_from_handle (int fd, HANDLE handle)
{
  tmp_pathbuf tp;
  CONSOLE_SCREEN_BUFFER_INFO buf;
  DCB dcb;
  unsigned bin = O_BINARY;
  device dev;

  first_fd_for_open = 0;

  if (!not_open (fd))
    return;

  SetLastError (0);
  DWORD access = 0;
  DWORD ft = GetFileType (handle);
  char *name = tp.c_get ();
  name[0] = '\0';
  if (ft == FILE_TYPE_UNKNOWN && GetLastError () == ERROR_INVALID_HANDLE)
    /* can't figure out what this is */;
  else if (ft == FILE_TYPE_PIPE)
    {
      int rcv = 0, len = sizeof (int);

      if (handle_to_fn (handle, name))
	dev.parse (name);
      else if (strcmp (name, ":sock:") == 0
	       /* NtQueryObject returns an error when called on an LSP socket
		  handle.  fhandler_socket::set_socket_handle tries to fetch
		  the underlying base socket, but this might fail. */
	       || (strcmp (name, unknown_file) == 0
		   && !::getsockopt ((SOCKET) handle, SOL_SOCKET, SO_RCVBUF,
				     (char *) &rcv, &len)))
	{
	  /* socket */
	  dev = *af_inet_dev;
	  name[0] = '\0';
	}
      else if (fd == 0)
	dev = *piper_dev;
      else
	dev = *pipew_dev;
    }
  else if (GetConsoleScreenBufferInfo (handle, &buf)
	   || GetNumberOfConsoleInputEvents (handle, (DWORD *) &buf))
    {
      /* Console I/O */
      if (myself->ctty > 0)
	dev.parse (myself->ctty);
      else
	{
	  dev.parse (FH_CONSOLE);
	  CloseHandle (handle);
	  handle = INVALID_HANDLE_VALUE;
	}
    }
  else if (GetCommState (handle, &dcb))
    /* FIXME: Not right - assumes ttyS0 */
    dev.parse (DEV_SERIAL_MAJOR, 0);
  else
    /* Try to figure it out from context - probably a disk file */
    handle_to_fn (handle, name);

  if (!name[0] && !dev)
    fds[fd] = NULL;
  else
    {
      fhandler_base *fh;

      if (dev)
	fh = build_fh_dev (dev);
      else
	fh = build_fh_name (name);

      if (!fh)
	return;

      if (name[0])
	{
	  bin = fh->pc_binmode ();
	  if (!bin)
	    {
	      bin = fh->get_default_fmode (O_RDWR);
	      if (!bin && dev)
		bin = O_BINARY;
	    }
	}

      IO_STATUS_BLOCK io;
      FILE_ACCESS_INFORMATION fai;
      int openflags = O_BINARY;

      /* Console windows are no kernel objects up to Windows 7/2008R2, so the
	 access mask returned by NtQueryInformationFile is meaningless.  CMD
	 always hands down stdin handles as R/O handles, but our tty slave
	 sides are R/W. */
      if (fh->is_tty ())
	{
	  openflags |= O_RDWR;
	  access |= GENERIC_READ | GENERIC_WRITE;
	}
      else if (!iscons_dev (dev)
	       && NT_SUCCESS (NtQueryInformationFile (handle, &io, &fai,
						      sizeof fai,
						      FileAccessInformation)))
	{
	  if (fai.AccessFlags & FILE_WRITE_DATA)
	    {
	      openflags |= O_WRONLY;
	      access |= GENERIC_WRITE;
	    }
	  if (fai.AccessFlags & FILE_READ_DATA)
	    {
	      openflags |= openflags & O_WRONLY ? O_RDWR : O_RDONLY;
	      access |= GENERIC_READ;
	    }
	}
      else if (fd == 0)
	{
	  openflags |= O_RDONLY;
	  access |= GENERIC_READ;
	}
      else
	{
	  openflags |= O_WRONLY;
	  access |= GENERIC_WRITE;  /* Should be rdwr for stderr but not sure that's
				       possible for some versions of handles */
	}
      if (!fh->init (handle, access, bin))
	api_fatal ("couldn't initialize fd %d for %s", fd, fh->get_name ());
      if (fh->ispipe ())
	{
	  fhandler_pipe *fhp = (fhandler_pipe *) fh;
	  fhp->set_pipe_buf_size ();
	  /* Set read pipe always to nonblocking */
	  fhp->set_pipe_non_blocking (fhp->get_device () == FH_PIPER ?
				      true : fhp->is_nonblocking ());
	}

      if (!fh->open_setup (openflags))
	api_fatal ("open_setup failed, %E");
      fh->usecount = 0;
      cygheap->fdtab[fd] = fh;
      cygheap->fdtab[fd]->inc_refcnt ();
      set_std_handle (fd);
      paranoid_printf ("fd %d, handle %p", fd, handle);
      fh->post_open_setup (fd);
    }
}

#define cnew(name, ...) \
  ({ \
    void* ptr = (void*) ccalloc (HEAP_FHANDLER, 1, sizeof (name)); \
    ptr ? new (ptr) name (__VA_ARGS__) : NULL; \
  })

#define cnew_no_ctor(name, ...) \
  ({ \
    void* ptr = (void*) ccalloc (HEAP_FHANDLER, 1, sizeof (name)); \
    ptr ? new (ptr) name (ptr) : NULL; \
  })

fhandler_base *
build_fh_name (const char *name, unsigned opt, suffix_info *si)
{
  path_conv pc (name, opt | PC_NULLEMPTY | PC_POSIX, si);
  if (pc.error)
    {
      fhandler_base *fh = cnew (fhandler_nodevice);
      if (fh)
	fh->set_error (pc.error);
      set_errno (fh ? pc.error : EMFILE);
      return fh;
    }

  return build_fh_pc (pc);
}

fhandler_base *
build_fh_dev (const device& dev, const char *unix_name)
{
  path_conv pc (dev);
  if (unix_name)
    pc.set_posix (unix_name);
  else
    pc.set_posix (dev.name ());
  return build_fh_pc (pc);
}

#define fh_unset ((fhandler_base *) 1)
static device last_tty_dev;
#define fh_last_tty_dev ((fhandler_termios *) cygheap->fdtab.find_archetype (last_tty_dev))

static fhandler_base *
fh_alloc (path_conv& pc)
{
  fhandler_base *fh = fh_unset;
  fhandler_base *fhraw = NULL;

  switch (pc.dev.get_major ())
    {
    case DEV_PTYS_MAJOR:
      fh = cnew (fhandler_pty_slave, pc.dev.get_minor ());
      break;
    case DEV_PTYM_MAJOR:
      fh = cnew (fhandler_pty_master, pc.dev.get_minor ());
      break;
    case DEV_FLOPPY_MAJOR:
    case DEV_CDROM_MAJOR:
    case DEV_SD_MAJOR:
    case DEV_SD1_MAJOR ... DEV_SD7_MAJOR:
    case DEV_SD_HIGHPART_START ... DEV_SD_HIGHPART_END:
      fh = cnew (fhandler_dev_floppy);
      break;
    case DEV_TAPE_MAJOR:
      fh = cnew (fhandler_dev_tape);
      break;
    case DEV_SERIAL_MAJOR:
      fh = cnew (fhandler_serial);
      break;
    case DEV_CONS_MAJOR:
      fh = cnew (fhandler_console, pc.dev);
      break;
    default:
      switch ((dev_t) pc.dev)
	{
	case FH_CONSOLE:
	case FH_CONIN:
	case FH_CONOUT:
	  fh = cnew (fhandler_console, pc.dev);
	  break;
	case FH_PTMX:
	  if (pc.isopen ())
	    fh = cnew (fhandler_pty_master, -1);
	  else
	    fhraw = cnew_no_ctor (fhandler_pty_master, -1);
	  break;
	case FH_WINDOWS:
	  fh = cnew (fhandler_windows);
	  break;
	case FH_FIFO:
	  fh = cnew (fhandler_fifo);
	  break;
	case FH_PIPE:
	case FH_PIPER:
	case FH_PIPEW:
	  fh = cnew (fhandler_pipe);
	  break;
	case FH_INET:
	  fh = cnew (fhandler_socket_inet);
	  break;
	case FH_LOCAL:
	  fh = cnew (fhandler_socket_local);
	  break;
#ifdef __WITH_AF_UNIX
	case FH_UNIX:
	  fh = cnew (fhandler_socket_unix);
	  break;
#endif /* __WITH_AF_UNIX */
	case FH_FS:
	  fh = cnew (fhandler_disk_file);
	  break;
	case FH_NULL:
	  fh = cnew (fhandler_dev_null);
	  break;
	case FH_ZERO:
	case FH_FULL:
	  fh = cnew (fhandler_dev_zero);
	  break;
	case FH_RANDOM:
	case FH_URANDOM:
	  fh = cnew (fhandler_dev_random);
	  break;
	case FH_CLIPBOARD:
	  fh = cnew (fhandler_dev_clipboard);
	  break;
	case FH_OSS_DSP:
	  fh = cnew (fhandler_dev_dsp);
	  break;
	case FH_PROC:
	  fh = cnew (fhandler_proc);
	  break;
	case FH_REGISTRY:
	  fh = cnew (fhandler_registry);
	  break;
	case FH_PROCESS:
	  fh = cnew (fhandler_process);
	  break;
	case FH_PROCESSFD:
	  fh = cnew (fhandler_process_fd);
	  break;
	case FH_PROCNET:
	  fh = cnew (fhandler_procnet);
	  break;
	case FH_PROCSYS:
	  fh = cnew (fhandler_procsys);
	  break;
	case FH_PROCSYSVIPC:
	  fh = cnew (fhandler_procsysvipc);
	  break;
	case FH_NETDRIVE:
	  fh = cnew (fhandler_netdrive);
	  break;
	case FH_DEV:
	  fh = cnew (fhandler_dev);
	  break;
	case FH_DEV_FD:
	  fh = cnew (fhandler_dev_fd);
	  break;
	case FH_CYGDRIVE:
	  fh = cnew (fhandler_cygdrive);
	  break;
	case FH_SIGNALFD:
	  fh = cnew (fhandler_signalfd);
	  break;
	case FH_TIMERFD:
	  fh = cnew (fhandler_timerfd);
	  break;
	case FH_MQUEUE:
	  fh = cnew (fhandler_mqueue);
	  break;
	case FH_TTY:
	  if (!pc.isopen ())
	    {
	      fhraw = cnew_no_ctor (fhandler_console, -1);
	      debug_printf ("not called from open for /dev/tty");
	    }
	  else if (myself->ctty <= 0 && last_tty_dev
		   && !myself->set_ctty (fh_last_tty_dev, 0))
	    debug_printf ("no /dev/tty assigned");
	  else if (myself->ctty > 0)
	    {
	      debug_printf ("determining /dev/tty assignment for ctty %p", myself->ctty);
	      if (iscons_dev (myself->ctty))
		fh = cnew (fhandler_console, pc.dev);
	      else
		fh = cnew (fhandler_pty_slave, myself->ctty);
	      if (fh->dev () != FH_NADA)
		fh->set_name ("/dev/tty");
	    }
	  break;
      }
    }

  /* If `fhraw' is set that means that this fhandler is just a dummy
     set up for stat().  Mock it up for use by stat without actually
     trying to do any real initialization.  */
  if (fhraw)
    {
      fh = fhraw;
      fh->set_name (pc);
      if (fh->use_archetype ())
	fh->archetype = fh;
    }
  if (fh == fh_unset)
    fh = cnew (fhandler_nodevice);
  else if (fh->dev () == FH_ERROR)
    {
      if (!pc.isopen () && pc.dev.isfs ())
	fh->dev () = pc.dev;	/* Special case: This file actually exists on
				   disk and we're not trying to open it so just
				   return the info from pc.  */
      else
	{
	  delete fh;
	  fh = NULL;
	}
    }
  return fh;
}

fhandler_base *
build_fh_pc (path_conv& pc)
{
  fhandler_base *fh = fh_alloc (pc);

  if (!fh)
    {
      set_errno (ENXIO);
      goto out;
    }

  if (!fh->use_archetype ())
    fh->set_name (pc);
  else if ((fh->archetype = cygheap->fdtab.find_archetype (fh->dev ())))
    {
      debug_printf ("found an archetype for %s(%d/%d) io_handle %p", fh->get_name (), fh->dev ().get_major (), fh->dev ().get_minor (),
		    fh->archetype->get_handle ());
      if (!fh->get_name ())
	fh->set_name (fh->archetype->dev ().name ());
    }
  else if (cygwin_finished_initializing && !pc.isopen ())
    fh->set_name (pc);
  else
    {
      if (!fh->get_name ())
	fh->set_name (fh->dev ().native ());
      fh->archetype = fh->clone ();
      debug_printf ("created an archetype (%p) for %s(%d/%d)", fh->archetype, fh->get_name (), fh->dev ().get_major (), fh->dev ().get_minor ());
      fh->archetype->archetype = NULL;
      *cygheap->fdtab.add_archetype () = fh->archetype;
    }


  /* Keep track of the last tty-like thing opened.  We could potentially want
     to open it if /dev/tty is referenced. */
  if (myself->ctty > 0 || !fh->is_tty () || !pc.isctty_capable ())
    last_tty_dev = FH_NADA;
  else
    last_tty_dev = fh->dev ();

out:
  debug_printf ("fh %p, dev %08x", fh, fh ? (dev_t) fh->dev () : 0);
  return fh;
}

fhandler_base *
dtable::dup_worker (fhandler_base *oldfh, int flags)
{
  fhandler_base *newfh = oldfh->clone ();
  if (!newfh)
    debug_printf ("clone failed");
  else
    {
      if (!oldfh->archetype)
	newfh->set_handle (NULL);

      newfh->pc.close_conv_handle ();
      if (oldfh->dup (newfh, flags))
	{
	  delete newfh;
	  newfh = NULL;
	  debug_printf ("oldfh->dup failed");
	}
      else
	{
	  /* Don't increment refcnt here since we don't know if this is a
	     allocated fd.  So we leave this chore to the caller. */

	  newfh->usecount = 0;
	  newfh->archetype_usecount (1);

	  /* The O_CLOEXEC flag enforces close-on-exec behaviour. */
	  newfh->set_close_on_exec (!!(flags & O_CLOEXEC));
	  debug_printf ("duped '%s' old %p, new %p", oldfh->get_name (),
			oldfh->get_handle (), newfh->get_handle ());
	}
    }
  return newfh;
}

int
dtable::dup3 (int oldfd, int newfd, int flags)
{
  int res = -1;
  fhandler_base *newfh = NULL;	// = NULL to avoid an incorrect warning

  debug_printf ("dup3 (%d, %d, %y)", oldfd, newfd, flags);
  lock ();
  bool do_unlock = true;
  bool unlock_on_return;
  if (!(flags & O_EXCL))
    unlock_on_return = true;	/* Relinquish lock on return */
  else
    {
      flags &= ~O_EXCL;
      unlock_on_return = false;	/* Return with lock set on success */
    }

  if (not_open (oldfd))
    {
      syscall_printf ("fd %d not open", oldfd);
      set_errno (EBADF);
      goto done;
    }
  if (newfd >= OPEN_MAX || newfd < 0)
    {
      syscall_printf ("new fd out of bounds: %d", newfd);
      set_errno (EBADF);
      goto done;
    }
  if ((flags & ~O_CLOEXEC) != 0)
    {
      syscall_printf ("invalid flags value %y", flags);
      set_errno (EINVAL);
      return -1;
    }

  /* This is a temporary kludge until all utilities can catch up with
     a change in behavior that implements linux functionality:  opening
     a tty should not automatically cause it to become the controlling
     tty for the process.  */
  if (newfd > 2)
    flags |= O_NOCTTY;

  if ((newfh = dup_worker (fds[oldfd], flags)) == NULL)
    {
      res = -1;
      goto done;
    }

  debug_printf ("newfh->io_handle %p, oldfh->io_handle %p, new win32_name %p, old win32_name %p",
		newfh->get_handle (), fds[oldfd]->get_handle (), newfh->get_win32_name (), fds[oldfd]->get_win32_name ());

  if (!not_open (newfd))
    close (newfd);
  else if ((size_t) newfd >= size
	   && find_unused_handle (newfd) < 0)
    /* couldn't extend fdtab */
    {
      newfh->close ();
      res = -1;
      goto done;
    }

  fds[newfd] = newfh;

  if ((res = newfd) <= 2)
    set_std_handle (res);
  do_unlock = unlock_on_return;

done:
  if (do_unlock)
    unlock ();
  syscall_printf ("%R = dup3(%d, %d, %y)", res, oldfd, newfd, flags);

  return res;
}

bool
dtable::select_read (int fd, select_stuff *ss)
{
  if (not_open (fd))
    {
      set_errno (EBADF);
      return false;
    }
  fhandler_base *fh = fds[fd];
  select_record *s = fh->select_read (ss);
  s->fd = fd;
  if (!s->fh)
    s->fh = fh;
  s->thread_errno = 0;
  debug_printf ("%s fd %d", fh->get_name (), fd);
  return true;
}

bool
dtable::select_write (int fd, select_stuff *ss)
{
  if (not_open (fd))
    {
      set_errno (EBADF);
      return NULL;
    }
  fhandler_base *fh = fds[fd];
  select_record *s = fh->select_write (ss);
  s->fd = fd;
  s->fh = fh;
  s->thread_errno = 0;
  debug_printf ("%s fd %d", fh->get_name (), fd);
  return true;
}

bool
dtable::select_except (int fd, select_stuff *ss)
{
  if (not_open (fd))
    {
      set_errno (EBADF);
      return NULL;
    }
  fhandler_base *fh = fds[fd];
  select_record *s = fh->select_except (ss);
  s->fd = fd;
  s->fh = fh;
  s->thread_errno = 0;
  debug_printf ("%s fd %d", fh->get_name (), fd);
  return true;
}

void
dtable::move_fd (int from, int to)
{
  // close (to); /* It is assumed that this is close-on-exec */
  fds[to] = fds[from];
  fds[from] = NULL;
}

void
dtable::set_file_pointers_for_exec ()
{
/* This is not POSIX-compliant so the function is only called for
   non-Cygwin processes. */
  LARGE_INTEGER eof = { QuadPart: 0 };

  lock ();
  fhandler_base *fh;
  for (size_t i = 0; i < size; i++)
    if ((fh = fds[i]) != NULL && fh->get_flags () & O_APPEND)
      SetFilePointerEx (fh->get_handle (), eof, NULL, FILE_END);
  unlock ();
}

void
dtable::fixup_close (size_t i, fhandler_base *fh)
{
  if (fh->archetype)
    {
      debug_printf ("closing fd %d since it is an archetype", i);
      fh->close_with_arch ();
    }
  release (i);
}

void
dtable::fixup_after_exec ()
{
  first_fd_for_open = 0;
  fhandler_base *fh;
  for (size_t i = 0; i < size; i++)
    if ((fh = fds[i]) != NULL)
      {
	fh->clear_readahead ();
	fh->fixup_after_exec ();
	/* Close the handle if it's close-on-exec or if an error was detected
	   (typically with opening a console in a gui app) by fixup_after_exec.
	 */
	if (fh->close_on_exec () || (!fh->nohandle () && !fh->get_handle ()))
	  fixup_close (i, fh);
	else if (fh->get_popen_pid ())
	  close (i);
	else if (i == 0)
	  SetStdHandle (std_consts[i], fh->get_handle ());
	else if (i <= 2)
	  SetStdHandle (std_consts[i], fh->get_output_handle ());
      }
}

void
dtable::fixup_after_fork (HANDLE parent)
{
  fhandler_base *fh;
  for (size_t i = 0; i < size; i++)
    if ((fh = fds[i]) != NULL)
      {
	if (fh->close_on_exec () || fh->need_fork_fixup ())
	  {
	    debug_printf ("fd %d (%s)", i, fh->get_name ());
	    fh->fixup_after_fork (parent);
	    if (!fh->nohandle () && !fh->get_handle ())
	      {
		/* This should actually never happen but it's here to make sure
		   we don't crash due to access of an unopened file handle.  */
		fixup_close (i, fh);
		continue;
	      }
	  }
	if (i == 0)
	  SetStdHandle (std_consts[i], fh->get_handle ());
	else if (i <= 2)
	  SetStdHandle (std_consts[i], fh->get_output_handle ());
      }
}

static void
decode_tty (char *buf, WCHAR *w32)
{
  int ttyn = wcstol (w32, NULL, 10);
  __ptsname (buf, ttyn);
}

/* Try to derive posix filename from given handle.  Return true if
   the handle is associated with a cygwin tty. */
static bool
handle_to_fn (HANDLE h, char *posix_fn)
{
  tmp_pathbuf tp;
  ULONG len = 0;
  WCHAR *maxmatchdos = NULL;
  PWCHAR device = tp.w_get ();
  int maxmatchlen = 0;
  OBJECT_NAME_INFORMATION *ntfn = (OBJECT_NAME_INFORMATION *) tp.w_get ();

  NTSTATUS status = NtQueryObject (h, ObjectNameInformation, ntfn, 65536, &len);
  if (!NT_SUCCESS (status))
    debug_printf ("NtQueryObject failed, %y", status);
  // NT seems to do this on an unopened file
  else if (!ntfn->Name.Buffer)
    debug_printf ("nt->Name.Buffer == NULL");
  else
    {
      WCHAR *w32 = ntfn->Name.Buffer;
      size_t w32len = ntfn->Name.Length / sizeof (WCHAR);
      w32[w32len] = L'\0';

      if (wcscasecmp (w32, DEV_NULL) == 0)
	{
	  strcpy (posix_fn, "/dev/null");
	  return false;
	}

      if (wcscasecmp (w32, DEV_SOCKET) == 0)
	{
	  strcpy (posix_fn, ":sock:");
	  return false;
	}

      if (wcsncasecmp (w32, DEV_NAMED_PIPE, DEV_NAMED_PIPE_LEN) == 0)
	{
	  w32 += DEV_NAMED_PIPE_LEN;
	  if (wcsncmp (w32, L"cygwin-", WCLEN (L"cygwin-")) != 0)
	    return false;
	  w32 += WCLEN (L"cygwin-");
	  /* Check for installation key and trailing dash. */
	  w32len = cygheap->installation_key.Length / sizeof (WCHAR);
	  if (w32len
	      && wcsncmp (w32, cygheap->installation_key.Buffer, w32len) != 0)
	    return false;
	  w32 += w32len;
	  if (*w32 != L'-')
	    return false;
	  ++w32;
	  bool istty = wcsncmp (w32, L"pty", WCLEN (L"pty")) == 0;
	  if (istty)
	    decode_tty (posix_fn, w32 + WCLEN (L"pty"));
	  else if (wcsncmp (w32, L"pipe", WCLEN (L"pipe")) == 0)
	    strcpy (posix_fn, "/dev/pipe");
	  return istty;
	}

      WCHAR fnbuf[64 * 1024];
      if (wcsncasecmp (w32, DEVICE_PREFIX, DEVICE_PREFIX_LEN) != 0
	  || !QueryDosDeviceW (NULL, fnbuf, sizeof (fnbuf) / sizeof (WCHAR)))
	{
	  sys_wcstombs (posix_fn, NT_MAX_PATH, w32, w32len);
	  return false;
	}

      for (WCHAR *s = fnbuf; *s; s = wcschr (s, '\0') + 1)
	{
	  if (!QueryDosDeviceW (s, device, NT_MAX_PATH))
	    continue;
	  if (wcschr (s, ':') == NULL)
	    continue;
	  WCHAR *q = wcsrchr (device, ';');
	  if (q)
	    {
	      WCHAR *r = wcschr (q, '\\');
	      if (r)
		wcscpy (q, r + 1);
	    }
	  int devlen = wcslen (device);
	  if (device[devlen - 1] == L'\\')
	    device[--devlen] = L'\0';
	  if (devlen < maxmatchlen)
	    continue;
	  if (wcsncmp (device, w32, devlen) != 0||
	      (w32[devlen] != L'\0' && w32[devlen] != L'\\'))
	    continue;
	  maxmatchlen = devlen;
	  maxmatchdos = s;
	  debug_printf ("current match '%W' = '%W'\n", s, device);
	}

      if (maxmatchlen)
	{
	  WCHAR *p = wcschr (w32 + DEVICE_PREFIX_LEN, L'\\');
	  size_t n = wcslen (maxmatchdos);
	  WCHAR ch;
	  if (!p)
	    ch = L'\0';
	  else
	    {
	      if (maxmatchdos[n - 1] == L'\\')
		n--;
	      w32 += maxmatchlen - n;
	      ch = L'\\';
	    }
	  memcpy (w32, maxmatchdos, n * sizeof (WCHAR));
	  w32[n] = ch;
	}
      else if (wcsncmp (w32, DEV_REMOTE, DEV_REMOTE_LEN) == 0)
	{
	  w32 += DEV_REMOTE_LEN - 2;
	  *w32 = L'\\';
	  debug_printf ("remote drive");
	}
      else if (wcsncmp (w32, DEV_REMOTE1, DEV_REMOTE1_LEN) == 0)
	{
	  w32 += DEV_REMOTE1_LEN - 2;
	  *w32 = L'\\';
	  debug_printf ("remote drive");
	}

      cygwin_conv_path (CCP_WIN_W_TO_POSIX | CCP_ABSOLUTE, w32, posix_fn,
			NT_MAX_PATH);

      debug_printf ("derived path '%W', posix '%s'", w32, posix_fn);
      return false;
    }

  strcpy (posix_fn,  unknown_file);
  return false;
}

void
dtable::fixup_before_fork (DWORD target_proc_id)
{
  lock ();
  fhandler_base *fh;
  for (size_t i = 0; i < size; i++)
    if ((fh = fds[i]) != NULL)
      {
	debug_printf ("fd %d (%s)", i, fh->get_name ());
	fh->fixup_before_fork_exec (target_proc_id);
      }
  unlock ();
}

void
dtable::fixup_before_exec (DWORD target_proc_id)
{
  lock ();
  fhandler_base *fh;
  for (size_t i = 0; i < size; i++)
    if ((fh = fds[i]) != NULL && !fh->close_on_exec ())
      {
	debug_printf ("fd %d (%s)", i, fh->get_name ());
	fh->fixup_before_fork_exec (target_proc_id);
      }
  unlock ();
}