/* cloexec.c - set or clear the close-on-exec descriptor flag

   Copyright (C) 1991, 2004-2006, 2009-2020 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU Lesser General Public License as published by

   the Free Software Foundation; either version 2.1 of the License, or

   (at your option) any later version.

   This program 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 Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program.  If not, see <https://www.gnu.org/licenses/>.

   The code is taken from glibc/manual/llio.texi  */

#include <config.h>

#include "cloexec.h"

#include <errno.h>

#include <fcntl.h>

#include <unistd.h>

/* Set the 'FD_CLOEXEC' flag of DESC if VALUE is true,

   or clear the flag if VALUE is false.

   Return 0 on success, or -1 on error with 'errno' set.

   Note that on MingW, this function does NOT protect DESC from being

   inherited into spawned children.  Instead, either use dup_cloexec

   followed by closing the original DESC, or use interfaces such as

   open or pipe2 that accept flags like O_CLOEXEC to create DESC

   non-inheritable in the first place.  */

int

set_cloexec_flag (int desc, bool value)

{

#ifdef F_SETFD

  int flags = fcntl (desc, F_GETFD, 0);

  if (0 <= flags)

    {

      int newflags = (value ? flags | FD_CLOEXEC : flags & ~FD_CLOEXEC);

      if (flags == newflags

          || fcntl (desc, F_SETFD, newflags) != -1)

        return 0;

    }

  return -1;

#else /* !F_SETFD */

  /* Use dup2 to reject invalid file descriptors; the cloexec flag

     will be unaffected.  */

  if (desc < 0)

    {

      errno = EBADF;

      return -1;

    }

  if (dup2 (desc, desc) < 0)

    /* errno is EBADF here.  */

    return -1;

  /* There is nothing we can do on this kind of platform.  Punt.  */

  return 0;

#endif /* !F_SETFD */

}

/* Duplicates a file handle FD, while marking the copy to be closed

   prior to exec or spawn.  Returns -1 and sets errno if FD could not

   be duplicated.  */

int

dup_cloexec (int fd)

{

  return fcntl (fd, F_DUPFD_CLOEXEC, 0);

}