1  /* cloexec.c - set or clear the close-on-exec descriptor flag
       2  
       3     Copyright (C) 1991, 2004-2006, 2009-2023 Free Software Foundation, Inc.
       4  
       5     This file is free software: you can redistribute it and/or modify
       6     it under the terms of the GNU Lesser General Public License as
       7     published by the Free Software Foundation; either version 2.1 of the
       8     License, or (at your option) any later version.
       9  
      10     This file is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      13     GNU Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public License
      16     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      17  
      18  /* The code is taken from glibc/manual/llio.texi  */
      19  
      20  #include <config.h>
      21  
      22  #include "cloexec.h"
      23  
      24  #include <errno.h>
      25  #include <fcntl.h>
      26  #include <unistd.h>
      27  
      28  /* Set the 'FD_CLOEXEC' flag of DESC if VALUE is true,
      29     or clear the flag if VALUE is false.
      30     Return 0 on success, or -1 on error with 'errno' set.
      31  
      32     Note that on MingW, this function does NOT protect DESC from being
      33     inherited into spawned children.  Instead, either use dup_cloexec
      34     followed by closing the original DESC, or use interfaces such as
      35     open or pipe2 that accept flags like O_CLOEXEC to create DESC
      36     non-inheritable in the first place.  */
      37  
      38  int
      39  set_cloexec_flag (int desc, bool value)
      40  {
      41  #ifdef F_SETFD
      42  
      43    int flags = fcntl (desc, F_GETFD, 0);
      44  
      45    if (0 <= flags)
      46      {
      47        int newflags = (value ? flags | FD_CLOEXEC : flags & ~FD_CLOEXEC);
      48  
      49        if (flags == newflags
      50            || fcntl (desc, F_SETFD, newflags) != -1)
      51          return 0;
      52      }
      53  
      54    return -1;
      55  
      56  #else /* !F_SETFD */
      57  
      58    /* Use dup2 to reject invalid file descriptors; the cloexec flag
      59       will be unaffected.  */
      60    if (desc < 0)
      61      {
      62        errno = EBADF;
      63        return -1;
      64      }
      65    if (dup2 (desc, desc) < 0)
      66      /* errno is EBADF here.  */
      67      return -1;
      68  
      69    /* There is nothing we can do on this kind of platform.  Punt.  */
      70    return 0;
      71  #endif /* !F_SETFD */
      72  }
      73  
      74  
      75  /* Duplicates a file handle FD, while marking the copy to be closed
      76     prior to exec or spawn.  Returns -1 and sets errno if FD could not
      77     be duplicated.  */
      78  
      79  int
      80  dup_cloexec (int fd)
      81  {
      82    return fcntl (fd, F_DUPFD_CLOEXEC, 0);
      83  }