kc3-lang/gnulib/lib/popen-safer.c

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• Hash : 990fa9d5
  Author :
  Date : 2017-08-14T13:04:46
  

  open: support O_CLOEXEC
  
  * NEWS, doc/posix-functions/open.texi:
  * doc/posix-functions/openat.texi: Document this.
  * lib/fcntl.in.h (O_CLOEXEC): Default to a nonzero value.
  (GNULIB_defined_O_CLOEXEC): New symbol.
  * lib/open.c: Include cloexec.h.
  (open): Support O_CLOEXEC.
  * lib/openat.c: Include cloexec.h.
  (rpl_openat): Support O_CLOEXEC.
  * lib/popen-safer.c: Do not include cloexec.h.
  (open_noinherit): Remove.
  (popen_safer): Use O_CLOEXEC instead of set_cloexec_flag.
  * lib/save-cwd.c: Do not include cloexec.h.
  (save_cwd): Use O_CLOEXEC instead of set_cloexec_flag.
  * m4/open-cloexec.m4: New file.
  * m4/open.m4 (gl_FUNC_OPEN): Require gl_PREPROC_O_CLOEXEC.
  Replace 'open' if O_CLOEXEC is not present.
  * m4/openat.m4 (gl_FUNC_OPENAT): Require gl_PREPROC_O_CLOEXEC.
  Replace 'openat' if O_CLOEXEC is not present.
  * modules/freopen (Depends-on): Depend on 'open' if replacing freopen.
  * modules/open (Files): Add m4/open-cloexec.m4.
  (Depends-on): Depend on cloexec if replacing 'open'.
  * modules/openat (Files): Add m4/open-cloexec.m4.
  (Depends-on): Depend on cloexec if replacing openat.
  * modules/popen-safer (Depends-on): Remove cloexec.
  * modules/save-cwd (Depends-on): Remove cloexec, and add
  fd-safer-flag and 'open'.
  

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• lib/popen-safer.c

• /* Invoke popen, but avoid some glitches.
  
     Copyright (C) 2009-2017 Free Software Foundation, Inc.
  
     This program 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 3 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 General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  
  /* Written by Eric Blake.  */
  
  #include <config.h>
  
  #include "stdio-safer.h"
  
  #include <errno.h>
  #include <fcntl.h>
  #include <unistd.h>
  
  /* Like popen, but do not return stdin, stdout, or stderr.  */
  
  FILE *
  popen_safer (char const *cmd, char const *mode)
  {
    /* Unfortunately, we cannot use the fopen_safer approach of using
       fdopen (dup_safer (fileno (popen (cmd, mode)))), because stdio
       libraries maintain hidden state tying the original fd to the pid
       to wait on when using pclose (this hidden state is also used to
       avoid fd leaks in subsequent popen calls).  So, we instead
       guarantee that all standard streams are open prior to the popen
       call (even though this puts more pressure on open fds), so that
       the original fd created by popen is safe.  */
    FILE *fp;
    int fd = open ("/dev/null", O_RDONLY | O_CLOEXEC);
    if (0 <= fd && fd <= STDERR_FILENO)
      {
        /* Maximum recursion depth is 3.  */
        int saved_errno;
        fp = popen_safer (cmd, mode);
        saved_errno = errno;
        close (fd);
        errno = saved_errno;
      }
    else
      {
        /* Either all fd's are tied up, or fd is safe and the real popen
           will reuse it.  */
        close (fd);
        fp = popen (cmd, mode);
      }
    return fp;
  }
  

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