231 lines
6.3 KiB
C
231 lines
6.3 KiB
C
/* Open a stream to a file.
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Copyright (C) 2007-2022 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible <bruno@clisp.org>, 2007. */
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/* If the user's config.h happens to include <stdio.h>, let it include only
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the system's <stdio.h> here, so that orig_fopen doesn't recurse to
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rpl_fopen. */
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#define _GL_ALREADY_INCLUDING_STDIO_H
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#include <config.h>
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/* Get the original definition of fopen. It might be defined as a macro. */
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#include <stdio.h>
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#undef _GL_ALREADY_INCLUDING_STDIO_H
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static FILE *
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orig_fopen (const char *filename, const char *mode)
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{
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return fopen (filename, mode);
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}
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/* Specification. */
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/* Write "stdio.h" here, not <stdio.h>, otherwise OSF/1 5.1 DTK cc eliminates
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this include because of the preliminary #include <stdio.h> above. */
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#include "stdio.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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FILE *
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rpl_fopen (const char *filename, const char *mode)
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{
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int open_direction;
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int open_flags;
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#if GNULIB_FOPEN_GNU
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bool open_flags_gnu;
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# define BUF_SIZE 80
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char fdopen_mode_buf[BUF_SIZE + 1];
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#endif
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#if defined _WIN32 && ! defined __CYGWIN__
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if (strcmp (filename, "/dev/null") == 0)
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filename = "NUL";
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#endif
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/* Parse the mode. */
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open_direction = 0;
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open_flags = 0;
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#if GNULIB_FOPEN_GNU
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open_flags_gnu = false;
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#endif
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{
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const char *p = mode;
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#if GNULIB_FOPEN_GNU
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char *q = fdopen_mode_buf;
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#endif
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for (; *p != '\0'; p++)
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{
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switch (*p)
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{
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case 'r':
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open_direction = O_RDONLY;
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#if GNULIB_FOPEN_GNU
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if (q < fdopen_mode_buf + BUF_SIZE)
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*q++ = *p;
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#endif
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continue;
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case 'w':
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open_direction = O_WRONLY;
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open_flags |= O_CREAT | O_TRUNC;
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#if GNULIB_FOPEN_GNU
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if (q < fdopen_mode_buf + BUF_SIZE)
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*q++ = *p;
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#endif
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continue;
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case 'a':
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open_direction = O_WRONLY;
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open_flags |= O_CREAT | O_APPEND;
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#if GNULIB_FOPEN_GNU
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if (q < fdopen_mode_buf + BUF_SIZE)
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*q++ = *p;
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#endif
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continue;
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case 'b':
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/* While it is non-standard, O_BINARY is guaranteed by
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gnulib <fcntl.h>. We can also assume that orig_fopen
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supports the 'b' flag. */
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open_flags |= O_BINARY;
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#if GNULIB_FOPEN_GNU
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if (q < fdopen_mode_buf + BUF_SIZE)
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*q++ = *p;
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#endif
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continue;
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case '+':
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open_direction = O_RDWR;
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#if GNULIB_FOPEN_GNU
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if (q < fdopen_mode_buf + BUF_SIZE)
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*q++ = *p;
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#endif
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continue;
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#if GNULIB_FOPEN_GNU
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case 'x':
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open_flags |= O_EXCL;
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open_flags_gnu = true;
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continue;
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case 'e':
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open_flags |= O_CLOEXEC;
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open_flags_gnu = true;
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continue;
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#endif
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default:
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break;
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}
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#if GNULIB_FOPEN_GNU
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/* The rest of the mode string can be a platform-dependent extension.
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Copy it unmodified. */
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{
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size_t len = strlen (p);
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if (len > fdopen_mode_buf + BUF_SIZE - q)
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len = fdopen_mode_buf + BUF_SIZE - q;
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memcpy (q, p, len);
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q += len;
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}
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#endif
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break;
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}
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#if GNULIB_FOPEN_GNU
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*q = '\0';
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#endif
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}
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#if FOPEN_TRAILING_SLASH_BUG
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/* Fail if the mode requires write access and the filename ends in a slash,
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as POSIX says such a filename must name a directory
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<https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:
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"A pathname that contains at least one non-<slash> character and that
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ends with one or more trailing <slash> characters shall not be resolved
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successfully unless the last pathname component before the trailing
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<slash> characters names an existing directory"
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If the named file already exists as a directory, then if a mode that
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requires write access is specified, fopen() must fail because POSIX
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<https://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html>
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says that it fails with errno = EISDIR in this case.
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If the named file does not exist or does not name a directory, then
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fopen() must fail since the file does not contain a '.' directory. */
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{
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size_t len = strlen (filename);
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if (len > 0 && filename[len - 1] == '/')
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{
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int fd;
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struct stat statbuf;
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FILE *fp;
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if (open_direction != O_RDONLY)
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{
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errno = EISDIR;
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return NULL;
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}
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fd = open (filename, open_direction | open_flags,
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S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
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if (fd < 0)
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return NULL;
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if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
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{
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close (fd);
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errno = ENOTDIR;
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return NULL;
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}
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# if GNULIB_FOPEN_GNU
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fp = fdopen (fd, fdopen_mode_buf);
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# else
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fp = fdopen (fd, mode);
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# endif
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if (fp == NULL)
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{
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int saved_errno = errno;
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close (fd);
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errno = saved_errno;
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}
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return fp;
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}
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}
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#endif
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#if GNULIB_FOPEN_GNU
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if (open_flags_gnu)
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{
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int fd;
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FILE *fp;
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fd = open (filename, open_direction | open_flags,
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S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
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if (fd < 0)
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return NULL;
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fp = fdopen (fd, fdopen_mode_buf);
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if (fp == NULL)
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{
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int saved_errno = errno;
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close (fd);
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errno = saved_errno;
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}
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return fp;
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}
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#endif
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return orig_fopen (filename, mode);
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}
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