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annotate lib/readlinkat.c @ 17769:05d77e098e6e

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readlinkat: port to AIX 7.1 * doc/posix-functions/readlink.texi (readlink): * doc/posix-functions/readlinkat.texi (readlinkat): Mention AIX porting problem. * lib/readlinkat.c (rpl_readlinkat) [HAVE_READLINKAT]: New function. * lib/unistd.in.h (readlinkat): Add replacement machinery. * m4/readlinkat.m4 (gl_FUNC_READLINKAT): Check readlinkat signature. * m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Add REPLACE_READLINKAT. * modules/readlinkat (configure.ac): Also compile replacement if REPLACE_READLINKAT. * modules/unistd (unistd.h): Substitute REPLACE_READLINKAT.
author Paul Eggert <eggert@cs.ucla.edu>
date Sat, 18 Oct 2014 22:35:28 -0700
parents 344018b6e5d7
children ab58d4870664
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1 /* Read a symlink relative to an open directory.
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2 Copyright (C) 2009-2014 Free Software Foundation, Inc.
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3
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4 This program is free software: you can redistribute it and/or modify
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5 it under the terms of the GNU General Public License as published by
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6 the Free Software Foundation; either version 3 of the License, or
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7 (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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16
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17 /* written by Eric Blake */
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18
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19 #include <config.h>
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20
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21 #include <unistd.h>
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22
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23 #if HAVE_READLINKAT
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24
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25 # undef readlinkat
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26
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27 ssize_t
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28 rpl_readlinkat (int fd, char const *file, char *buf, size_t len)
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29 {
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30 return readlinkat (fd, file, buf, len);
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31 }
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32
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33 #else
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34
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35 /* Gnulib provides a readlink stub for mingw; use it for distinction
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36 between EINVAL and ENOENT, rather than always failing with ENOSYS. */
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37
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38 /* POSIX 2008 says that unlike readlink, readlinkat returns 0 for
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39 success instead of the buffer length. But this would render
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40 readlinkat worthless since readlink does not guarantee a
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41 NUL-terminated buffer. Assume this was a bug in POSIX. */
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42
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43 /* Read the contents of symlink FILE into buffer BUF of size LEN, in the
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44 directory open on descriptor FD. If possible, do it without changing
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45 the working directory. Otherwise, resort to using save_cwd/fchdir,
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46 then readlink/restore_cwd. If either the save_cwd or the restore_cwd
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47 fails, then give a diagnostic and exit nonzero. */
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48
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49 # define AT_FUNC_NAME readlinkat
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50 # define AT_FUNC_F1 readlink
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51 # define AT_FUNC_POST_FILE_PARAM_DECLS , char *buf, size_t len
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52 # define AT_FUNC_POST_FILE_ARGS , buf, len
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53 # define AT_FUNC_RESULT ssize_t
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54 # include "at-func.c"
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55 # undef AT_FUNC_NAME
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56 # undef AT_FUNC_F1
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57 # undef AT_FUNC_POST_FILE_PARAM_DECLS
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58 # undef AT_FUNC_POST_FILE_ARGS
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59 # undef AT_FUNC_RESULT
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60
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61 #endif