1 /* areadlinkat.c -- readlinkat wrapper to return malloc'd link name
2 Unlike xreadlinkat, only call exit on failure to change directory.
3
4 Copyright (C) 2001, 2003-2007, 2009-2021 Free Software Foundation, Inc.
5
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <https://www.gnu.org/licenses/>. */
18
19 /* Written by Jim Meyering <jim@meyering.net>,
20 and Bruno Haible <bruno@clisp.org>,
21 and Eric Blake <ebb9@byu.net>. */
22
23 #include <config.h>
24
25 /* Specification. */
26 #include "areadlink.h"
27
28 #include <stdlib.h>
29
30 #include "careadlinkat.h"
31
32 #if HAVE_READLINKAT
33
34 /* Call readlinkat to get the symbolic link value of FILENAME relative to FD.
35 Return a pointer to that NUL-terminated string in malloc'd storage.
36 If readlinkat fails, return NULL and set errno (although failure to
37 change directory will issue a diagnostic and exit).
38 If allocation fails, or if the link value is longer than SIZE_MAX :-),
39 return NULL and set errno to ENOMEM. */
40
41 char *
areadlinkat(int fd,char const * filename)42 areadlinkat (int fd, char const *filename)
43 {
44 return careadlinkat (fd, filename, NULL, 0, NULL, readlinkat);
45 }
46
47 #else /* !HAVE_READLINKAT */
48
49 /* It is more efficient to change directories only once and call
50 areadlink, rather than repeatedly call the replacement
51 readlinkat. */
52
53 # define AT_FUNC_NAME areadlinkat
54 # define AT_FUNC_F1 areadlink
55 # define AT_FUNC_POST_FILE_PARAM_DECLS /* empty */
56 # define AT_FUNC_POST_FILE_ARGS /* empty */
57 # define AT_FUNC_RESULT char *
58 # define AT_FUNC_FAIL NULL
59 # include "at-func.c"
60 # undef AT_FUNC_NAME
61 # undef AT_FUNC_F1
62 # undef AT_FUNC_POST_FILE_PARAM_DECLS
63 # undef AT_FUNC_POST_FILE_ARGS
64 # undef AT_FUNC_RESULT
65 # undef AT_FUNC_FAIL
66
67 #endif /* !HAVE_READLINKAT */
68