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annotate lib/areadlink.c @ 11224:5aa57cee93aa

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avoid gcc 3.4.3 bug on long double NaN on Irix 6.5 * tests/nan.h (NaNl): Rewrite as function on Irix, to avoid compilation bug by using runtime conversion. * m4/isfinite.m4 (gl_ISFINITE): Likewise. * m4/isnanl.m4 (gl_FUNC_ISNANL): Likewise. * modules/ceill-tests (Files): Use nan.h. * modules/floorl-tests (Files): Likewise. * modules/frexpl-tests (Files): Likewise. * modules/isnanl-tests (Files): Likewise. * modules/ldexpl-tests (Files): Likewise. * modules/roundl-tests (Files): Likewise. * modules/truncl-tests (Files): Likewise. * tests/test-ceill.c (main): Use a working NaN. * tests/test-floorl.c (main): Likewise. * tests/test-frexpl.c (main): Likewise. * tests/test-isnan.c (test_long_double): Likewise. * tests/test-isnanl.h (main): Likewise. * tests/test-ldexpl.h (main): Likewise. * tests/test-roundl.h (main): Likewise. * tests/test-truncl.h (main): Likewise. See http://lists.gnu.org/archive/html/bug-gnulib/2009-02/msg00190.html. Signed-off-by: Eric Blake <ebb9@byu.net>
author Eric Blake <ebb9@byu.net>
date Thu, 26 Feb 2009 20:18:42 -0700
parents bbbbbf4cd1c5
children 1fd105be1362
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9217
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1 /* areadlink.c -- readlink wrapper to return the link name in malloc'd storage
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2 Unlike xreadlink and xreadlink_with_size, don't ever call exit.
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3
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4 Copyright (C) 2001, 2003-2007 Free Software Foundation, Inc.
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5
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6 This program is free software: you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
9309
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8 the Free Software Foundation; either version 3 of the License, or
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9 (at your option) any later version.
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10
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11 This program is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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18
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19 /* Written by Jim Meyering <jim@meyering.net>
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20 and Bruno Haible <bruno@clisp.org>. */
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21
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22 #include <config.h>
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23
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24 /* Specification. */
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25 #include "areadlink.h"
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26
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27 #include <string.h>
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28 #include <errno.h>
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29 #include <limits.h>
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30 #include <sys/types.h>
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31 #include <stdlib.h>
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32 #include <unistd.h>
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33
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34 #ifndef SIZE_MAX
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35 # define SIZE_MAX ((size_t) -1)
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36 #endif
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37 #ifndef SSIZE_MAX
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38 # define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
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39 #endif
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40
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41 /* Call readlink to get the symbolic link value of FILENAME.
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42 Return a pointer to that NUL-terminated string in malloc'd storage.
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43 If readlink fails, return NULL and set errno.
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44 If realloc fails, or if the link value is longer than SIZE_MAX :-),
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45 return NULL and set errno to ENOMEM. */
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46
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47 char *
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48 areadlink (char const *filename)
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49 {
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50 /* The initial buffer size for the link value. A power of 2
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51 detects arithmetic overflow earlier, but is not required. */
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52 #define INITIAL_BUF_SIZE 1024
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53
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54 /* Allocate the initial buffer on the stack. This way, in the common
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55 case of a symlink of small size, we get away with a single small malloc()
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56 instead of a big malloc() followed by a shrinking realloc(). */
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57 char initial_buf[INITIAL_BUF_SIZE];
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58
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59 char *buffer = initial_buf;
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60 size_t buf_size = sizeof (initial_buf);
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61
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62 while (1)
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63 {
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64 /* Attempt to read the link into the current buffer. */
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65 ssize_t link_length = readlink (filename, buffer, buf_size);
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66
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67 /* On AIX 5L v5.3 and HP-UX 11i v2 04/09, readlink returns -1
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68 with errno == ERANGE if the buffer is too small. */
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69 if (link_length < 0 && errno != ERANGE)
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70 {
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71 if (buffer != initial_buf)
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72 {
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73 int saved_errno = errno;
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74 free (buffer);
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75 errno = saved_errno;
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76 }
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77 return NULL;
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78 }
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79
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80 if ((size_t) link_length < buf_size)
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81 {
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82 buffer[link_length++] = '\0';
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83
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84 /* Return it in a chunk of memory as small as possible. */
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85 if (buffer == initial_buf)
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86 {
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87 buffer = (char *) malloc (link_length);
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88 if (buffer == NULL)
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89 /* errno is ENOMEM. */
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90 return NULL;
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91 memcpy (buffer, initial_buf, link_length);
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92 }
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93 else
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94 {
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95 /* Shrink buffer before returning it. */
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96 if ((size_t) link_length < buf_size)
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97 {
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98 char *smaller_buffer = (char *) realloc (buffer, link_length);
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99
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100 if (smaller_buffer != NULL)
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101 buffer = smaller_buffer;
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102 }
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103 }
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104 return buffer;
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105 }
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106
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107 if (buffer != initial_buf)
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108 free (buffer);
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109 buf_size *= 2;
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110 if (SSIZE_MAX < buf_size || (SIZE_MAX / 2 < SSIZE_MAX && buf_size == 0))
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111 {
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112 errno = ENOMEM;
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113 return NULL;
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114 }
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115 buffer = (char *) malloc (buf_size);
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116 if (buffer == NULL)
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117 /* errno is ENOMEM. */
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118 return NULL;
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119 }
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120 }