1 /* Emulate link on platforms that lack it, namely native Windows platforms.
2
3 Copyright (C) 2009-2021 Free Software Foundation, Inc.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3, or (at your option)
8 any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, see <https://www.gnu.org/licenses/>. */
17
18 #include <config.h>
19
20 #include <unistd.h>
21
22 #include <errno.h>
23 #include <stdlib.h>
24 #include <string.h>
25 #include <sys/stat.h>
26
27 #if !HAVE_LINK
28 # if defined _WIN32 && ! defined __CYGWIN__
29
30 # define WIN32_LEAN_AND_MEAN
31 # include <windows.h>
32
33 /* Don't assume that UNICODE is not defined. */
34 # undef GetModuleHandle
35 # define GetModuleHandle GetModuleHandleA
36 # undef CreateHardLink
37 # define CreateHardLink CreateHardLinkA
38
39 # if !(_WIN32_WINNT >= _WIN32_WINNT_WINXP)
40
41 /* Avoid warnings from gcc -Wcast-function-type. */
42 # define GetProcAddress \
43 (void *) GetProcAddress
44
45 /* CreateHardLink was introduced only in Windows 2000. */
46 typedef BOOL (WINAPI * CreateHardLinkFuncType) (LPCSTR lpFileName,
47 LPCSTR lpExistingFileName,
48 LPSECURITY_ATTRIBUTES lpSecurityAttributes);
49 static CreateHardLinkFuncType CreateHardLinkFunc = NULL;
50 static BOOL initialized = FALSE;
51
52 static void
initialize(void)53 initialize (void)
54 {
55 HMODULE kernel32 = GetModuleHandle ("kernel32.dll");
56 if (kernel32 != NULL)
57 {
58 CreateHardLinkFunc =
59 (CreateHardLinkFuncType) GetProcAddress (kernel32, "CreateHardLinkA");
60 }
61 initialized = TRUE;
62 }
63
64 # else
65
66 # define CreateHardLinkFunc CreateHardLink
67
68 # endif
69
70 int
link(const char * file1,const char * file2)71 link (const char *file1, const char *file2)
72 {
73 char *dir;
74 size_t len1 = strlen (file1);
75 size_t len2 = strlen (file2);
76
77 # if !(_WIN32_WINNT >= _WIN32_WINNT_WINXP)
78 if (!initialized)
79 initialize ();
80 # endif
81
82 if (CreateHardLinkFunc == NULL)
83 {
84 /* System does not support hard links. */
85 errno = EPERM;
86 return -1;
87 }
88 /* Reject trailing slashes on non-directories; native Windows does not
89 support hard-linking directories. */
90 if ((len1 && (file1[len1 - 1] == '/' || file1[len1 - 1] == '\\'))
91 || (len2 && (file2[len2 - 1] == '/' || file2[len2 - 1] == '\\')))
92 {
93 /* If stat() fails, then link() should fail for the same reason. */
94 struct stat st;
95 if (stat (file1, &st))
96 {
97 if (errno == EOVERFLOW)
98 /* It's surely a file, not a directory (see stat-w32.c). */
99 errno = ENOTDIR;
100 return -1;
101 }
102 if (!S_ISDIR (st.st_mode))
103 errno = ENOTDIR;
104 else
105 errno = EPERM;
106 return -1;
107 }
108 /* CreateHardLink("b/.","a",NULL) creates file "b", so we must check
109 that dirname(file2) exists. */
110 dir = strdup (file2);
111 if (!dir)
112 return -1;
113 {
114 struct stat st;
115 char *p = strchr (dir, '\0');
116 while (dir < p && (*--p != '/' && *p != '\\'));
117 *p = '\0';
118 if (p != dir && stat (dir, &st) != 0 && errno != EOVERFLOW)
119 {
120 int saved_errno = errno;
121 free (dir);
122 errno = saved_errno;
123 return -1;
124 }
125 free (dir);
126 }
127 /* Now create the link. */
128 if (CreateHardLinkFunc (file2, file1, NULL) == 0)
129 {
130 /* It is not documented which errors CreateHardLink() can produce.
131 * The following conversions are based on tests on a Windows XP SP2
132 * system. */
133 DWORD err = GetLastError ();
134 switch (err)
135 {
136 case ERROR_ACCESS_DENIED:
137 errno = EACCES;
138 break;
139
140 case ERROR_INVALID_FUNCTION: /* fs does not support hard links */
141 errno = EPERM;
142 break;
143
144 case ERROR_NOT_SAME_DEVICE:
145 errno = EXDEV;
146 break;
147
148 case ERROR_PATH_NOT_FOUND:
149 case ERROR_FILE_NOT_FOUND:
150 errno = ENOENT;
151 break;
152
153 case ERROR_INVALID_PARAMETER:
154 errno = ENAMETOOLONG;
155 break;
156
157 case ERROR_TOO_MANY_LINKS:
158 errno = EMLINK;
159 break;
160
161 case ERROR_ALREADY_EXISTS:
162 errno = EEXIST;
163 break;
164
165 default:
166 errno = EIO;
167 }
168 return -1;
169 }
170
171 return 0;
172 }
173
174 # else /* !Windows */
175
176 # error "This platform lacks a link function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib."
177
178 # endif /* !Windows */
179 #else /* HAVE_LINK */
180
181 # undef link
182
183 /* Create a hard link from FILE1 to FILE2, working around platform bugs. */
184 int
rpl_link(char const * file1,char const * file2)185 rpl_link (char const *file1, char const *file2)
186 {
187 size_t len1;
188 size_t len2;
189 struct stat st;
190
191 /* Don't allow IRIX to dereference dangling file2 symlink. */
192 if (lstat (file2, &st) == 0 || errno == EOVERFLOW)
193 {
194 errno = EEXIST;
195 return -1;
196 }
197
198 /* Reject trailing slashes on non-directories. */
199 len1 = strlen (file1);
200 len2 = strlen (file2);
201 if ((len1 && file1[len1 - 1] == '/')
202 || (len2 && file2[len2 - 1] == '/'))
203 {
204 /* Let link() decide whether hard-linking directories is legal.
205 If stat() fails, then link() should fail for the same reason
206 (although on Solaris 9, link("file/","oops") mistakenly
207 succeeds); if stat() succeeds, require a directory. */
208 if (stat (file1, &st))
209 return -1;
210 if (!S_ISDIR (st.st_mode))
211 {
212 errno = ENOTDIR;
213 return -1;
214 }
215 }
216 else
217 {
218 /* Fix Cygwin 1.5.x bug where link("a","b/.") creates file "b". */
219 char *dir = strdup (file2);
220 char *p;
221 if (!dir)
222 return -1;
223 /* We already know file2 does not end in slash. Strip off the
224 basename, then check that the dirname exists. */
225 p = strrchr (dir, '/');
226 if (p)
227 {
228 *p = '\0';
229 if (stat (dir, &st) != 0 && errno != EOVERFLOW)
230 {
231 int saved_errno = errno;
232 free (dir);
233 errno = saved_errno;
234 return -1;
235 }
236 }
237 free (dir);
238 }
239 return link (file1, file2);
240 }
241 #endif /* HAVE_LINK */
242