1 /* Emulate link on platforms that lack it, namely native Windows platforms.
2
3 Copyright (C) 2009-2023 Free Software Foundation, Inc.
4
5 This file is free software: you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as
7 published by the Free Software Foundation; either version 2.1 of the
8 License, or (at your option) any later version.
9
10 This file 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 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser 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
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
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 free (dir);
121 return -1;
122 }
123 free (dir);
124 }
125 /* Now create the link. */
126 if (CreateHardLinkFunc (file2, file1, NULL) == 0)
127 {
128 /* It is not documented which errors CreateHardLink() can produce.
129 * The following conversions are based on tests on a Windows XP SP2
130 * system. */
131 DWORD err = GetLastError ();
132 switch (err)
133 {
134 case ERROR_ACCESS_DENIED:
135 errno = EACCES;
136 break;
137
138 case ERROR_INVALID_FUNCTION: /* fs does not support hard links */
139 errno = EPERM;
140 break;
141
142 case ERROR_NOT_SAME_DEVICE:
143 errno = EXDEV;
144 break;
145
146 case ERROR_PATH_NOT_FOUND:
147 case ERROR_FILE_NOT_FOUND:
148 errno = ENOENT;
149 break;
150
151 case ERROR_INVALID_PARAMETER:
152 errno = ENAMETOOLONG;
153 break;
154
155 case ERROR_TOO_MANY_LINKS:
156 errno = EMLINK;
157 break;
158
159 case ERROR_ALREADY_EXISTS:
160 errno = EEXIST;
161 break;
162
163 default:
164 errno = EIO;
165 }
166 return -1;
167 }
168
169 return 0;
170 }
171
172 # else /* !Windows */
173
174 # error "This platform lacks a link function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib."
175
176 # endif /* !Windows */
177 #else /* HAVE_LINK */
178
179 # undef link
180
181 /* Create a hard link from FILE1 to FILE2, working around platform bugs. */
182 int
183 rpl_link (char const *file1, char const *file2)
184 {
185 size_t len1;
186 size_t len2;
187 struct stat st;
188
189 /* Don't allow IRIX to dereference dangling file2 symlink. */
190 if (lstat (file2, &st) == 0 || errno == EOVERFLOW)
191 {
192 errno = EEXIST;
193 return -1;
194 }
195
196 /* Reject trailing slashes on non-directories. */
197 len1 = strlen (file1);
198 len2 = strlen (file2);
199 if ((len1 && file1[len1 - 1] == '/')
200 || (len2 && file2[len2 - 1] == '/'))
201 {
202 /* Let link() decide whether hard-linking directories is legal.
203 If stat() fails, then link() should fail for the same reason
204 (although on Solaris 9, link("file/","oops") mistakenly
205 succeeds); if stat() succeeds, require a directory. */
206 if (stat (file1, &st))
207 return -1;
208 if (!S_ISDIR (st.st_mode))
209 {
210 errno = ENOTDIR;
211 return -1;
212 }
213 }
214 else
215 {
216 /* Fix Cygwin 1.5.x bug where link("a","b/.") creates file "b". */
217 char *dir = strdup (file2);
218 char *p;
219 if (!dir)
220 return -1;
221 /* We already know file2 does not end in slash. Strip off the
222 basename, then check that the dirname exists. */
223 p = strrchr (dir, '/');
224 if (p)
225 {
226 *p = '\0';
227 if (stat (dir, &st) != 0 && errno != EOVERFLOW)
228 {
229 free (dir);
230 return -1;
231 }
232 }
233 free (dir);
234 }
235 return link (file1, file2);
236 }
237 #endif /* HAVE_LINK */