tempfile: prefer is_tempfile_active to bare access
[git/git.git] / tempfile.c
CommitLineData
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1/*
2 * State diagram and cleanup
3 * -------------------------
4 *
5 * If the program exits while a temporary file is active, we want to
6 * make sure that we remove it. This is done by remembering the active
7 * temporary files in a linked list, `tempfile_list`. An `atexit(3)`
8 * handler and a signal handler are registered, to clean up any active
9 * temporary files.
10 *
11 * Because the signal handler can run at any time, `tempfile_list` and
12 * the `tempfile` objects that comprise it must be kept in
13 * self-consistent states at all times.
14 *
15 * The possible states of a `tempfile` object are as follows:
16 *
17 * - Uninitialized. In this state the object's `on_list` field must be
18 * zero but the rest of its contents need not be initialized. As
19 * soon as the object is used in any way, it is irrevocably
20 * registered in `tempfile_list`, and `on_list` is set.
21 *
22 * - Active, file open (after `create_tempfile()` or
23 * `reopen_tempfile()`). In this state:
24 *
25 * - the temporary file exists
26 * - `active` is set
27 * - `filename` holds the filename of the temporary file
28 * - `fd` holds a file descriptor open for writing to it
29 * - `fp` holds a pointer to an open `FILE` object if and only if
30 * `fdopen_tempfile()` has been called on the object
31 * - `owner` holds the PID of the process that created the file
32 *
49bd0fc2 33 * - Active, file closed (after `close_tempfile_gently()`). Same
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34 * as the previous state, except that the temporary file is closed,
35 * `fd` is -1, and `fp` is `NULL`.
36 *
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37 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
38 * failed attempt to create a temporary file). In this state:
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39 *
40 * - `active` is unset
41 * - `filename` is empty (usually, though there are transitory
42 * states in which this condition doesn't hold). Client code should
43 * *not* rely on the filename being empty in this state.
44 * - `fd` is -1 and `fp` is `NULL`
45 * - the object is left registered in the `tempfile_list`, and
46 * `on_list` is set.
47 *
48 * A temporary file is owned by the process that created it. The
49 * `tempfile` has an `owner` field that records the owner's PID. This
50 * field is used to prevent a forked process from deleting a temporary
51 * file created by its parent.
52 */
53
54#include "cache.h"
55#include "tempfile.h"
56#include "sigchain.h"
57
58static struct tempfile *volatile tempfile_list;
59
60static void remove_tempfiles(int skip_fclose)
61{
62 pid_t me = getpid();
63
64 while (tempfile_list) {
65 if (tempfile_list->owner == me) {
66 /* fclose() is not safe to call in a signal handler */
67 if (skip_fclose)
68 tempfile_list->fp = NULL;
69 delete_tempfile(tempfile_list);
70 }
71 tempfile_list = tempfile_list->next;
72 }
73}
74
75static void remove_tempfiles_on_exit(void)
76{
77 remove_tempfiles(0);
78}
79
80static void remove_tempfiles_on_signal(int signo)
81{
82 remove_tempfiles(1);
83 sigchain_pop(signo);
84 raise(signo);
85}
86
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87/*
88 * Initialize *tempfile if necessary and add it to tempfile_list.
89 */
90static void prepare_tempfile_object(struct tempfile *tempfile)
1a9d15db 91{
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92 if (!tempfile_list) {
93 /* One-time initialization */
94 sigchain_push_common(remove_tempfiles_on_signal);
95 atexit(remove_tempfiles_on_exit);
96 }
97
e6fc2673 98 if (is_tempfile_active(tempfile))
7eba6ce5 99 die("BUG: prepare_tempfile_object called for active object");
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100 if (!tempfile->on_list) {
101 /* Initialize *tempfile and add it to tempfile_list: */
102 tempfile->fd = -1;
103 tempfile->fp = NULL;
104 tempfile->active = 0;
105 tempfile->owner = 0;
7eba6ce5 106 strbuf_init(&tempfile->filename, 0);
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107 tempfile->next = tempfile_list;
108 tempfile_list = tempfile;
109 tempfile->on_list = 1;
110 } else if (tempfile->filename.len) {
111 /* This shouldn't happen, but better safe than sorry. */
7eba6ce5 112 die("BUG: prepare_tempfile_object called for improperly-reset object");
1a9d15db 113 }
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114}
115
116/* Make sure errno contains a meaningful value on error */
117int create_tempfile(struct tempfile *tempfile, const char *path)
118{
119 prepare_tempfile_object(tempfile);
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120
121 strbuf_add_absolute_path(&tempfile->filename, path);
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122 tempfile->fd = open(tempfile->filename.buf,
123 O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666);
124 if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
125 /* Try again w/o O_CLOEXEC: the kernel might not support it */
126 tempfile->fd = open(tempfile->filename.buf,
127 O_RDWR | O_CREAT | O_EXCL, 0666);
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128 if (tempfile->fd < 0) {
129 strbuf_reset(&tempfile->filename);
130 return -1;
131 }
132 tempfile->owner = getpid();
133 tempfile->active = 1;
134 if (adjust_shared_perm(tempfile->filename.buf)) {
135 int save_errno = errno;
136 error("cannot fix permission bits on %s", tempfile->filename.buf);
137 delete_tempfile(tempfile);
138 errno = save_errno;
139 return -1;
140 }
141 return tempfile->fd;
142}
143
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144void register_tempfile(struct tempfile *tempfile, const char *path)
145{
146 prepare_tempfile_object(tempfile);
147 strbuf_add_absolute_path(&tempfile->filename, path);
148 tempfile->owner = getpid();
149 tempfile->active = 1;
150}
151
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152int mks_tempfile_sm(struct tempfile *tempfile,
153 const char *template, int suffixlen, int mode)
154{
155 prepare_tempfile_object(tempfile);
156
157 strbuf_add_absolute_path(&tempfile->filename, template);
158 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
159 if (tempfile->fd < 0) {
160 strbuf_reset(&tempfile->filename);
161 return -1;
162 }
163 tempfile->owner = getpid();
164 tempfile->active = 1;
165 return tempfile->fd;
166}
167
168int mks_tempfile_tsm(struct tempfile *tempfile,
169 const char *template, int suffixlen, int mode)
170{
171 const char *tmpdir;
172
173 prepare_tempfile_object(tempfile);
174
175 tmpdir = getenv("TMPDIR");
176 if (!tmpdir)
177 tmpdir = "/tmp";
178
179 strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
180 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
181 if (tempfile->fd < 0) {
182 strbuf_reset(&tempfile->filename);
183 return -1;
184 }
185 tempfile->owner = getpid();
186 tempfile->active = 1;
187 return tempfile->fd;
188}
189
190int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
191{
192 int fd;
193 struct strbuf full_template = STRBUF_INIT;
194
195 strbuf_add_absolute_path(&full_template, template);
196 fd = mks_tempfile_m(tempfile, full_template.buf, mode);
197 if (fd < 0)
198 die_errno("Unable to create temporary file '%s'",
199 full_template.buf);
200
201 strbuf_release(&full_template);
202 return fd;
203}
204
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205FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
206{
e6fc2673 207 if (!is_tempfile_active(tempfile))
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208 die("BUG: fdopen_tempfile() called for inactive object");
209 if (tempfile->fp)
210 die("BUG: fdopen_tempfile() called for open object");
211
212 tempfile->fp = fdopen(tempfile->fd, mode);
213 return tempfile->fp;
214}
215
216const char *get_tempfile_path(struct tempfile *tempfile)
217{
e6fc2673 218 if (!is_tempfile_active(tempfile))
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219 die("BUG: get_tempfile_path() called for inactive object");
220 return tempfile->filename.buf;
221}
222
223int get_tempfile_fd(struct tempfile *tempfile)
224{
e6fc2673 225 if (!is_tempfile_active(tempfile))
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226 die("BUG: get_tempfile_fd() called for inactive object");
227 return tempfile->fd;
228}
229
230FILE *get_tempfile_fp(struct tempfile *tempfile)
231{
e6fc2673 232 if (!is_tempfile_active(tempfile))
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233 die("BUG: get_tempfile_fp() called for inactive object");
234 return tempfile->fp;
235}
236
49bd0fc2 237int close_tempfile_gently(struct tempfile *tempfile)
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238{
239 int fd = tempfile->fd;
240 FILE *fp = tempfile->fp;
241 int err;
242
243 if (fd < 0)
244 return 0;
245
246 tempfile->fd = -1;
247 if (fp) {
248 tempfile->fp = NULL;
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249 if (ferror(fp)) {
250 err = -1;
251 if (!fclose(fp))
252 errno = EIO;
253 } else {
254 err = fclose(fp);
255 }
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256 } else {
257 err = close(fd);
258 }
259
49bd0fc2 260 return err ? -1 : 0;
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261}
262
263int reopen_tempfile(struct tempfile *tempfile)
264{
265 if (0 <= tempfile->fd)
266 die("BUG: reopen_tempfile called for an open object");
e6fc2673 267 if (!is_tempfile_active(tempfile))
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268 die("BUG: reopen_tempfile called for an inactive object");
269 tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
270 return tempfile->fd;
271}
272
273int rename_tempfile(struct tempfile *tempfile, const char *path)
274{
e6fc2673 275 if (!is_tempfile_active(tempfile))
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276 die("BUG: rename_tempfile called for inactive object");
277
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278 if (close_tempfile_gently(tempfile)) {
279 delete_tempfile(tempfile);
1a9d15db 280 return -1;
49bd0fc2 281 }
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282
283 if (rename(tempfile->filename.buf, path)) {
284 int save_errno = errno;
285 delete_tempfile(tempfile);
286 errno = save_errno;
287 return -1;
288 }
289
290 tempfile->active = 0;
291 strbuf_reset(&tempfile->filename);
292 return 0;
293}
294
295void delete_tempfile(struct tempfile *tempfile)
296{
e6fc2673 297 if (!is_tempfile_active(tempfile))
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298 return;
299
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300 close_tempfile_gently(tempfile);
301 unlink_or_warn(tempfile->filename.buf);
302 tempfile->active = 0;
303 strbuf_reset(&tempfile->filename);
1a9d15db 304}