tempfile.con commit Merge branch 'nd/clear-gitenv-upon-use-of-alias' (28ab768)
   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 *
  33 * - Active, file closed (after successful `close_tempfile()`). Same
  34 *   as the previous state, except that the temporary file is closed,
  35 *   `fd` is -1, and `fp` is `NULL`.
  36 *
  37 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, a
  38 *   failed attempt to create a temporary file, or a failed
  39 *   `close_tempfile()`). In this state:
  40 *
  41 *   - `active` is unset
  42 *   - `filename` is empty (usually, though there are transitory
  43 *     states in which this condition doesn't hold). Client code should
  44 *     *not* rely on the filename being empty in this state.
  45 *   - `fd` is -1 and `fp` is `NULL`
  46 *   - the object is left registered in the `tempfile_list`, and
  47 *     `on_list` is set.
  48 *
  49 * A temporary file is owned by the process that created it. The
  50 * `tempfile` has an `owner` field that records the owner's PID. This
  51 * field is used to prevent a forked process from deleting a temporary
  52 * file created by its parent.
  53 */
  54
  55#include "cache.h"
  56#include "tempfile.h"
  57#include "sigchain.h"
  58
  59static struct tempfile *volatile tempfile_list;
  60
  61static void remove_tempfiles(int skip_fclose)
  62{
  63        pid_t me = getpid();
  64
  65        while (tempfile_list) {
  66                if (tempfile_list->owner == me) {
  67                        /* fclose() is not safe to call in a signal handler */
  68                        if (skip_fclose)
  69                                tempfile_list->fp = NULL;
  70                        delete_tempfile(tempfile_list);
  71                }
  72                tempfile_list = tempfile_list->next;
  73        }
  74}
  75
  76static void remove_tempfiles_on_exit(void)
  77{
  78        remove_tempfiles(0);
  79}
  80
  81static void remove_tempfiles_on_signal(int signo)
  82{
  83        remove_tempfiles(1);
  84        sigchain_pop(signo);
  85        raise(signo);
  86}
  87
  88/*
  89 * Initialize *tempfile if necessary and add it to tempfile_list.
  90 */
  91static void prepare_tempfile_object(struct tempfile *tempfile)
  92{
  93        if (!tempfile_list) {
  94                /* One-time initialization */
  95                sigchain_push_common(remove_tempfiles_on_signal);
  96                atexit(remove_tempfiles_on_exit);
  97        }
  98
  99        if (tempfile->active)
 100                die("BUG: prepare_tempfile_object called for active object");
 101        if (!tempfile->on_list) {
 102                /* Initialize *tempfile and add it to tempfile_list: */
 103                tempfile->fd = -1;
 104                tempfile->fp = NULL;
 105                tempfile->active = 0;
 106                tempfile->owner = 0;
 107                strbuf_init(&tempfile->filename, 0);
 108                tempfile->next = tempfile_list;
 109                tempfile_list = tempfile;
 110                tempfile->on_list = 1;
 111        } else if (tempfile->filename.len) {
 112                /* This shouldn't happen, but better safe than sorry. */
 113                die("BUG: prepare_tempfile_object called for improperly-reset object");
 114        }
 115}
 116
 117/* Make sure errno contains a meaningful value on error */
 118int create_tempfile(struct tempfile *tempfile, const char *path)
 119{
 120        prepare_tempfile_object(tempfile);
 121
 122        strbuf_add_absolute_path(&tempfile->filename, path);
 123        tempfile->fd = open(tempfile->filename.buf, O_RDWR | O_CREAT | O_EXCL, 0666);
 124        if (tempfile->fd < 0) {
 125                strbuf_reset(&tempfile->filename);
 126                return -1;
 127        }
 128        tempfile->owner = getpid();
 129        tempfile->active = 1;
 130        if (adjust_shared_perm(tempfile->filename.buf)) {
 131                int save_errno = errno;
 132                error("cannot fix permission bits on %s", tempfile->filename.buf);
 133                delete_tempfile(tempfile);
 134                errno = save_errno;
 135                return -1;
 136        }
 137        return tempfile->fd;
 138}
 139
 140void register_tempfile(struct tempfile *tempfile, const char *path)
 141{
 142        prepare_tempfile_object(tempfile);
 143        strbuf_add_absolute_path(&tempfile->filename, path);
 144        tempfile->owner = getpid();
 145        tempfile->active = 1;
 146}
 147
 148int mks_tempfile_sm(struct tempfile *tempfile,
 149                    const char *template, int suffixlen, int mode)
 150{
 151        prepare_tempfile_object(tempfile);
 152
 153        strbuf_add_absolute_path(&tempfile->filename, template);
 154        tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 155        if (tempfile->fd < 0) {
 156                strbuf_reset(&tempfile->filename);
 157                return -1;
 158        }
 159        tempfile->owner = getpid();
 160        tempfile->active = 1;
 161        return tempfile->fd;
 162}
 163
 164int mks_tempfile_tsm(struct tempfile *tempfile,
 165                     const char *template, int suffixlen, int mode)
 166{
 167        const char *tmpdir;
 168
 169        prepare_tempfile_object(tempfile);
 170
 171        tmpdir = getenv("TMPDIR");
 172        if (!tmpdir)
 173                tmpdir = "/tmp";
 174
 175        strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
 176        tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
 177        if (tempfile->fd < 0) {
 178                strbuf_reset(&tempfile->filename);
 179                return -1;
 180        }
 181        tempfile->owner = getpid();
 182        tempfile->active = 1;
 183        return tempfile->fd;
 184}
 185
 186int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
 187{
 188        int fd;
 189        struct strbuf full_template = STRBUF_INIT;
 190
 191        strbuf_add_absolute_path(&full_template, template);
 192        fd = mks_tempfile_m(tempfile, full_template.buf, mode);
 193        if (fd < 0)
 194                die_errno("Unable to create temporary file '%s'",
 195                          full_template.buf);
 196
 197        strbuf_release(&full_template);
 198        return fd;
 199}
 200
 201FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
 202{
 203        if (!tempfile->active)
 204                die("BUG: fdopen_tempfile() called for inactive object");
 205        if (tempfile->fp)
 206                die("BUG: fdopen_tempfile() called for open object");
 207
 208        tempfile->fp = fdopen(tempfile->fd, mode);
 209        return tempfile->fp;
 210}
 211
 212const char *get_tempfile_path(struct tempfile *tempfile)
 213{
 214        if (!tempfile->active)
 215                die("BUG: get_tempfile_path() called for inactive object");
 216        return tempfile->filename.buf;
 217}
 218
 219int get_tempfile_fd(struct tempfile *tempfile)
 220{
 221        if (!tempfile->active)
 222                die("BUG: get_tempfile_fd() called for inactive object");
 223        return tempfile->fd;
 224}
 225
 226FILE *get_tempfile_fp(struct tempfile *tempfile)
 227{
 228        if (!tempfile->active)
 229                die("BUG: get_tempfile_fp() called for inactive object");
 230        return tempfile->fp;
 231}
 232
 233int close_tempfile(struct tempfile *tempfile)
 234{
 235        int fd = tempfile->fd;
 236        FILE *fp = tempfile->fp;
 237        int err;
 238
 239        if (fd < 0)
 240                return 0;
 241
 242        tempfile->fd = -1;
 243        if (fp) {
 244                tempfile->fp = NULL;
 245
 246                /*
 247                 * Note: no short-circuiting here; we want to fclose()
 248                 * in any case!
 249                 */
 250                err = ferror(fp) | fclose(fp);
 251        } else {
 252                err = close(fd);
 253        }
 254
 255        if (err) {
 256                int save_errno = errno;
 257                delete_tempfile(tempfile);
 258                errno = save_errno;
 259                return -1;
 260        }
 261
 262        return 0;
 263}
 264
 265int reopen_tempfile(struct tempfile *tempfile)
 266{
 267        if (0 <= tempfile->fd)
 268                die("BUG: reopen_tempfile called for an open object");
 269        if (!tempfile->active)
 270                die("BUG: reopen_tempfile called for an inactive object");
 271        tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
 272        return tempfile->fd;
 273}
 274
 275int rename_tempfile(struct tempfile *tempfile, const char *path)
 276{
 277        if (!tempfile->active)
 278                die("BUG: rename_tempfile called for inactive object");
 279
 280        if (close_tempfile(tempfile))
 281                return -1;
 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{
 297        if (!tempfile->active)
 298                return;
 299
 300        if (!close_tempfile(tempfile)) {
 301                unlink_or_warn(tempfile->filename.buf);
 302                tempfile->active = 0;
 303                strbuf_reset(&tempfile->filename);
 304        }
 305}