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422a21c6a0
Once a "struct tempfile" is added to the global cleanup list, it is never removed. This means that its storage must remain valid for the lifetime of the program. For single-use tempfiles and locks, this isn't a big deal: we just declare the struct static. But for library code which may take multiple simultaneous locks (like the ref code), they're forced to allocate a struct on the heap and leak it. This is mostly OK in practice. The size of the leak is bounded by the number of refs, and most programs exit after operating on a fixed number of refs (and allocate simultaneous memory proportional to the number of ref updates in the first place). But: 1. It isn't hard to imagine a real leak: a program which runs for a long time taking a series of ref update instructions and fulfilling them one by one. I don't think we have such a program now, but it's certainly plausible. 2. The leaked entries appear as false positives to tools like valgrind. Let's relax this rule by keeping only "active" tempfiles on the list. We can do this easily by moving the list-add operation from prepare_tempfile_object to activate_tempfile, and adding a deletion in deactivate_tempfile. Existing callers do not need to be updated immediately. They'll continue to leak any tempfile objects they may have allocated, but that's no different than the status quo. We can clean them up individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
314 lines
8.1 KiB
C
314 lines
8.1 KiB
C
/*
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* State diagram and cleanup
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* -------------------------
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*
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* If the program exits while a temporary file is active, we want to
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* make sure that we remove it. This is done by remembering the active
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* temporary files in a linked list, `tempfile_list`. An `atexit(3)`
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* handler and a signal handler are registered, to clean up any active
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* temporary files.
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*
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* Because the signal handler can run at any time, `tempfile_list` and
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* the `tempfile` objects that comprise it must be kept in
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* self-consistent states at all times.
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*
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* The possible states of a `tempfile` object are as follows:
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*
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* - Uninitialized. In this state the object's `on_list` field must be
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* zero but the rest of its contents need not be initialized. As
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* soon as the object is used in any way, it is irrevocably
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* registered in `tempfile_list`, and `on_list` is set.
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*
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* - Active, file open (after `create_tempfile()` or
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* `reopen_tempfile()`). In this state:
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*
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* - the temporary file exists
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* - `active` is set
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* - `filename` holds the filename of the temporary file
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* - `fd` holds a file descriptor open for writing to it
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* - `fp` holds a pointer to an open `FILE` object if and only if
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* `fdopen_tempfile()` has been called on the object
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* - `owner` holds the PID of the process that created the file
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*
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* - Active, file closed (after `close_tempfile_gently()`). Same
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* as the previous state, except that the temporary file is closed,
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* `fd` is -1, and `fp` is `NULL`.
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*
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* - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
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* failed attempt to create a temporary file). In this state:
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*
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* - `active` is unset
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* - `filename` is empty (usually, though there are transitory
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* states in which this condition doesn't hold). Client code should
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* *not* rely on the filename being empty in this state.
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* - `fd` is -1 and `fp` is `NULL`
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* - the object is removed from `tempfile_list` (but could be used again)
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*
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* A temporary file is owned by the process that created it. The
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* `tempfile` has an `owner` field that records the owner's PID. This
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* field is used to prevent a forked process from deleting a temporary
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* file created by its parent.
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*/
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#include "cache.h"
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#include "tempfile.h"
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#include "sigchain.h"
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static VOLATILE_LIST_HEAD(tempfile_list);
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static void remove_tempfiles(int in_signal_handler)
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{
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pid_t me = getpid();
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volatile struct volatile_list_head *pos;
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list_for_each(pos, &tempfile_list) {
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struct tempfile *p = list_entry(pos, struct tempfile, list);
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if (!is_tempfile_active(p) || p->owner != me)
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continue;
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if (p->fd >= 0)
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close(p->fd);
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if (in_signal_handler)
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unlink(p->filename.buf);
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else
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unlink_or_warn(p->filename.buf);
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p->active = 0;
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}
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}
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static void remove_tempfiles_on_exit(void)
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{
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remove_tempfiles(0);
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}
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static void remove_tempfiles_on_signal(int signo)
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{
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remove_tempfiles(1);
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sigchain_pop(signo);
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raise(signo);
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}
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static void prepare_tempfile_object(struct tempfile *tempfile)
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{
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tempfile->fd = -1;
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tempfile->fp = NULL;
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tempfile->active = 0;
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tempfile->owner = 0;
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INIT_LIST_HEAD(&tempfile->list);
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strbuf_init(&tempfile->filename, 0);
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}
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static void activate_tempfile(struct tempfile *tempfile)
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{
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static int initialized;
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if (is_tempfile_active(tempfile))
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BUG("activate_tempfile called for active object");
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if (!initialized) {
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sigchain_push_common(remove_tempfiles_on_signal);
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atexit(remove_tempfiles_on_exit);
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initialized = 1;
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}
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volatile_list_add(&tempfile->list, &tempfile_list);
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tempfile->owner = getpid();
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tempfile->active = 1;
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}
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static void deactivate_tempfile(struct tempfile *tempfile)
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{
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tempfile->active = 0;
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strbuf_release(&tempfile->filename);
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volatile_list_del(&tempfile->list);
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}
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/* Make sure errno contains a meaningful value on error */
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int create_tempfile(struct tempfile *tempfile, const char *path)
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{
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prepare_tempfile_object(tempfile);
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strbuf_add_absolute_path(&tempfile->filename, path);
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tempfile->fd = open(tempfile->filename.buf,
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O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666);
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if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
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/* Try again w/o O_CLOEXEC: the kernel might not support it */
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tempfile->fd = open(tempfile->filename.buf,
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O_RDWR | O_CREAT | O_EXCL, 0666);
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if (tempfile->fd < 0) {
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deactivate_tempfile(tempfile);
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return -1;
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}
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activate_tempfile(tempfile);
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if (adjust_shared_perm(tempfile->filename.buf)) {
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int save_errno = errno;
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error("cannot fix permission bits on %s", tempfile->filename.buf);
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delete_tempfile(tempfile);
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errno = save_errno;
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return -1;
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}
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return tempfile->fd;
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}
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void register_tempfile(struct tempfile *tempfile, const char *path)
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{
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prepare_tempfile_object(tempfile);
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strbuf_add_absolute_path(&tempfile->filename, path);
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activate_tempfile(tempfile);
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}
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int mks_tempfile_sm(struct tempfile *tempfile,
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const char *template, int suffixlen, int mode)
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{
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prepare_tempfile_object(tempfile);
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strbuf_add_absolute_path(&tempfile->filename, template);
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tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
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if (tempfile->fd < 0) {
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deactivate_tempfile(tempfile);
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return -1;
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}
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activate_tempfile(tempfile);
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return tempfile->fd;
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}
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int mks_tempfile_tsm(struct tempfile *tempfile,
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const char *template, int suffixlen, int mode)
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{
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const char *tmpdir;
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prepare_tempfile_object(tempfile);
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tmpdir = getenv("TMPDIR");
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if (!tmpdir)
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tmpdir = "/tmp";
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strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
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tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
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if (tempfile->fd < 0) {
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deactivate_tempfile(tempfile);
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return -1;
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}
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activate_tempfile(tempfile);
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return tempfile->fd;
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}
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int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
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{
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int fd;
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struct strbuf full_template = STRBUF_INIT;
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strbuf_add_absolute_path(&full_template, template);
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fd = mks_tempfile_m(tempfile, full_template.buf, mode);
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if (fd < 0)
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die_errno("Unable to create temporary file '%s'",
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full_template.buf);
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strbuf_release(&full_template);
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return fd;
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}
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FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
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{
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if (!is_tempfile_active(tempfile))
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BUG("fdopen_tempfile() called for inactive object");
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if (tempfile->fp)
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BUG("fdopen_tempfile() called for open object");
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tempfile->fp = fdopen(tempfile->fd, mode);
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return tempfile->fp;
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}
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const char *get_tempfile_path(struct tempfile *tempfile)
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{
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if (!is_tempfile_active(tempfile))
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BUG("get_tempfile_path() called for inactive object");
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return tempfile->filename.buf;
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}
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int get_tempfile_fd(struct tempfile *tempfile)
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{
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if (!is_tempfile_active(tempfile))
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BUG("get_tempfile_fd() called for inactive object");
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return tempfile->fd;
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}
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FILE *get_tempfile_fp(struct tempfile *tempfile)
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{
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if (!is_tempfile_active(tempfile))
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BUG("get_tempfile_fp() called for inactive object");
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return tempfile->fp;
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}
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int close_tempfile_gently(struct tempfile *tempfile)
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{
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int fd;
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FILE *fp;
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int err;
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if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
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return 0;
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fd = tempfile->fd;
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fp = tempfile->fp;
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tempfile->fd = -1;
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if (fp) {
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tempfile->fp = NULL;
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if (ferror(fp)) {
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err = -1;
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if (!fclose(fp))
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errno = EIO;
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} else {
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err = fclose(fp);
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}
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} else {
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err = close(fd);
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}
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return err ? -1 : 0;
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}
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int reopen_tempfile(struct tempfile *tempfile)
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{
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if (!is_tempfile_active(tempfile))
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BUG("reopen_tempfile called for an inactive object");
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if (0 <= tempfile->fd)
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BUG("reopen_tempfile called for an open object");
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tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
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return tempfile->fd;
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}
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int rename_tempfile(struct tempfile *tempfile, const char *path)
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{
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if (!is_tempfile_active(tempfile))
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BUG("rename_tempfile called for inactive object");
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if (close_tempfile_gently(tempfile)) {
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delete_tempfile(tempfile);
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return -1;
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}
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if (rename(tempfile->filename.buf, path)) {
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int save_errno = errno;
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delete_tempfile(tempfile);
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errno = save_errno;
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return -1;
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}
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deactivate_tempfile(tempfile);
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return 0;
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}
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void delete_tempfile(struct tempfile *tempfile)
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{
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if (!is_tempfile_active(tempfile))
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return;
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close_tempfile_gently(tempfile);
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unlink_or_warn(tempfile->filename.buf);
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deactivate_tempfile(tempfile);
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}
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