git

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/*
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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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 * - Inactive/unallocated. The only way to get a tempfile is via a creation
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 *   function like create_tempfile(). Once allocated, the tempfile is on the
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 *   global tempfile_list and considered active.
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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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 *   - `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). The struct is removed from
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 *   the global tempfile_list and deallocated.
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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 "git-compat-util.h"
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#include "abspath.h"
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#include "path.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 int remove_template_directory(struct tempfile *tempfile,
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				      int in_signal_handler)
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{
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	if (tempfile->directory) {
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		if (in_signal_handler)
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			return rmdir(tempfile->directory);
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		else
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			return rmdir_or_warn(tempfile->directory);
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	}
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	return 0;
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}
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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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		remove_template_directory(p, in_signal_handler);
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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 struct tempfile *new_tempfile(void)
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{
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	struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
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	tempfile->fd = -1;
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	tempfile->fp = NULL;
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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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	tempfile->directory = NULL;
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	return tempfile;
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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 (!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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}
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static void deactivate_tempfile(struct tempfile *tempfile)
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{
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	volatile_list_del(&tempfile->list);
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	strbuf_release(&tempfile->filename);
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	free(tempfile->directory);
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	free(tempfile);
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}
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/* Make sure errno contains a meaningful value on error */
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struct tempfile *create_tempfile_mode(const char *path, int mode)
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{
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	struct tempfile *tempfile = new_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, mode);
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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, mode);
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	if (tempfile->fd < 0) {
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		deactivate_tempfile(tempfile);
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		return NULL;
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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 NULL;
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	}
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	return tempfile;
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}
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struct tempfile *register_tempfile(const char *path)
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{
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	struct tempfile *tempfile = new_tempfile();
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	strbuf_add_absolute_path(&tempfile->filename, path);
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	activate_tempfile(tempfile);
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	return tempfile;
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}
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struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
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{
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	struct tempfile *tempfile = new_tempfile();
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	strbuf_add_absolute_path(&tempfile->filename, 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 NULL;
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	}
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	activate_tempfile(tempfile);
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	return tempfile;
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}
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struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
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{
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	struct tempfile *tempfile = new_tempfile();
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	const char *tmpdir;
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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, 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 NULL;
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	}
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	activate_tempfile(tempfile);
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	return tempfile;
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}
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struct tempfile *mks_tempfile_dt(const char *directory_template,
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				 const char *filename)
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{
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	struct tempfile *tempfile;
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	const char *tmpdir;
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	struct strbuf sb = STRBUF_INIT;
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	int fd;
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	size_t directorylen;
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	if (!ends_with(directory_template, "XXXXXX")) {
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		errno = EINVAL;
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		return NULL;
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	}
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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(&sb, "%s/%s", tmpdir, directory_template);
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	directorylen = sb.len;
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	if (!mkdtemp(sb.buf)) {
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		int orig_errno = errno;
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		strbuf_release(&sb);
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		errno = orig_errno;
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		return NULL;
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	}
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	strbuf_addf(&sb, "/%s", filename);
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	fd = open(sb.buf, O_CREAT | O_EXCL | O_RDWR, 0600);
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	if (fd < 0) {
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		int orig_errno = errno;
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		strbuf_setlen(&sb, directorylen);
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		rmdir(sb.buf);
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		strbuf_release(&sb);
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		errno = orig_errno;
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		return NULL;
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	}
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	tempfile = new_tempfile();
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	strbuf_swap(&tempfile->filename, &sb);
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	tempfile->directory = xmemdupz(tempfile->filename.buf, directorylen);
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	tempfile->fd = fd;
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	activate_tempfile(tempfile);
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	return tempfile;
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}
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struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
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{
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	struct tempfile *tempfile;
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	struct strbuf full_template = STRBUF_INIT;
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	strbuf_add_absolute_path(&full_template, filename_template);
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	tempfile = mks_tempfile_m(full_template.buf, mode);
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	if (!tempfile)
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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 tempfile;
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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|O_TRUNC);
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	return tempfile->fd;
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}
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int rename_tempfile(struct tempfile **tempfile_p, const char *path)
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{
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	struct tempfile *tempfile = *tempfile_p;
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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_p);
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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_p);
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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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	*tempfile_p = NULL;
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	return 0;
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}
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int delete_tempfile(struct tempfile **tempfile_p)
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{
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	struct tempfile *tempfile = *tempfile_p;
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	int err = 0;
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	if (!is_tempfile_active(tempfile))
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		return 0;
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	err |= close_tempfile_gently(tempfile);
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	err |= unlink_or_warn(tempfile->filename.buf);
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	err |= remove_template_directory(tempfile, 0);
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	deactivate_tempfile(tempfile);
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	*tempfile_p = NULL;
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	return err ? -1 : 0;
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}
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