git/tempfile.c

/*
 * State diagram and cleanup
 * -------------------------
 *
 * If the program exits while a temporary file is active, we want to
 * make sure that we remove it. This is done by remembering the active
 * temporary files in a linked list, `tempfile_list`. An `atexit(3)`
 * handler and a signal handler are registered, to clean up any active
 * temporary files.
 *
 * Because the signal handler can run at any time, `tempfile_list` and
 * the `tempfile` objects that comprise it must be kept in
 * self-consistent states at all times.
 *
 * The possible states of a `tempfile` object are as follows:
 *
 * - Inactive/unallocated. The only way to get a tempfile is via a creation
 *   function like create_tempfile(). Once allocated, the tempfile is on the
 *   global tempfile_list and considered active.
 *
 * - Active, file open (after `create_tempfile()` or
 *   `reopen_tempfile()`). In this state:
 *
 *   - the temporary file exists
 *   - `filename` holds the filename of the temporary file
 *   - `fd` holds a file descriptor open for writing to it
 *   - `fp` holds a pointer to an open `FILE` object if and only if
 *     `fdopen_tempfile()` has been called on the object
 *   - `owner` holds the PID of the process that created the file
 *
 * - Active, file closed (after `close_tempfile_gently()`). Same
 *   as the previous state, except that the temporary file is closed,
 *   `fd` is -1, and `fp` is `NULL`.
 *
 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
 *   failed attempt to create a temporary file). The struct is removed from
 *   the global tempfile_list and deallocated.
 *
 * A temporary file is owned by the process that created it. The
 * `tempfile` has an `owner` field that records the owner's PID. This
 * field is used to prevent a forked process from deleting a temporary
 * file created by its parent.
 */

#include "git-compat-util.h"
#include "abspath.h"
#include "path.h"
#include "tempfile.h"
#include "sigchain.h"

static VOLATILE_LIST_HEAD(tempfile_list);

static int remove_template_directory(struct tempfile *tempfile,
				      int in_signal_handler)
{ … }

static void remove_tempfiles(int in_signal_handler)
{ … }

static void remove_tempfiles_on_exit(void)
{ … }

static void remove_tempfiles_on_signal(int signo)
{ … }

static struct tempfile *new_tempfile(void)
{ … }

static void activate_tempfile(struct tempfile *tempfile)
{ … }

static void deactivate_tempfile(struct tempfile *tempfile)
{ … }

/* Make sure errno contains a meaningful value on error */
struct tempfile *create_tempfile_mode(const char *path, int mode)
{ … }

struct tempfile *register_tempfile(const char *path)
{ … }

struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
{ … }

struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
{ … }

struct tempfile *mks_tempfile_dt(const char *directory_template,
				 const char *filename)
{ … }

struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
{ … }

FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
{ … }

const char *get_tempfile_path(struct tempfile *tempfile)
{ … }

int get_tempfile_fd(struct tempfile *tempfile)
{ … }

FILE *get_tempfile_fp(struct tempfile *tempfile)
{ … }

int close_tempfile_gently(struct tempfile *tempfile)
{ … }

int reopen_tempfile(struct tempfile *tempfile)
{ … }

int rename_tempfile(struct tempfile **tempfile_p, const char *path)
{ … }

int delete_tempfile(struct tempfile **tempfile_p)
{ … }