/* Lock files for editing.
- Copyright (C) 1985-1987, 1993-1994, 1996, 1998-2012
- Free Software Foundation, Inc.
+ Copyright (C) 1985-1987, 1993-1994, 1996, 1998-2013 Free Software
+ Foundation, Inc.
This file is part of GNU Emacs.
#include <sys/stat.h>
#include <signal.h>
#include <stdio.h>
-#include <setjmp.h>
#ifdef HAVE_PWD_H
#include <pwd.h>
#include <errno.h>
#include "lisp.h"
-#include "buffer.h"
#include "character.h"
+#include "buffer.h"
#include "coding.h"
#include "systime.h"
+#ifdef WINDOWSNT
+#include <share.h>
+#include "w32.h" /* for dostounix_filename */
+#endif
#ifdef CLASH_DETECTION
/* Return the time of the last system boot. */
static time_t boot_time;
-static int boot_time_initialized;
+static bool boot_time_initialized;
#ifdef BOOT_TIME
-static void get_boot_time_1 (const char *, int);
+static void get_boot_time_1 (const char *, bool);
#endif
static time_t
{
char cmd_string[sizeof WTMP_FILE ".19.gz"];
Lisp_Object tempname, filename;
- int delete_flag = 0;
+ bool delete_flag = 0;
filename = Qnil;
- sprintf (cmd_string, "%s.%d", WTMP_FILE, counter);
- tempname = build_string (cmd_string);
+ tempname = make_formatted_string
+ (cmd_string, "%s.%d", WTMP_FILE, counter);
if (! NILP (Ffile_exists_p (tempname)))
filename = tempname;
else
{
- sprintf (cmd_string, "%s.%d.gz", WTMP_FILE, counter);
- tempname = build_string (cmd_string);
+ tempname = make_formatted_string (cmd_string, "%s.%d.gz",
+ WTMP_FILE, counter);
if (! NILP (Ffile_exists_p (tempname)))
{
Lisp_Object args[6];
If FILENAME is zero, use the same file as before;
if no FILENAME has ever been specified, this is the utmp file.
- Use the newest reboot record if NEWEST is nonzero,
+ Use the newest reboot record if NEWEST,
the first reboot record otherwise.
Ignore all reboot records on or before BOOT_TIME.
Success is indicated by setting BOOT_TIME to a larger value. */
void
-get_boot_time_1 (const char *filename, int newest)
+get_boot_time_1 (const char *filename, bool newest)
{
struct utmp ut, *utp;
int desc;
#define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0)
-/* Write the name of the lock file for FN into LFNAME. Length will be
- that of FN plus two more for the leading `.#' plus 1 for the
- trailing period plus one for the digit after it plus one for the
- null. */
-#define MAKE_LOCK_NAME(lock, file) \
- (lock = (char *) alloca (SBYTES (file) + 2 + 1 + 1 + 1), \
- fill_in_lock_file_name (lock, (file)))
+/* Write the name of the lock file for FNAME into LOCKNAME. Length
+ will be that of FN plus two more for the leading `.#' plus 1 for
+ the trailing period plus one for the digit after it plus one for
+ the null. */
+#define MAKE_LOCK_NAME(LOCKNAME, FNAME) \
+ (LOCKNAME = alloca (SBYTES (FNAME) + 2 + 1 + 1 + 1), \
+ fill_in_lock_file_name (LOCKNAME, (FNAME)))
+
+#ifdef WINDOWSNT
+/* 256 chars for user, 1024 chars for host, 10 digits for each of 2 int's. */
+#define MAX_LFINFO (256 + 1024 + 10 + 10 + 2)
+ /* min size: .@PID */
+#define IS_LOCK_FILE(ST) (MAX_LFINFO >= (ST).st_size && (ST).st_size >= 3)
+#else
+#define IS_LOCK_FILE(ST) S_ISLNK ((ST).st_mode)
+#endif
static void
fill_in_lock_file_name (register char *lockfile, register Lisp_Object fn)
{
+ ptrdiff_t length = SBYTES (fn);
register char *p;
struct stat st;
int count = 0;
/* Shift the nondirectory part of the file name (including the null)
right two characters. Here is one of the places where we'd have to
do something to support 14-character-max file names. */
- for (p = lockfile + strlen (lockfile); p != lockfile && *p != '/'; p--)
+ for (p = lockfile + length; p != lockfile && *p != '/'; p--)
p[2] = *p;
/* Insert the `.#'. */
p[1] = '.';
p[2] = '#';
- p = p + strlen (p);
+ p = lockfile + length + 2;
- while (lstat (lockfile, &st) == 0 && !S_ISLNK (st.st_mode))
+ while (lstat (lockfile, &st) == 0 && !IS_LOCK_FILE (st))
{
if (count > 9)
{
}
}
+static int
+create_lock_file (char *lfname, char *lock_info_str, bool force)
+{
+ int err;
+
+#ifdef WINDOWSNT
+ /* Symlinks are supported only by latest versions of Windows, and
+ creating them is a privileged operation that often triggers UAC
+ elevation prompts. Therefore, instead of using symlinks, we
+ create a regular file with the lock info written as its
+ contents. */
+ {
+ /* Deny everybody else any kind of access to the file until we are
+ done writing it and close the handle. This makes the entire
+ open/write/close operation atomic, as far as other processes
+ are concerned. */
+ int fd = _sopen (lfname,
+ _O_WRONLY | _O_BINARY | _O_CREAT | _O_EXCL | _O_NOINHERIT,
+ _SH_DENYRW, S_IREAD | S_IWRITE);
+
+ if (fd < 0 && errno == EEXIST && force)
+ fd = _sopen (lfname, _O_WRONLY | _O_BINARY | _O_TRUNC |_O_NOINHERIT,
+ _SH_DENYRW, S_IREAD | S_IWRITE);
+ if (fd >= 0)
+ {
+ ssize_t lock_info_len = strlen (lock_info_str);
+
+ err = 0;
+ if (emacs_write (fd, lock_info_str, lock_info_len) != lock_info_len)
+ err = -1;
+ if (emacs_close (fd))
+ err = -1;
+ }
+ else
+ err = -1;
+ }
+#else
+ err = symlink (lock_info_str, lfname);
+ if (errno == EEXIST && force)
+ {
+ unlink (lfname);
+ err = symlink (lock_info_str, lfname);
+ }
+#endif
+
+ return err;
+}
+
/* Lock the lock file named LFNAME.
- If FORCE is nonzero, we do so even if it is already locked.
- Return 1 if successful, 0 if not. */
+ If FORCE, do so even if it is already locked.
+ Return true if successful. */
-static int
-lock_file_1 (char *lfname, int force)
+static bool
+lock_file_1 (char *lfname, bool force)
{
- register int err;
- printmax_t boot, pid;
- const char *user_name;
- const char *host_name;
- char *lock_info_str;
- ptrdiff_t lock_info_size;
+ int err;
int symlink_errno;
USE_SAFE_ALLOCA;
/* Call this first because it can GC. */
- boot = get_boot_time ();
-
- if (STRINGP (Fuser_login_name (Qnil)))
- user_name = SSDATA (Fuser_login_name (Qnil));
- else
- user_name = "";
- if (STRINGP (Fsystem_name ()))
- host_name = SSDATA (Fsystem_name ());
- else
- host_name = "";
- lock_info_size = (strlen (user_name) + strlen (host_name)
- + 2 * INT_STRLEN_BOUND (printmax_t)
- + sizeof "@.:");
- SAFE_ALLOCA (lock_info_str, char *, lock_info_size);
- pid = getpid ();
+ printmax_t boot = get_boot_time ();
+
+ Lisp_Object luser_name = Fuser_login_name (Qnil);
+ char const *user_name = STRINGP (luser_name) ? SSDATA (luser_name) : "";
+ Lisp_Object lhost_name = Fsystem_name ();
+ char const *host_name = STRINGP (lhost_name) ? SSDATA (lhost_name) : "";
+ ptrdiff_t lock_info_size = (strlen (user_name) + strlen (host_name)
+ + 2 * INT_STRLEN_BOUND (printmax_t)
+ + sizeof "@.:");
+ char *lock_info_str = SAFE_ALLOCA (lock_info_size);
+ printmax_t pid = getpid ();
esprintf (lock_info_str, boot ? "%s@%s.%"pMd":%"pMd : "%s@%s.%"pMd,
user_name, host_name, pid, boot);
-
- err = symlink (lock_info_str, lfname);
- if (errno == EEXIST && force)
- {
- unlink (lfname);
- err = symlink (lock_info_str, lfname);
- }
+ err = create_lock_file (lfname, lock_info_str, force);
symlink_errno = errno;
SAFE_FREE ();
return err == 0;
}
-/* Return 1 if times A and B are no more than one second apart. */
+/* Return true if times A and B are no more than one second apart. */
-static int
+static bool
within_one_second (time_t a, time_t b)
{
return (a - b >= -1 && a - b <= 1);
}
\f
+static Lisp_Object
+read_lock_data (char *lfname)
+{
+#ifndef WINDOWSNT
+ return emacs_readlinkat (AT_FDCWD, lfname);
+#else
+ int fd = emacs_open (lfname, O_RDONLY | O_BINARY, S_IREAD);
+ ssize_t nbytes;
+ char lfinfo[MAX_LFINFO + 1];
+
+ if (fd < 0)
+ return Qnil;
+
+ nbytes = emacs_read (fd, lfinfo, MAX_LFINFO);
+ emacs_close (fd);
+
+ if (nbytes > 0)
+ {
+ lfinfo[nbytes] = '\0';
+ return build_string (lfinfo);
+ }
+ else
+ return Qnil;
+#endif
+}
+
/* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete,
1 if another process owns it (and set OWNER (if non-null) to info),
2 if the current process owns it,
lock_info_type local_owner;
intmax_t n;
char *at, *dot, *colon;
- char readlink_buf[READLINK_BUFSIZE];
- char *lfinfo = emacs_readlink (lfname, readlink_buf);
+ Lisp_Object lfinfo_object = read_lock_data (lfname);
+ char *lfinfo;
+ struct gcpro gcpro1;
/* If nonexistent lock file, all is well; otherwise, got strange error. */
- if (!lfinfo)
+ if (NILP (lfinfo_object))
return errno == ENOENT ? 0 : -1;
+ lfinfo = SSDATA (lfinfo_object);
/* Even if the caller doesn't want the owner info, we still have to
read it to determine return value. */
at = strrchr (lfinfo, '@');
dot = strrchr (lfinfo, '.');
if (!at || !dot)
- {
- if (lfinfo != readlink_buf)
- xfree (lfinfo);
- return -1;
- }
+ return -1;
len = at - lfinfo;
- owner->user = (char *) xmalloc (len + 1);
+ GCPRO1 (lfinfo_object);
+ owner->user = xmalloc (len + 1);
memcpy (owner->user, lfinfo, len);
owner->user[len] = 0;
/* The host is everything in between. */
len = dot - at - 1;
- owner->host = (char *) xmalloc (len + 1);
+ owner->host = xmalloc (len + 1);
memcpy (owner->host, at + 1, len);
owner->host[len] = 0;
/* We're done looking at the link info. */
- if (lfinfo != readlink_buf)
- xfree (lfinfo);
+ UNGCPRO;
/* On current host? */
if (STRINGP (Fsystem_name ())
static int
lock_if_free (lock_info_type *clasher, register char *lfname)
{
- while (lock_file_1 (lfname, 0) == 0)
+ while (! lock_file_1 (lfname, 0))
{
int locker;
struct gcpro gcpro1;
USE_SAFE_ALLOCA;
+ /* Don't do locking if the user has opted out. */
+ if (! create_lockfiles)
+ return;
+
/* Don't do locking while dumping Emacs.
Uncompressing wtmp files uses call-process, which does not work
in an uninitialized Emacs. */
orig_fn = fn;
GCPRO1 (fn);
fn = Fexpand_file_name (fn, Qnil);
+#ifdef WINDOWSNT
+ /* Ensure we have only '/' separators, to avoid problems with
+ looking (inside fill_in_lock_file_name) for backslashes in file
+ names encoded by some DBCS codepage. */
+ dostounix_filename (SSDATA (fn), 1);
+#endif
encoded_fn = ENCODE_FILE (fn);
/* Create the name of the lock-file for file fn */
locker_size = (strlen (lock_info.user) + strlen (lock_info.host)
+ INT_STRLEN_BOUND (printmax_t)
+ sizeof "@ (pid )");
- SAFE_ALLOCA (locker, char *, locker_size);
+ locker = SAFE_ALLOCA (locker_size);
pid = lock_info.pid;
esprintf (locker, "%s@%s (pid %"pMd")",
lock_info.user, lock_info.host, pid);
return ret;
}
-\f
-/* Initialization functions. */
-
-void
-init_filelock (void)
-{
- boot_time = 0;
- boot_time_initialized = 0;
-}
#endif /* CLASH_DETECTION */
doc: /* The directory for writing temporary files. */);
Vtemporary_file_directory = Qnil;
+ DEFVAR_BOOL ("create-lockfiles", create_lockfiles,
+ doc: /* Non-nil means use lockfiles to avoid editing collisions. */);
+ create_lockfiles = 1;
+
#ifdef CLASH_DETECTION
defsubr (&Sunlock_buffer);
defsubr (&Slock_buffer);