/* Lock files for editing.
- Copyright (C) 1985, 1986, 1987, 1993, 1994, 1996, 1998, 1999, 2000, 2001,
- 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 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>
#endif
#include <sys/file.h>
-#ifdef HAVE_FCNTL_H
#include <fcntl.h>
-#endif
-#ifdef HAVE_STRING_H
-#include <string.h>
-#endif
-
-#ifdef HAVE_UNISTD_H
#include <unistd.h>
-#endif
#ifdef __FreeBSD__
#include <sys/sysctl.h>
#endif /* __FreeBSD__ */
#include <errno.h>
-#ifndef errno
-extern int errno;
-#endif
+
+#include <c-ctype.h>
#include "lisp.h"
-#include "buffer.h"
#include "character.h"
+#include "buffer.h"
#include "coding.h"
#include "systime.h"
-
-/* The directory for writing temporary files. */
-
-Lisp_Object Vtemporary_file_directory;
+#ifdef WINDOWSNT
+#include <share.h>
+#include <sys/socket.h> /* for fcntl */
+#include "w32.h" /* for dostounix_filename */
+#endif
#ifdef CLASH_DETECTION
#include <utmp.h>
#endif
-#if !defined (S_ISLNK) && defined (S_IFLNK)
-#define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
-#endif
-
/* A file whose last-modified time is just after the most recent boot.
Define this to be NULL to disable checking for this file. */
#ifndef BOOT_TIME_FILE
#define WTMP_FILE "/var/log/wtmp"
#endif
-/* The strategy: to lock a file FN, create a symlink .#FN in FN's
+/* Normally use a symbolic link to represent a lock.
+ The strategy: to lock a file FN, create a symlink .#FN in FN's
directory, with link data `user@host.pid'. This avoids a single
mount (== failure) point for lock files.
has contributed this implementation for Emacs), and was designed by
Ethan Jacobson, Kimbo Mundy, and others.
- --karl@cs.umb.edu/karl@hq.ileaf.com. */
+ --karl@cs.umb.edu/karl@hq.ileaf.com.
+
+ On some file systems, notably those of MS-Windows, symbolic links
+ do not work well, so instead of a symlink .#FN -> 'user@host.pid',
+ the lock is a regular file .#FN with contents 'user@host.pid'. To
+ establish a lock, a nonce file is created and then renamed to .#FN.
+ On MS-Windows this renaming is atomic unless the lock is forcibly
+ acquired. On other systems the renaming is atomic if the lock is
+ forcibly acquired; if not, the renaming is done via hard links,
+ which is good enough for lock-file purposes.
+
+ To summarize, race conditions can occur with either:
+
+ * Forced locks on MS-Windows systems.
+
+ * Non-forced locks on non-MS-Windows systems that support neither
+ hard nor symbolic links. */
\f
/* Return the time of the last system boot. */
static time_t boot_time;
-static int boot_time_initialized;
-
-extern Lisp_Object Vshell_file_name;
+static bool boot_time_initialized;
#ifdef BOOT_TIME
-static void get_boot_time_1 P_ ((char *, int));
+static void get_boot_time_1 (const char *, bool);
#endif
static time_t
-get_boot_time ()
+get_boot_time (void)
{
#if defined (BOOT_TIME)
int counter;
since utmp is typically much smaller than wtmp.
Passing a null pointer causes get_boot_time_1
to inspect the default file, namely utmp. */
- get_boot_time_1 ((char *) 0, 0);
+ get_boot_time_1 (0, 0);
if (boot_time)
return boot_time;
/* If we did not find a boot time in wtmp, look at wtmp, and so on. */
for (counter = 0; counter < 20 && ! boot_time; counter++)
{
- char cmd_string[100];
+ 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];
character long prefix, and call make_temp_file with
second arg non-zero, so that it will add not more
than 6 characters to the prefix. */
- tempname = Fexpand_file_name (build_string ("wt"),
+ filename = Fexpand_file_name (build_string ("wt"),
Vtemporary_file_directory);
- tempname = make_temp_name (tempname, 1);
- args[0] = Vshell_file_name;
+ filename = make_temp_name (filename, 1);
+ args[0] = build_string ("gzip");
args[1] = Qnil;
- args[2] = Qnil;
+ args[2] = list2 (QCfile, filename);
args[3] = Qnil;
- args[4] = build_string ("-c");
- sprintf (cmd_string, "gunzip < %s.%d.gz > %s",
- WTMP_FILE, counter, SDATA (tempname));
- args[5] = build_string (cmd_string);
+ args[4] = build_string ("-cd");
+ args[5] = tempname;
Fcall_process (6, args);
- filename = tempname;
delete_flag = 1;
}
}
if (! NILP (filename))
{
- get_boot_time_1 (SDATA (filename), 1);
+ get_boot_time_1 (SSDATA (filename), 1);
if (delete_flag)
- unlink (SDATA (filename));
+ unlink (SSDATA (filename));
}
}
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 (filename, newest)
- char *filename;
- int newest;
+get_boot_time_1 (const char *filename, bool newest)
{
struct utmp ut, *utp;
- int desc;
if (filename)
{
/* On some versions of IRIX, opening a nonexistent file name
is likely to crash in the utmp routines. */
- desc = emacs_open (filename, O_RDONLY, 0);
- if (desc < 0)
+ if (faccessat (AT_FDCWD, filename, R_OK, AT_EACCESS) != 0)
return;
- emacs_close (desc);
-
utmpname (filename);
}
}
#endif /* BOOT_TIME */
\f
+/* An arbitrary limit on lock contents length. 8 K should be plenty
+ big enough in practice. */
+enum { MAX_LFINFO = 8 * 1024 };
+
/* Here is the structure that stores information about a lock. */
typedef struct
{
- char *user;
- char *host;
- unsigned long pid;
- time_t boot_time;
-} lock_info_type;
+ /* Location of '@', '.', ':' in USER. If there's no colon, COLON
+ points to the end of USER. */
+ char *at, *dot, *colon;
-/* When we read the info back, we might need this much more,
- enough for decimal representation plus null. */
-#define LOCK_PID_MAX (4 * sizeof (unsigned long))
+ /* Lock file contents USER@HOST.PID with an optional :BOOT_TIME
+ appended. This memory is used as a lock file contents buffer, so
+ it needs room for MAX_LFINFO + 1 bytes. A string " (pid NNNN)"
+ may be appended to the USER@HOST while generating a diagnostic,
+ so make room for its extra bytes (as opposed to ".NNNN") too. */
+ char user[MAX_LFINFO + 1 + sizeof " (pid )" - sizeof "."];
+} lock_info_type;
-/* Free the two dynamically-allocated pieces in PTR. */
-#define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0)
+/* Write the name of the lock file for FNAME into LOCKNAME. Length
+ will be that of FNAME plus two more for the leading ".#", plus one
+ for the null. */
+#define MAKE_LOCK_NAME(lockname, fname) \
+ (lockname = SAFE_ALLOCA (SBYTES (fname) + 2 + 1), \
+ fill_in_lock_file_name (lockname, fname))
+static void
+fill_in_lock_file_name (char *lockfile, Lisp_Object fn)
+{
+ char *last_slash = memrchr (SSDATA (fn), '/', SBYTES (fn));
+ char *base = last_slash + 1;
+ ptrdiff_t dirlen = base - SSDATA (fn);
+ memcpy (lockfile, SSDATA (fn), dirlen);
+ lockfile[dirlen] = '.';
+ lockfile[dirlen + 1] = '#';
+ strcpy (lockfile + dirlen + 2, base);
+}
-/* 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)))
+/* For some reason Linux kernels return EPERM on file systems that do
+ not support hard or symbolic links. This symbol documents the quirk.
+ There is no way to tell whether a symlink call fails due to
+ permissions issues or because links are not supported, but luckily
+ the lock file code should work either way. */
+enum { LINKS_MIGHT_NOT_WORK = EPERM };
-static void
-fill_in_lock_file_name (lockfile, fn)
- register char *lockfile;
- register Lisp_Object fn;
+/* Rename OLD to NEW. If FORCE, replace any existing NEW.
+ It is OK if there are temporarily two hard links to OLD.
+ Return 0 if successful, -1 (setting errno) otherwise. */
+static int
+rename_lock_file (char const *old, char const *new, bool force)
{
- register char *p;
- struct stat st;
- int count = 0;
+#ifdef WINDOWSNT
+ return sys_rename_replace (old, new, force);
+#else
+ if (! force)
+ {
+ struct stat st;
+
+ if (link (old, new) == 0)
+ return unlink (old) == 0 || errno == ENOENT ? 0 : -1;
+ if (errno != ENOSYS && errno != LINKS_MIGHT_NOT_WORK)
+ return -1;
+
+ /* 'link' does not work on this file system. This can occur on
+ a GNU/Linux host mounting a FAT32 file system. Fall back on
+ 'rename' after checking that NEW does not exist. There is a
+ potential race condition since some other process may create
+ NEW immediately after the existence check, but it's the best
+ we can portably do here. */
+ if (lstat (new, &st) == 0 || errno == EOVERFLOW)
+ {
+ errno = EEXIST;
+ return -1;
+ }
+ if (errno != ENOENT)
+ return -1;
+ }
- strcpy (lockfile, SDATA (fn));
+ return rename (old, new);
+#endif
+}
- /* 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--)
- p[2] = *p;
+/* Create the lock file LFNAME with contents LOCK_INFO_STR. Return 0 if
+ successful, an errno value on failure. If FORCE, remove any
+ existing LFNAME if necessary. */
- /* Insert the `.#'. */
- p[1] = '.';
- p[2] = '#';
+static int
+create_lock_file (char *lfname, char *lock_info_str, bool force)
+{
+#ifdef WINDOWSNT
+ /* Symlinks are supported only by later versions of Windows, and
+ creating them is a privileged operation that often triggers
+ User Account Control elevation prompts. Avoid the problem by
+ pretending that 'symlink' does not work. */
+ int err = ENOSYS;
+#else
+ int err = symlink (lock_info_str, lfname) == 0 ? 0 : errno;
+#endif
- p = p + strlen (p);
+ if (err == EEXIST && force)
+ {
+ unlink (lfname);
+ err = symlink (lock_info_str, lfname) == 0 ? 0 : errno;
+ }
- while (lstat (lockfile, &st) == 0 && !S_ISLNK (st.st_mode))
+ if (err == ENOSYS || err == LINKS_MIGHT_NOT_WORK || err == ENAMETOOLONG)
{
- if (count > 9)
+ static char const nonce_base[] = ".#-emacsXXXXXX";
+ char *last_slash = strrchr (lfname, '/');
+ ptrdiff_t lfdirlen = last_slash + 1 - lfname;
+ USE_SAFE_ALLOCA;
+ char *nonce = SAFE_ALLOCA (lfdirlen + sizeof nonce_base);
+ int fd;
+ memcpy (nonce, lfname, lfdirlen);
+ strcpy (nonce + lfdirlen, nonce_base);
+
+ fd = mkostemp (nonce, O_BINARY | O_CLOEXEC);
+ if (fd < 0)
+ err = errno;
+ else
{
- *p = '\0';
- return;
+ ptrdiff_t lock_info_len;
+ if (! O_CLOEXEC)
+ fcntl (fd, F_SETFD, FD_CLOEXEC);
+ lock_info_len = strlen (lock_info_str);
+ err = 0;
+ /* Use 'write', not 'emacs_write', as garbage collection
+ might signal an error, which would leak FD. */
+ if (write (fd, lock_info_str, lock_info_len) != lock_info_len
+ || fchmod (fd, S_IRUSR | S_IRGRP | S_IROTH) != 0)
+ err = errno;
+ /* There is no need to call fsync here, as the contents of
+ the lock file need not survive system crashes. */
+ if (emacs_close (fd) != 0)
+ err = errno;
+ if (!err && rename_lock_file (nonce, lfname, force) != 0)
+ err = errno;
+ if (err)
+ unlink (nonce);
}
- sprintf (p, ".%d", count++);
+
+ SAFE_FREE ();
}
+
+ 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 0 if successful, an error number on failure. */
static int
-lock_file_1 (lfname, force)
- char *lfname;
- int force;
+lock_file_1 (char *lfname, bool force)
{
- register int err;
- time_t boot_time;
- char *user_name;
- char *host_name;
- char *lock_info_str;
-
/* Call this first because it can GC. */
- boot_time = get_boot_time ();
-
- if (STRINGP (Fuser_login_name (Qnil)))
- user_name = (char *)SDATA (Fuser_login_name (Qnil));
- else
- user_name = "";
- if (STRINGP (Fsystem_name ()))
- host_name = (char *)SDATA (Fsystem_name ());
- else
- host_name = "";
- lock_info_str = (char *)alloca (strlen (user_name) + strlen (host_name)
- + LOCK_PID_MAX + 30);
+ printmax_t boot = get_boot_time ();
- if (boot_time)
- sprintf (lock_info_str, "%s@%s.%lu:%lu", user_name, host_name,
- (unsigned long) getpid (), (unsigned long) boot_time);
- else
- sprintf (lock_info_str, "%s@%s.%lu", user_name, host_name,
- (unsigned long) getpid ());
+ 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) : "";
+ char lock_info_str[MAX_LFINFO + 1];
+ printmax_t pid = getpid ();
- err = symlink (lock_info_str, lfname);
- if (errno == EEXIST && force)
+ if (boot)
{
- unlink (lfname);
- err = symlink (lock_info_str, lfname);
+ if (sizeof lock_info_str
+ <= snprintf (lock_info_str, sizeof lock_info_str,
+ "%s@%s.%"pMd":%"pMd,
+ user_name, host_name, pid, boot))
+ return ENAMETOOLONG;
}
+ else if (sizeof lock_info_str
+ <= snprintf (lock_info_str, sizeof lock_info_str,
+ "%s@%s.%"pMd,
+ user_name, host_name, pid))
+ return ENAMETOOLONG;
- return err == 0;
+ return create_lock_file (lfname, lock_info_str, force);
}
-/* 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. */
-int
-within_one_second (a, b)
- time_t a, b;
+static bool
+within_one_second (time_t a, time_t b)
{
return (a - b >= -1 && a - b <= 1);
}
\f
+/* On systems lacking ELOOP, test for an errno value that shouldn't occur. */
+#ifndef ELOOP
+# define ELOOP (-1)
+#endif
+
+/* Read the data for the lock file LFNAME into LFINFO. Read at most
+ MAX_LFINFO + 1 bytes. Return the number of bytes read, or -1
+ (setting errno) on error. */
+
+static ptrdiff_t
+read_lock_data (char *lfname, char lfinfo[MAX_LFINFO + 1])
+{
+ ptrdiff_t nbytes;
+
+ while ((nbytes = readlinkat (AT_FDCWD, lfname, lfinfo, MAX_LFINFO + 1)) < 0
+ && errno == EINVAL)
+ {
+ int fd = emacs_open (lfname, O_RDONLY | O_BINARY | O_NOFOLLOW, 0);
+ if (0 <= fd)
+ {
+ /* Use read, not emacs_read, since FD isn't unwind-protected. */
+ ptrdiff_t read_bytes = read (fd, lfinfo, MAX_LFINFO + 1);
+ int read_errno = errno;
+ if (emacs_close (fd) != 0)
+ return -1;
+ errno = read_errno;
+ return read_bytes;
+ }
+
+ if (errno != ELOOP)
+ return -1;
+
+ /* readlinkat saw a non-symlink, but emacs_open saw a symlink.
+ The former must have been removed and replaced by the latter.
+ Try again. */
+ QUIT;
+ }
+
+ return nbytes;
+}
+
/* 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,
or -1 if something is wrong with the locking mechanism. */
static int
-current_lock_owner (owner, lfname)
- lock_info_type *owner;
- char *lfname;
+current_lock_owner (lock_info_type *owner, char *lfname)
{
-#ifndef index
- extern char *rindex (), *index ();
-#endif
- int len, ret;
- int local_owner = 0;
- char *at, *dot, *colon;
- char *lfinfo = 0;
- int bufsize = 50;
- /* Read arbitrarily-long contents of symlink. Similar code in
- file-symlink-p in fileio.c. */
- do
- {
- bufsize *= 2;
- lfinfo = (char *) xrealloc (lfinfo, bufsize);
- errno = 0;
- len = readlink (lfname, lfinfo, bufsize);
-#ifdef ERANGE
- /* HP-UX reports ERANGE if the buffer is too small. */
- if (len == -1 && errno == ERANGE)
- len = bufsize;
-#endif
- }
- while (len >= bufsize);
-
- /* If nonexistent lock file, all is well; otherwise, got strange error. */
- if (len == -1)
- {
- xfree (lfinfo);
- return errno == ENOENT ? 0 : -1;
- }
-
- /* Link info exists, so `len' is its length. Null terminate. */
- lfinfo[len] = 0;
+ int ret;
+ lock_info_type local_owner;
+ ptrdiff_t lfinfolen;
+ intmax_t pid, boot_time;
+ char *at, *dot, *lfinfo_end;
/* Even if the caller doesn't want the owner info, we still have to
- read it to determine return value, so allocate it. */
+ read it to determine return value. */
if (!owner)
- {
- owner = (lock_info_type *) alloca (sizeof (lock_info_type));
- local_owner = 1;
- }
+ owner = &local_owner;
+
+ /* If nonexistent lock file, all is well; otherwise, got strange error. */
+ lfinfolen = read_lock_data (lfname, owner->user);
+ if (lfinfolen < 0)
+ return errno == ENOENT ? 0 : -1;
+ if (MAX_LFINFO < lfinfolen)
+ return -1;
+ owner->user[lfinfolen] = 0;
/* Parse USER@HOST.PID:BOOT_TIME. If can't parse, return -1. */
/* The USER is everything before the last @. */
- at = rindex (lfinfo, '@');
- dot = rindex (lfinfo, '.');
- if (!at || !dot)
- {
- xfree (lfinfo);
- return -1;
- }
- len = at - lfinfo;
- owner->user = (char *) xmalloc (len + 1);
- strncpy (owner->user, lfinfo, len);
- owner->user[len] = 0;
+ owner->at = at = memrchr (owner->user, '@', lfinfolen);
+ if (!at)
+ return -1;
+ owner->dot = dot = strrchr (at, '.');
+ if (!dot)
+ return -1;
/* The PID is everything from the last `.' to the `:'. */
- owner->pid = atoi (dot + 1);
- colon = dot;
- while (*colon && *colon != ':')
- colon++;
+ if (! c_isdigit (dot[1]))
+ return -1;
+ errno = 0;
+ pid = strtoimax (dot + 1, &owner->colon, 10);
+ if (errno == ERANGE)
+ pid = -1;
+
/* After the `:', if there is one, comes the boot time. */
- if (*colon == ':')
- owner->boot_time = atoi (colon + 1);
- else
- owner->boot_time = 0;
+ switch (owner->colon[0])
+ {
+ case 0:
+ boot_time = 0;
+ lfinfo_end = owner->colon;
+ break;
- /* The host is everything in between. */
- len = dot - at - 1;
- owner->host = (char *) xmalloc (len + 1);
- strncpy (owner->host, at + 1, len);
- owner->host[len] = 0;
+ case ':':
+ if (! c_isdigit (owner->colon[1]))
+ return -1;
+ boot_time = strtoimax (owner->colon + 1, &lfinfo_end, 10);
+ break;
- /* We're done looking at the link info. */
- xfree (lfinfo);
+ default:
+ return -1;
+ }
+ if (lfinfo_end != owner->user + lfinfolen)
+ return -1;
/* On current host? */
- if (STRINGP (Fsystem_name ())
- && strcmp (owner->host, SDATA (Fsystem_name ())) == 0)
+ if (STRINGP (Vsystem_name)
+ && dot - (at + 1) == SBYTES (Vsystem_name)
+ && memcmp (at + 1, SSDATA (Vsystem_name), SBYTES (Vsystem_name)) == 0)
{
- if (owner->pid == getpid ())
+ if (pid == getpid ())
ret = 2; /* We own it. */
- else if (owner->pid > 0
- && (kill (owner->pid, 0) >= 0 || errno == EPERM)
- && (owner->boot_time == 0
- || within_one_second (owner->boot_time, get_boot_time ())))
+ else if (0 < pid && pid <= TYPE_MAXIMUM (pid_t)
+ && (kill (pid, 0) >= 0 || errno == EPERM)
+ && (boot_time == 0
+ || (boot_time <= TYPE_MAXIMUM (time_t)
+ && within_one_second (boot_time, get_boot_time ()))))
ret = 1; /* An existing process on this machine owns it. */
- /* The owner process is dead or has a strange pid (<=0), so try to
+ /* The owner process is dead or has a strange pid, so try to
zap the lockfile. */
- else if (unlink (lfname) < 0)
- ret = -1;
else
- ret = 0;
+ return unlink (lfname);
}
else
{ /* If we wanted to support the check for stale locks on remote machines,
ret = 1;
}
- /* Avoid garbage. */
- if (local_owner || ret <= 0)
- {
- FREE_LOCK_INFO (*owner);
- }
return ret;
}
Return -1 if cannot lock for any other reason. */
static int
-lock_if_free (clasher, lfname)
- lock_info_type *clasher;
- register char *lfname;
+lock_if_free (lock_info_type *clasher, char *lfname)
{
- while (lock_file_1 (lfname, 0) == 0)
+ int err;
+ while ((err = lock_file_1 (lfname, 0)) == EEXIST)
{
- int locker;
-
- if (errno != EEXIST)
- return -1;
-
- locker = current_lock_owner (clasher, lfname);
- if (locker == 2)
- {
- FREE_LOCK_INFO (*clasher);
- return 0; /* We ourselves locked it. */
- }
- else if (locker == 1)
- return 1; /* Someone else has it. */
- else if (locker == -1)
- return -1; /* current_lock_owner returned strange error. */
+ switch (current_lock_owner (clasher, lfname))
+ {
+ case 2:
+ return 0; /* We ourselves locked it. */
+ case 1:
+ return 1; /* Someone else has it. */
+ case -1:
+ return -1; /* current_lock_owner returned strange error. */
+ }
/* We deleted a stale lock; try again to lock the file. */
}
- return 0;
+
+ return err ? -1 : 0;
}
/* lock_file locks file FN,
decided to go ahead without locking.
When this returns, either the lock is locked for us,
+ or lock creation failed,
or the user has said to go ahead without locking.
If the file is locked by someone else, this calls
take away the lock, or return nil meaning ignore the lock. */
void
-lock_file (fn)
- Lisp_Object fn;
+lock_file (Lisp_Object fn)
{
- register Lisp_Object attack, orig_fn, encoded_fn;
- register char *lfname, *locker;
+ Lisp_Object orig_fn, encoded_fn;
+ char *lfname;
lock_info_type lock_info;
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
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));
+#endif
encoded_fn = ENCODE_FILE (fn);
/* Create the name of the lock-file for file fn */
call1 (intern ("ask-user-about-supersession-threat"), fn);
}
- UNGCPRO;
- /* Try to lock the lock. */
- if (lock_if_free (&lock_info, lfname) <= 0)
- /* Return now if we have locked it, or if lock creation failed */
- return;
-
- /* Else consider breaking the lock */
- locker = (char *) alloca (strlen (lock_info.user) + strlen (lock_info.host)
- + LOCK_PID_MAX + 9);
- sprintf (locker, "%s@%s (pid %lu)", lock_info.user, lock_info.host,
- lock_info.pid);
- FREE_LOCK_INFO (lock_info);
-
- attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker));
- if (!NILP (attack))
- /* User says take the lock */
+ /* Try to lock the lock. */
+ if (0 < lock_if_free (&lock_info, lfname))
{
- lock_file_1 (lfname, 1);
- return;
+ /* Someone else has the lock. Consider breaking it. */
+ Lisp_Object attack;
+ char *dot = lock_info.dot;
+ ptrdiff_t pidlen = lock_info.colon - (dot + 1);
+ static char const replacement[] = " (pid ";
+ int replacementlen = sizeof replacement - 1;
+ memmove (dot + replacementlen, dot + 1, pidlen);
+ strcpy (dot + replacementlen + pidlen, ")");
+ memcpy (dot, replacement, replacementlen);
+ attack = call2 (intern ("ask-user-about-lock"), fn,
+ build_string (lock_info.user));
+ /* Take the lock if the user said so. */
+ if (!NILP (attack))
+ lock_file_1 (lfname, 1);
}
- /* User says ignore the lock */
+
+ UNGCPRO;
+ SAFE_FREE ();
}
void
-unlock_file (fn)
- register Lisp_Object fn;
+unlock_file (Lisp_Object fn)
{
- register char *lfname;
+ char *lfname;
+ USE_SAFE_ALLOCA;
fn = Fexpand_file_name (fn, Qnil);
fn = ENCODE_FILE (fn);
if (current_lock_owner (0, lfname) == 2)
unlink (lfname);
+
+ SAFE_FREE ();
}
void
-unlock_all_files ()
+unlock_all_files (void)
{
- register Lisp_Object tail;
+ register Lisp_Object tail, buf;
register struct buffer *b;
- for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail))
+ FOR_EACH_LIVE_BUFFER (tail, buf)
{
- b = XBUFFER (XCDR (XCAR (tail)));
- if (STRINGP (b->file_truename) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b))
- {
- unlock_file(b->file_truename);
- }
+ b = XBUFFER (buf);
+ if (STRINGP (BVAR (b, file_truename))
+ && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b))
+ unlock_file (BVAR (b, file_truename));
}
}
\f
doc: /* Lock FILE, if current buffer is modified.
FILE defaults to current buffer's visited file,
or else nothing is done if current buffer isn't visiting a file. */)
- (file)
- Lisp_Object file;
+ (Lisp_Object file)
{
if (NILP (file))
- file = current_buffer->file_truename;
+ file = BVAR (current_buffer, file_truename);
else
CHECK_STRING (file);
if (SAVE_MODIFF < MODIFF
doc: /* Unlock the file visited in the current buffer.
If the buffer is not modified, this does nothing because the file
should not be locked in that case. */)
- ()
+ (void)
{
if (SAVE_MODIFF < MODIFF
- && STRINGP (current_buffer->file_truename))
- unlock_file (current_buffer->file_truename);
+ && STRINGP (BVAR (current_buffer, file_truename)))
+ unlock_file (BVAR (current_buffer, file_truename));
return Qnil;
}
/* Unlock the file visited in buffer BUFFER. */
void
-unlock_buffer (buffer)
- struct buffer *buffer;
+unlock_buffer (struct buffer *buffer)
{
if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer)
- && STRINGP (buffer->file_truename))
- unlock_file (buffer->file_truename);
+ && STRINGP (BVAR (buffer, file_truename)))
+ unlock_file (BVAR (buffer, file_truename));
}
DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 1, 1, 0,
doc: /* Return a value indicating whether FILENAME is locked.
The value is nil if the FILENAME is not locked,
t if it is locked by you, else a string saying which user has locked it. */)
- (filename)
- Lisp_Object filename;
+ (Lisp_Object filename)
{
Lisp_Object ret;
- register char *lfname;
+ char *lfname;
int owner;
lock_info_type locker;
+ USE_SAFE_ALLOCA;
filename = Fexpand_file_name (filename, Qnil);
else if (owner == 2)
ret = Qt;
else
- ret = build_string (locker.user);
-
- if (owner > 0)
- FREE_LOCK_INFO (locker);
+ ret = make_string (locker.user, locker.at - locker.user);
+ SAFE_FREE ();
return ret;
}
-\f
-/* Initialization functions. */
-void
-init_filelock ()
-{
- boot_time = 0;
- boot_time_initialized = 0;
-}
+#endif /* CLASH_DETECTION */
void
-syms_of_filelock ()
+syms_of_filelock (void)
{
- DEFVAR_LISP ("temporary-file-directory", &Vtemporary_file_directory,
+ DEFVAR_LISP ("temporary-file-directory", Vtemporary_file_directory,
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);
defsubr (&Sfile_locked_p);
+#endif
}
-
-#endif /* CLASH_DETECTION */
-
-/* arch-tag: e062676d-50b2-4be0-ab96-197c81b181a1
- (do not change this comment) */