FILE's lock is now always .#FILE and may be a regular file.

[bpt/emacs.git] / src / ChangeLog

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+2013-03-05  Paul Eggert  <eggert@cs.ucla.edu>
+
+       FILE's lock is now always .#FILE and may be a regular file (Bug#13807).
+       * filelock.c: Include <c-ctype.h>.
+       (MAX_LFINFO): New top-level constant.
+       (lock_info_type): Remove members pid, boot_time.  Add members at,
+       dot, colon.  Change user member to be the entire buffer, not a
+       pointer.  This allows us to handle the case where a foreign
+       pid or boot time exceeds the local range.  All uses changed.
+       (LINKS_MIGHT_NOT_WORK): New constant.
+       (FREE_LOCK_INFO): Remove, as the pieces no longer need freeing.
+       (defined_WINDOWSNT): Remove.
+       (MAKE_LOCK_NAME, file_in_lock_file_name):
+       Always use .#FILE (not .#-FILE) for the file lock,
+       even if it is a regular file.
+       (rename_lock_file): New function.
+       (create_lock_file): Use it.
+       (create_lock_file, read_lock_data):
+       Prefer a symbolic link for the lock file, falling back on a
+       regular file if symlinks don't work.  Do not try to create
+       symlinks on MS-Windows, due to security hassles.  Stick with
+       POSIXish functions (open, read, write, close, fchmod, readlink, symlink,
+       link, rename, unlink, mkstemp) when creating locks, as a GNUish
+       host may be using a Windowsish file system, and cannot use
+       MS-Windows-only system calls.  Fall back on mktemp if mkstemp
+       doesn't work.  Don't fail merely because of a symlink-contents
+       length limit in the current file system; fall back on regular
+       files.  Increase the symlink contents length limit to 8 KiB, this
+       should be big enough for any real use and doesn't crunch the
+       stack.
+       (create_lock_file, lock_file_1, read_lock_data):
+       Simplify allocation of lock file buffers now that they fit in 8 KiB.
+       (lock_file_1): Return error number, not bool.  All callers changed.
+       (ELOOP): New macro, if not already defined.
+       (read_lock_data): Return size of lock file contents, not Lisp object.
+       All callers changed.  Handle a race condition if some other process
+       replaces a regular-file lock with a symlink lock or vice versa,
+       while we're trying to read the lock.
+       (current_lock_owner): Parse contents more carefully, to help avoid
+       confusing a regular-file lock with some other application's use
+       of the file.  Check for lock file contents being too long, or
+       not parsing correctly.
+       (current_lock_owner, lock_file):
+       Allow foreign pid and boot times that exceed the local range.
+       (current_lock_owner, lock_if_free, lock_file):
+       Simplify allocation of lock file contents.
+       * w32.c (sys_rename_replace): New function, containing most of
+       the contents of the old sys_rename.
+       (sys_rename): Use it.
+       (fchmod): New dummy function.
+       * w32.h (sys_rename_replace, fchmod): New decls.
+
 2013-03-05  Eli Zaretskii  <eliz@gnu.org>
 
        * bidi.c (bidi_resolve_explicit_1): Don't call CHAR_TO_BYTE or