SCCS version control cannot cope when latest delta is of type 'removed'

SCCS version control cannot cope when latest delta is of type 'removed'

[Chet Wood]

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In GNU Emacs 21.4.1 (sparc-sun-solaris2.8, X toolkit)
 of 2005-12-14 on pkg-build
configured using `configure  --prefix=/pkg/gnu --x-includes=/usr/openwin/include:/usr/dt/include --x-libraries=/usr/openwin/lib:/usr/dt/lib --with-x --with-x-toolkit=athena --without-toolkit-scroll-bars --with-xpm --with-tiff --with-jpeg --with-gif --with-png'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

In the shell using regular sccs commands, or in emacs using C-x C-q,
check out an sccs-versioned file that has had its latest delta
removed. Then, in another emacs session, VC commands, such as
vc-directory or vc-next-action, fail.

When vc-sccs-workfile-version(file) searches for the latest version
number in the sccs file, it searches for "^Ad D". However, there can
be another type of delta, namely "^Ad R". In this case, the delta does
not really exist-- it was removed, leaving this delta entry as a
"bread crumb" in the sccs file. The search is limited to the first
delta entry, so it fails and the function returns nil, and as a
result, a blank version number is passed to vcdiff and it fails.

I tried changing the search to accept [D|R] but it then returns the
removed delta number, which does not really exist, and other errors
ensue. 

(This scenario happens sometimes when the Sun CodeManager configuration
management tool is used. It apparently inserts its own bookkeeping
comments by adding and removing a delta. It seems to happen when a new
file is added to the workspace, then the workspace is putback to
another workspace.)

Suggested Fix:
The search should skip the top delta in the sccs file if it is of type
"removed", and return the version number of the next delta.
But IMHO it would be more robust to run the command "sccs
prt filename" to obtain the version, rather than relying on the
internal file format, assuming this works on all platforms.

A workaround is to make a change to the checked-out file (like adding
a blank line to the end or any other change) and check it back
in outside of emacs, creating a real latest delta. Then it can be
checked out again, and should work fine.

Thanks.

Chet Wood
Sun Microsystems


Recent input:
C-x C-b C-x o C-n C-n o C-p C-p C-p C-p C-p C-SPC C-n 
C-n C-n C-n C-n <escape> w C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-n C-SPC C-n 
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n 
C-n C-x C-x C-x C-x C-x C-x C-x C-x <escape> w M-x 
e m a c s - r e p SPC <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> r e p o r SPC b SPC u SPC <backspace> <backspace> 
<backspace> SPC SPC SPC <return>

Recent messages:
vc-sccs-workfile-version
Reading directory /home/cwood/tmp/p/...done
Buffer includes 3 directories
Getting version information... 
Running vcdiff on /home/cwood/tmp/p/SCCS/s.x_10.h...
vc-do-command: Running vcdiff...FAILED (status 2)
Reading directory /home/cwood/tmp/p/...done
Mark set [2 times]
Saved text from ";; Codemgr inserts and deletes a delta i"
Loading emacsbug...done

Re: SCCS version control cannot cope when latest delta is of type 'removed'

[Kevin Rodgers]

Chet Wood wrote:
 > In the shell using regular sccs commands, or in emacs using C-x C-q,
 > check out an sccs-versioned file that has had its latest delta
 > removed. Then, in another emacs session, VC commands, such as
 > vc-directory or vc-next-action, fail.
 >
 > When vc-sccs-workfile-version(file) searches for the latest version
 > number in the sccs file, it searches for "^Ad D". However, there can
 > be another type of delta, namely "^Ad R". In this case, the delta does
 > not really exist-- it was removed, leaving this delta entry as a
 > "bread crumb" in the sccs file. The search is limited to the first
 > delta entry, so it fails and the function returns nil, and as a
 > result, a blank version number is passed to vcdiff and it fails.
 >
 > I tried changing the search to accept [D|R] but it then returns the
 > removed delta number, which does not really exist, and other errors
 > ensue.
 >
 > (This scenario happens sometimes when the Sun CodeManager configuration
 > management tool is used. It apparently inserts its own bookkeeping
 > comments by adding and removing a delta. It seems to happen when a new
 > file is added to the workspace, then the workspace is putback to
 > another workspace.)
 >
 > Suggested Fix:
 > The search should skip the top delta in the sccs file if it is of type
 > "removed", and return the version number of the next delta.
 > But IMHO it would be more robust to run the command "sccs
 > prt filename" to obtain the version, rather than relying on the
 > internal file format, assuming this works on all platforms.

Your second suggestion may be more robust, but since vc-parse-buffer
returns a useful value to vc-sccs-workfile-version, I think we can take
advantage of that to implement a simple fix:

2006-10-27  Kevin Rodgers  <ihs_4664@yahoo.com>

	* vc-sccs.el (vc-sccs-workfile-version): If the top delta entry
           was removed, return the next entry.


*** vc-sccs.el~	2006-04-22 06:42:26.750000000 -0600
--- vc-sccs.el	2006-10-27 15:53:08.760978700 -0600
***************
*** 144,150 ****
       ;; rather than just the first entry, because the
       ;; first entry might be a deleted ("R") version.
       (vc-insert-file (vc-name file) "^\001e\n\001[^s]")
!     (vc-parse-buffer "^\001d D \\([^ ]+\\)" 1)))

   (defun vc-sccs-checkout-model (file)
     "SCCS-specific version of `vc-checkout-model'."
--- 144,155 ----
       ;; rather than just the first entry, because the
       ;; first entry might be a deleted ("R") version.
       (vc-insert-file (vc-name file) "^\001e\n\001[^s]")
!     (let ((top-delta (save-excursion	; vc-parse-buffer changes point
! 		       (vc-parse-buffer "^\001d \\([DR]\\) \\([^ ]+\\)" 2))))
!       (if (and top-delta
! 	       (equal (match-string 1) "R")) ; the delta entry was Removed
! 	  (vc-parse-buffer "^\001d D \\([^ ]+\\)" 1)
! 	top-delta))))

   (defun vc-sccs-checkout-model (file)
     "SCCS-specific version of `vc-checkout-model'."

 > A workaround is to make a change to the checked-out file (like adding
 > a blank line to the end or any other change) and check it back
 > in outside of emacs, creating a real latest delta. Then it can be
 > checked out again, and should work fine.

-- 
Kevin

Re: SCCS version control cannot cope when latest delta is of type 'removed'

[Kevin Rodgers]

Kevin Rodgers wrote:
> Chet Wood wrote:
>  > Suggested Fix:
>  > The search should skip the top delta in the sccs file if it is of type
>  > "removed", and return the version number of the next delta.
>  > But IMHO it would be more robust to run the command "sccs
>  > prt filename" to obtain the version, rather than relying on the
>  > internal file format, assuming this works on all platforms.
> 
> Your second suggestion may be more robust, but since vc-parse-buffer
> returns a useful value to vc-sccs-workfile-version, I think we can take
> advantage of that to implement a simple fix:

Sorry for that hastily-posted cruft.  This problem is already fixed
in the development version; you should be able to use the same fix in
Emacs 21:

(defun vc-sccs-workfile-version (file)
   "SCCS-specific version of `vc-workfile-version'."
   (with-temp-buffer
     ;; The workfile version is always the latest version number.
     ;; To find this number, search the entire delta table,
     ;; rather than just the first entry, because the
     ;; first entry might be a deleted ("R") version.
     (vc-insert-file (vc-name file) "^\001e\n\001[^s]")
     (vc-parse-buffer "^\001d D \\([^ ]+\\)" 1)))

-- 
Kevin