vc RCS mode parsing problem.

[Bill Cattey]

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In GNU Emacs 21.1.1 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2002-06-04 on snuggle.mit.edu
configured using `configure  --with-x-toolkit --sharedstatedir=/var/tmp 
--with-pop --with-hesiod --with-kerberos'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: 
  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:

Repeat by:

1. create file, testing.txt containing "Hello world\n"

2. copy the file to testing.txt,v (IE create a file that might
be mistaken for an RCS file)

3. start emacs

4. use ^X^F to read the file in.

5. See error, "Wrong type argument: stringp, nil"

----

Commentary:  In Emacs 20.7, the same symtoms result from a much
simpler cause: vc-consult-rcs-headers attempts to parse the RCS file,
discovers it cant, and returns nil instead of a status string.

The new vc-fetch-master-state function in emacs 21 is supposed to
remedy this situation, but does not.  Perhaps someone more familiar
with the code can sort out why, in this case, we never throw the
"Error getting state of RCS file" error.  The enclosed backtrace shows
that workfile-version is ending up nil instead of a useful string
to pass to regexp-quote.

Recent input:
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
M-x e v a l SPC e x SPC <return> ( s e t q SPC d e 
b u g - o n m <backspace> - e r r o r SPC t ) <return> 
C-x C-f / t m p / t e s t i n g . t x t <return> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<menu-bar> <help-menu> <report-emacs-bug>

Recent messages:
Loading image...done
Loading tooltip...done
For information about the GNU Project and its goals, type C-h C-p.
t
Loading view...done
vc-rcs-fetch-master-state: 
Loading debug...done
Entering debugger...
 [2 times]
Loading emacsbug...done

Backtrace:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  regexp-quote(nil)
  vc-rcs-fetch-master-state("/tmp/testing.txt" nil)
  vc-rcs-state("/tmp/testing.txt")
  vc-rcs-state-heuristic("/tmp/testing.txt")
  apply(vc-rcs-state-heuristic "/tmp/testing.txt")
  vc-call-backend(RCS state-heuristic "/tmp/testing.txt")
  vc-state("/tmp/testing.txt")
  vc-default-mode-line-string(RCS "/tmp/testing.txt")
  apply(vc-default-mode-line-string RCS "/tmp/testing.txt")
  vc-call-backend(RCS mode-line-string "/tmp/testing.txt")
  vc-mode-line("/tmp/testing.txt")
  vc-find-file-hook()
  run-hooks(find-file-hooks)
  after-find-file(nil t)
  find-file-noselect-1(#<buffer testing.txt> "/tmp/testing.txt" nil nil 
"/tmp/testing.txt" (1867882 775))
  find-file-noselect("/tmp/testing.txt" nil nil 1)
  find-file("/tmp/testing.txt" 1)
  call-interactively(find-file)