CEDET

Following is a patch for semantic-tag-buffer function to verify that a
file exists before attempting to call find-file-noselect on it.



=== modified file 'cedet-trunk/semantic/semantic-tag.el'
--- cedet-trunk/semantic/semantic-tag.el	2011-05-01 16:34:08 +0000
+++ cedet-trunk/semantic/semantic-tag.el	2011-07-20 17:00:10 +0000
@@ -193,7 +193,8 @@
 	buff
       ;; TAG has an originating file, read that file into a buffer, and
       ;; return it.
-     (if (semantic--tag-get-property tag :filename)
+     (if (and (semantic--tag-get-property tag :filename)
+              (file-exists-p (semantic--tag-get-property tag :filename)))
 	 (save-match-data
 	   (find-file-noselect (semantic--tag-get-property tag :filename)))
        ;; TAG is not in Emacs right now, no buffer is available.



I needed to add this when my emacs23 got into a state where push-mark
failed due to the missing file.  I was completely hosed, because I could
not even yank (i.e., Control-y)!  Adding the check above allowed me to
get out of this state so that I could go on.

I'm sorry, but I did not save the stack trace.  However I remembr that
it all started with this advice

    (defadvice push-mark (around semantic-mru-bookmark activate)
      "Push a mark at LOCATION with NOMSG and ACTIVATE passed to `push-mark'.
    If `semantic-mru-bookmark-mode' is active, also push a tag onto
    the mru bookmark stack."
      (semantic-mrub-push semantic-mru-bookmark-ring
    		      (point)
    		      'mark)
      ad-do-it)

which ended up iterating over some kind of ring which contained entries
for files that were removed since the data in the ring was created.
Perhaps the fact that I work with multiple branches of the same set of
files exacerbate the code?  That is I often edit files that are almost
identical within different directory trees.  I also often remove one or
more trees with "rm -rf" after having visited files that get deleted.

The one line change is something that worked for me to recover my emacs
session.  I do not propose that it should be a fix that gets checked in,
but as something that illustrates a possible bug.