A ton of marker entry in buffer-und-list

[Yuan Fu]

I’ve been playing around with undo recently. I used primitive-undo to undo some 
entries in the buffer-undo-list, and a ton of (#marker . -1) was added to the 
buffer-undo-list:

(nil
 ("a" . 27)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)
 (#<marker at 27 in a> . -1)

… hundreds of this.

Any idea of what is happening? What is this marker?

I don’t expect anyone to look at my code, but if you want to see it, here it is:

vundo.el
Description: Binary data

The idea is to display an undo-tree and move between nodes with f/b/n/p. You 
can enable it with M-x vundo RET.

Yuan