bug#46908: 28.0.50; Dozens of spurious markers in buffer-undo-list

[Michael Heerdegen]

martin rudalics <rudalics@gmx.at> writes:

> So you mean that we really have two problems here, both caused by
> `push-mark'?  IIUC a marker is "thrown out of the rings" when its buffer
> gets deleted or a marker is pushed on a "full" ring.  I suppose that
> "invalidating" markers in these cases should be safe.

But actually that doesn't help, markers pointing to nowhere are not
removed from buffer-undo-list by garbage-collect.

> But how comes that `add-to-history' affects `buffer-undo-list'?

`add-to-history' has no relevance here, no.  There mere existence of a
marker in any buffer does, IIUC, cause it to be referenced by
buffer-undo-list sooner or later, because undoing and redoing inside
text containing a marker is not always without ambiguity regarding
marker positioning, so the undo system adds hints to buffer-undo-list
how these markers must be placed/repositioned.

Michael.