RE: How did that happen?

[Drew Adams <drew.adams@oracle.com>]

> I just had emacs getting into this strange state: Everything seemed
> normal, except for one little thing: The cursor would jump to the
> beginning of the line after I inserted any character. This happened
> everywhere, including in the minibuffer.
> 
> Needless to say, this made emacs difficult to use to say the least.
> The only thing I could think of checking was if something had gotten
> into after-change-functions, but its value was as expected:
> (mew-draft-dynamic-highlight t), global value nil. (What fun to type
> stuff like C-h v -retfa C-e -ahc C-e nuf TAB in order to
> investigate!)
> 
> Unfortunately, I haven't the faintest idea how to trigger this
> behaviour, or I would submit a bug report right away.
> 
> Does anyone here have any notion what could possibly trigger this
> behaviour? Or suggestions for what I might try, should I encounter
> it again? I had to terminate that instance – it is just too painful to
> run two instances of emacs simultaneously, or I might have kept it
> around so I could investigate it some more.

My wild guess is that an error causes the current operation to be
interrupted, and point is returned to bol (where it was sent by
part of the operation).  If it happens after each insertion, perhaps
it occurs during a function on `post-command-hook'.

You might not be able to use `debug-on-entry' for those functions,
but if it happens again you could at least do a binary search to
determine which of them is problematic, and then, say, use `message'
to track its progress.