bug#13796: 24.3.50; Minor bug in "(elisp) Managing Overlays"

bug#13796: 24.3.50; Minor bug in "(elisp) Managing Overlays"

[Xue Fuqiao]

In (info "(elisp) Managing Overlays"):

 -- Function: move-overlay overlay start end &optional buffer
[...]
     This is the only valid way to change the endpoints of an overlay.
[...]

 -- Function: remove-overlays &optional start end name value
     This function removes all the overlays between START and END whose
     property NAME has the value VALUE.  It can move the endpoints of
     the overlays in the region, or split them.

I think both `move-overlay' and `remove-overlays' can change the
endpoints of an overlay.  So maybe it is a bug here.



In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.6.0)
 of 2013-02-24 on Emacs
Bzr revision: 111865 rgm@gnu.org-20130223220645-ym5xjdm8i09p2huy
Windowing system distributor `The X.Org Foundation', version 11.0.11300000
System Description:	Ubuntu 12.10

Configured using:
 `configure --config-cache --enable-link-time-optimization'

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

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  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

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<help-echo> <menu> r e - e m b <backspace> - b u g 
<tab> <return>

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mm-util mail-prsvr mail-utils time-date tooltip ediff-hook vc-hooks
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fringe tabulated-list newcomment lisp-mode register page menu-bar
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multi-tty emacs)

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao

bug#13796: 24.3.50; Minor bug in "(elisp) Managing Overlays"

[Glenn Morris]

Xue Fuqiao wrote:

> I think both `move-overlay' and `remove-overlays' can change the
> endpoints of an overlay.  So maybe it is a bug here.

remove-overlays may move them as a side effect. This does not invalidate
the point that

     This is the only valid way to change the endpoints of an overlay.
     Do not try modifying the markers in the overlay by hand, as that
     fails to update other vital data structures and can cause some
     overlays to be "lost".

is trying to make. Anyway, remove-overlays uses move-overlays.

bug#13796: 24.3.50; Minor bug in "(elisp) Managing Overlays"

[Stefan Monnier]

>      This is the only valid way to change the endpoints of an overlay.
>      Do not try modifying the markers in the overlay by hand, as that
>      fails to update other vital data structures and can cause some
>      overlays to be "lost".

I'm wondering exactly what kind of "modifying the markers in the overlay
by hand" is being referred to here,


        Stefan