bug#64580: 30.0.50; Comment describing Lisp_Overlay object in src/lisp.h:2590 is not current

[Ihor Radchenko <yantar92@posteo.net>]

Hi,

I am not reading lisp.h, trying to understand the Lisp object layout.
The comments are generally excellent, but I just stumbled upon
Lisp_Overlay definition, where the comment appears to be outdated and
only reflects the past times when overlays did not yet use itree:

/* START and END are markers in the overlay's buffer, and
   PLIST is the overlay's property list.  */
struct Lisp_Overlay
/* An overlay's real data content is:
   - plist
   - buffer (really there are two buffer pointers, one per marker,
     and both points to the same buffer)
   - insertion type of both ends (per-marker fields)
   - start & start byte (of start marker)
   - end & end byte (of end marker)
   - next (singly linked list of overlays)
   - next fields of start and end markers (singly linked list of markers).
   I.e. 9words plus 2 bits, 3words of which are for external linked lists.
*/
  {
    union vectorlike_header header;
    Lisp_Object plist;
    struct buffer *buffer;        /* eassert (live buffer || NULL). */
    struct itree_node *interval;
  } GCALIGNED_STRUCT;

START and END are no longer in the struct. NEXT fields are also no
longer applicable, even via itree_node struct.


In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.38, cairo version 1.17.8) of 2023-07-06 built on localhost
Repository revision: d97b77e6c66db46b198c696f83458aa141794727
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Gentoo Linux

-- 
Ihor Radchenko // yantar92,
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