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From: Matt Armstrong <matt@rfc20.org>
To: "Gerd Möllmann" <gerd.moellmann@gmail.com>
Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
Subject: Re: noverlay branch
Date: Fri, 07 Oct 2022 08:34:14 -0700	[thread overview]
Message-ID: <874jwffy15.fsf@rfc20.org> (raw)
In-Reply-To: <m2zge89rqg.fsf@Mini.fritz.box>

Gerd Möllmann <gerd.moellmann@gmail.com> writes:

> Matt Armstrong <matt@rfc20.org> writes:
>
>>> Clang libstd++ uses NULL, BTW, and I already wondered a little bit why.
>>
>> I believe GNU libstdc++ does not use sentinel nodes either.  I have yet
>> to see see sentinel nodes used in an optimized tree implementation.
>
> I looked it up a few days ago, out of interest, and GCC's rb-tree uses
> sentinels, in Git master at least.  Somewhere in this thread I posted
> where to look in GCC's Git repo, I can't remember ATM.

It uses a sentinel for the parent of the root node (a "header") but it
does not use a sentinel node for null at the leaves.  The easiest way to
see it is by looking at the code for GNU libstdc++ "minimum()" algorithm
on trees, which walks left ponters down to a leaf node:

https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libstdc%2B%2B-v3/include/bits/stl_tree.h;h=a4de61417652a288e361a55fcc8bb7a9838c58a5;hb=HEAD#l112
    _S_minimum(_Base_ptr __x) _GLIBCXX_NOEXCEPT
    {
      while (__x->_M_left != 0) __x = __x->_M_left;
      return __x;
    }

For the header node, see
https://gcc.gnu.org/git?p=gcc.git;a=blob;f=libstdc%2B%2B-v3/include/bits/stl_tree.h;h=a4de61417652a288e361a55fcc8bb7a9838c58a5;hb=HEAD#l89



  parent reply	other threads:[~2022-10-07 15:34 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-25 22:38 noverlay branch Stefan Monnier
2022-09-25 22:50 ` Lars Ingebrigtsen
2022-09-25 22:56   ` Stefan Monnier
2022-09-26  2:52 ` Ihor Radchenko
2022-09-26  3:17   ` Stefan Monnier
2022-09-26  6:11   ` Eli Zaretskii
2022-09-26 13:08     ` Ihor Radchenko
2022-09-26 15:59       ` Eli Zaretskii
     [not found]         ` <87v8ovdosz.fsf@localhost>
2022-10-08  6:57           ` Eli Zaretskii
2022-10-09  3:25             ` Matt Armstrong
2022-10-09  4:30               ` Eli Zaretskii
2022-10-09  3:23           ` Matt Armstrong
2022-10-09  3:47           ` Stefan Monnier
2022-10-13 12:09             ` Ihor Radchenko
2022-09-29 18:12       ` Stefan Monnier
2022-09-27  5:12 ` Matt Armstrong
2022-09-27  6:53   ` Eli Zaretskii
2022-09-27 17:31     ` Matt Armstrong
2022-09-27 18:45       ` Stefan Monnier
2022-09-28 23:09   ` Stefan Monnier
2022-09-29 14:54     ` Gerd Möllmann
2022-09-29 21:36       ` Stefan Monnier
2022-09-30  5:20         ` Gerd Möllmann
2022-10-06  4:47         ` Matt Armstrong
2022-10-06  5:43           ` Gerd Möllmann
2022-10-07  4:11             ` Matt Armstrong
2022-10-07  4:34               ` Gerd Möllmann
2022-10-07 13:33                 ` Stefan Monnier
2022-10-07 14:29                   ` Gerd Möllmann
2022-10-07 14:51                     ` Stefan Monnier
2022-10-07 15:12                       ` Gerd Möllmann
2022-10-07 17:12                         ` Stefan Monnier
2022-10-07 14:56                   ` Stefan Monnier
2022-10-07 15:59                   ` Matt Armstrong
2022-10-07 15:34                 ` Matt Armstrong [this message]
2022-10-06 12:08           ` Stefan Monnier
2022-09-27  8:39 ` Gerd Möllmann
2022-09-27  9:38   ` Eli Zaretskii
2022-10-06 20:41 ` Matt Armstrong
2022-10-07 16:51 ` Matt Armstrong
2022-10-07 18:28   ` Stefan Monnier
2022-10-08 23:33     ` Matt Armstrong
2022-10-09  3:44       ` Matt Armstrong
2022-10-09  4:12       ` Stefan Monnier
2022-10-09 15:34         ` Stefan Monnier
2022-10-10  2:57           ` Matt Armstrong
2022-10-10  6:24             ` Eli Zaretskii
2022-10-10 16:26               ` Matt Armstrong
2022-10-10 14:44             ` Stefan Monnier
2022-10-11  3:46               ` Matt Armstrong
2022-10-11  4:09                 ` Stefan Monnier
2022-10-11 18:02                   ` Matt Armstrong
2022-10-11 18:59                     ` Stefan Monnier
2022-10-12  5:18                       ` Matt Armstrong
2022-10-12 18:02                         ` Stefan Monnier
2022-10-12 22:26                           ` Matt Armstrong
2022-10-13  4:03                             ` Stefan Monnier
2022-10-09 23:47       ` Stefan Monnier
2022-10-10  0:05         ` Emanuel Berg
2022-10-10 16:27           ` Matt Armstrong
2022-10-10 16:33         ` Matt Armstrong
2022-10-10 18:32           ` Matt Armstrong
2022-10-11 16:06             ` Stefan Monnier
2022-10-12 17:33               ` Matt Armstrong
2022-10-13  3:59                 ` Stefan Monnier
2022-10-16 21:53                   ` Matt Armstrong
2022-10-23  4:49 ` Matt Armstrong
2022-10-24  9:14   ` Stefan Kangas
2022-10-24 16:21     ` Matt Armstrong
2022-10-24 12:51   ` Eli Zaretskii
2022-10-25 20:57     ` Dmitry Gutov

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