git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Junio C Hamano <gitster@pobox.com>
To: Brandon Casey <drafnel@gmail.com>
Cc: "Martin Ågren" <martin.agren@gmail.com>,
	"git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: [PATCH v2 3/4] strbuf_setlen: don't write to strbuf_slopbuf
Date: Thu, 24 Aug 2017 09:52:11 -0700	[thread overview]
Message-ID: <xmqqpobkx610.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <CA+sFfMdMgrGBhECegBe09c38nRM+Zt5JK4gJaZ96DO-9zC-8qA@mail.gmail.com> (Brandon Casey's message of "Wed, 23 Aug 2017 14:54:56 -0700")

Brandon Casey <drafnel@gmail.com> writes:

> Ah, you probably meant something like this:
>
>    const char strbuf_slopbuf = '\0';
>
> which gcc will apparently place in the read-only segment.  I did not know that.

Yes but I highly suspect that it would be very compiler dependent
and not something the language lawyers would recommend us to rely
on.

My response was primarily to answer "why?" with "because we did not
bother".  The above is a mere tangent, i.e. "multiple copies of
empty strings is a horrible implementation (and there would be a way
to do it with a single instance)".

>    #define STRBUF_INIT  { .alloc = 0, .len = 0, .buf = (char*) &strbuf_slopbuf }
>
> respectively.  Yeah, that's definitely preferable to a macro.
> Something similar could be done in object.c.

What is the main objective for doing this change?  The "make sure we
do not write into that slopbuf" assert() bothers you and you want to
replace it with an address in the read-only segment?

  parent reply	other threads:[~2017-08-24 16:52 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-15 12:53 [PATCH/RFC 0/5] Some ThreadSanitizer-results Martin Ågren
2017-08-15 12:53 ` [PATCH 1/5] convert: initialize attr_action in convert_attrs Martin Ågren
2017-08-15 14:17   ` Torsten Bögershausen
2017-08-15 14:29     ` Torsten Bögershausen
2017-08-15 14:40     ` Martin Ågren
2017-08-15 12:53 ` [PATCH 2/5] pack-objects: take lock before accessing `remaining` Martin Ågren
2017-08-15 19:50   ` Johannes Sixt
2017-08-15 12:53 ` [PATCH 3/5] Makefile: define GIT_THREAD_SANITIZER Martin Ågren
2017-08-15 12:53 ` [PATCH 4/5] strbuf_reset: don't write to slopbuf with ThreadSanitizer Martin Ågren
2017-08-15 18:43   ` Junio C Hamano
2017-08-15 19:06     ` Martin Ågren
2017-08-15 19:19       ` Junio C Hamano
2017-08-15 12:53 ` [PATCH 5/5] ThreadSanitizer: add suppressions Martin Ågren
2017-08-15 12:53 ` tsan: t3008: hashmap_add touches size from multiple threads Martin Ågren
2017-08-15 17:59   ` Jeff Hostetler
2017-08-15 18:17     ` Stefan Beller
2017-08-15 18:40       ` Martin Ågren
2017-08-15 18:48         ` Stefan Beller
2017-08-15 19:21           ` Martin Ågren
2017-08-15 20:46             ` Jeff Hostetler
2017-08-30 18:59   ` [PATCH] hashmap: address ThreadSanitizer concerns Jeff Hostetler
2017-08-30 18:59     ` [PATCH] hashmap: add API to disable item counting when threaded Jeff Hostetler
2017-09-01 23:31       ` Johannes Schindelin
2017-09-01 23:50         ` Jonathan Nieder
2017-09-05 16:39           ` Jeff Hostetler
2017-09-05 17:13             ` Martin Ågren
2017-09-02  8:17         ` Jeff King
2017-09-04 15:59           ` Johannes Schindelin
2017-09-05 16:54           ` Jeff Hostetler
2017-09-06  3:43           ` Junio C Hamano
2017-09-05 16:33         ` Jeff Hostetler
2017-09-02  8:05       ` Jeff King
2017-09-05 17:07         ` Jeff Hostetler
2017-09-02  8:39       ` Simon Ruderich
2017-09-06  1:24       ` Junio C Hamano
2017-09-06 15:33         ` Jeff Hostetler
2017-09-06 15:43     ` [PATCH v2] hashmap: address ThreadSanitizer concerns Jeff Hostetler
2017-09-06 15:43       ` [PATCH v2] hashmap: add API to disable item counting when threaded Jeff Hostetler
2017-08-15 12:53 ` tsan: t5400: set_try_to_free_routine Martin Ågren
2017-08-15 17:35   ` Stefan Beller
2017-08-15 18:44     ` Martin Ågren
2017-08-17 10:57   ` Jeff King
2017-08-20 10:06 ` [PATCH/RFC 0/5] Some ThreadSanitizer-results Jeff King
2017-08-20 10:45   ` Martin Ågren
2017-08-21 17:43 ` [PATCH v2 0/4] " Martin Ågren
2017-08-21 17:43   ` [PATCH v2 1/4] convert: always initialize attr_action in convert_attrs Martin Ågren
2017-08-21 17:43   ` [PATCH v2 2/4] pack-objects: take lock before accessing `remaining` Martin Ågren
2017-08-21 17:43   ` [PATCH v2 3/4] strbuf_setlen: don't write to strbuf_slopbuf Martin Ågren
2017-08-23 17:24     ` Junio C Hamano
2017-08-23 17:43       ` Martin Ågren
2017-08-23 18:30         ` Junio C Hamano
2017-08-23 20:37     ` Brandon Casey
2017-08-23 21:04       ` Junio C Hamano
2017-08-23 21:20         ` Brandon Casey
2017-08-23 21:54           ` Brandon Casey
2017-08-23 22:11             ` Brandon Casey
2017-08-24 16:52             ` Junio C Hamano [this message]
2017-08-24 18:29               ` Brandon Casey
2017-08-24 19:16                 ` Martin Ågren
2017-08-23 22:24           ` Junio C Hamano
2017-08-23 22:39             ` Brandon Casey
2017-08-21 17:43   ` [PATCH v2 4/4] ThreadSanitizer: add suppressions Martin Ågren
2017-08-25 17:04     ` Jeff King
2017-08-28 20:56   ` [PATCH v2 0/4] Some ThreadSanitizer-results Jeff Hostetler

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=xmqqpobkx610.fsf@gitster.mtv.corp.google.com \
    --to=gitster@pobox.com \
    --cc=drafnel@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=martin.agren@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).