Git Mailing List Archive mirror
 help / color / mirror / Atom feed
From: Felipe Contreras <felipe.contreras@gmail.com>
To: phillip.wood@dunelm.org.uk
Cc: demerphq <demerphq@gmail.com>, Junio C Hamano <gitster@pobox.com>,
	Emily Shaffer <nasamuffin@google.com>,
	Git List <git@vger.kernel.org>, Jonathan Nieder <jrn@google.com>,
	Jose Lopes <jabolopes@google.com>,
	Aleksandr Mikhailov <avmikhailov@google.com>
Subject: Re: Proposal/Discussion: Turning parts of Git into libraries
Date: Thu, 23 Mar 2023 17:22:02 -0600	[thread overview]
Message-ID: <CAMP44s1Qqd2cYcf7OGxz1-PY-8TF2KG+9jPEWMrnCaCfPe_1sw@mail.gmail.com> (raw)
In-Reply-To: <4222af90-bd6b-d970-2829-1ddfaeb770bf@dunelm.org.uk>

On Sat, Feb 18, 2023 at 5:12 AM Phillip Wood <phillip.wood123@gmail.com> wrote:
>
> On 18/02/2023 01:59, demerphq wrote:
> > On Sat, 18 Feb 2023 at 00:24, Junio C Hamano <gitster@pobox.com> wrote:
> >>
> >> Emily Shaffer <nasamuffin@google.com> writes:
> >>
> >>> Basically, if this effort turns out not to be fruitful as a whole, I'd
> >>> like for us to still have left a positive impact on the codebase.
> >>> ...
> >>> So what's next? Naturally, I'm looking forward to a spirited
> >>> discussion about this topic - I'd like to know which concerns haven't
> >>> been addressed and figure out whether we can find a way around them,
> >>> and generally build awareness of this effort with the community.
> >>
> >> On of the gravest concerns is that the devil is in the details.
> >>
> >> For example, "die() is inconvenient to callers, let's propagate
> >> errors up the callchain" is an easy thing to say, but it would take
> >> much more than "let's propagate errors up" to libify something like
> >> check_connected() to do the same thing without spawning a separate
> >> process that is expected to exit with failure.
> >
> >
> > What does "propagate errors up the callchain" mean?  One
> > interpretation I can think of seems quite horrible, but another seems
> > quite doable and reasonable and likely not even very invasive of the
> > existing code:
> >
> > You can use setjmp/longjmp to implement a form of "try", so that
> > errors dont have to be *explicitly* returned *in* the call chain. And
> > you could probably do so without changing very much of the existing
> > code at all, and maintain a high level of conceptual alignment with
> > the current code strategy.
>
> Using setjmp/longjmp is an interesting suggestion, I think lua does
> something similar to what you describe for perl. However I think both of
> those use a allocator with garbage collection. I worry that using
> longjmp in git would be more invasive (or result in more memory leaks)
> as we'd need to to guard each allocation with some code to clean it up
> and then propagate the error. That means we're back to manually
> propagating errors up the call chain in many cases.

We could just use talloc [1].

All the downstream code can create objects that are descendents of the
master object, when the "exception" occurs the code is sent back to
where the master object was created, it's destroyed, and all the
children are destroyed as well.

I've played around with both talloc and stack contexts and I don't see
how this isn't doable.

Cheers.

[1] https://talloc.samba.org/talloc/doc/html/index.html

-- 
Felipe Contreras

  reply	other threads:[~2023-03-23 23:22 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-17 21:12 Proposal/Discussion: Turning parts of Git into libraries Emily Shaffer
2023-02-17 21:21 ` brian m. carlson
2023-02-17 21:38   ` Emily Shaffer
2023-02-17 22:41     ` brian m. carlson
2023-02-17 22:49       ` Emily Shaffer
2023-02-22 19:34         ` Jeff King
2023-02-24 20:31           ` Emily Shaffer
2023-02-24 21:41             ` Jeff King
2023-02-24 22:59             ` Junio C Hamano
2023-02-17 22:04   ` rsbecker
2023-02-17 22:48     ` brian m. carlson
2023-02-17 22:57 ` Junio C Hamano
2023-02-18  1:59   ` demerphq
2023-02-18 10:36     ` Phillip Wood
2023-03-23 23:22       ` Felipe Contreras [this message]
2023-03-23 23:30         ` rsbecker
2023-03-23 23:34           ` Felipe Contreras
2023-03-23 23:42             ` rsbecker
2023-03-23 23:55               ` Felipe Contreras
2023-03-24 19:27                 ` rsbecker
2023-03-24 21:21                   ` Felipe Contreras
2023-03-24 22:06                     ` rsbecker
2023-03-24 22:29                       ` Felipe Contreras
2023-02-21 21:42   ` Emily Shaffer
2023-02-22  0:22     ` Junio C Hamano
2023-02-18  4:05 ` Elijah Newren
2023-02-21 22:06   ` Emily Shaffer
2023-02-22  8:23     ` Elijah Newren
2023-02-22 19:25     ` Jeff King
2023-02-21 19:09 ` Taylor Blau
2023-02-21 22:27   ` Emily Shaffer
2023-02-22  1:44 ` Victoria Dye
2023-02-25  1:48   ` Jonathan Tan
2023-02-22 14:55 ` Derrick Stolee
2023-02-24 21:06   ` Emily Shaffer
2023-03-23 23:37 ` Felipe Contreras
2023-03-23 23:44   ` rsbecker

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

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

  git send-email \
    --in-reply-to=CAMP44s1Qqd2cYcf7OGxz1-PY-8TF2KG+9jPEWMrnCaCfPe_1sw@mail.gmail.com \
    --to=felipe.contreras@gmail.com \
    --cc=avmikhailov@google.com \
    --cc=demerphq@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=jabolopes@google.com \
    --cc=jrn@google.com \
    --cc=nasamuffin@google.com \
    --cc=phillip.wood@dunelm.org.uk \
    /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.
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).