From: Taylor Blau <ttaylorr@openai.com>
Date: Fri, 24 Jul 2026 21:20:41 GMT
Subject: Re: [PATCH] branch: avoid slow strvec Coccinelle matching
Message-ID: <amPXKfnoTzUuuyMN@com-79390>
In-Reply-To: <xmqq33x89zn9.fsf@gitster.g>

On Fri, Jul 24, 2026 at 08:27:06AM -0700, Junio C Hamano wrote:
> tnyman@openai.com writes:
>
> > From: Ted Nyman <tnyman@openai.com>
> >
> > The --delete-merged implementation declares a loop index at function
> > scope and reuses it to walk its strvec of upstreams and its list of
> > candidate branches. Coccinelle 1.1.1 spends hours matching this against
> > the separate_loop_index rule in tools/coccinelle/strvec.cocci, causing
> > the static-analysis job on 'seen' to reach its six-hour timeout.
> > ...
> > The CI failure reproduces locally with Coccinelle 1.1.1: applying
> > strvec.cocci to the original builtin/branch.c still times out with
> > "spatch --timeout 120". With this change, the same check completes in
> > 0.06 seconds.
>
> Impressive.  Nicely analyzed.
>
> Even though this is very much like bending the code only to appease
> the checker, the resulting code is arguably better in this
> particular case, so I do not feel as bad as I have on other
> occasions when we had to work around deficiencies in our tools [*].

Agreed. I don't think we should ever bend over backwards to appease a
static analysis tool, *especially* when it results in worse looking
code. But this case is a strict improvement, and just so happens to
address the Coccinelle issue. ;-)

> I see Harald already took this in the latest update.  Thanks for
> working well together.

Yup. Thanks, both.

Thanks,
Taylor