Re: [PATCH v3 00/11] cocci: make "incremental" possible + a ccache-like tool

From: Jeff King <peff@peff.net>
Date: Oct 17, 2022, 17:50 UTC
Message-ID: <Y02V0E0JRSNa4Sb9@coredump.intra.peff.net>
In-Reply-To: <cover-v3-00.11-00000000000-20221014T152552Z-avarab@gmail.com>

On Fri, Oct 14, 2022 at 05:31:16PM +0200, Ævar Arnfjörð Bjarmason wrote:

> The big change in this belated v3 is that we now run against a
> concatenated version of all our *.cocci files. This is something I
> discussed with Jeff King at Git Merge, after having confirmed the
> viability of that approach on the cocci mailing list.

Is that safe? The last time it was brought up on this list (AFAIK) was in:

  https://lore.kernel.org/git/alpine.DEB.2.20.1808030755350.2446@hadrien/

where Julia said:

  I'm surprised that the above cat command would work.  Semantic patch rules
  have names, and Coccinelle will not be happy isf two rules have the same
  name.  Some may also have variables declared in initializers, although
  perhaps the ones in the kernel don't do this.  Causing these variables to
  be shared would not have a good effect.

  Putting everything together can also go counter to the optimizations that
  Coccinelle provides. [...]

Maybe we don't do any of the things that could trigger problems in our spatch rules. But it's not clear to me what we're risking. Do you have a link for further discussion?

-Peff