Re: [cocci] [PATCH] add usage-strings ci check and amend remaining usage strings

From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Julia Lawall <julia.lawall@inria.fr>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Abhradeep Chakraborty" <chakrabortyabhradeep79@gmail.com>,
	git <git@vger.kernel.org>,
	cocci@inria.fr
Subject: Re: [cocci] [PATCH] add usage-strings ci check and amend remaining usage strings
Date: Fri, 25 Feb 2022 16:03:55 +0100 (CET)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.2202251601040.11118@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2202221436320.2556@hadrien>

[-- Attachment #1: Type: text/plain, Size: 1679 bytes --]

Hi Julia,

On Tue, 22 Feb 2022, Julia Lawall wrote:

> [I]f there are some cases that are useful to do statically, with only
> local information, then using Coccinelle could be useful to get the
> problem out of the way once and for all.  Coccinelle doesn't support
> much processing of strings directly, but you can always write some
> python code to test the contents of a string and to create a new one.
>
> Let me know if you want to try this.  You can also check, eg the demo
> demos/pythontococci.cocci to see how to create code in a python script and
> then use it in a normal SmPL rule.
>
> If some context has to be taken into account and the context in the same
> function, then that can also be done with Coccinelle, eg
>
> A
> ...
> B
>
> matches the case where after an A there is a B on all execution paths
> (except perhaps those that end in an error exit) and
>
> A
> ... when exists
> B
>
> matches the case where there is a B sometime after executing A, even if
> that does not always occur.
>
> If the context that you are interested in is in a called function or is in
> the calling context, then Coccinelle might not be the ideal choice.
> Coccinelle works on one function at a time, so to do anything
> interprocedural, you have to do some hacks.

Right. The code in question is not actually calling a function, but a
macro, and passes a literal string to the macro that we would want to
check statically.

I did have my doubts that it would be easy with Coccinelle, but since Ævar
seemed so confident, I tried it, struggled, and decided to follow up with
you.

Thank you for confirming my suspicion!
Johannes