From: Julia Lawall <julia.lawall@lip6.fr>
To: Nicholas Mc Guire <der.herr@hofr.at>
Cc: Cocci@systeme.lip6.fr
Subject: Re: [Cocci] RFC catching hidden code in if conditions
Date: Mon, 25 Mar 2019 14:14:20 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1903251412450.3543@hadrien> (raw)
In-Reply-To: <20190325130358.GA7492@osadl.at>
On Mon, 25 Mar 2019, Nicholas Mc Guire wrote:
>
> HI !
>
> Noticed that the nuveau driver uses a fair number of if (var=val,boolean-condition){}
> which while legal C-code just makes it hard to read - and some seems buggy
> actually. The below spatch find about 50 cases - not sure though if this is
> actually complete ?
Maybe it would be good to forward it to the nouveau people and see what
they think about it? I think that checkpatch already complains about
assignments in if conditions, and the whole thing with the comma makes it
look even more unpleasant.
julia
>
> thx!
> hofrat
>
> /// Check for unconditional code "hiding" in an if condition
> /// effectively that code is unconditionally executed before
> /// reaching the actual branch statement - which just makes it
> /// hard to read and thus is always wrong.
> /// Some of the cases found also look buggy
> /// In other cases some excess () are left in place in the
> /// generated patches - so some postprocessing may be needed.
> ///
> /// As of 5.0-rc8 all 50 cases look like they are found and fixed
> /// correctly - incorrectly only in the sense that the patched
> /// code is equivalent to the original code. but as this is in
> /// the nouveau driver only it might well be that this only
> /// fits that specific pattern and others might have wilder ways
> /// to achieve the same - so confidence Low for now
> ///
> // Confidence: Low
> // Comments:
> // Options: --no-includes --include-headers
>
> virtual patch
> virtual report
>
> @badif@
> position p;
> statement S;
> expression E1,E2;
> @@
>
> if@p (E1,E2) S
>
> @script:python depends on report@
> p << badif.p;
> @@
>
> msg = "unconditional code hiding in if condition"
> coccilib.report.print_report(p[0],msg)
>
> @fixbadif depends on badif && patch@
> position p=badif.p;
> statement S;
> expression E1=badif.E1,E2=badif.E2;
> @@
>
> + E1;
> if@p (
> - E1,
> E2)
> S
>
> _______________________________________________
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> Cocci@systeme.lip6.fr
> https://systeme.lip6.fr/mailman/listinfo/cocci
>
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next prev parent reply other threads:[~2019-03-25 13:14 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-25 13:03 [Cocci] RFC catching hidden code in if conditions Nicholas Mc Guire
2019-03-25 13:14 ` Julia Lawall [this message]
2019-03-26 19:04 ` Markus Elfring
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