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Date: Tue, 16 Jun 2009 16:54:15 +0200
Message-ID: <a63d67fe0906160754ub38679ag9493d5090a9ca0c0@mail.gmail.com>
Subject: Re: smatch 1.53 released
From: Dan Carpenter <error27@gmail.com>
To: Christian Kujau <lists@nerdbynature.de>
Cc: Andi Kleen <andi@firstfloor.org>, LKML <linux-kernel@vger.kernel.org>
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On 6/9/09, Christian Kujau <lists@nerdbynature.de> wrote:
> On Thu, 4 Jun 2009, Dan Carpenter wrote:
>>> Smatch is a source code checker for C.  Right now the focus is on
>>> checking
>>> for kernel bugs.
>
> Hm, smatch is pretty noisy. I'm getting hundreds of warnings and errors on
> a randconfig build: http://nerdbynature.de/bits/smatch/
>
> False positives or real issues?
>

If itīs not in drivers/ itīs a false positive.  Otherwise there is a
95% chance it is a false positive.  In an ideal world there would be
no bugs and no false positives.  But itīs easier to fix the bugs
smatch reports than to fix smatch so probably eventually it will be
100% false positives.

Quite a lot of the time, I donīt know the code well enough to say
whether a bug is a false positive or not.  Check the bits that you
care about.  The smatch output format is designed for vim.  "vim
filename.c +lineno"

If there was some way to get rid of the "field" messages that would
reduce the false positive count by 20.
kernel/trace/trace_functions_graph.c +808 print_graph_function(14)
error: dereferencing undefined:  'field'
I donīt see a heuristic to do that.

The rest are smatch bugs.  Code like:
foo->bar = NULL;
foo = frob();
foo->bar->baz = x;  // smatch thinks this is a bug since foo->bar was
set to NULL.

Sometimes running smatch with the --debug option can help to find
where smatch gets it wrong.  kchecker also takes the --debug option.

regards,
dan carpenter

> Thanks,
> Christian.
> --
> BOFH excuse #182:
>
> endothermal recalibration
>