Re: smatch 1.53 released

From: Dan Carpenter
Date: Tue Jun 16 2009 - 10:54:26 EST

On 6/9/09, Christian Kujau <lists@xxxxxxxxxxxxxxx> 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:
> False positives or real issues?

If it´s not in drivers/ it´s 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 it´s 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 don´t 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 don´t 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.

dan carpenter

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