Re: [RFC/PATCH] Makefile: add cppcheck target

From: Chris Packham <judge.packham@gmail.com>
Date: Dec 14, 2016, 08:33 UTC
Message-ID: <CAFOYHZBRq=5FGswQZSYbn0JdrEv+xqLm6gdpD_nE+1L_CfPHEw@mail.gmail.com>
In-Reply-To: <20161213121510.5o5axuwzztbxcvfd@sigill.intra.peff.net>

On Wed, Dec 14, 2016 at 1:15 AM, Jeff King <peff@peff.net> wrote:

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> On Tue, Dec 13, 2016 at 10:22:25PM +1300, Chris Packham wrote:
>
>> $ make cppcheck
>> cppcheck --force --quiet --inline-suppr  .
>> [compat/nedmalloc/malloc.c.h:4093]: (error) Possible null pointer dereference: sp
>> [compat/nedmalloc/malloc.c.h:4106]: (error) Possible null pointer dereference: sp
>> [compat/nedmalloc/nedmalloc.c:551]: (error) Expression '*(&p.mycache)=TlsAlloc(),TLS_OUT_OF_INDEXES==*(&p.mycache)' depends on order of evaluation of side effects
>> [compat/regex/regcomp.c:3086]: (error) Memory leak: sbcset
>> [compat/regex/regcomp.c:3634]: (error) Memory leak: sbcset
>> [compat/regex/regcomp.c:3086]: (error) Memory leak: mbcset
>> [compat/regex/regcomp.c:3634]: (error) Memory leak: mbcset
>> [compat/regex/regcomp.c:2802]: (error) Uninitialized variable: table_size
>> [compat/regex/regcomp.c:2805]: (error) Uninitialized variable: table_size
>> [compat/regex/regcomp.c:532]: (error) Memory leak: fastmap
>> [t/t4051/appended1.c:3]: (error) Invalid number of character '{' when these macros are defined: ''.
>> [t/t4051/appended2.c:35]: (error) Invalid number of character '{' when these macros are defined: ''.
>>
>> The last 2 are just false positives from test data. I haven't looked
>> into any of the others.
>
> I think these last two are a good sign that we need to be feeding the
> list of source files to cppcheck. I tried your patch and it also started
> looking in t/perf/build, which are old versions of git built to serve
> the performance-testing suite.
>
> See the way that the "tags" target is handled for a possible approach.
>
> My main complaint with any static checker is how we can handle false
> positives. I think our use of "-Wall -Werror" is successful because it's
> not too hard to keep the normal state to zero warnings. Looking at the
> output of cppcheck on my system (which is different than on yours!),

I think you get a similar class of problems with different compilers (different gcc versions, clang, msvc). Although this appears to be mitigated already with the diverse developers in the git community.

> I do see a few real problems, but many false positives, too.
> Unfortunately, one of the false positives is:
>
>   int foo = foo;

On I side note I have often wondered how this actually works to avoid the uninitialised-ness of foo. I can see how some compilers may be fooled into thinking that foo has been set but that doesn't actually end up with foo having a deterministic value.

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> to silence -Wuninitialized, which causes cppcheck to complain that "foo"
> is uninitialized. I'm worried we will end up with two static checkers
> fighting each other, and no good way to please both.
>
> -Peff