[cfe-dev] [Analyzer] Tips on how to fix PR22954 ? (false positive memory leak warning)

[Gábor Horváth]

On 16 July 2015 at 14:59, Pierre Gousseau <pierregousseau14 at gmail.com>
wrote:

> Ping !
> Adding analyzer experts to cc.
>

Did you add them to bcc? I can not see them in CC. (So added them. Sorry in
case it is redundant.)

>
> Regards,
>
> Pierre Gousseau
> SN Systems - Sony Computer Entertainment
>
> On 2 July 2015 at 09:06, Pierre Gousseau <pierregousseau14 at gmail.com>
> wrote:
>
>> Dear All,
>>
>> I have been looking into PR22954 which has been kindly raised by krzystof
>> at https://llvm.org/bugs/show_bug.cgi?id=22954
>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D22954&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=CnzuN65ENJ1H9py9XLiRvC_UQz6u3oG6GUNn7_wosSM&m=LxmcVZkm5xIjs1yr1VLtb4m0d77DEnuuKxA5OWJy0ik&s=20DofY-XUAVm4jp531KRZXRDke5d_wY6icOWPvtHJoA&e=>
>> and being new to this area of Clang I would appreciate any tips on how to
>> fix it.
>>
>> To me the root of the issue seems to originate from the CString checker
>> as it performs invalidation of the destination buffer.
>> Given the snippet below:
>> -----------------
>> struct aa { char *s; char data[32];};
>> ...
>> a.s = malloc(nbytes);
>> memcpy(a.data, source, len);
>> ...
>> -----------------
>> As the CString checker handles the memcpy call, it requests the
>> invalidation of the 'a.data' region. But the invalidation worker seems to
>> consider that the whole memory region of 'a' has to be invalidated. The
>> Malloc checker is not made aware of this causing the false positive.
>>
>> It seems a short term fix could be to detect this specific case and have
>> the CString checker notify the Malloc checker that it should stop tracking
>> 'a.s'.
>> However this solution would reduce the number of genuine defects detected.
>>
>> So I would be grateful if someone could give some hints on how to provide
>> the right solution.
>>
>> Regards,
>>
>> Pierre Gousseau
>> SN Systems - Sony Computer Entertainment
>>
>
>
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