distinguishing gcc compilation valgrind false positives

[Zdenek Sojka]

Hello Jeff,

---------- Původní e-mail ----------
Od: Jeff Law via Gcc <gcc@gcc.gnu.org>
Komu: Paul Floyd <paulf@free.fr>, gcc@gcc.gnu.org
Datum: 24. 11. 2021 20:33:02
Předmět: Re: distinguishing gcc compilation valgrind false positives 
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On 11/24/2021 12:15 PM, Paul Floyd via Gcc wrote: 
> 
> On 24/11/2021 20:05, Zdenek Sojka via Gcc wrote: 
>> Hello, 
>> 
>> from time to time, I come upon a testcase that failed during the 
>> automated 
>> runs, but passes during reduction; there are valgrind warnings present, 
>> however. How do I distinguish what warnings are valid and which are 
>> false 
>> positives? Is there any way gcc could prevent generating the false 
>> positives? 
> 
> 
> What makes you think that any are false positives? 
> 
> Memcheck generally has a low false positive rate (though I am little 
> biased). 
> 
> You need to read the source and decide based on that. 
Agreed.  Work from the assumption it's a real GCC issue until proven 
otherwise. 

I believe GCC has annotations to help valgrind that are turned on by a 
magic configuration option as well. 
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I have gcc configured with --enable-valgrind-annotations , if that is the 
one you are talking about?


 
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Finally, there is an issue with sparsesets that will trigger a warning 
from valgrind.  Those are the only ones I would consistently ignore from 
GCC. 

Jeff "






Yes I remember those - but it would be nice to get rid of them anyway, at 
least to simplify testcase reduction by having no valgrind warning on a 
clean build.




I could also use a valgrind suppression file; this is also part of my 
question, if there is one readily available




Thanks,
Zdenek




 
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