[klee-dev] Different behavior of KLEE when testing `dircolors` with "--optimize=true/false" option

[Daniel Schemmel]

Hi Haoxin,


The described behavior is indeed very odd. Luckily, the `assembly.ll` 
that is generated by KLEE shows that this is an actual optimization 
error - the code that is intended to print your messages does not exist 
anymore. This means that the issue lies either with the LLVM 
optimization passes, or in our usage of them.


As you were using fairly old LLVM versions (LLVM 9 & 10 support is about 
to be removed from KLEE <https://github.com/klee/klee/pull/1686>), I 
tried to reproduce the issue in a few different configurations:


- LLVM 9 (KLEE master): REPRODUCED

- LLVM 10 (KLEE master): REPRODUCED
- LLVM 11 (KLEE master): NOT reproduced
- LLVM 12 (KLEE master): NOT reproduced

- LLVM 13 (docker.io/klee/klee): NOT reproduced
- LLVM 14 (KLEE master): NOT reproduced
- LLVM 15 (#1664 <https://github.com/klee/klee/pull/1664>): NOT reproduced
- LLVM 16 (#1664 <https://github.com/klee/klee/pull/1664>): requires an 
additional include in xmalloc.c to compile; NOT reproduced


Since this bug only occurs with the two LLVM versions that are about to 
be removed in the next few days anyway, and there is a hard break (none 
of the newer versions exhibit the same behavior), I tend towards 
assuming that this specific issue probably stems from an old LLVM bug 
that has since been rectified.


Best,
Daniel


On 2024-01-31 06:58, TU Haoxin wrote:
> Hi Nguyen,
>
> Just installed and run this case using KLEE-3.0 with LLVM-10, and it 
> seems the issue is still reproducible for KLEE 3.
>
> Please check more here: 
> https://gist.github.com/haoxintu/183dda2923965d1e33f64ad59c7f5338#other-trials 
> <https://gist.github.com/haoxintu/183dda2923965d1e33f64ad59c7f5338#other-trials>
>
>
> Thanks,
> Haoxin
>
>
>
> ------------------------------------------------------------------------
> *From:* Nguyễn Gia Phong
> *Sent:* Wednesday, January 31, 2024 13:34
> *To:* TU Haoxin; klee-dev at imperial.ac.uk
> *Subject:* Re: [klee-dev] Different behavior of KLEE when testing 
> `dircolors` with "--optimize=true/false" option
>
> On 2024-01-31 at 05:07+00:00, TU Haoxin wrote:
> > The behavior is that KLEE fails to fork at a branch
> > that should be forked with the option --optimize option enabled
> > (i.e., --optimize=true).  While the --optimize option is disabled
> > i.e., --optimize=false), the branch can be successfully forked [...]
> >
> > ### Reproduce the behavior
> > #### Enviroment
> > * KLEE-2.1 (also tested KLEE-2.3, and they behave the same)
>
> Just curious, is the issue reproducible for KLEE 3?
>
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