[klee-dev] Question about KLEE Implementation on Collecting Symbolic Variables

[Nowack, Martin]

Hi Oleg,

Ah - yeah there is. The name is `klee::findSymbolicObjects` but it’s a bit hidden: https://github.com/klee/klee/blob/fc83f06b17221bf5ef20e30d9da1ccff927beb17/include/klee/Expr/ExprUtil.h#L38 and https://github.com/klee/klee/blob/fc83f06b17221bf5ef20e30d9da1ccff927beb17/lib/Expr/ExprUtil.cpp#L123

In a nutshell, it’s a tree traversal and returns all used arrays.
This functionality is only really required in KLEE’s current implementation when a solver is called to generate assignments for expressions, e.g.:
https://github.com/klee/klee/blob/fc83f06b17221bf5ef20e30d9da1ccff927beb17/lib/Solver/STPSolver.cpp#L233. Therefore, it’s not really visible.

Best,
Martin





> On 12. Dec 2023, at 14:23, Oleg Sokolsky <sokolsky at cis.upenn.edu> wrote:
> 
> Hi Martin,
> 
> Thanks for the quick response.  Our question was slightly different, let me clarify.  Given an instance of the Expr object, we want to obtain the set of symbolic names used in that instance.  ExprPPrinter does it, for example, but in a very specific way and, frankly, we struggled to understand how it works.  We were wondering if there is a generic way to do it.  I was expecting a visitor in the Expr hierarchy, or something similar, but could not find it.
> 
> Thanks again,
> Oleg
> 
> On 12/12/23 05:42, Nowack, Martin wrote:
>> Hi Haozhi Fan,
>> 
>> The symbolic names are generated using the call `klee_make_symbolic` indirectly or directly in your software under test.
>> KLEE tracks the memory object that have been associated with these calls (https://github.com/klee/klee/blob/fc83f06b17221bf5ef20e30d9da1ccff927beb17/lib/Core/Executor.cpp*L4435) and assigns it an array that has the same name or similar name that is unique.
>> Reading from this memory will result in read expressions that reference this array and are later used as part of the solver calls.
>> 
>> Best,
>> Martin
>> 
>>> On 11. Dec 2023, at 20:07, Haozhi Fan <h3fan at seas.upenn.edu> wrote:
>>> 
>>> Dear klee-dev members,
>>> 
>>> I was wondering if you could share some insight into how KLEE collects the set of symbolic names from an expression? Namely, how does KLEE generate the kquery for a specific path condition and from which files should I be looking for the details of such implementation? Thank you!
>>> 
>>> Best regards,
>>> Haozhi Fan
>>> _______________________________________________
>>> klee-dev mailing list
>>> klee-dev at imperial.ac.uk
>>> https://mailman.ic.ac.uk/mailman/listinfo/klee-dev
>> 
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