runtimeverification / runtimeverification/mir-semantics

Problems matching a symbolic stack (stacks ending in a list variable)

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Dominant language
Python
Stars
52
Forks
5
PR merge metrics
No merged PRs in 30d

Description

Rules for terminatorKindReturn and #setArgFromStack which access the top stack frame do not work (in HS backend running symbolic execution) when the stack ends in a list-sorted variable, like

<stack> StackFrame(_, _, _, _, _LOCALS) REST_OF_STACK </stack>

When replacing REST_OF_STACK with .List the rule is getting applied again.

  • Analyse this further using a K claim with LHS having a stack with a variable
  • Possibly a bug in HS backend (list matching weakness)
  • It is not the call to size(LIST)

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the terminatorKindReturn and #setArgFromStack rules and reproduce the symbolic-execution case using a K claim whose left-hand side has a stack variable. Compare the list-variable stack with the .List case in the HS backend, and determine whether the matching behavior is a backend bug; done means the cause and a focused resolution are established.

Written by the indexing model from the issue text.

Assessment

Tech stack
haskell
Domain
backend, compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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