UnionDomain.meet: Throw Uncomparable exception for abstract unions with different active fields#1109
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UnionDomain.meet: Throw Uncomparable exception for abstract unions with different active fields#1109
UnionDomain.meet: Throw Uncomparable exception for abstract unions with different active fields#1109Conversation
…ncompatibleIKinds-exception.
…t active fields, use it in BaseInvariant. The refinement by BaseInvariant to handle branching used VD.meet, which caused issue #1105, due to the behavior of UnionDomain.meet: The meet of unions with different active fields can result in a bottom value. This led to e.g. spuriously dead code. This commit adds a function try_meet to the valueDomain, the union domain, and those domains that may contain a union domain element: structs, arrays, blobs. The function try_meet in the union domain throws an exception in the case the fields of the unions for which a meet was tried did not coincide. In case this exception occurs, the BaseInvariant does not perform refinement.
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The exact behavior on analyzer/tests/regression/27-inv_invariants/19-union-char-int.c Lines 3 to 18 in 14929ca Whether this actually holds may e.g. depend on the endianness of the machine. But this is a separate issue. |
sim642
reviewed
Jul 11, 2023
…different active fields," This reverts commit 6f12ce2.
…not match. Raise an Lattice.Uncomparable exception when the active fields of the unions that the meet is applied to, do not match. Catch Uncomparable exception in BaseInvarian, and do not do refinement in case the exception is thrown during the VD.meet.
VD.try_meet function and use it instead of VD.meet in BaseInvariantUnionDomain.meet: Throw Uncomparable exception for abstract unions with different active fields
sim642
reviewed
Jul 14, 2023
The definition of the meet via Lattice.Prod (Field) (Values) is equivalent and thus does not need to be overwritten.
sim642
approved these changes
Jul 20, 2023
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I had to readd the explicit |
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Edit: This PR changes the
meetof theUnionDomainsuch that it throws aUncomparableexception, as suggested below: #1109 (comment). TheBaseInvariantthat uses theVD.meetcatches theUncomparableexception and does not do a refinement in case it is thrown.On test case
27/18both branches of anifcomparing two unions are no longer considered dead, and test27/19does no longer crashes with theIncompatbileIkindException.Fixes #1105.
Previous Approach
This adds a functionValueDomain.try_meet, a version of themeetthat may fail for unions with different active fields and use it in BaseInvariant. @michael-schwarz and I discussed this today.The refinement by BaseInvariant to handle branching used VD.meet, which caused issue #1105, due to the behavior of UnionDomain.meet: The meet of unions with different active fields can result in a bottom value.This led to e.g. spuriously dead code.
This adds a functiontry_meetto theVvalueDomain, the union domain, and those domains that may contain a union domain element: structs, arrays, blobs. The functiontry_meetin the union domain throws an exception if the fields of the unions for which a meet was tried do not coincide.