This repo contains a version of clang that is being modified to support Checked C. Checked C is an extension to C that lets programmers write C code that is guaranteed by the compiler to be type-safe.
This PR fixes a bug with the way equivalent expressions were being recorded in RecordEqualityWithTarget.
In an assignment such as x++, x += 1, x = x + 1, etc., SameValue is empty after calling UpdateSameValueAfterAssignment (since the RHS x + 1 of the assignment uses the value of the LHS x). This meant that SrcAllowedInEquivExprs was false in RecordEqualityWithTarget, so the mapping x => x + 1 was added to TargetSrcEquality. The information in TargetSrcEquality is added to EquivExprs in ValidateBoundsContext, so EquivExprs would contain a set that contained both x and x + 1 only while checking bounds after the current top-level statement.
This PR adds an AllowTempEquality argument to RecordEqualityWithTarget that controls whether the mapping Target => Src is permitted to be added to TargetSrcEquality. UpdateSameValueAfterAssignment now returns true if State.SameValue was unchanged by the assignment (if the RHS of the assignment uses the value of the LHS, then at least one expression will be removed from State.SameValue if State.SameValue was initially nonempty). If State.SameValue was unchanged by the assignment, then temporary equality is allowed to be recorded between Target and Src.
This PR fixes a bug with the way equivalent expressions were being recorded in
RecordEqualityWithTarget.In an assignment such as
x++,x += 1,x = x + 1, etc.,SameValueis empty after callingUpdateSameValueAfterAssignment(since the RHSx + 1of the assignment uses the value of the LHSx). This meant thatSrcAllowedInEquivExprswasfalseinRecordEqualityWithTarget, so the mappingx => x + 1was added toTargetSrcEquality. The information inTargetSrcEqualityis added toEquivExprsinValidateBoundsContext, soEquivExprswould contain a set that contained bothxandx + 1only while checking bounds after the current top-level statement.This PR adds an
AllowTempEqualityargument toRecordEqualityWithTargetthat controls whether the mappingTarget => Srcis permitted to be added toTargetSrcEquality.UpdateSameValueAfterAssignmentnow returnstrueifState.SameValuewas unchanged by the assignment (if the RHS of the assignment uses the value of the LHS, then at least one expression will be removed fromState.SameValueifState.SameValuewas initially nonempty). IfState.SameValuewas unchanged by the assignment, then temporary equality is allowed to be recorded betweenTargetandSrc.