[PATCH] D149259: [analyzer][NFC] Use std::optional instead of custom "empty" state

[Donát Nagy via Phabricator via cfe-commits]

donat.nagy created this revision.
donat.nagy added reviewers: steakhal, dkrupp, gamesh411.
Herald added subscribers: manas, ASDenysPetrov, martong, Szelethus, 
mikhail.ramalho, a.sidorin, rnkovacs, szepet, baloghadamsoftware, xazax.hun.
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donat.nagy requested review of this revision.
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This commit eliminates the uninitialized error state from the class 
RegionRawOffsetV2 (which is locally used by the Clang Static Analyzer
checker alpha.security.ArrayBoundV2) and replaces its use with std::optional.

Motivated by https://reviews.llvm.org/D148355#inline-1437928


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149259

Files:
  clang/lib/StaticAnalyzer/Checkers/ArrayBoundCheckerV2.cpp


Index: clang/lib/StaticAnalyzer/Checkers/ArrayBoundCheckerV2.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/ArrayBoundCheckerV2.cpp
+++ clang/lib/StaticAnalyzer/Checkers/ArrayBoundCheckerV2.cpp
@@ -51,19 +51,16 @@
 class RegionRawOffsetV2 {
 private:
   const SubRegion *baseRegion;
-  SVal byteOffset;
-
-  RegionRawOffsetV2()
-    : baseRegion(nullptr), byteOffset(UnknownVal()) {}
+  NonLoc byteOffset;
 
 public:
   RegionRawOffsetV2(const SubRegion *base, NonLoc offset)
       : baseRegion(base), byteOffset(offset) { assert(base); }
 
-  NonLoc getByteOffset() const { return byteOffset.castAs<NonLoc>(); }
+  NonLoc getByteOffset() const { return byteOffset; }
   const SubRegion *getRegion() const { return baseRegion; }
 
-  static RegionRawOffsetV2 computeOffset(ProgramStateRef state,
+  static std::optional<RegionRawOffsetV2> computeOffset(ProgramStateRef state,
                                          SValBuilder &svalBuilder,
                                          SVal location);
 
@@ -158,16 +155,16 @@
   ProgramStateRef state = checkerContext.getState();
 
   SValBuilder &svalBuilder = checkerContext.getSValBuilder();
-  const RegionRawOffsetV2 &rawOffset =
+  const std::optional<RegionRawOffsetV2> &rawOffset =
     RegionRawOffsetV2::computeOffset(state, svalBuilder, location);
 
-  if (!rawOffset.getRegion())
+  if (!rawOffset)
     return;
 
-  NonLoc ByteOffset = rawOffset.getByteOffset();
+  NonLoc ByteOffset = rawOffset->getByteOffset();
 
   // CHECK LOWER BOUND
-  const MemSpaceRegion *SR = rawOffset.getRegion()->getMemorySpace();
+  const MemSpaceRegion *SR = rawOffset->getRegion()->getMemorySpace();
   if (!llvm::isa<UnknownSpaceRegion>(SR)) {
     // A pointer to UnknownSpaceRegion may point to the middle of
     // an allocated region.
@@ -188,7 +185,7 @@
 
   // CHECK UPPER BOUND
   DefinedOrUnknownSVal Size =
-      getDynamicExtent(state, rawOffset.getRegion(), svalBuilder);
+      getDynamicExtent(state, rawOffset->getRegion(), svalBuilder);
   if (auto KnownSize = Size.getAs<NonLoc>()) {
     auto [state_withinUpperBound, state_exceedsUpperBound] =
         compareValueToThreshold(state, ByteOffset, *KnownSize, svalBuilder);
@@ -310,7 +307,7 @@
 
 /// Compute a raw byte offset from a base region.  Used for array bounds
 /// checking.
-RegionRawOffsetV2 RegionRawOffsetV2::computeOffset(ProgramStateRef state,
+std::optional<RegionRawOffsetV2> RegionRawOffsetV2::computeOffset(ProgramStateRef state,
                                                    SValBuilder &svalBuilder,
                                                    SVal location)
 {
@@ -324,18 +321,18 @@
           if (auto Offset = getValue(offset, svalBuilder).getAs<NonLoc>())
             return RegionRawOffsetV2(subReg, *Offset);
         }
-        return RegionRawOffsetV2();
+        return {};
       }
       case MemRegion::ElementRegionKind: {
         const ElementRegion *elemReg = cast<ElementRegion>(region);
         SVal index = elemReg->getIndex();
         if (!isa<NonLoc>(index))
-          return RegionRawOffsetV2();
+          return {};
         QualType elemType = elemReg->getElementType();
         // If the element is an incomplete type, go no further.
         ASTContext &astContext = svalBuilder.getContext();
         if (elemType->isIncompleteType())
-          return RegionRawOffsetV2();
+          return {};
 
         // Update the offset.
         offset = addValue(state,
@@ -347,14 +344,14 @@
                           svalBuilder);
 
         if (offset.isUnknownOrUndef())
-          return RegionRawOffsetV2();
+          return {};
 
         region = elemReg->getSuperRegion();
         continue;
       }
     }
   }
-  return RegionRawOffsetV2();
+  return {};
 }
 
 void ento::registerArrayBoundCheckerV2(CheckerManager &mgr) {

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