[analyzer] Support modeling no-op BaseToDerived casts in ExprEngine.

Introduce a new MemRegion sub-class, CXXDerivedObjectRegion, which is
the opposite of CXXBaseObjectRegion, to represent such casts. Such region is
a bit weird because it is by design bigger than its super-region.
But it's not harmful when it is put on top of a SymbolicRegion
that has unknown extent anyway.

Offset computation for CXXDerivedObjectRegion and proper modeling of casts
still remains to be implemented.

Differential Revision: https://reviews.llvm.org/D51191

llvm-svn: 340984

1 files changed, 47 insertions, 6 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/MemRegion.cpp b/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
index cb2122c7749..a3d3eb26615 100644
--- a/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
+++ b/clang/lib/StaticAnalyzer/Core/MemRegion.cpp
@@ -225,6 +225,10 @@ QualType CXXBaseObjectRegion::getValueType() const {
   return QualType(getDecl()->getTypeForDecl(), 0);
 }
 
+QualType CXXDerivedObjectRegion::getValueType() const {
+  return QualType(getDecl()->getTypeForDecl(), 0);
+}
+
 //===----------------------------------------------------------------------===//
 // FoldingSet profiling.
 //===----------------------------------------------------------------------===//
@@ -404,6 +408,17 @@ void CXXBaseObjectRegion::Profile(llvm::FoldingSetNodeID &ID) const {
   ProfileRegion(ID, getDecl(), isVirtual(), superRegion);
 }
 
+void CXXDerivedObjectRegion::ProfileRegion(llvm::FoldingSetNodeID &ID,
+                                           const CXXRecordDecl *RD,
+                                           const MemRegion *SReg) {
+  ID.AddPointer(RD);
+  ID.AddPointer(SReg);
+}
+
+void CXXDerivedObjectRegion::Profile(llvm::FoldingSetNodeID &ID) const {
+  ProfileRegion(ID, getDecl(), superRegion);
+}
+
 //===----------------------------------------------------------------------===//
 // Region anchors.
 //===----------------------------------------------------------------------===//
@@ -475,7 +490,11 @@ void CXXTempObjectRegion::dumpToStream(raw_ostream &os) const {
 }
 
 void CXXBaseObjectRegion::dumpToStream(raw_ostream &os) const {
-  os << "base{" << superRegion << ',' << getDecl()->getName() << '}';
+  os << "Base{" << superRegion << ',' << getDecl()->getName() << '}';
+}
+
+void CXXDerivedObjectRegion::dumpToStream(raw_ostream &os) const {
+  os << "Derived{" << superRegion << ',' << getDecl()->getName() << '}';
 }
 
 void CXXThisRegion::dumpToStream(raw_ostream &os) const {
@@ -483,7 +502,7 @@ void CXXThisRegion::dumpToStream(raw_ostream &os) const {
 }
 
 void ElementRegion::dumpToStream(raw_ostream &os) const {
-  os << "element{" << superRegion << ','
+  os << "Element{" << superRegion << ','
      << Index << ',' << getElementType().getAsString() << '}';
 }
 
@@ -492,7 +511,7 @@ void FieldRegion::dumpToStream(raw_ostream &os) const {
 }
 
 void ObjCIvarRegion::dumpToStream(raw_ostream &os) const {
-  os << "ivar{" << superRegion << ',' << *getDecl() << '}';
+  os << "Ivar{" << superRegion << ',' << *getDecl() << '}';
 }
 
 void StringRegion::dumpToStream(raw_ostream &os) const {
@@ -630,6 +649,14 @@ void CXXBaseObjectRegion::printPrettyAsExpr(raw_ostream &os) const {
   superRegion->printPrettyAsExpr(os);
 }
 
+bool CXXDerivedObjectRegion::canPrintPrettyAsExpr() const {
+  return superRegion->canPrintPrettyAsExpr();
+}
+
+void CXXDerivedObjectRegion::printPrettyAsExpr(raw_ostream &os) const {
+  superRegion->printPrettyAsExpr(os);
+}
+
 std::string MemRegion::getDescriptiveName(bool UseQuotes) const {
   std::string VariableName;
   std::string ArrayIndices;
@@ -1061,6 +1088,12 @@ MemRegionManager::getCXXBaseObjectRegion(const CXXRecordDecl *RD,
   return getSubRegion<CXXBaseObjectRegion>(RD, IsVirtual, Super);
 }
 
+const CXXDerivedObjectRegion *
+MemRegionManager::getCXXDerivedObjectRegion(const CXXRecordDecl *RD,
+                                            const SubRegion *Super) {
+  return getSubRegion<CXXDerivedObjectRegion>(RD, Super);
+}
+
 const CXXThisRegion*
 MemRegionManager::getCXXThisRegion(QualType thisPointerTy,
                                    const LocationContext *LC) {
@@ -1131,6 +1164,7 @@ const MemRegion *MemRegion::getBaseRegion() const {
       case MemRegion::FieldRegionKind:
       case MemRegion::ObjCIvarRegionKind:
       case MemRegion::CXXBaseObjectRegionKind:
+      case MemRegion::CXXDerivedObjectRegionKind:
         R = cast<SubRegion>(R)->getSuperRegion();
         continue;
       default:
@@ -1149,7 +1183,7 @@ bool MemRegion::isSubRegionOf(const MemRegion *R) const {
 // View handling.
 //===----------------------------------------------------------------------===//
 
-const MemRegion *MemRegion::StripCasts(bool StripBaseCasts) const {
+const MemRegion *MemRegion::StripCasts(bool StripBaseAndDerivedCasts) const {
   const MemRegion *R = this;
   while (true) {
     switch (R->getKind()) {
@@ -1161,9 +1195,10 @@ const MemRegion *MemRegion::StripCasts(bool StripBaseCasts) const {
       break;
     }
     case CXXBaseObjectRegionKind:
-      if (!StripBaseCasts)
+    case CXXDerivedObjectRegionKind:
+      if (!StripBaseAndDerivedCasts)
         return R;
-      R = cast<CXXBaseObjectRegion>(R)->getSuperRegion();
+      R = cast<TypedValueRegion>(R)->getSuperRegion();
       break;
     default:
       return R;
@@ -1344,6 +1379,12 @@ static RegionOffset calculateOffset(const MemRegion *R) {
       Offset += BaseOffset.getQuantity() * R->getContext().getCharWidth();
       break;
     }
+
+    case MemRegion::CXXDerivedObjectRegionKind: {
+      // TODO: Store the base type in the CXXDerivedObjectRegion and use it.
+      goto Finish;
+    }
+
     case MemRegion::ElementRegionKind: {
       const auto *ER = cast<ElementRegion>(R);
       R = ER->getSuperRegion();