lib/Checker/Store.cpp

   1 //== Store.cpp - Interface for maps from Locations to Values ----*- C++ -*--==//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 //  This file defined the types Store and StoreManager.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "clang/GR/PathSensitive/Store.h"
  15 #include "clang/GR/PathSensitive/GRState.h"
  16 #include "clang/AST/CharUnits.h"
  17
  18 using namespace clang;
  19
  20 StoreManager::StoreManager(GRStateManager &stateMgr)
  21   : svalBuilder(stateMgr.getSValBuilder()), StateMgr(stateMgr),
  22     MRMgr(svalBuilder.getRegionManager()), Ctx(stateMgr.getContext()) {}
  23
  24 Store StoreManager::EnterStackFrame(const GRState *state,
  25                                     const StackFrameContext *frame) {
  26   return state->getStore();
  27 }
  28
  29 const MemRegion *StoreManager::MakeElementRegion(const MemRegion *Base,
  30                                               QualType EleTy, uint64_t index) {
  31   NonLoc idx = svalBuilder.makeArrayIndex(index);
  32   return MRMgr.getElementRegion(EleTy, idx, Base, svalBuilder.getContext());
  33 }
  34
  35 // FIXME: Merge with the implementation of the same method in MemRegion.cpp
  36 static bool IsCompleteType(ASTContext &Ctx, QualType Ty) {
  37   if (const RecordType *RT = Ty->getAs<RecordType>()) {
  38     const RecordDecl *D = RT->getDecl();
  39     if (!D->getDefinition())
  40       return false;
  41   }
  42
  43   return true;
  44 }
  45
  46 const ElementRegion *StoreManager::GetElementZeroRegion(const MemRegion *R,
  47                                                         QualType T) {
  48   NonLoc idx = svalBuilder.makeZeroArrayIndex();
  49   assert(!T.isNull());
  50   return MRMgr.getElementRegion(T, idx, R, Ctx);
  51 }
  52
  53 const MemRegion *StoreManager::CastRegion(const MemRegion *R, QualType CastToTy) {
  54
  55   ASTContext& Ctx = StateMgr.getContext();
  56
  57   // Handle casts to Objective-C objects.
  58   if (CastToTy->isObjCObjectPointerType())
  59     return R->StripCasts();
  60
  61   if (CastToTy->isBlockPointerType()) {
  62     // FIXME: We may need different solutions, depending on the symbol
  63     // involved.  Blocks can be casted to/from 'id', as they can be treated
  64     // as Objective-C objects.  This could possibly be handled by enhancing
  65     // our reasoning of downcasts of symbolic objects.
  66     if (isa<CodeTextRegion>(R) || isa<SymbolicRegion>(R))
  67       return R;
  68
  69     // We don't know what to make of it.  Return a NULL region, which
  70     // will be interpretted as UnknownVal.
  71     return NULL;
  72   }
  73
  74   // Now assume we are casting from pointer to pointer. Other cases should
  75   // already be handled.
  76   QualType PointeeTy = CastToTy->getAs<PointerType>()->getPointeeType();
  77   QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy);
  78
  79   // Handle casts to void*.  We just pass the region through.
  80   if (CanonPointeeTy.getLocalUnqualifiedType() == Ctx.VoidTy)
  81     return R;
  82
  83   // Handle casts from compatible types.
  84   if (R->isBoundable())
  85     if (const TypedRegion *TR = dyn_cast<TypedRegion>(R)) {
  86       QualType ObjTy = Ctx.getCanonicalType(TR->getValueType());
  87       if (CanonPointeeTy == ObjTy)
  88         return R;
  89     }
  90
  91   // Process region cast according to the kind of the region being cast.
  92   switch (R->getKind()) {
  93     case MemRegion::CXXThisRegionKind:
  94     case MemRegion::GenericMemSpaceRegionKind:
  95     case MemRegion::StackLocalsSpaceRegionKind:
  96     case MemRegion::StackArgumentsSpaceRegionKind:
  97     case MemRegion::HeapSpaceRegionKind:
  98     case MemRegion::UnknownSpaceRegionKind:
  99     case MemRegion::NonStaticGlobalSpaceRegionKind:
 100     case MemRegion::StaticGlobalSpaceRegionKind: {
 101       assert(0 && "Invalid region cast");
 102       break;
 103     }
 104
 105     case MemRegion::FunctionTextRegionKind:
 106     case MemRegion::BlockTextRegionKind:
 107     case MemRegion::BlockDataRegionKind:
 108     case MemRegion::StringRegionKind:
 109       // FIXME: Need to handle arbitrary downcasts.
 110     case MemRegion::SymbolicRegionKind:
 111     case MemRegion::AllocaRegionKind:
 112     case MemRegion::CompoundLiteralRegionKind:
 113     case MemRegion::FieldRegionKind:
 114     case MemRegion::ObjCIvarRegionKind:
 115     case MemRegion::VarRegionKind:
 116     case MemRegion::CXXTempObjectRegionKind:
 117     case MemRegion::CXXBaseObjectRegionKind:
 118       return MakeElementRegion(R, PointeeTy);
 119
 120     case MemRegion::ElementRegionKind: {
 121       // If we are casting from an ElementRegion to another type, the
 122       // algorithm is as follows:
 123       //
 124       // (1) Compute the "raw offset" of the ElementRegion from the
 125       //     base region.  This is done by calling 'getAsRawOffset()'.
 126       //
 127       // (2a) If we get a 'RegionRawOffset' after calling
 128       //      'getAsRawOffset()', determine if the absolute offset
 129       //      can be exactly divided into chunks of the size of the
 130       //      casted-pointee type.  If so, create a new ElementRegion with
 131       //      the pointee-cast type as the new ElementType and the index
 132       //      being the offset divded by the chunk size.  If not, create
 133       //      a new ElementRegion at offset 0 off the raw offset region.
 134       //
 135       // (2b) If we don't a get a 'RegionRawOffset' after calling
 136       //      'getAsRawOffset()', it means that we are at offset 0.
 137       //
 138       // FIXME: Handle symbolic raw offsets.
 139
 140       const ElementRegion *elementR = cast<ElementRegion>(R);
 141       const RegionRawOffset &rawOff = elementR->getAsArrayOffset();
 142       const MemRegion *baseR = rawOff.getRegion();
 143
 144       // If we cannot compute a raw offset, throw up our hands and return
 145       // a NULL MemRegion*.
 146       if (!baseR)
 147         return NULL;
 148
 149       CharUnits off = CharUnits::fromQuantity(rawOff.getByteOffset());
 150
 151       if (off.isZero()) {
 152         // Edge case: we are at 0 bytes off the beginning of baseR.  We
 153         // check to see if type we are casting to is the same as the base
 154         // region.  If so, just return the base region.
 155         if (const TypedRegion *TR = dyn_cast<TypedRegion>(baseR)) {
 156           QualType ObjTy = Ctx.getCanonicalType(TR->getValueType());
 157           QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy);
 158           if (CanonPointeeTy == ObjTy)
 159             return baseR;
 160         }
 161
 162         // Otherwise, create a new ElementRegion at offset 0.
 163         return MakeElementRegion(baseR, PointeeTy);
 164       }
 165
 166       // We have a non-zero offset from the base region.  We want to determine
 167       // if the offset can be evenly divided by sizeof(PointeeTy).  If so,
 168       // we create an ElementRegion whose index is that value.  Otherwise, we
 169       // create two ElementRegions, one that reflects a raw offset and the other
 170       // that reflects the cast.
 171
 172       // Compute the index for the new ElementRegion.
 173       int64_t newIndex = 0;
 174       const MemRegion *newSuperR = 0;
 175
 176       // We can only compute sizeof(PointeeTy) if it is a complete type.
 177       if (IsCompleteType(Ctx, PointeeTy)) {
 178         // Compute the size in **bytes**.
 179         CharUnits pointeeTySize = Ctx.getTypeSizeInChars(PointeeTy);
 180         if (!pointeeTySize.isZero()) {
 181           // Is the offset a multiple of the size?  If so, we can layer the
 182           // ElementRegion (with elementType == PointeeTy) directly on top of
 183           // the base region.
 184           if (off % pointeeTySize == 0) {
 185             newIndex = off / pointeeTySize;
 186             newSuperR = baseR;
 187           }
 188         }
 189       }
 190
 191       if (!newSuperR) {
 192         // Create an intermediate ElementRegion to represent the raw byte.
 193         // This will be the super region of the final ElementRegion.
 194         newSuperR = MakeElementRegion(baseR, Ctx.CharTy, off.getQuantity());
 195       }
 196
 197       return MakeElementRegion(newSuperR, PointeeTy, newIndex);
 198     }
 199   }
 200
 201   assert(0 && "unreachable");
 202   return 0;
 203 }
 204
 205
 206 /// CastRetrievedVal - Used by subclasses of StoreManager to implement
 207 ///  implicit casts that arise from loads from regions that are reinterpreted
 208 ///  as another region.
 209 SVal StoreManager::CastRetrievedVal(SVal V, const TypedRegion *R,
 210                                     QualType castTy, bool performTestOnly) {
 211
 212   if (castTy.isNull())
 213     return V;
 214
 215   ASTContext &Ctx = svalBuilder.getContext();
 216
 217   if (performTestOnly) {
 218     // Automatically translate references to pointers.
 219     QualType T = R->getValueType();
 220     if (const ReferenceType *RT = T->getAs<ReferenceType>())
 221       T = Ctx.getPointerType(RT->getPointeeType());
 222
 223     assert(svalBuilder.getContext().hasSameUnqualifiedType(castTy, T));
 224     return V;
 225   }
 226
 227   if (const Loc *L = dyn_cast<Loc>(&V))
 228     return svalBuilder.evalCastL(*L, castTy);
 229   else if (const NonLoc *NL = dyn_cast<NonLoc>(&V))
 230     return svalBuilder.evalCastNL(*NL, castTy);
 231
 232   return V;
 233 }
 234
 235 SVal StoreManager::getLValueFieldOrIvar(const Decl* D, SVal Base) {
 236   if (Base.isUnknownOrUndef())
 237     return Base;
 238
 239   Loc BaseL = cast<Loc>(Base);
 240   const MemRegion* BaseR = 0;
 241
 242   switch (BaseL.getSubKind()) {
 243   case loc::MemRegionKind:
 244     BaseR = cast<loc::MemRegionVal>(BaseL).getRegion();
 245     break;
 246
 247   case loc::GotoLabelKind:
 248     // These are anormal cases. Flag an undefined value.
 249     return UndefinedVal();
 250
 251   case loc::ConcreteIntKind:
 252     // While these seem funny, this can happen through casts.
 253     // FIXME: What we should return is the field offset.  For example,
 254     //  add the field offset to the integer value.  That way funny things
 255     //  like this work properly:  &(((struct foo *) 0xa)->f)
 256     return Base;
 257
 258   default:
 259     assert(0 && "Unhandled Base.");
 260     return Base;
 261   }
 262
 263   // NOTE: We must have this check first because ObjCIvarDecl is a subclass
 264   // of FieldDecl.
 265   if (const ObjCIvarDecl *ID = dyn_cast<ObjCIvarDecl>(D))
 266     return loc::MemRegionVal(MRMgr.getObjCIvarRegion(ID, BaseR));
 267
 268   return loc::MemRegionVal(MRMgr.getFieldRegion(cast<FieldDecl>(D), BaseR));
 269 }
 270
 271 SVal StoreManager::getLValueElement(QualType elementType, NonLoc Offset,
 272                                     SVal Base) {
 273
 274   // If the base is an unknown or undefined value, just return it back.
 275   // FIXME: For absolute pointer addresses, we just return that value back as
 276   //  well, although in reality we should return the offset added to that
 277   //  value.
 278   if (Base.isUnknownOrUndef() || isa<loc::ConcreteInt>(Base))
 279     return Base;
 280
 281   const MemRegion* BaseRegion = cast<loc::MemRegionVal>(Base).getRegion();
 282
 283   // Pointer of any type can be cast and used as array base.
 284   const ElementRegion *ElemR = dyn_cast<ElementRegion>(BaseRegion);
 285
 286   // Convert the offset to the appropriate size and signedness.
 287   Offset = cast<NonLoc>(svalBuilder.convertToArrayIndex(Offset));
 288
 289   if (!ElemR) {
 290     //
 291     // If the base region is not an ElementRegion, create one.
 292     // This can happen in the following example:
 293     //
 294     //   char *p = __builtin_alloc(10);
 295     //   p[1] = 8;
 296     //
 297     //  Observe that 'p' binds to an AllocaRegion.
 298     //
 299     return loc::MemRegionVal(MRMgr.getElementRegion(elementType, Offset,
 300                                                     BaseRegion, Ctx));
 301   }
 302
 303   SVal BaseIdx = ElemR->getIndex();
 304
 305   if (!isa<nonloc::ConcreteInt>(BaseIdx))
 306     return UnknownVal();
 307
 308   const llvm::APSInt& BaseIdxI = cast<nonloc::ConcreteInt>(BaseIdx).getValue();
 309
 310   // Only allow non-integer offsets if the base region has no offset itself.
 311   // FIXME: This is a somewhat arbitrary restriction. We should be using
 312   // SValBuilder here to add the two offsets without checking their types.
 313   if (!isa<nonloc::ConcreteInt>(Offset)) {
 314     if (isa<ElementRegion>(BaseRegion->StripCasts()))
 315       return UnknownVal();
 316
 317     return loc::MemRegionVal(MRMgr.getElementRegion(elementType, Offset,
 318                                                     ElemR->getSuperRegion(),
 319                                                     Ctx));
 320   }
 321
 322   const llvm::APSInt& OffI = cast<nonloc::ConcreteInt>(Offset).getValue();
 323   assert(BaseIdxI.isSigned());
 324
 325   // Compute the new index.
 326   nonloc::ConcreteInt NewIdx(svalBuilder.getBasicValueFactory().getValue(BaseIdxI +
 327                                                                     OffI));
 328
 329   // Construct the new ElementRegion.
 330   const MemRegion *ArrayR = ElemR->getSuperRegion();
 331   return loc::MemRegionVal(MRMgr.getElementRegion(elementType, NewIdx, ArrayR,
 332                                                   Ctx));
 333 }