lib/StaticAnalyzer/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/StaticAnalyzer/PathSensitive/Store.h"
  15 #include "clang/StaticAnalyzer/PathSensitive/GRState.h"
  16 #include "clang/AST/CharUnits.h"
  17
  18 using namespace clang;
  19 using namespace ento;
  20
  21 StoreManager::StoreManager(GRStateManager &stateMgr)
  22   : svalBuilder(stateMgr.getSValBuilder()), StateMgr(stateMgr),
  23     MRMgr(svalBuilder.getRegionManager()), Ctx(stateMgr.getContext()) {}
  24
  25 Store StoreManager::EnterStackFrame(const GRState *state,
  26                                     const StackFrameContext *frame) {
  27   return state->getStore();
  28 }
  29
  30 const MemRegion *StoreManager::MakeElementRegion(const MemRegion *Base,
  31                                               QualType EleTy, uint64_t index) {
  32   NonLoc idx = svalBuilder.makeArrayIndex(index);
  33   return MRMgr.getElementRegion(EleTy, idx, Base, svalBuilder.getContext());
  34 }
  35
  36 // FIXME: Merge with the implementation of the same method in MemRegion.cpp
  37 static bool IsCompleteType(ASTContext &Ctx, QualType Ty) {
  38   if (const RecordType *RT = Ty->getAs<RecordType>()) {
  39     const RecordDecl *D = RT->getDecl();
  40     if (!D->getDefinition())
  41       return false;
  42   }
  43
  44   return true;
  45 }
  46
  47 const ElementRegion *StoreManager::GetElementZeroRegion(const MemRegion *R,
  48                                                         QualType T) {
  49   NonLoc idx = svalBuilder.makeZeroArrayIndex();
  50   assert(!T.isNull());
  51   return MRMgr.getElementRegion(T, idx, R, Ctx);
  52 }
  53
  54 const MemRegion *StoreManager::CastRegion(const MemRegion *R, QualType CastToTy) {
  55
  56   ASTContext& Ctx = StateMgr.getContext();
  57
  58   // Handle casts to Objective-C objects.
  59   if (CastToTy->isObjCObjectPointerType())
  60     return R->StripCasts();
  61
  62   if (CastToTy->isBlockPointerType()) {
  63     // FIXME: We may need different solutions, depending on the symbol
  64     // involved.  Blocks can be casted to/from 'id', as they can be treated
  65     // as Objective-C objects.  This could possibly be handled by enhancing
  66     // our reasoning of downcasts of symbolic objects.
  67     if (isa<CodeTextRegion>(R) || isa<SymbolicRegion>(R))
  68       return R;
  69
  70     // We don't know what to make of it.  Return a NULL region, which
  71     // will be interpretted as UnknownVal.
  72     return NULL;
  73   }
  74
  75   // Now assume we are casting from pointer to pointer. Other cases should
  76   // already be handled.
  77   QualType PointeeTy = CastToTy->getAs<PointerType>()->getPointeeType();
  78   QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy);
  79
  80   // Handle casts to void*.  We just pass the region through.
  81   if (CanonPointeeTy.getLocalUnqualifiedType() == Ctx.VoidTy)
  82     return R;
  83
  84   // Handle casts from compatible types.
  85   if (R->isBoundable())
  86     if (const TypedRegion *TR = dyn_cast<TypedRegion>(R)) {
  87       QualType ObjTy = Ctx.getCanonicalType(TR->getValueType());
  88       if (CanonPointeeTy == ObjTy)
  89         return R;
  90     }
  91
  92   // Process region cast according to the kind of the region being cast.
  93   switch (R->getKind()) {
  94     case MemRegion::CXXThisRegionKind:
  95     case MemRegion::GenericMemSpaceRegionKind:
  96     case MemRegion::StackLocalsSpaceRegionKind:
  97     case MemRegion::StackArgumentsSpaceRegionKind:
  98     case MemRegion::HeapSpaceRegionKind:
  99     case MemRegion::UnknownSpaceRegionKind:
 100     case MemRegion::NonStaticGlobalSpaceRegionKind:
 101     case MemRegion::StaticGlobalSpaceRegionKind: {
 102       assert(0 && "Invalid region cast");
 103       break;
 104     }
 105
 106     case MemRegion::FunctionTextRegionKind:
 107     case MemRegion::BlockTextRegionKind:
 108     case MemRegion::BlockDataRegionKind:
 109     case MemRegion::StringRegionKind:
 110       // FIXME: Need to handle arbitrary downcasts.
 111     case MemRegion::SymbolicRegionKind:
 112     case MemRegion::AllocaRegionKind:
 113     case MemRegion::CompoundLiteralRegionKind:
 114     case MemRegion::FieldRegionKind:
 115     case MemRegion::ObjCIvarRegionKind:
 116     case MemRegion::VarRegionKind:
 117     case MemRegion::CXXTempObjectRegionKind:
 118     case MemRegion::CXXBaseObjectRegionKind:
 119       return MakeElementRegion(R, PointeeTy);
 120
 121     case MemRegion::ElementRegionKind: {
 122       // If we are casting from an ElementRegion to another type, the
 123       // algorithm is as follows:
 124       //
 125       // (1) Compute the "raw offset" of the ElementRegion from the
 126       //     base region.  This is done by calling 'getAsRawOffset()'.
 127       //
 128       // (2a) If we get a 'RegionRawOffset' after calling
 129       //      'getAsRawOffset()', determine if the absolute offset
 130       //      can be exactly divided into chunks of the size of the
 131       //      casted-pointee type.  If so, create a new ElementRegion with
 132       //      the pointee-cast type as the new ElementType and the index
 133       //      being the offset divded by the chunk size.  If not, create
 134       //      a new ElementRegion at offset 0 off the raw offset region.
 135       //
 136       // (2b) If we don't a get a 'RegionRawOffset' after calling
 137       //      'getAsRawOffset()', it means that we are at offset 0.
 138       //
 139       // FIXME: Handle symbolic raw offsets.
 140
 141       const ElementRegion *elementR = cast<ElementRegion>(R);
 142       const RegionRawOffset &rawOff = elementR->getAsArrayOffset();
 143       const MemRegion *baseR = rawOff.getRegion();
 144
 145       // If we cannot compute a raw offset, throw up our hands and return
 146       // a NULL MemRegion*.
 147       if (!baseR)
 148         return NULL;
 149
 150       CharUnits off = CharUnits::fromQuantity(rawOff.getByteOffset());
 151
 152       if (off.isZero()) {
 153         // Edge case: we are at 0 bytes off the beginning of baseR.  We
 154         // check to see if type we are casting to is the same as the base
 155         // region.  If so, just return the base region.
 156         if (const TypedRegion *TR = dyn_cast<TypedRegion>(baseR)) {
 157           QualType ObjTy = Ctx.getCanonicalType(TR->getValueType());
 158           QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy);
 159           if (CanonPointeeTy == ObjTy)
 160             return baseR;
 161         }
 162
 163         // Otherwise, create a new ElementRegion at offset 0.
 164         return MakeElementRegion(baseR, PointeeTy);
 165       }
 166
 167       // We have a non-zero offset from the base region.  We want to determine
 168       // if the offset can be evenly divided by sizeof(PointeeTy).  If so,
 169       // we create an ElementRegion whose index is that value.  Otherwise, we
 170       // create two ElementRegions, one that reflects a raw offset and the other
 171       // that reflects the cast.
 172
 173       // Compute the index for the new ElementRegion.
 174       int64_t newIndex = 0;
 175       const MemRegion *newSuperR = 0;
 176
 177       // We can only compute sizeof(PointeeTy) if it is a complete type.
 178       if (IsCompleteType(Ctx, PointeeTy)) {
 179         // Compute the size in **bytes**.
 180         CharUnits pointeeTySize = Ctx.getTypeSizeInChars(PointeeTy);
 181         if (!pointeeTySize.isZero()) {
 182           // Is the offset a multiple of the size?  If so, we can layer the
 183           // ElementRegion (with elementType == PointeeTy) directly on top of
 184           // the base region.
 185           if (off % pointeeTySize == 0) {
 186             newIndex = off / pointeeTySize;
 187             newSuperR = baseR;
 188           }
 189         }
 190       }
 191
 192       if (!newSuperR) {
 193         // Create an intermediate ElementRegion to represent the raw byte.
 194         // This will be the super region of the final ElementRegion.
 195         newSuperR = MakeElementRegion(baseR, Ctx.CharTy, off.getQuantity());
 196       }
 197
 198       return MakeElementRegion(newSuperR, PointeeTy, newIndex);
 199     }
 200   }
 201
 202   assert(0 && "unreachable");
 203   return 0;
 204 }
 205
 206
 207 /// CastRetrievedVal - Used by subclasses of StoreManager to implement
 208 ///  implicit casts that arise from loads from regions that are reinterpreted
 209 ///  as another region.
 210 SVal StoreManager::CastRetrievedVal(SVal V, const TypedRegion *R,
 211                                     QualType castTy, bool performTestOnly) {
 212
 213   if (castTy.isNull())
 214     return V;
 215
 216   ASTContext &Ctx = svalBuilder.getContext();
 217
 218   if (performTestOnly) {
 219     // Automatically translate references to pointers.
 220     QualType T = R->getValueType();
 221     if (const ReferenceType *RT = T->getAs<ReferenceType>())
 222       T = Ctx.getPointerType(RT->getPointeeType());
 223
 224     assert(svalBuilder.getContext().hasSameUnqualifiedType(castTy, T));
 225     return V;
 226   }
 227
 228   if (const Loc *L = dyn_cast<Loc>(&V))
 229     return svalBuilder.evalCastL(*L, castTy);
 230   else if (const NonLoc *NL = dyn_cast<NonLoc>(&V))
 231     return svalBuilder.evalCastNL(*NL, castTy);
 232
 233   return V;
 234 }
 235
 236 SVal StoreManager::getLValueFieldOrIvar(const Decl* D, SVal Base) {
 237   if (Base.isUnknownOrUndef())
 238     return Base;
 239
 240   Loc BaseL = cast<Loc>(Base);
 241   const MemRegion* BaseR = 0;
 242
 243   switch (BaseL.getSubKind()) {
 244   case loc::MemRegionKind:
 245     BaseR = cast<loc::MemRegionVal>(BaseL).getRegion();
 246     break;
 247
 248   case loc::GotoLabelKind:
 249     // These are anormal cases. Flag an undefined value.
 250     return UndefinedVal();
 251
 252   case loc::ConcreteIntKind:
 253     // While these seem funny, this can happen through casts.
 254     // FIXME: What we should return is the field offset.  For example,
 255     //  add the field offset to the integer value.  That way funny things
 256     //  like this work properly:  &(((struct foo *) 0xa)->f)
 257     return Base;
 258
 259   default:
 260     assert(0 && "Unhandled Base.");
 261     return Base;
 262   }
 263
 264   // NOTE: We must have this check first because ObjCIvarDecl is a subclass
 265   // of FieldDecl.
 266   if (const ObjCIvarDecl *ID = dyn_cast<ObjCIvarDecl>(D))
 267     return loc::MemRegionVal(MRMgr.getObjCIvarRegion(ID, BaseR));
 268
 269   return loc::MemRegionVal(MRMgr.getFieldRegion(cast<FieldDecl>(D), BaseR));
 270 }
 271
 272 SVal StoreManager::getLValueElement(QualType elementType, NonLoc Offset,
 273                                     SVal Base) {
 274
 275   // If the base is an unknown or undefined value, just return it back.
 276   // FIXME: For absolute pointer addresses, we just return that value back as
 277   //  well, although in reality we should return the offset added to that
 278   //  value.
 279   if (Base.isUnknownOrUndef() || isa<loc::ConcreteInt>(Base))
 280     return Base;
 281
 282   const MemRegion* BaseRegion = cast<loc::MemRegionVal>(Base).getRegion();
 283
 284   // Pointer of any type can be cast and used as array base.
 285   const ElementRegion *ElemR = dyn_cast<ElementRegion>(BaseRegion);
 286
 287   // Convert the offset to the appropriate size and signedness.
 288   Offset = cast<NonLoc>(svalBuilder.convertToArrayIndex(Offset));
 289
 290   if (!ElemR) {
 291     //
 292     // If the base region is not an ElementRegion, create one.
 293     // This can happen in the following example:
 294     //
 295     //   char *p = __builtin_alloc(10);
 296     //   p[1] = 8;
 297     //
 298     //  Observe that 'p' binds to an AllocaRegion.
 299     //
 300     return loc::MemRegionVal(MRMgr.getElementRegion(elementType, Offset,
 301                                                     BaseRegion, Ctx));
 302   }
 303
 304   SVal BaseIdx = ElemR->getIndex();
 305
 306   if (!isa<nonloc::ConcreteInt>(BaseIdx))
 307     return UnknownVal();
 308
 309   const llvm::APSInt& BaseIdxI = cast<nonloc::ConcreteInt>(BaseIdx).getValue();
 310
 311   // Only allow non-integer offsets if the base region has no offset itself.
 312   // FIXME: This is a somewhat arbitrary restriction. We should be using
 313   // SValBuilder here to add the two offsets without checking their types.
 314   if (!isa<nonloc::ConcreteInt>(Offset)) {
 315     if (isa<ElementRegion>(BaseRegion->StripCasts()))
 316       return UnknownVal();
 317
 318     return loc::MemRegionVal(MRMgr.getElementRegion(elementType, Offset,
 319                                                     ElemR->getSuperRegion(),
 320                                                     Ctx));
 321   }
 322
 323   const llvm::APSInt& OffI = cast<nonloc::ConcreteInt>(Offset).getValue();
 324   assert(BaseIdxI.isSigned());
 325
 326   // Compute the new index.
 327   nonloc::ConcreteInt NewIdx(svalBuilder.getBasicValueFactory().getValue(BaseIdxI +
 328                                                                     OffI));
 329
 330   // Construct the new ElementRegion.
 331   const MemRegion *ArrayR = ElemR->getSuperRegion();
 332   return loc::MemRegionVal(MRMgr.getElementRegion(elementType, NewIdx, ArrayR,
 333                                                   Ctx));
 334 }