Add a new symbol type, SymbolExtent, to represent the extents of memory regions that may not be known at compile-time (such as those created by malloc). This replaces the old setExtent/getExtent API on Store, which used the GRState's GDM to store SVals.

Also adds a getKnownValue() method to SValuator, which gets the integer value of an SVal if it is known to only have one possible value. There are more places in the code that could be using this, but in general we want to be dealing entirely in SVals, so its usefulness is limited.

The only visible functionality change is that extents are now honored for any DeclRegion, such as fields and Objective-C ivars, rather than just variables. This shows up in bounds-checking and cast-size-checking.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107577 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 115 deletions

diff --git a/lib/Checker/RegionStore.cpp b/lib/Checker/RegionStore.cpp
index 8a64ec8d24..7164b832c2 100644
--- a/lib/Checker/RegionStore.cpp
+++ b/lib/Checker/RegionStore.cpp
@@ -118,22 +118,6 @@ public:
 }
 
 //===----------------------------------------------------------------------===//
-// Region "Extents"
-//===----------------------------------------------------------------------===//
-//
-//  MemRegions represent chunks of memory with a size (their "extent").  This
-//  GDM entry tracks the extents for regions.  Extents are in bytes.
-//
-namespace { class RegionExtents {}; }
-static int RegionExtentsIndex = 0;
-namespace clang {
-  template<> struct GRStateTrait<RegionExtents>
-    : public GRStatePartialTrait<llvm::ImmutableMap<const MemRegion*, SVal> > {
-    static void* GDMIndex() { return &RegionExtentsIndex; }
-  };
-}
-
-//===----------------------------------------------------------------------===//
 // Utility functions.
 //===----------------------------------------------------------------------===//
 
@@ -380,18 +364,7 @@ public: // Part of public interface to class.
   // Region "extents".
   //===------------------------------------------------------------------===//
 
-  const GRState *setExtent(const GRState *state,const MemRegion* R,SVal Extent){
-    return state->set<RegionExtents>(R, Extent);
-  }
-
-  Optional<SVal> getExtent(const GRState *state, const MemRegion *R) {
-    const SVal *V = state->get<RegionExtents>(R);
-    if (V)
-      return *V;
-    else
-      return Optional<SVal>();
-  }
-
+  // FIXME: This method will soon be eliminated; see the note in Store.h.
   DefinedOrUnknownSVal getSizeInElements(const GRState *state,
                                          const MemRegion* R, QualType EleTy);
 
@@ -772,88 +745,19 @@ Store RegionStoreManager::InvalidateRegions(Store store,
 DefinedOrUnknownSVal RegionStoreManager::getSizeInElements(const GRState *state,
                                                            const MemRegion *R,
                                                            QualType EleTy) {
+  SVal Size = cast<SubRegion>(R)->getExtent(ValMgr);
+  SValuator &SVator = ValMgr.getSValuator();
+  const llvm::APSInt *SizeInt = SVator.getKnownValue(state, Size);
+  if (!SizeInt)
+    return UnknownVal();
 
-  switch (R->getKind()) {
-    case MemRegion::CXXThisRegionKind:
-      assert(0 && "Cannot get size of 'this' region");
-    case MemRegion::GenericMemSpaceRegionKind:
-    case MemRegion::StackLocalsSpaceRegionKind:
-    case MemRegion::StackArgumentsSpaceRegionKind:
-    case MemRegion::HeapSpaceRegionKind:
-    case MemRegion::NonStaticGlobalSpaceRegionKind:
-    case MemRegion::StaticGlobalSpaceRegionKind:
-    case MemRegion::UnknownSpaceRegionKind:
-      assert(0 && "Cannot index into a MemSpace");
-      return UnknownVal();
-
-    case MemRegion::FunctionTextRegionKind:
-    case MemRegion::BlockTextRegionKind:
-    case MemRegion::BlockDataRegionKind:
-      // Technically this can happen if people do funny things with casts.
-      return UnknownVal();
-
-      // Not yet handled.
-    case MemRegion::AllocaRegionKind:
-    case MemRegion::CompoundLiteralRegionKind:
-    case MemRegion::ElementRegionKind:
-    case MemRegion::FieldRegionKind:
-    case MemRegion::ObjCIvarRegionKind:
-    case MemRegion::CXXObjectRegionKind:
-      return UnknownVal();
-
-    case MemRegion::SymbolicRegionKind: {
-      const SVal *Size = state->get<RegionExtents>(R);
-      if (!Size)
-        return UnknownVal();
-      const nonloc::ConcreteInt *CI = dyn_cast<nonloc::ConcreteInt>(Size);
-      if (!CI)
-        return UnknownVal();
-
-      CharUnits RegionSize =
-        CharUnits::fromQuantity(CI->getValue().getSExtValue());
-      CharUnits EleSize = getContext().getTypeSizeInChars(EleTy);
-      assert(RegionSize % EleSize == 0);
-
-      return ValMgr.makeIntVal(RegionSize / EleSize, false);
-    }
-
-    case MemRegion::StringRegionKind: {
-      const StringLiteral* Str = cast<StringRegion>(R)->getStringLiteral();
-      // We intentionally made the size value signed because it participates in
-      // operations with signed indices.
-      return ValMgr.makeIntVal(Str->getByteLength()+1, false);
-    }
-
-    case MemRegion::VarRegionKind: {
-      const VarRegion* VR = cast<VarRegion>(R);
-      ASTContext& Ctx = getContext();
-      // Get the type of the variable.
-      QualType T = VR->getDesugaredValueType(Ctx);
-
-      // FIXME: Handle variable-length arrays.
-      if (isa<VariableArrayType>(T))
-        return UnknownVal();
-
-      CharUnits EleSize = Ctx.getTypeSizeInChars(EleTy);
-
-      if (const ConstantArrayType* CAT = dyn_cast<ConstantArrayType>(T)) {
-        // return the size as signed integer.
-        CharUnits RealEleSize = Ctx.getTypeSizeInChars(CAT->getElementType());
-        CharUnits::QuantityType EleRatio = RealEleSize / EleSize;
-        int64_t Length = CAT->getSize().getSExtValue();
-        return ValMgr.makeIntVal(Length * EleRatio, false);
-      }
-
-      // Clients can reinterpret ordinary variables as arrays, possibly of
-      // another type. The width is rounded down to ensure that an access is
-      // entirely within bounds.
-      CharUnits VarSize = Ctx.getTypeSizeInChars(T);
-      return ValMgr.makeIntVal(VarSize / EleSize, false);
-    }
-  }
+  CharUnits RegionSize = CharUnits::fromQuantity(SizeInt->getSExtValue());
+  CharUnits EleSize = getContext().getTypeSizeInChars(EleTy);
 
-  assert(0 && "Unreachable");
-  return UnknownVal();
+  // If a variable is reinterpreted as a type that doesn't fit into a larger
+  // type evenly, round it down.
+  // This is a signed value, since it's used in arithmetic with signed indices.
+  return ValMgr.makeIntVal(RegionSize / EleSize, false);
 }
 
 //===----------------------------------------------------------------------===//
@@ -1954,13 +1858,6 @@ const GRState *RegionStoreManager::RemoveDeadBindings(GRState &state,
   }
   state.setStore(B.getRoot());
   const GRState *s = StateMgr.getPersistentState(state);
-  // Remove the extents of dead symbolic regions.
-  llvm::ImmutableMap<const MemRegion*,SVal> Extents = s->get<RegionExtents>();
-  for (llvm::ImmutableMap<const MemRegion *, SVal>::iterator I=Extents.begin(),
-         E = Extents.end(); I != E; ++I) {
-    if (!W.isVisited(I->first))
-      s = s->remove<RegionExtents>(I->first);
-  }
   return s;
 }