1 files changed, 138 insertions, 0 deletions
diff --git a/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp b/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp
new file mode 100644
index 0000000..ba46e17
--- /dev/null
+++ b/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp
@@ -0,0 +1,138 @@
+//=== VLASizeChecker.cpp - Undefined dereference checker --------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This defines VLASizeChecker, a builtin check in ExprEngine that 
+// performs checks for declaration of VLA of undefined or zero size.
+// In addition, VLASizeChecker is responsible for defining the extent
+// of the MemRegion that represents a VLA.
+//
+//===----------------------------------------------------------------------===//
+
+#include "InternalChecks.h"
+#include "clang/AST/CharUnits.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerVisitor.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class VLASizeChecker : public CheckerVisitor<VLASizeChecker> {
+  BugType *BT_zero;
+  BugType *BT_undef;
+  
+public:
+  VLASizeChecker() : BT_zero(0), BT_undef(0) {}
+  static void *getTag() { static int tag = 0; return &tag; }
+  void PreVisitDeclStmt(CheckerContext &C, const DeclStmt *DS);
+};
+} // end anonymous namespace
+
+void ento::RegisterVLASizeChecker(ExprEngine &Eng) {
+  Eng.registerCheck(new VLASizeChecker());
+}
+
+void VLASizeChecker::PreVisitDeclStmt(CheckerContext &C, const DeclStmt *DS) {
+  if (!DS->isSingleDecl())
+    return;
+  
+  const VarDecl *VD = dyn_cast<VarDecl>(DS->getSingleDecl());
+  if (!VD)
+    return;
+
+  ASTContext &Ctx = C.getASTContext();
+  const VariableArrayType *VLA = Ctx.getAsVariableArrayType(VD->getType());
+  if (!VLA)
+    return;
+
+  // FIXME: Handle multi-dimensional VLAs.
+  const Expr* SE = VLA->getSizeExpr();
+  const GRState *state = C.getState();
+  SVal sizeV = state->getSVal(SE);
+
+  if (sizeV.isUndef()) {
+    // Generate an error node.
+    ExplodedNode *N = C.generateSink();
+    if (!N)
+      return;
+    
+    if (!BT_undef)
+      BT_undef = new BuiltinBug("Declared variable-length array (VLA) uses a "
+                                "garbage value as its size");
+
+    EnhancedBugReport *report =
+      new EnhancedBugReport(*BT_undef, BT_undef->getName(), N);
+    report->addRange(SE->getSourceRange());
+    report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, SE);
+    C.EmitReport(report);
+    return;
+  }
+
+  // See if the size value is known. It can't be undefined because we would have
+  // warned about that already.
+  if (sizeV.isUnknown())
+    return;
+  
+  // Check if the size is zero.
+  DefinedSVal sizeD = cast<DefinedSVal>(sizeV);
+
+  const GRState *stateNotZero, *stateZero;
+  llvm::tie(stateNotZero, stateZero) = state->assume(sizeD);
+
+  if (stateZero && !stateNotZero) {
+    ExplodedNode* N = C.generateSink(stateZero);
+    if (!BT_zero)
+      BT_zero = new BuiltinBug("Declared variable-length array (VLA) has zero "
+                               "size");
+
+    EnhancedBugReport *report =
+      new EnhancedBugReport(*BT_zero, BT_zero->getName(), N);
+    report->addRange(SE->getSourceRange());
+    report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, SE);
+    C.EmitReport(report);
+    return;
+  }
+ 
+  // From this point on, assume that the size is not zero.
+  state = stateNotZero;
+
+  // VLASizeChecker is responsible for defining the extent of the array being
+  // declared. We do this by multiplying the array length by the element size,
+  // then matching that with the array region's extent symbol.
+
+  // Convert the array length to size_t.
+  SValBuilder &svalBuilder = C.getSValBuilder();
+  QualType SizeTy = Ctx.getSizeType();
+  NonLoc ArrayLength = cast<NonLoc>(svalBuilder.evalCast(sizeD, SizeTy, 
+                                                         SE->getType()));
+
+  // Get the element size.
+  CharUnits EleSize = Ctx.getTypeSizeInChars(VLA->getElementType());
+  SVal EleSizeVal = svalBuilder.makeIntVal(EleSize.getQuantity(), SizeTy);
+
+  // Multiply the array length by the element size.
+  SVal ArraySizeVal = svalBuilder.evalBinOpNN(state, BO_Mul, ArrayLength,
+                                              cast<NonLoc>(EleSizeVal), SizeTy);
+
+  // Finally, assume that the array's extent matches the given size.
+  const LocationContext *LC = C.getPredecessor()->getLocationContext();
+  DefinedOrUnknownSVal Extent =
+    state->getRegion(VD, LC)->getExtent(svalBuilder);
+  DefinedOrUnknownSVal ArraySize = cast<DefinedOrUnknownSVal>(ArraySizeVal);
+  DefinedOrUnknownSVal sizeIsKnown =
+    svalBuilder.evalEQ(state, Extent, ArraySize);
+  state = state->assume(sizeIsKnown, true);
+
+  // Assume should not fail at this point.
+  assert(state);
+
+  // Remember our assumptions!
+  C.addTransition(state);
+}