1 files changed, 205 insertions, 0 deletions
diff --git a/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp b/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
new file mode 100644
index 0000000..606ac4a
--- /dev/null
+++ b/lib/StaticAnalyzer/Checkers/DereferenceChecker.cpp
@@ -0,0 +1,205 @@
+//== NullDerefChecker.cpp - Null 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 NullDerefChecker, a builtin check in ExprEngine that performs
+// checks for null pointers at loads and stores.
+//
+//===----------------------------------------------------------------------===//
+
+#include "InternalChecks.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Checkers/DereferenceChecker.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/Checker.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class DereferenceChecker : public Checker {
+  BuiltinBug *BT_null;
+  BuiltinBug *BT_undef;
+  llvm::SmallVector<ExplodedNode*, 2> ImplicitNullDerefNodes;
+public:
+  DereferenceChecker() : BT_null(0), BT_undef(0) {}
+  static void *getTag() { static int tag = 0; return &tag; }
+  void visitLocation(CheckerContext &C, const Stmt *S, SVal location,
+                     bool isLoad);
+
+  std::pair<ExplodedNode * const*, ExplodedNode * const*>
+  getImplicitNodes() const {
+    return std::make_pair(ImplicitNullDerefNodes.data(),
+                          ImplicitNullDerefNodes.data() +
+                          ImplicitNullDerefNodes.size());
+  }
+  void AddDerefSource(llvm::raw_ostream &os,
+                      llvm::SmallVectorImpl<SourceRange> &Ranges,
+                      const Expr *Ex, bool loadedFrom = false);
+};
+} // end anonymous namespace
+
+void ento::RegisterDereferenceChecker(ExprEngine &Eng) {
+  Eng.registerCheck(new DereferenceChecker());
+}
+
+std::pair<ExplodedNode * const *, ExplodedNode * const *>
+ento::GetImplicitNullDereferences(ExprEngine &Eng) {
+  DereferenceChecker *checker = Eng.getChecker<DereferenceChecker>();
+  if (!checker)
+    return std::make_pair((ExplodedNode * const *) 0,
+                          (ExplodedNode * const *) 0);
+  return checker->getImplicitNodes();
+}
+
+void DereferenceChecker::AddDerefSource(llvm::raw_ostream &os,
+                                     llvm::SmallVectorImpl<SourceRange> &Ranges,
+                                        const Expr *Ex,
+                                        bool loadedFrom) {
+  Ex = Ex->IgnoreParenLValueCasts();
+  switch (Ex->getStmtClass()) {
+    default:
+      return;
+    case Stmt::DeclRefExprClass: {
+      const DeclRefExpr *DR = cast<DeclRefExpr>(Ex);
+      if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
+        os << " (" << (loadedFrom ? "loaded from" : "from")
+           << " variable '" <<  VD->getName() << "')";
+        Ranges.push_back(DR->getSourceRange());
+      }
+      return;
+    }
+    case Stmt::MemberExprClass: {
+      const MemberExpr *ME = cast<MemberExpr>(Ex);
+      os << " (" << (loadedFrom ? "loaded from" : "via")
+         << " field '" << ME->getMemberNameInfo() << "')";
+      SourceLocation L = ME->getMemberLoc();
+      Ranges.push_back(SourceRange(L, L));
+      break;
+    }
+  }
+}
+
+void DereferenceChecker::visitLocation(CheckerContext &C, const Stmt *S,
+                                       SVal l, bool isLoad) {
+  // Check for dereference of an undefined value.
+  if (l.isUndef()) {
+    if (ExplodedNode *N = C.generateSink()) {
+      if (!BT_undef)
+        BT_undef = new BuiltinBug("Dereference of undefined pointer value");
+
+      EnhancedBugReport *report =
+        new EnhancedBugReport(*BT_undef, BT_undef->getDescription(), N);
+      report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
+                                bugreporter::GetDerefExpr(N));
+      C.EmitReport(report);
+    }
+    return;
+  }
+
+  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(l);
+
+  // Check for null dereferences.
+  if (!isa<Loc>(location))
+    return;
+
+  const GRState *state = C.getState();
+  const GRState *notNullState, *nullState;
+  llvm::tie(notNullState, nullState) = state->assume(location);
+
+  // The explicit NULL case.
+  if (nullState) {
+    if (!notNullState) {
+      // Generate an error node.
+      ExplodedNode *N = C.generateSink(nullState);
+      if (!N)
+        return;
+
+      // We know that 'location' cannot be non-null.  This is what
+      // we call an "explicit" null dereference.
+      if (!BT_null)
+        BT_null = new BuiltinBug("Dereference of null pointer");
+
+      llvm::SmallString<100> buf;
+      llvm::SmallVector<SourceRange, 2> Ranges;
+      
+      // Walk through lvalue casts to get the original expression
+      // that syntactically caused the load.
+      if (const Expr *expr = dyn_cast<Expr>(S))
+        S = expr->IgnoreParenLValueCasts();
+
+      switch (S->getStmtClass()) {
+        case Stmt::ArraySubscriptExprClass: {
+          llvm::raw_svector_ostream os(buf);
+          os << "Array access";
+          const ArraySubscriptExpr *AE = cast<ArraySubscriptExpr>(S);
+          AddDerefSource(os, Ranges, AE->getBase()->IgnoreParenCasts());
+          os << " results in a null pointer dereference";
+          break;
+        }
+        case Stmt::UnaryOperatorClass: {
+          llvm::raw_svector_ostream os(buf);
+          os << "Dereference of null pointer";
+          const UnaryOperator *U = cast<UnaryOperator>(S);
+          AddDerefSource(os, Ranges, U->getSubExpr()->IgnoreParens(), true);
+          break;
+        }
+        case Stmt::MemberExprClass: {
+          const MemberExpr *M = cast<MemberExpr>(S);
+          if (M->isArrow()) {
+            llvm::raw_svector_ostream os(buf);
+            os << "Access to field '" << M->getMemberNameInfo()
+               << "' results in a dereference of a null pointer";
+            AddDerefSource(os, Ranges, M->getBase()->IgnoreParenCasts(), true);
+          }
+          break;
+        }
+        case Stmt::ObjCIvarRefExprClass: {
+          const ObjCIvarRefExpr *IV = cast<ObjCIvarRefExpr>(S);
+          if (const DeclRefExpr *DR =
+              dyn_cast<DeclRefExpr>(IV->getBase()->IgnoreParenCasts())) {
+            if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
+              llvm::raw_svector_ostream os(buf);
+              os << "Instance variable access (via '" << VD->getName()
+                 << "') results in a null pointer dereference";
+            }
+          }
+          Ranges.push_back(IV->getSourceRange());
+          break;
+        }
+        default:
+          break;
+      }
+
+      EnhancedBugReport *report =
+        new EnhancedBugReport(*BT_null,
+                              buf.empty() ? BT_null->getDescription():buf.str(),
+                              N);
+
+      report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
+                                bugreporter::GetDerefExpr(N));
+
+      for (llvm::SmallVectorImpl<SourceRange>::iterator
+            I = Ranges.begin(), E = Ranges.end(); I!=E; ++I)
+        report->addRange(*I);
+
+      C.EmitReport(report);
+      return;
+    }
+    else {
+      // Otherwise, we have the case where the location could either be
+      // null or not-null.  Record the error node as an "implicit" null
+      // dereference.
+      if (ExplodedNode *N = C.generateSink(nullState))
+        ImplicitNullDerefNodes.push_back(N);
+    }
+  }
+
+  // From this point forward, we know that the location is not null.
+  C.addTransition(notNullState);
+}