Add check for pointer arithmetic on non-array variables.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@86538 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/CMakeLists.txt

@@ -38,6 +38,7 @@ add_clang_library(clangAnalysis
   NSAutoreleasePoolChecker.cpp
   NSErrorChecker.cpp
   PathDiagnostic.cpp
+  PointerArithChecker.cpp
   PointerSubChecker.cpp
   RangeConstraintManager.cpp
   RegionStore.cpp

lib/Analysis/GRExprEngineInternalChecks.cpp

@@ -413,6 +413,7 @@ void GRExprEngine::RegisterInternalChecks() {
   RegisterReturnStackAddressChecker(*this);
   RegisterReturnUndefChecker(*this);
   RegisterPointerSubChecker(*this);
+  RegisterPointerArithChecker(*this);
   RegisterFixedAddressChecker(*this);
   // Note that this must be registered after ReturnStackAddressChecker.
   RegisterReturnPointerRangeChecker(*this);

lib/Analysis/GRExprEngineInternalChecks.h

@@ -25,6 +25,7 @@ void RegisterReturnStackAddressChecker(GRExprEngine &Eng);
 void RegisterReturnUndefChecker(GRExprEngine &Eng);
 void RegisterVLASizeChecker(GRExprEngine &Eng);
 void RegisterPointerSubChecker(GRExprEngine &Eng);
+void RegisterPointerArithChecker(GRExprEngine &Eng);
 void RegisterFixedAddressChecker(GRExprEngine &Eng);
 void RegisterCastToStructChecker(GRExprEngine &Eng);
 } // end clang namespace

lib/Analysis/PointerArithChecker.cpp

+//=== PointerArithChecker.cpp - Pointer arithmetic checker -----*- C++ -*--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This files defines PointerArithChecker, a builtin checker that checks for
+// pointer arithmetic on locations other than array elements.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/PathSensitive/CheckerVisitor.h"
+#include "GRExprEngineInternalChecks.h"
+
+using namespace clang;
+
+namespace {
+class VISIBILITY_HIDDEN PointerArithChecker 
+  : public CheckerVisitor<PointerArithChecker> {
+  BuiltinBug *BT;
+public:
+  PointerArithChecker() : BT(0) {}
+  static void *getTag();
+  void PreVisitBinaryOperator(CheckerContext &C, const BinaryOperator *B);
+};
+}
+
+void *PointerArithChecker::getTag() {
+  static int x;
+  return &x;
+}
+
+void PointerArithChecker::PreVisitBinaryOperator(CheckerContext &C,
+                                                 const BinaryOperator *B) {
+  if (B->getOpcode() != BinaryOperator::Sub &&
+      B->getOpcode() != BinaryOperator::Add)
+    return;
+
+  const GRState *state = C.getState();
+  SVal LV = state->getSVal(B->getLHS());
+  SVal RV = state->getSVal(B->getRHS());
+
+  const MemRegion *LR = LV.getAsRegion();
+
+  if (!LR || !RV.isConstant())
+    return;
+
+  // If pointer arithmetic is done on variables of non-array type, this often
+  // means behavior rely on memory organization, which is dangerous.
+  if (isa<VarRegion>(LR) || isa<CodeTextRegion>(LR) || 
+      isa<CompoundLiteralRegion>(LR)) {
+
+    if (ExplodedNode *N = C.GenerateNode(B)) {
+      if (!BT)
+        BT = new BuiltinBug("Dangerous pointer arithmetic",
+                            "Pointer arithmetic done on non-array variables "
+                            "means reliance on memory layout, which is "
+                            "dangerous.");
+      RangedBugReport *R = new RangedBugReport(*BT,BT->getDescription().c_str(),
+                                               N);
+      R->addRange(B->getSourceRange());
+      C.EmitReport(R);
+    }
+  }
+}
+
+void clang::RegisterPointerArithChecker(GRExprEngine &Eng) {
+  Eng.registerCheck(new PointerArithChecker());
+}

test/Analysis/ptr-arith.c

@@ -41,3 +41,12 @@ void f4() {
   int *p;
   p = (int*) 0x10000; // expected-warning{{Using a fixed address is not portable because that address will probably not be valid in all environments or platforms.}}
 }
+
+void f5() {
+  int x, y;
+  int *p;
+  p = &x + 1;  // expected-warning{{Pointer arithmetic done on non array variables means reliance on memory layout, which is dangerous.}}
+
+  int a[10];
+  p = a + 1; // no-warning
+}