From 222e2a7620e6520ffaf4fc4e69d79c18da31542e Mon Sep 17 00:00:00 2001
From: "Zancanaro; Carlo" <czan8762@plang3.cs.usyd.edu.au>
Date: Mon, 24 Sep 2012 09:58:17 +1000
Subject: Add the clang library to the repo (with some of my changes, too).

---
 .../StaticAnalyzer/Checkers/PointerSubChecker.cpp  | 76 ++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp

(limited to 'clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp')

diff --git a/clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp
new file mode 100644
index 0000000..fa5c6a3
--- /dev/null
+++ b/clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp
@@ -0,0 +1,76 @@
+//=== PointerSubChecker.cpp - Pointer subtraction 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 PointerSubChecker, a builtin checker that checks for
+// pointer subtractions on two pointers pointing to different memory chunks. 
+// This check corresponds to CWE-469.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ClangSACheckers.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class PointerSubChecker 
+  : public Checker< check::PreStmt<BinaryOperator> > {
+  mutable OwningPtr<BuiltinBug> BT;
+
+public:
+  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
+};
+}
+
+void PointerSubChecker::checkPreStmt(const BinaryOperator *B,
+                                     CheckerContext &C) const {
+  // When doing pointer subtraction, if the two pointers do not point to the
+  // same memory chunk, emit a warning.
+  if (B->getOpcode() != BO_Sub)
+    return;
+
+  ProgramStateRef state = C.getState();
+  const LocationContext *LCtx = C.getLocationContext();
+  SVal LV = state->getSVal(B->getLHS(), LCtx);
+  SVal RV = state->getSVal(B->getRHS(), LCtx);
+
+  const MemRegion *LR = LV.getAsRegion();
+  const MemRegion *RR = RV.getAsRegion();
+
+  if (!(LR && RR))
+    return;
+
+  const MemRegion *BaseLR = LR->getBaseRegion();
+  const MemRegion *BaseRR = RR->getBaseRegion();
+
+  if (BaseLR == BaseRR)
+    return;
+
+  // Allow arithmetic on different symbolic regions.
+  if (isa<SymbolicRegion>(BaseLR) || isa<SymbolicRegion>(BaseRR))
+    return;
+
+  if (ExplodedNode *N = C.addTransition()) {
+    if (!BT)
+      BT.reset(new BuiltinBug("Pointer subtraction", 
+                          "Subtraction of two pointers that do not point to "
+                          "the same memory chunk may cause incorrect result."));
+    BugReport *R = new BugReport(*BT, BT->getDescription(), N);
+    R->addRange(B->getSourceRange());
+    C.EmitReport(R);
+  }
+}
+
+void ento::registerPointerSubChecker(CheckerManager &mgr) {
+  mgr.registerChecker<PointerSubChecker>();
+}
-- 
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