DivZeroChecker.cpp revision ec8605f1d7ec846dbf51047bfd5c56d32d1ff91c 
1//== DivZeroChecker.cpp - Division by zero checker --------------*- C++ -*--==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This defines DivZeroChecker, a builtin check in ExprEngine that performs
11// checks for division by zeros.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "clang/StaticAnalyzer/Core/Checker.h"
17#include "clang/StaticAnalyzer/Core/CheckerManager.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20
21using namespace clang;
22using namespace ento;
23
24namespace {
25class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > {
26  mutable llvm::OwningPtr<BuiltinBug> BT;
27public:
28  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
29};
30} // end anonymous namespace
31
32void DivZeroChecker::checkPreStmt(const BinaryOperator *B,
33                                  CheckerContext &C) const {
34  BinaryOperator::Opcode Op = B->getOpcode();
35  if (Op != BO_Div &&
36      Op != BO_Rem &&
37      Op != BO_DivAssign &&
38      Op != BO_RemAssign)
39    return;
40
41  if (!B->getRHS()->getType()->isIntegerType() ||
42      !B->getRHS()->getType()->isScalarType())
43    return;
44
45  SVal Denom = C.getState()->getSVal(B->getRHS());
46  const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom);
47
48  // Divide-by-undefined handled in the generic checking for uses of
49  // undefined values.
50  if (!DV)
51    return;
52
53  // Check for divide by zero.
54  ConstraintManager &CM = C.getConstraintManager();
55  const GRState *stateNotZero, *stateZero;
56  llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
57
58  if (stateZero && !stateNotZero) {
59    if (ExplodedNode *N = C.generateSink(stateZero)) {
60      if (!BT)
61        BT.reset(new BuiltinBug("Division by zero"));
62
63      EnhancedBugReport *R =
64        new EnhancedBugReport(*BT, BT->getDescription(), N);
65
66      R->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
67                           bugreporter::GetDenomExpr(N));
68
69      C.EmitReport(R);
70    }
71    return;
72  }
73
74  // If we get here, then the denom should not be zero. We abandon the implicit
75  // zero denom case for now.
76  C.addTransition(stateNotZero);
77}
78
79void ento::registerDivZeroChecker(CheckerManager &mgr) {
80  mgr.registerChecker<DivZeroChecker>();
81}
82