DivZeroChecker.cpp revision 00bd44d5677783527d7517c1ffe45e4d75a0f56f 
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#include "llvm/ADT/STLExtras.h"
21
22using namespace clang;
23using namespace ento;
24
25namespace {
26class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > {
27  mutable llvm::OwningPtr<BuiltinBug> BT;
28  void reportBug(const char *Msg,
29                 ProgramStateRef StateZero,
30                 CheckerContext &C) const ;
31public:
32  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
33};
34} // end anonymous namespace
35
36void DivZeroChecker::reportBug(const char *Msg,
37                               ProgramStateRef StateZero,
38                               CheckerContext &C) const {
39  if (ExplodedNode *N = C.generateSink(StateZero)) {
40    if (!BT)
41      BT.reset(new BuiltinBug("Division by zero"));
42
43    BugReport *R =
44      new BugReport(*BT, Msg, N);
45
46    R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
47                                 bugreporter::GetDenomExpr(N)));
48
49    C.EmitReport(R);
50  }
51}
52
53void DivZeroChecker::checkPreStmt(const BinaryOperator *B,
54                                  CheckerContext &C) const {
55  BinaryOperator::Opcode Op = B->getOpcode();
56  if (Op != BO_Div &&
57      Op != BO_Rem &&
58      Op != BO_DivAssign &&
59      Op != BO_RemAssign)
60    return;
61
62  if (!B->getRHS()->getType()->isIntegerType() ||
63      !B->getRHS()->getType()->isScalarType())
64    return;
65
66  SVal Denom = C.getState()->getSVal(B->getRHS(), C.getLocationContext());
67  const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom);
68
69  // Divide-by-undefined handled in the generic checking for uses of
70  // undefined values.
71  if (!DV)
72    return;
73
74  // Check for divide by zero.
75  ConstraintManager &CM = C.getConstraintManager();
76  ProgramStateRef stateNotZero, stateZero;
77  llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
78
79  if (!stateNotZero) {
80    assert(stateZero);
81    reportBug("Division by zero", stateZero, C);
82    return;
83  }
84
85  bool TaintedD = C.getState()->isTainted(*DV);
86  if ((stateNotZero && stateZero && TaintedD)) {
87    reportBug("Division by a tainted value, possibly zero", stateZero, C);
88    return;
89  }
90
91  // If we get here, then the denom should not be zero. We abandon the implicit
92  // zero denom case for now.
93  C.addTransition(stateNotZero);
94}
95
96void ento::registerDivZeroChecker(CheckerManager &mgr) {
97  mgr.registerChecker<DivZeroChecker>();
98}
99