DivZeroChecker.cpp revision 8bef8238181a30e52dea380789a7e2d760eac532 
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;
27  void reportBug(const char *Msg,
28                 ProgramStateRef StateZero,
29                 CheckerContext &C) const ;
30public:
31  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
32};
33} // end anonymous namespace
34
35void DivZeroChecker::reportBug(const char *Msg,
36                               ProgramStateRef StateZero,
37                               CheckerContext &C) const {
38  if (ExplodedNode *N = C.generateSink(StateZero)) {
39    if (!BT)
40      BT.reset(new BuiltinBug("Division by zero"));
41
42    BugReport *R =
43      new BugReport(*BT, Msg, N);
44
45    R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
46                                 bugreporter::GetDenomExpr(N)));
47
48    C.EmitReport(R);
49  }
50}
51
52void DivZeroChecker::checkPreStmt(const BinaryOperator *B,
53                                  CheckerContext &C) const {
54  BinaryOperator::Opcode Op = B->getOpcode();
55  if (Op != BO_Div &&
56      Op != BO_Rem &&
57      Op != BO_DivAssign &&
58      Op != BO_RemAssign)
59    return;
60
61  if (!B->getRHS()->getType()->isIntegerType() ||
62      !B->getRHS()->getType()->isScalarType())
63    return;
64
65  SVal Denom = C.getState()->getSVal(B->getRHS(), C.getLocationContext());
66  const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom);
67
68  // Divide-by-undefined handled in the generic checking for uses of
69  // undefined values.
70  if (!DV)
71    return;
72
73  // Check for divide by zero.
74  ConstraintManager &CM = C.getConstraintManager();
75  ProgramStateRef stateNotZero, stateZero;
76  llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
77
78  if (!stateNotZero) {
79    assert(stateZero);
80    reportBug("Division by zero", stateZero, C);
81    return;
82  }
83
84  bool TaintedD = C.getState()->isTainted(*DV);
85  if ((stateNotZero && stateZero && TaintedD)) {
86    reportBug("Division by a tainted value, possibly zero", stateZero, C);
87    return;
88  }
89
90  // If we get here, then the denom should not be zero. We abandon the implicit
91  // zero denom case for now.
92  C.addTransition(stateNotZero);
93}
94
95void ento::registerDivZeroChecker(CheckerManager &mgr) {
96  mgr.registerChecker<DivZeroChecker>();
97}
98