DivZeroChecker.cpp revision 55fc873017f10f6f566b182b70f6fc22aefa3464 
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/BugReporter/BugType.h"
17#include "clang/StaticAnalyzer/Core/Checker.h"
18#include "clang/StaticAnalyzer/Core/CheckerManager.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20
21using namespace clang;
22using namespace ento;
23
24namespace {
25class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > {
26  mutable 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 = new BugReport(*BT, Msg, N);
43    bugreporter::trackNullOrUndefValue(N, bugreporter::GetDenomExpr(N), *R);
44    C.emitReport(R);
45  }
46}
47
48void DivZeroChecker::checkPreStmt(const BinaryOperator *B,
49                                  CheckerContext &C) const {
50  BinaryOperator::Opcode Op = B->getOpcode();
51  if (Op != BO_Div &&
52      Op != BO_Rem &&
53      Op != BO_DivAssign &&
54      Op != BO_RemAssign)
55    return;
56
57  if (!B->getRHS()->getType()->isScalarType())
58    return;
59
60  SVal Denom = C.getState()->getSVal(B->getRHS(), C.getLocationContext());
61  const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom);
62
63  // Divide-by-undefined handled in the generic checking for uses of
64  // undefined values.
65  if (!DV)
66    return;
67
68  // Check for divide by zero.
69  ConstraintManager &CM = C.getConstraintManager();
70  ProgramStateRef stateNotZero, stateZero;
71  llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
72
73  if (!stateNotZero) {
74    assert(stateZero);
75    reportBug("Division by zero", stateZero, C);
76    return;
77  }
78
79  bool TaintedD = C.getState()->isTainted(*DV);
80  if ((stateNotZero && stateZero && TaintedD)) {
81    reportBug("Division by a tainted value, possibly zero", stateZero, C);
82    return;
83  }
84
85  // If we get here, then the denom should not be zero. We abandon the implicit
86  // zero denom case for now.
87  C.addTransition(stateNotZero);
88}
89
90void ento::registerDivZeroChecker(CheckerManager &mgr) {
91  mgr.registerChecker<DivZeroChecker>();
92}
93