DivZeroChecker.cpp revision 341825 
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 std::unique_ptr<BuiltinBug> BT;
27  void reportBug(const char *Msg, ProgramStateRef StateZero, CheckerContext &C,
28                 std::unique_ptr<BugReporterVisitor> Visitor = nullptr) const;
29
30public:
31  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
32};
33} // end anonymous namespace
34
35void DivZeroChecker::reportBug(
36    const char *Msg, ProgramStateRef StateZero, CheckerContext &C,
37    std::unique_ptr<BugReporterVisitor> Visitor) const {
38  if (ExplodedNode *N = C.generateErrorNode(StateZero)) {
39    if (!BT)
40      BT.reset(new BuiltinBug(this, "Division by zero"));
41
42    auto R = llvm::make_unique<BugReport>(*BT, Msg, N);
43    R->addVisitor(std::move(Visitor));
44    bugreporter::trackNullOrUndefValue(N, bugreporter::GetDenomExpr(N), *R);
45    C.emitReport(std::move(R));
46  }
47}
48
49void DivZeroChecker::checkPreStmt(const BinaryOperator *B,
50                                  CheckerContext &C) const {
51  BinaryOperator::Opcode Op = B->getOpcode();
52  if (Op != BO_Div &&
53      Op != BO_Rem &&
54      Op != BO_DivAssign &&
55      Op != BO_RemAssign)
56    return;
57
58  if (!B->getRHS()->getType()->isScalarType())
59    return;
60
61  SVal Denom = C.getSVal(B->getRHS());
62  Optional<DefinedSVal> DV = Denom.getAs<DefinedSVal>();
63
64  // Divide-by-undefined handled in the generic checking for uses of
65  // undefined values.
66  if (!DV)
67    return;
68
69  // Check for divide by zero.
70  ConstraintManager &CM = C.getConstraintManager();
71  ProgramStateRef stateNotZero, stateZero;
72  std::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
73
74  if (!stateNotZero) {
75    assert(stateZero);
76    reportBug("Division by zero", stateZero, C);
77    return;
78  }
79
80  bool TaintedD = C.getState()->isTainted(*DV);
81  if ((stateNotZero && stateZero && TaintedD)) {
82    reportBug("Division by a tainted value, possibly zero", stateZero, C,
83              llvm::make_unique<TaintBugVisitor>(*DV));
84    return;
85  }
86
87  // If we get here, then the denom should not be zero. We abandon the implicit
88  // zero denom case for now.
89  C.addTransition(stateNotZero);
90}
91
92void ento::registerDivZeroChecker(CheckerManager &mgr) {
93  mgr.registerChecker<DivZeroChecker>();
94}
95