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
21 using namespace clang;
22 using namespace ento;
23
24 namespace {
25 class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > {
26 mutable llvm::OwningPtr<BuiltinBug> BT;
27 public:
28 void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
29 };
30 } // end anonymous namespace
31
checkPreStmt(const BinaryOperator * B,CheckerContext & C) const32 void 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
registerDivZeroChecker(CheckerManager & mgr)79 void ento::registerDivZeroChecker(CheckerManager &mgr) {
80 mgr.registerChecker<DivZeroChecker>();
81 }
82