DivZeroChecker.cpp revision 685379965c1b105ce89cf4f6c60810932b7f4d0d
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 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 bugreporter::addTrackNullOrUndefValueVisitor(N, 46 bugreporter::GetDenomExpr(N), 47 R); 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()->isScalarType()) 62 return; 63 64 SVal Denom = C.getState()->getSVal(B->getRHS(), C.getLocationContext()); 65 const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom); 66 67 // Divide-by-undefined handled in the generic checking for uses of 68 // undefined values. 69 if (!DV) 70 return; 71 72 // Check for divide by zero. 73 ConstraintManager &CM = C.getConstraintManager(); 74 ProgramStateRef stateNotZero, stateZero; 75 llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV); 76 77 if (!stateNotZero) { 78 assert(stateZero); 79 reportBug("Division by zero", stateZero, C); 80 return; 81 } 82 83 bool TaintedD = C.getState()->isTainted(*DV); 84 if ((stateNotZero && stateZero && TaintedD)) { 85 reportBug("Division by a tainted value, possibly zero", stateZero, C); 86 return; 87 } 88 89 // If we get here, then the denom should not be zero. We abandon the implicit 90 // zero denom case for now. 91 C.addTransition(stateNotZero); 92} 93 94void ento::registerDivZeroChecker(CheckerManager &mgr) { 95 mgr.registerChecker<DivZeroChecker>(); 96} 97