DivZeroChecker.cpp revision a1f81bb0e55749a1414b1b5124bb83b9052ff2ac
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 = 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