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      1 //== BoolAssignmentChecker.cpp - Boolean assignment checker -----*- C++ -*--==//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 //
      9 // This defines BoolAssignmentChecker, a builtin check in ExprEngine that
     10 // performs checks for assignment of non-Boolean values to Boolean variables.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
     15 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
     16 #include "clang/StaticAnalyzer/Core/Checker.h"
     17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
     18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
     19 
     20 using namespace clang;
     21 using namespace ento;
     22 
     23 namespace {
     24   class BoolAssignmentChecker : public Checker< check::Bind > {
     25     mutable std::unique_ptr<BuiltinBug> BT;
     26     void emitReport(ProgramStateRef state, CheckerContext &C) const;
     27   public:
     28     void checkBind(SVal loc, SVal val, const Stmt *S, CheckerContext &C) const;
     29   };
     30 } // end anonymous namespace
     31 
     32 void BoolAssignmentChecker::emitReport(ProgramStateRef state,
     33                                        CheckerContext &C) const {
     34   if (ExplodedNode *N = C.generateNonFatalErrorNode(state)) {
     35     if (!BT)
     36       BT.reset(new BuiltinBug(this, "Assignment of a non-Boolean value"));
     37 
     38     C.emitReport(
     39         std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N));
     40   }
     41 }
     42 
     43 static bool isBooleanType(QualType Ty) {
     44   if (Ty->isBooleanType()) // C++ or C99
     45     return true;
     46 
     47   if (const TypedefType *TT = Ty->getAs<TypedefType>())
     48     return TT->getDecl()->getName() == "BOOL"   || // Objective-C
     49            TT->getDecl()->getName() == "_Bool"  || // stdbool.h < C99
     50            TT->getDecl()->getName() == "Boolean";  // MacTypes.h
     51 
     52   return false;
     53 }
     54 
     55 void BoolAssignmentChecker::checkBind(SVal loc, SVal val, const Stmt *S,
     56                                       CheckerContext &C) const {
     57 
     58   // We are only interested in stores into Booleans.
     59   const TypedValueRegion *TR =
     60     dyn_cast_or_null<TypedValueRegion>(loc.getAsRegion());
     61 
     62   if (!TR)
     63     return;
     64 
     65   QualType valTy = TR->getValueType();
     66 
     67   if (!isBooleanType(valTy))
     68     return;
     69 
     70   // Get the value of the right-hand side.  We only care about values
     71   // that are defined (UnknownVals and UndefinedVals are handled by other
     72   // checkers).
     73   Optional<NonLoc> NV = val.getAs<NonLoc>();
     74   if (!NV)
     75     return;
     76 
     77   // Check if the assigned value meets our criteria for correctness.  It must
     78   // be a value that is either 0 or 1.  One way to check this is to see if
     79   // the value is possibly < 0 (for a negative value) or greater than 1.
     80   ProgramStateRef state = C.getState();
     81   SValBuilder &svalBuilder = C.getSValBuilder();
     82   BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
     83   ConstraintManager &CM = C.getConstraintManager();
     84 
     85   llvm::APSInt Zero = BVF.getValue(0, valTy);
     86   llvm::APSInt One = BVF.getValue(1, valTy);
     87 
     88   ProgramStateRef StIn, StOut;
     89   std::tie(StIn, StOut) = CM.assumeInclusiveRangeDual(state, *NV, Zero, One);
     90 
     91   if (!StIn)
     92     emitReport(StOut, C);
     93 }
     94 
     95 void ento::registerBoolAssignmentChecker(CheckerManager &mgr) {
     96     mgr.registerChecker<BoolAssignmentChecker>();
     97 }
     98 
     99 bool ento::shouldRegisterBoolAssignmentChecker(const CheckerManager &mgr) {
    100   return true;
    101 }
    102