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