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//== BoolAssignmentChecker.cpp - Boolean assignment checker -----*- C++ -*--==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This defines BoolAssignmentChecker, a builtin check in ExprEngine that
// performs checks for assignment of non-Boolean values to Boolean variables.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
namespace {
class BoolAssignmentChecker : public Checker< check::Bind > {
mutable std::unique_ptr<BuiltinBug> BT;
void emitReport(ProgramStateRef state, CheckerContext &C) const;
public:
void checkBind(SVal loc, SVal val, const Stmt *S, CheckerContext &C) const;
};
} // end anonymous namespace
void BoolAssignmentChecker::emitReport(ProgramStateRef state,
CheckerContext &C) const {
if (ExplodedNode *N = C.generateNonFatalErrorNode(state)) {
if (!BT)
BT.reset(new BuiltinBug(this, "Assignment of a non-Boolean value"));
C.emitReport(llvm::make_unique<BugReport>(*BT, BT->getDescription(), N));
}
}
static bool isBooleanType(QualType Ty) {
if (Ty->isBooleanType()) // C++ or C99
return true;
if (const TypedefType *TT = Ty->getAs<TypedefType>())
return TT->getDecl()->getName() == "BOOL" || // Objective-C
TT->getDecl()->getName() == "_Bool" || // stdbool.h < C99
TT->getDecl()->getName() == "Boolean"; // MacTypes.h
return false;
}
void BoolAssignmentChecker::checkBind(SVal loc, SVal val, const Stmt *S,
CheckerContext &C) const {
// We are only interested in stores into Booleans.
const TypedValueRegion *TR =
dyn_cast_or_null<TypedValueRegion>(loc.getAsRegion());
if (!TR)
return;
QualType valTy = TR->getValueType();
if (!isBooleanType(valTy))
return;
// Get the value of the right-hand side. We only care about values
// that are defined (UnknownVals and UndefinedVals are handled by other
// checkers).
Optional<DefinedSVal> DV = val.getAs<DefinedSVal>();
if (!DV)
return;
// Check if the assigned value meets our criteria for correctness. It must
// be a value that is either 0 or 1. One way to check this is to see if
// the value is possibly < 0 (for a negative value) or greater than 1.
ProgramStateRef state = C.getState();
SValBuilder &svalBuilder = C.getSValBuilder();
ConstraintManager &CM = C.getConstraintManager();
// First, ensure that the value is >= 0.
DefinedSVal zeroVal = svalBuilder.makeIntVal(0, valTy);
SVal greaterThanOrEqualToZeroVal =
svalBuilder.evalBinOp(state, BO_GE, *DV, zeroVal,
svalBuilder.getConditionType());
Optional<DefinedSVal> greaterThanEqualToZero =
greaterThanOrEqualToZeroVal.getAs<DefinedSVal>();
if (!greaterThanEqualToZero) {
// The SValBuilder cannot construct a valid SVal for this condition.
// This means we cannot properly reason about it.
return;
}
ProgramStateRef stateLT, stateGE;
std::tie(stateGE, stateLT) = CM.assumeDual(state, *greaterThanEqualToZero);
// Is it possible for the value to be less than zero?
if (stateLT) {
// It is possible for the value to be less than zero. We only
// want to emit a warning, however, if that value is fully constrained.
// If it it possible for the value to be >= 0, then essentially the
// value is underconstrained and there is nothing left to be done.
if (!stateGE)
emitReport(stateLT, C);
// In either case, we are done.
return;
}
// If we reach here, it must be the case that the value is constrained
// to only be >= 0.
assert(stateGE == state);
// At this point we know that the value is >= 0.
// Now check to ensure that the value is <= 1.
DefinedSVal OneVal = svalBuilder.makeIntVal(1, valTy);
SVal lessThanEqToOneVal =
svalBuilder.evalBinOp(state, BO_LE, *DV, OneVal,
svalBuilder.getConditionType());
Optional<DefinedSVal> lessThanEqToOne =
lessThanEqToOneVal.getAs<DefinedSVal>();
if (!lessThanEqToOne) {
// The SValBuilder cannot construct a valid SVal for this condition.
// This means we cannot properly reason about it.
return;
}
ProgramStateRef stateGT, stateLE;
std::tie(stateLE, stateGT) = CM.assumeDual(state, *lessThanEqToOne);
// Is it possible for the value to be greater than one?
if (stateGT) {
// It is possible for the value to be greater than one. We only
// want to emit a warning, however, if that value is fully constrained.
// If it is possible for the value to be <= 1, then essentially the
// value is underconstrained and there is nothing left to be done.
if (!stateLE)
emitReport(stateGT, C);
// In either case, we are done.
return;
}
// If we reach here, it must be the case that the value is constrained
// to only be <= 1.
assert(stateLE == state);
}
void ento::registerBoolAssignmentChecker(CheckerManager &mgr) {
mgr.registerChecker<BoolAssignmentChecker>();
}
bool ento::shouldRegisterBoolAssignmentChecker(const LangOptions &LO) {
return true;
}
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