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//===- CastValueChecker - Model implementation of custom RTTIs --*- 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 CastValueChecker which models casts of custom RTTIs.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "llvm/ADT/Optional.h"
using namespace clang;
using namespace ento;
namespace {
class CastValueChecker : public Checker<eval::Call> {
using CastCheck =
std::function<void(const CastValueChecker *, const CallExpr *,
DefinedOrUnknownSVal, CheckerContext &)>;
public:
// We have three cases to evaluate a cast:
// 1) The parameter is non-null, the return value is non-null
// 2) The parameter is non-null, the return value is null
// 3) The parameter is null, the return value is null
//
// cast: 1; dyn_cast: 1, 2; cast_or_null: 1, 3; dyn_cast_or_null: 1, 2, 3.
bool evalCall(const CallEvent &Call, CheckerContext &C) const;
private:
// These are known in the LLVM project.
const CallDescriptionMap<CastCheck> CDM = {
{{{"llvm", "cast"}, 1}, &CastValueChecker::evalCast},
{{{"llvm", "dyn_cast"}, 1}, &CastValueChecker::evalDynCast},
{{{"llvm", "cast_or_null"}, 1}, &CastValueChecker::evalCastOrNull},
{{{"llvm", "dyn_cast_or_null"}, 1},
&CastValueChecker::evalDynCastOrNull}};
void evalCast(const CallExpr *CE, DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const;
void evalDynCast(const CallExpr *CE, DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const;
void evalCastOrNull(const CallExpr *CE, DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const;
void evalDynCastOrNull(const CallExpr *CE, DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const;
};
} // namespace
static std::string getCastName(const Expr *Cast) {
return Cast->getType()->getPointeeCXXRecordDecl()->getNameAsString();
}
static void evalNonNullParamNonNullReturn(const CallExpr *CE,
DefinedOrUnknownSVal ParamDV,
CheckerContext &C) {
ProgramStateRef State = C.getState()->assume(ParamDV, true);
if (!State)
return;
State = State->BindExpr(CE, C.getLocationContext(), ParamDV, false);
std::string CastFromName = getCastName(CE->getArg(0));
std::string CastToName = getCastName(CE);
const NoteTag *CastTag = C.getNoteTag(
[CastFromName, CastToName](BugReport &) -> std::string {
SmallString<128> Msg;
llvm::raw_svector_ostream Out(Msg);
Out << "Assuming dynamic cast from '" << CastFromName << "' to '"
<< CastToName << "' succeeds";
return Out.str();
},
/*IsPrunable=*/true);
C.addTransition(State, CastTag);
}
static void evalNonNullParamNullReturn(const CallExpr *CE,
DefinedOrUnknownSVal ParamDV,
CheckerContext &C) {
ProgramStateRef State = C.getState()->assume(ParamDV, true);
if (!State)
return;
State = State->BindExpr(CE, C.getLocationContext(),
C.getSValBuilder().makeNull(), false);
std::string CastFromName = getCastName(CE->getArg(0));
std::string CastToName = getCastName(CE);
const NoteTag *CastTag = C.getNoteTag(
[CastFromName, CastToName](BugReport &) -> std::string {
SmallString<128> Msg;
llvm::raw_svector_ostream Out(Msg);
Out << "Assuming dynamic cast from '" << CastFromName << "' to '"
<< CastToName << "' fails";
return Out.str();
},
/*IsPrunable=*/true);
C.addTransition(State, CastTag);
}
static void evalNullParamNullReturn(const CallExpr *CE,
DefinedOrUnknownSVal ParamDV,
CheckerContext &C) {
ProgramStateRef State = C.getState()->assume(ParamDV, false);
if (!State)
return;
State = State->BindExpr(CE, C.getLocationContext(),
C.getSValBuilder().makeNull(), false);
const NoteTag *CastTag =
C.getNoteTag("Assuming null pointer is passed into cast",
/*IsPrunable=*/true);
C.addTransition(State, CastTag);
}
void CastValueChecker::evalCast(const CallExpr *CE,
DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const {
evalNonNullParamNonNullReturn(CE, ParamDV, C);
}
void CastValueChecker::evalDynCast(const CallExpr *CE,
DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const {
evalNonNullParamNonNullReturn(CE, ParamDV, C);
evalNonNullParamNullReturn(CE, ParamDV, C);
}
void CastValueChecker::evalCastOrNull(const CallExpr *CE,
DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const {
evalNonNullParamNonNullReturn(CE, ParamDV, C);
evalNullParamNullReturn(CE, ParamDV, C);
}
void CastValueChecker::evalDynCastOrNull(const CallExpr *CE,
DefinedOrUnknownSVal ParamDV,
CheckerContext &C) const {
evalNonNullParamNonNullReturn(CE, ParamDV, C);
evalNonNullParamNullReturn(CE, ParamDV, C);
evalNullParamNullReturn(CE, ParamDV, C);
}
bool CastValueChecker::evalCall(const CallEvent &Call,
CheckerContext &C) const {
const CastCheck *Check = CDM.lookup(Call);
if (!Check)
return false;
const auto *CE = cast<CallExpr>(Call.getOriginExpr());
if (!CE)
return false;
// If we cannot obtain both of the classes we cannot be sure how to model it.
if (!CE->getType()->getPointeeCXXRecordDecl() ||
!CE->getArg(0)->getType()->getPointeeCXXRecordDecl())
return false;
SVal ParamV = Call.getArgSVal(0);
auto ParamDV = ParamV.getAs<DefinedOrUnknownSVal>();
if (!ParamDV)
return false;
(*Check)(this, CE, *ParamDV, C);
return true;
}
void ento::registerCastValueChecker(CheckerManager &Mgr) {
Mgr.registerChecker<CastValueChecker>();
}
bool ento::shouldRegisterCastValueChecker(const LangOptions &LO) {
return true;
}
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