//=== CXXSelfAssignmentChecker.cpp -----------------------------*- 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 file defines CXXSelfAssignmentChecker, which tests all custom defined

// copy and move assignment operators for the case of self assignment, thus

// where the parameter refers to the same location where the this pointer

// points to. The checker itself does not do any checks at all, but it

// causes the analyzer to check every copy and move assignment operator twice:

// once for when 'this' aliases with the parameter and once for when it may not.

// It is the task of the other enabled checkers to find the bugs in these two

// different cases.

//

//===----------------------------------------------------------------------===//

#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"

#include "clang/StaticAnalyzer/Core/Checker.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"

using namespace clang;

using namespace ento;

namespace {

class CXXSelfAssignmentChecker : public Checker<check::BeginFunction> {

public:

  CXXSelfAssignmentChecker();

  void checkBeginFunction(CheckerContext &C) const;

};

}

CXXSelfAssignmentChecker::CXXSelfAssignmentChecker() {}

void CXXSelfAssignmentChecker::checkBeginFunction(CheckerContext &C) const {

  if (!C.inTopFrame())

    return;

  const auto *LCtx = C.getLocationContext();

  const auto *MD = dyn_cast<CXXMethodDecl>(LCtx->getDecl());

  if (!MD)

    return;

  if (!MD->isCopyAssignmentOperator() && 
!MD->isMoveAssignmentOperator()132
)

    return;

  auto &State = C.getState();

  auto &SVB = C.getSValBuilder();

  auto ThisVal =

      State->getSVal(SVB.getCXXThis(MD, LCtx->getStackFrame()));

  auto Param = SVB.makeLoc(State->getRegion(MD->getParamDecl(0), LCtx));

  auto ParamVal = State->getSVal(Param);

  ProgramStateRef SelfAssignState = State->bindLoc(Param, ThisVal, LCtx);

  const NoteTag *SelfAssignTag =

    C.getNoteTag([MD](PathSensitiveBugReport &BR) -> std::string {

        SmallString<256> Msg;

        llvm::raw_svector_ostream Out(Msg);

        Out << "Assuming " << MD->getParamDecl(0)->getName() << " == *this";

        return std::string(Out.str());

      });

  C.addTransition(SelfAssignState, SelfAssignTag);

  ProgramStateRef NonSelfAssignState = State->bindLoc(Param, ParamVal, LCtx);

  const NoteTag *NonSelfAssignTag =

    C.getNoteTag([MD](PathSensitiveBugReport &BR) -> std::string {

        SmallString<256> Msg;

        llvm::raw_svector_ostream Out(Msg);

        Out << "Assuming " << MD->getParamDecl(0)->getName() << " != *this";

        return std::string(Out.str());

      });

  C.addTransition(NonSelfAssignState, NonSelfAssignTag);

}

void ento::registerCXXSelfAssignmentChecker(CheckerManager &Mgr) {

  Mgr.registerChecker<CXXSelfAssignmentChecker>();

}

bool ento::shouldRegisterCXXSelfAssignmentChecker(const CheckerManager &mgr) {

  return true;

}