//===--- UndefinedAssignmentChecker.h ---------------------------*- 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 UndefinedAssignmentChecker, a builtin check in ExprEngine that

// checks for assigning undefined values.

//

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

#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 UndefinedAssignmentChecker

  : public Checker<check::Bind> {

  mutable std::unique_ptr<BugType> BT;

public:

  void checkBind(SVal location, SVal val, const Stmt *S,

                 CheckerContext &C) const;

};

}

void UndefinedAssignmentChecker::checkBind(SVal location, SVal val,

                                           const Stmt *StoreE,

                                           CheckerContext &C) const {

  if (!val.isUndef())

    return;

  // Do not report assignments of uninitialized values inside swap functions.

  // This should allow to swap partially uninitialized structs

  if (const FunctionDecl *EnclosingFunctionDecl =

      dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))

    if (C.getCalleeName(EnclosingFunctionDecl) == "swap")

      return;

  ExplodedNode *N = C.generateErrorNode();

  if (!N)

    return;

  static const char *const DefaultMsg =

      "Assigned value is garbage or undefined";

  if (!BT)

    BT.reset(new BugType(this, DefaultMsg));

  // Generate a report for this bug.

  llvm::SmallString<128> Str;

  llvm::raw_svector_ostream OS(Str);

  const Expr *ex = nullptr;

  while (StoreE) {

    if (const UnaryOperator *U = dyn_cast<UnaryOperator>(StoreE)) {

      OS << "The expression is an uninitialized value. "

            "The computed value will also be garbage";

      ex = U->getSubExpr();

      break;

    }

    if (const BinaryOperator *B = dyn_cast<BinaryOperator>(StoreE)) {

      if (B->isCompoundAssignmentOp()) {

        if (C.getSVal(B->getLHS()).isUndef()) {

          OS << "The left expression of the compound assignment is an "

                "uninitialized value. The computed value will also be garbage";

          ex = B->getLHS();

          break;

        }

      }

      ex = B->getRHS();

      break;

    }

    if (const DeclStmt *DS = dyn_cast<DeclStmt>(StoreE)) {

      const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());

      ex = VD->getInit();

    }

    if (const auto *CD =

            dyn_cast<CXXConstructorDecl>(C.getStackFrame()->getDecl())) {

      if (CD->isImplicit()) {

        for (auto *I : CD->inits()) {

          if (I->getInit()->IgnoreImpCasts() == StoreE) {

            OS << "Value assigned to field '" << I->getMember()->getName()

               << "' in implicit constructor is garbage or undefined";

            break;

          }

        }

      }

    }

    break;

  }

  if (OS.str().empty())

    OS << DefaultMsg;

  auto R = std::make_unique<PathSensitiveBugReport>(*BT, OS.str(), N);

  if (ex) {

    R->addRange(ex->getSourceRange());

    bugreporter::trackExpressionValue(N, ex, *R);

  }

  C.emitReport(std::move(R));

}

void ento::registerUndefinedAssignmentChecker(CheckerManager &mgr) {

  mgr.registerChecker<UndefinedAssignmentChecker>();

}

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

  return true;

}