//== SValExplainer.h - Symbolic value explainer -----------------*- 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 SValExplainer, a class for pretty-printing a

//  human-readable description of a symbolic value. For example,

//  "reg_$0<x>" is turned into "initial value of variable 'x'".

//

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

#ifndef LLVM_CLANG_STATICANALYZER_CHECKERS_SVALEXPLAINER_H

#define LLVM_CLANG_STATICANALYZER_CHECKERS_SVALEXPLAINER_H

#include "clang/AST/Attr.h"

#include "clang/AST/DeclCXX.h"

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

#include "llvm/ADT/StringExtras.h"

namespace clang {

namespace ento {

class SValExplainer : public FullSValVisitor<SValExplainer, std::string> {

private:

  ASTContext &ACtx;

  std::string printStmt(const Stmt *S) {

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    S->printPretty(OS, nullptr, PrintingPolicy(ACtx.getLangOpts()));

    return Str;

  }

  bool isThisObject(const SymbolicRegion *R) {

    if (auto S = dyn_cast<SymbolRegionValue>(R->getSymbol()))

      if (isa<CXXThisRegion>(S->getRegion()))

        return true;

    return false;

  }

public:

  SValExplainer(ASTContext &Ctx) : ACtx(Ctx) {}

  std::string VisitUnknownVal(UnknownVal V) {

    return "unknown value";

  }

  std::string VisitUndefinedVal(UndefinedVal V) {

    return "undefined value";

  }

  std::string VisitLocMemRegionVal(loc::MemRegionVal V) {

    const MemRegion *R = V.getRegion();

    // Avoid the weird "pointer to pointee of ...".

    if (auto SR = dyn_cast<SymbolicRegion>(R)) {

      // However, "pointer to 'this' object" is fine.

      if (!isThisObject(SR))

        return Visit(SR->getSymbol());

    }

    return "pointer to " + Visit(R);

  }

  std::string VisitLocConcreteInt(loc::ConcreteInt V) {

    const llvm::APSInt &I = V.getValue();

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    OS << "concrete memory address '" << I << "'";

    return Str;

  }

  std::string VisitNonLocSymbolVal(nonloc::SymbolVal V) {

    return Visit(V.getSymbol());

  }

  std::string VisitNonLocConcreteInt(nonloc::ConcreteInt V) {

    const llvm::APSInt &I = V.getValue();

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    OS << (I.isSigned() ? "signed " : 
"unsigned "0
) << I.getBitWidth()

       << "-bit integer '" << I << "'";

    return Str;

  }

  std::string VisitNonLocLazyCompoundVal(nonloc::LazyCompoundVal V) {

    return "lazily frozen compound value of " + Visit(V.getRegion());

  }

  std::string VisitSymbolRegionValue(const SymbolRegionValue *S) {

    const MemRegion *R = S->getRegion();

    // Special handling for argument values.

    if (auto V = dyn_cast<VarRegion>(R))

      if (auto D = dyn_cast<ParmVarDecl>(V->getDecl()))

        return "argument '" + D->getQualifiedNameAsString() + "'";

    return "initial value of " + Visit(R);

  }

  std::string VisitSymbolConjured(const SymbolConjured *S) {

    return "symbol of type '" + S->getType().getAsString() +

           "' conjured at statement '" + printStmt(S->getStmt()) + "'";

  }

  std::string VisitSymbolDerived(const SymbolDerived *S) {

    return "value derived from (" + Visit(S->getParentSymbol()) +

           ") for " + Visit(S->getRegion());

  }

  std::string VisitSymbolExtent(const SymbolExtent *S) {

    return "extent of " + Visit(S->getRegion());

  }

  std::string VisitSymbolMetadata(const SymbolMetadata *S) {

    return "metadata of type '" + S->getType().getAsString() + "' tied to " +

           Visit(S->getRegion());

  }

  std::string VisitSymIntExpr(const SymIntExpr *S) {

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    OS << "(" << Visit(S->getLHS()) << ") "

       << std::string(BinaryOperator::getOpcodeStr(S->getOpcode())) << " "

       << S->getRHS();

    return Str;

  }

  // TODO: IntSymExpr doesn't appear in practice.

  // Add the relevant code once it does.

  std::string VisitSymSymExpr(const SymSymExpr *S) {

    return "(" + Visit(S->getLHS()) + ") " +

           std::string(BinaryOperator::getOpcodeStr(S->getOpcode())) +

           " (" + Visit(S->getRHS()) + ")";

  }

  // TODO: SymbolCast doesn't appear in practice.

  // Add the relevant code once it does.

  std::string VisitSymbolicRegion(const SymbolicRegion *R) {

    // Explain 'this' object here.

    // TODO: Explain CXXThisRegion itself, find a way to test it.

    if (isThisObject(R))

      return "'this' object";

    // Objective-C objects are not normal symbolic regions. At least,

    // they're always on the heap.

    if (R->getSymbol()->getType()

            .getCanonicalType()->getAs<ObjCObjectPointerType>())

      return "object at " + Visit(R->getSymbol());

    // Other heap-based symbolic regions are also special.

    if (isa<HeapSpaceRegion>(R->getMemorySpace()))

      return "heap segment that starts at " + Visit(R->getSymbol());

    return "pointee of " + Visit(R->getSymbol());

  }

  std::string VisitAllocaRegion(const AllocaRegion *R) {

    return "region allocated by '" + printStmt(R->getExpr()) + "'";

  }

  std::string VisitCompoundLiteralRegion(const CompoundLiteralRegion *R) {

    return "compound literal " + printStmt(R->getLiteralExpr());

  }

  std::string VisitStringRegion(const StringRegion *R) {

    return "string literal " + R->getString();

  }

  std::string VisitElementRegion(const ElementRegion *R) {

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    OS << "element of type '" << R->getElementType() << "' with index ";

    // For concrete index: omit type of the index integer.

    if (auto I = R->getIndex().getAs<nonloc::ConcreteInt>())

      OS << I->getValue();

    else

      OS << "'" << Visit(R->getIndex()) << "'";

    OS << " of " + Visit(R->getSuperRegion());

    return Str;

  }

  std::string VisitNonParamVarRegion(const NonParamVarRegion *R) {

    const VarDecl *VD = R->getDecl();

    std::string Name = VD->getQualifiedNameAsString();

    if (isa<ParmVarDecl>(VD))

      return "parameter '" + Name + "'";

    else if (VD->hasAttr<BlocksAttr>())

      return "block variable '" + Name + "'";

    else if (VD->hasLocalStorage())

      return "local variable '" + Name + "'";

    else if (VD->isStaticLocal())

      return "static local variable '" + Name + "'";

    else if (VD->hasGlobalStorage())

      return "global variable '" + Name + "'";

    else

      llvm_unreachable("A variable is either local or global");

  }

  std::string VisitObjCIvarRegion(const ObjCIvarRegion *R) {

    return "instance variable '" + R->getDecl()->getNameAsString() + "' of " +

           Visit(R->getSuperRegion());

  }

  std::string VisitFieldRegion(const FieldRegion *R) {

    return "field '" + R->getDecl()->getNameAsString() + "' of " +

           Visit(R->getSuperRegion());

  }

  std::string VisitCXXTempObjectRegion(const CXXTempObjectRegion *R) {

    return "temporary object constructed at statement '" +

           printStmt(R->getExpr()) + "'";

  }

  std::string VisitCXXBaseObjectRegion(const CXXBaseObjectRegion *R) {

    return "base object '" + R->getDecl()->getQualifiedNameAsString() +

           "' inside " + Visit(R->getSuperRegion());

  }

  std::string VisitParamVarRegion(const ParamVarRegion *R) {

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    const ParmVarDecl *PVD = R->getDecl();

    std::string Name = PVD->getQualifiedNameAsString();

    if (!Name.empty()) {

      OS << "parameter '" << Name << "'";

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

    }

    unsigned Index = R->getIndex() + 1;

    OS << Index << llvm::getOrdinalSuffix(Index) << " parameter of ";

    const Decl *Parent = R->getStackFrame()->getDecl();

    if (const auto *FD = dyn_cast<FunctionDecl>(Parent))

      OS << "function '" << FD->getQualifiedNameAsString() << "()'";

    else if (const auto *CD = dyn_cast<CXXConstructorDecl>(Parent))

      OS << "C++ constructor '" << CD->getQualifiedNameAsString() << "()'";

    else if (const auto *MD = dyn_cast<ObjCMethodDecl>(Parent)) {

      if (MD->isClassMethod())

        OS << "Objective-C method '+" << MD->getQualifiedNameAsString() << "'";

      else

        OS << "Objective-C method '-" << MD->getQualifiedNameAsString() << "'";

    } else if (isa<BlockDecl>(Parent)) {

      if (cast<BlockDecl>(Parent)->isConversionFromLambda())

        OS << "lambda";

      else

        OS << "block";

    }

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

  }

  std::string VisitSVal(SVal V) {

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    OS << V;

    return "a value unsupported by the explainer: (" +

           std::string(OS.str()) + ")";

  }

  std::string VisitSymExpr(SymbolRef S) {

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    S->dumpToStream(OS);

    return "a symbolic expression unsupported by the explainer: (" +

           std::string(OS.str()) + ")";

  }

  std::string VisitMemRegion(const MemRegion *R) {

    std::string Str;

    llvm::raw_string_ostream OS(Str);

    OS << R;

    return "a memory region unsupported by the explainer (" +

           std::string(OS.str()) + ")";

  }

};

} // end namespace ento

} // end namespace clang

#endif