clang/lib/StaticAnalyzer/Checkers/UninitializedObject/UninitializedPointee.cpp

//===----- UninitializedPointer.cpp ------------------------------*- C++ -*-==//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines functions and methods for handling pointers and references
// to reduce the size and complexity of UninitializedObjectChecker.cpp.
//
// To read about command line options and a description what this checker does,
// refer to UninitializedObjectChecker.cpp.
//
// To read about how the checker works, refer to the comments in
// UninitializedObject.h.
//
//===----------------------------------------------------------------------===//

#include "../ClangSACheckers.h"
#include "UninitializedObject.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicTypeMap.h"

using namespace clang;
using namespace clang::ento;

namespace {

/// Represents a pointer or a reference field.
class LocField final : public FieldNode {
  /// We'll store whether the pointee or the pointer itself is uninitialited.
  const bool IsDereferenced;

public:
  LocField(const FieldRegion *FR, const bool IsDereferenced = true)
      : FieldNode(FR), IsDereferenced(IsDereferenced) {}

  virtual void printNoteMsg(llvm::raw_ostream &Out) const override {
    if (IsDereferenced)
      Out << "uninitialized pointee ";
    else
      Out << "uninitialized pointer ";
  }

  virtual void printPrefix(llvm::raw_ostream &Out) const override {}

  virtual void printNode(llvm::raw_ostream &Out) const override {
    Out << getVariableName(getDecl());
  }

  virtual void printSeparator(llvm::raw_ostream &Out) const override {
    if (getDecl()->getType()->isPointerType())
      Out << "->";
    else
      Out << '.';
  }
};

/// Represents a void* field that needs to be casted back to its dynamic type
/// for a correct note message.
class NeedsCastLocField final : public FieldNode {
  QualType CastBackType;

public:
  NeedsCastLocField(const FieldRegion *FR, const QualType &T)
      : FieldNode(FR), CastBackType(T) {}

  virtual void printNoteMsg(llvm::raw_ostream &Out) const override {
    Out << "uninitialized pointee ";
  }

  virtual void printPrefix(llvm::raw_ostream &Out) const override {
    Out << "static_cast" << '<' << CastBackType.getAsString() << ">(";
  }

  virtual void printNode(llvm::raw_ostream &Out) const override {
    Out << getVariableName(getDecl()) << ')';
  }

  virtual void printSeparator(llvm::raw_ostream &Out) const override {
    Out << "->";
  }
};

} // end of anonymous namespace

// Utility function declarations.

/// Returns whether T can be (transitively) dereferenced to a void pointer type
/// (void*, void**, ...). The type of the region behind a void pointer isn't
/// known, and thus FD can not be analyzed.
static bool isVoidPointer(QualType T);

/// Dereferences \p V and returns the value and dynamic type of the pointee, as
/// well as whether \p FR needs to be casted back to that type. If for whatever
/// reason dereferencing fails, returns with None.
static llvm::Optional<std::tuple<SVal, QualType, bool>>
dereference(ProgramStateRef State, const FieldRegion *FR);

//===----------------------------------------------------------------------===//
//                   Methods for FindUninitializedFields.
//===----------------------------------------------------------------------===//

// Note that pointers/references don't contain fields themselves, so in this
// function we won't add anything to LocalChain.
bool FindUninitializedFields::isPointerOrReferenceUninit(
    const FieldRegion *FR, FieldChainInfo LocalChain) {

  assert((FR->getDecl()->getType()->isAnyPointerType() ||
          FR->getDecl()->getType()->isReferenceType() ||
          FR->getDecl()->getType()->isBlockPointerType()) &&
         "This method only checks pointer/reference objects!");

  SVal V = State->getSVal(FR);

  if (V.isUnknown() || V.getAs<loc::ConcreteInt>()) {
    IsAnyFieldInitialized = true;
    return false;
  }

  if (V.isUndef()) {
    return addFieldToUninits(
        LocalChain.add(LocField(FR, /*IsDereferenced*/ false)));
  }

  if (!CheckPointeeInitialization) {
    IsAnyFieldInitialized = true;
    return false;
  }

  // At this point the pointer itself is initialized and points to a valid
  // location, we'll now check the pointee.
  llvm::Optional<std::tuple<SVal, QualType, bool>> DerefInfo =
      dereference(State, FR);
  if (!DerefInfo) {
    IsAnyFieldInitialized = true;
    return false;
  }

  V = std::get<0>(*DerefInfo);
  QualType DynT = std::get<1>(*DerefInfo);
  bool NeedsCastBack = std::get<2>(*DerefInfo);

  // If FR is a pointer pointing to a non-primitive type.
  if (Optional<nonloc::LazyCompoundVal> RecordV =
          V.getAs<nonloc::LazyCompoundVal>()) {

    const TypedValueRegion *R = RecordV->getRegion();

    if (DynT->getPointeeType()->isStructureOrClassType()) {
      if (NeedsCastBack)
        return isNonUnionUninit(R, LocalChain.add(NeedsCastLocField(FR, DynT)));
      return isNonUnionUninit(R, LocalChain.add(LocField(FR)));
    }

    if (DynT->getPointeeType()->isUnionType()) {
      if (isUnionUninit(R)) {
        if (NeedsCastBack)
          return addFieldToUninits(LocalChain.add(NeedsCastLocField(FR, DynT)));
        return addFieldToUninits(LocalChain.add(LocField(FR)));
      } else {
        IsAnyFieldInitialized = true;
        return false;
      }
    }

    if (DynT->getPointeeType()->isArrayType()) {
      IsAnyFieldInitialized = true;
      return false;
    }

    llvm_unreachable("All cases are handled!");
  }

  assert((isPrimitiveType(DynT->getPointeeType()) || DynT->isAnyPointerType() ||
          DynT->isReferenceType()) &&
         "At this point FR must either have a primitive dynamic type, or it "
         "must be a null, undefined, unknown or concrete pointer!");

  if (isPrimitiveUninit(V)) {
    if (NeedsCastBack)
      return addFieldToUninits(LocalChain.add(NeedsCastLocField(FR, DynT)));
    return addFieldToUninits(LocalChain.add(LocField(FR)));
  }

  IsAnyFieldInitialized = true;
  return false;
}

//===----------------------------------------------------------------------===//
//                           Utility functions.
//===----------------------------------------------------------------------===//

static bool isVoidPointer(QualType T) {
  while (!T.isNull()) {
    if (T->isVoidPointerType())
      return true;
    T = T->getPointeeType();
  }
  return false;
}

static llvm::Optional<std::tuple<SVal, QualType, bool>>
dereference(ProgramStateRef State, const FieldRegion *FR) {

  DynamicTypeInfo DynTInfo;
  QualType DynT;

  // If the static type of the field is a void pointer, we need to cast it back
  // to the dynamic type before dereferencing.
  bool NeedsCastBack = isVoidPointer(FR->getDecl()->getType());

  SVal V = State->getSVal(FR);
  assert(V.getAs<loc::MemRegionVal>() && "V must be loc::MemRegionVal!");

  // If V is multiple pointer value, we'll dereference it again (e.g.: int** ->
  // int*).
  // TODO: Dereference according to the dynamic type to avoid infinite loop for
  // these kind of fields:
  //   int **ptr = reinterpret_cast<int **>(&ptr);
  while (auto Tmp = V.getAs<loc::MemRegionVal>()) {
    // We can't reason about symbolic regions, assume its initialized.
    // Note that this also avoids a potential infinite recursion, because
    // constructors for list-like classes are checked without being called, and
    // the Static Analyzer will construct a symbolic region for Node *next; or
    // similar code snippets.
    if (Tmp->getRegion()->getSymbolicBase()) {
      return None;
    }

    DynTInfo = getDynamicTypeInfo(State, Tmp->getRegion());
    if (!DynTInfo.isValid()) {
      return None;
    }

    DynT = DynTInfo.getType();

    if (isVoidPointer(DynT)) {
      return None;
    }

    V = State->getSVal(*Tmp, DynT);
  }

  return std::make_tuple(V, DynT, NeedsCastBack);
}