C++ Sema::CheckBaseClassAccess方法代码示例

/// TryStaticMemberPointerUpcast - Tests whether a conversion according to
/// C++ 5.2.9p9 is valid:
///
///   An rvalue of type "pointer to member of D of type cv1 T" can be
///   converted to an rvalue of type "pointer to member of B of type cv2 T",
///   where B is a base class of D [...].
///
TryCastResult
TryStaticMemberPointerUpcast(Sema &Self, QualType SrcType, QualType DestType,
                             bool CStyle, const SourceRange &OpRange,
                             unsigned &msg)
{
  const MemberPointerType *DestMemPtr = DestType->getAs<MemberPointerType>();
  if (!DestMemPtr)
    return TC_NotApplicable;
  const MemberPointerType *SrcMemPtr = SrcType->getAs<MemberPointerType>();
  if (!SrcMemPtr) {
    msg = diag::err_bad_static_cast_member_pointer_nonmp;
    return TC_NotApplicable;
  }

  // T == T, modulo cv
  if (Self.Context.getCanonicalType(
        SrcMemPtr->getPointeeType().getUnqualifiedType()) !=
      Self.Context.getCanonicalType(DestMemPtr->getPointeeType().
                                    getUnqualifiedType()))
    return TC_NotApplicable;

  // B base of D
  QualType SrcClass(SrcMemPtr->getClass(), 0);
  QualType DestClass(DestMemPtr->getClass(), 0);
  BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/!CStyle,
                  /*DetectVirtual=*/true);
  if (!Self.IsDerivedFrom(SrcClass, DestClass, Paths)) {
    return TC_NotApplicable;
  }

  // B is a base of D. But is it an allowed base? If not, it's a hard error.
  if (Paths.isAmbiguous(DestClass)) {
    Paths.clear();
    Paths.setRecordingPaths(true);
    bool StillOkay = Self.IsDerivedFrom(SrcClass, DestClass, Paths);
    assert(StillOkay);
    StillOkay = StillOkay;
    std::string PathDisplayStr = Self.getAmbiguousPathsDisplayString(Paths);
    Self.Diag(OpRange.getBegin(), diag::err_ambiguous_memptr_conv)
      << 1 << SrcClass << DestClass << PathDisplayStr << OpRange;
    msg = 0;
    return TC_Failed;
  }

  if (const RecordType *VBase = Paths.getDetectedVirtual()) {
    Self.Diag(OpRange.getBegin(), diag::err_memptr_conv_via_virtual)
      << SrcClass << DestClass << QualType(VBase, 0) << OpRange;
    msg = 0;
    return TC_Failed;
  }

  if (!CStyle && Self.CheckBaseClassAccess(DestType, SrcType,
                          diag::err_downcast_from_inaccessible_base, Paths,
                          OpRange.getBegin(), DeclarationName())) {
    msg = 0;
    return TC_Failed;
  }

  return TC_Success;
}

/// TryStaticDowncast - Common functionality of TryStaticReferenceDowncast and
/// TryStaticPointerDowncast. Tests whether a static downcast from SrcType to
/// DestType, both of which must be canonical, is possible and allowed.
TryCastResult
TryStaticDowncast(Sema &Self, QualType SrcType, QualType DestType,
                  bool CStyle, const SourceRange &OpRange, QualType OrigSrcType,
                  QualType OrigDestType, unsigned &msg)
{
  // Downcast can only happen in class hierarchies, so we need classes.
  if (!DestType->isRecordType() || !SrcType->isRecordType()) {
    return TC_NotApplicable;
  }

  BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/!CStyle,
                  /*DetectVirtual=*/true);
  if (!Self.IsDerivedFrom(DestType, SrcType, Paths)) {
    return TC_NotApplicable;
  }

  // Target type does derive from source type. Now we're serious. If an error
  // appears now, it's not ignored.
  // This may not be entirely in line with the standard. Take for example:
  // struct A {};
  // struct B : virtual A {
  //   B(A&);
  // };
  // 
  // void f()
  // {
  //   (void)static_cast<const B&>(*((A*)0));
  // }
  // As far as the standard is concerned, p5 does not apply (A is virtual), so
  // p2 should be used instead - "const B& t(*((A*)0));" is perfectly valid.
  // However, both GCC and Comeau reject this example, and accepting it would
  // mean more complex code if we're to preserve the nice error message.
  // FIXME: Being 100% compliant here would be nice to have.

  // Must preserve cv, as always, unless we're in C-style mode.
  if (!CStyle && !DestType.isAtLeastAsQualifiedAs(SrcType)) {
    msg = diag::err_bad_cxx_cast_const_away;
    return TC_Failed;
  }

  if (Paths.isAmbiguous(SrcType.getUnqualifiedType())) {
    // This code is analoguous to that in CheckDerivedToBaseConversion, except
    // that it builds the paths in reverse order.
    // To sum up: record all paths to the base and build a nice string from
    // them. Use it to spice up the error message.
    if (!Paths.isRecordingPaths()) {
      Paths.clear();
      Paths.setRecordingPaths(true);
      Self.IsDerivedFrom(DestType, SrcType, Paths);
    }
    std::string PathDisplayStr;
    std::set<unsigned> DisplayedPaths;
    for (BasePaths::paths_iterator PI = Paths.begin(), PE = Paths.end();
         PI != PE; ++PI) {
      if (DisplayedPaths.insert(PI->back().SubobjectNumber).second) {
        // We haven't displayed a path to this particular base
        // class subobject yet.
        PathDisplayStr += "\n    ";
        for (BasePath::const_reverse_iterator EI = PI->rbegin(),EE = PI->rend();
             EI != EE; ++EI)
          PathDisplayStr += EI->Base->getType().getAsString() + " -> ";
        PathDisplayStr += DestType.getAsString();
      }
    }

    Self.Diag(OpRange.getBegin(), diag::err_ambiguous_base_to_derived_cast)
      << SrcType.getUnqualifiedType() << DestType.getUnqualifiedType()
      << PathDisplayStr << OpRange;
    msg = 0;
    return TC_Failed;
  }

  if (Paths.getDetectedVirtual() != 0) {
    QualType VirtualBase(Paths.getDetectedVirtual(), 0);
    Self.Diag(OpRange.getBegin(), diag::err_static_downcast_via_virtual)
      << OrigSrcType << OrigDestType << VirtualBase << OpRange;
    msg = 0;
    return TC_Failed;
  }

  if (!CStyle && Self.CheckBaseClassAccess(DestType, SrcType,
                          diag::err_downcast_from_inaccessible_base, Paths,
                          OpRange.getBegin(), DeclarationName())) {
    msg = 0;
    return TC_Failed;
  }

  return TC_Success;
}