lldb/source/Plugins/Language/ObjC/NSSet.cpp

//===-- NSSet.cpp ---------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "NSSet.h"
#include "CFBasicHash.h"

#include "Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.h"
#include "lldb/DataFormatters/FormattersHelpers.h"
#include "lldb/Target/Language.h"
#include "lldb/Target/Target.h"
#include "lldb/Utility/DataBufferHeap.h"
#include "lldb/Utility/Endian.h"
#include "lldb/Utility/Status.h"
#include "lldb/Utility/Stream.h"
#include "lldb/ValueObject/ValueObject.h"
#include "lldb/ValueObject/ValueObjectConstResult.h"

#include "llvm/Support/Error.h"

using namespace lldb;
using namespace lldb_private;
using namespace lldb_private::formatters;

std::map<ConstString, CXXFunctionSummaryFormat::Callback> &
NSSet_Additionals::GetAdditionalSummaries() {
  static std::map<ConstString, CXXFunctionSummaryFormat::Callback> g_map;
  return g_map;
}

std::map<ConstString, CXXSyntheticChildren::CreateFrontEndCallback> &
NSSet_Additionals::GetAdditionalSynthetics() {
  static std::map<ConstString, CXXSyntheticChildren::CreateFrontEndCallback>
      g_map;
  return g_map;
}

namespace lldb_private {
namespace formatters {
class NSSetISyntheticFrontEnd : public SyntheticChildrenFrontEnd {
public:
  NSSetISyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);

  ~NSSetISyntheticFrontEnd() override;

  llvm::Expected<uint32_t> CalculateNumChildren() override;

  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;

  lldb::ChildCacheState Update() override;

private:
  struct DataDescriptor_32 {
    uint32_t _used : 26;
    uint32_t _szidx : 6;
  };

  struct DataDescriptor_64 {
    uint64_t _used : 58;
    uint32_t _szidx : 6;
  };

  struct SetItemDescriptor {
    lldb::addr_t item_ptr;
    lldb::ValueObjectSP valobj_sp;
  };

  ExecutionContextRef m_exe_ctx_ref;
  uint8_t m_ptr_size = 8;
  DataDescriptor_32 *m_data_32 = nullptr;
  DataDescriptor_64 *m_data_64 = nullptr;
  lldb::addr_t m_data_ptr = LLDB_INVALID_ADDRESS;
  std::vector<SetItemDescriptor> m_children;
};

class NSCFSetSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
public:
  NSCFSetSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);

  llvm::Expected<uint32_t> CalculateNumChildren() override;

  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;

  lldb::ChildCacheState Update() override;

private:
  struct SetItemDescriptor {
    lldb::addr_t item_ptr;
    lldb::ValueObjectSP valobj_sp;
  };

  ExecutionContextRef m_exe_ctx_ref;
  uint8_t m_ptr_size = 8;
  lldb::ByteOrder m_order = lldb::eByteOrderInvalid;

  CFBasicHash m_hashtable;

  CompilerType m_pair_type;
  std::vector<SetItemDescriptor> m_children;
};

template <typename D32, typename D64>
class GenericNSSetMSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
public:
  GenericNSSetMSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);

  ~GenericNSSetMSyntheticFrontEnd() override;

  llvm::Expected<uint32_t> CalculateNumChildren() override;

  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;

  lldb::ChildCacheState Update() override;

private:

  struct SetItemDescriptor {
    lldb::addr_t item_ptr;
    lldb::ValueObjectSP valobj_sp;
  };

  ExecutionContextRef m_exe_ctx_ref;
  uint8_t m_ptr_size = 8;
  D32 *m_data_32;
  D64 *m_data_64;
  std::vector<SetItemDescriptor> m_children;
};
  
namespace Foundation1300 {
  struct DataDescriptor_32 {
    uint32_t _used : 26;
    uint32_t _size;
    uint32_t _mutations;
    uint32_t _objs_addr;
  };
  
  struct DataDescriptor_64 {
    uint64_t _used : 58;
    uint64_t _size;
    uint64_t _mutations;
    uint64_t _objs_addr;
  };
  
  using NSSetMSyntheticFrontEnd =
      GenericNSSetMSyntheticFrontEnd<DataDescriptor_32, DataDescriptor_64>;
}
  
namespace Foundation1428 {
  struct DataDescriptor_32 {
    uint32_t _used : 26;
    uint32_t _size;
    uint32_t _objs_addr;
    uint32_t _mutations;
  };
  
  struct DataDescriptor_64 {
    uint64_t _used : 58;
    uint64_t _size;
    uint64_t _objs_addr;
    uint64_t _mutations;
  };
  
  using NSSetMSyntheticFrontEnd =
      GenericNSSetMSyntheticFrontEnd<DataDescriptor_32, DataDescriptor_64>;
}
  
namespace Foundation1437 {
  struct DataDescriptor_32 {
    uint32_t _cow;
    // __table storage
    uint32_t _objs_addr;
    uint32_t _muts;
    uint32_t _used : 26;
    uint32_t _szidx : 6;
  };
  
  struct DataDescriptor_64 {
    uint64_t _cow;
    // __Table storage
    uint64_t _objs_addr;
    uint32_t _muts;
    uint32_t _used : 26;
    uint32_t _szidx : 6;
  };
  
  using NSSetMSyntheticFrontEnd =
      GenericNSSetMSyntheticFrontEnd<DataDescriptor_32, DataDescriptor_64>;
  
  template <typename DD>
  uint64_t
  __NSSetMSize_Impl(lldb_private::Process &process, lldb::addr_t valobj_addr,
                    Status &error) {
    const lldb::addr_t start_of_descriptor =
        valobj_addr + process.GetAddressByteSize();
    DD descriptor = DD();
    process.ReadMemory(start_of_descriptor, &descriptor, sizeof(descriptor),
                       error);
    if (error.Fail()) {
      return 0;
    }
    return descriptor._used;
  }
  
  uint64_t
  __NSSetMSize(lldb_private::Process &process, lldb::addr_t valobj_addr,
               Status &error) {
    if (process.GetAddressByteSize() == 4) {
      return __NSSetMSize_Impl<DataDescriptor_32>(process, valobj_addr, error);
    } else {
      return __NSSetMSize_Impl<DataDescriptor_64>(process, valobj_addr, error);
    }
  }
  } // namespace Foundation1437
} // namespace formatters
} // namespace lldb_private

template <bool cf_style>
bool lldb_private::formatters::NSSetSummaryProvider(
    ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
  static constexpr llvm::StringLiteral g_TypeHint("NSSet");

  ProcessSP process_sp = valobj.GetProcessSP();
  if (!process_sp)
    return false;

  ObjCLanguageRuntime *runtime = ObjCLanguageRuntime::Get(*process_sp);

  if (!runtime)
    return false;

  ObjCLanguageRuntime::ClassDescriptorSP descriptor(
      runtime->GetClassDescriptor(valobj));

  if (!descriptor || !descriptor->IsValid())
    return false;

  uint32_t ptr_size = process_sp->GetAddressByteSize();
  bool is_64bit = (ptr_size == 8);

  lldb::addr_t valobj_addr = valobj.GetValueAsUnsigned(0);

  if (!valobj_addr)
    return false;

  uint64_t value = 0;

  ConstString class_name(descriptor->GetClassName());
  llvm::StringRef class_name_ref(class_name.GetStringRef());

  static constexpr llvm::StringLiteral g_SetI("__NSSetI");
  static constexpr llvm::StringLiteral g_OrderedSetI("__NSOrderedSetI");
  static constexpr llvm::StringLiteral g_SetM("__NSSetM");
  static constexpr llvm::StringLiteral g_SetCF("__NSCFSet");
  static constexpr llvm::StringLiteral g_SetCFRef("CFSetRef");

  if (class_name_ref.empty())
    return false;

  if (class_name_ref == g_SetI || class_name_ref == g_OrderedSetI) {
    Status error;
    value = process_sp->ReadUnsignedIntegerFromMemory(valobj_addr + ptr_size,
                                                      ptr_size, 0, error);
    if (error.Fail())
      return false;
    value &= (is_64bit ? ~0xFC00000000000000UL : ~0xFC000000U);
  } else if (class_name_ref == g_SetM) {
    AppleObjCRuntime *apple_runtime =
        llvm::dyn_cast_or_null<AppleObjCRuntime>(runtime);
    Status error;
    if (apple_runtime && apple_runtime->GetFoundationVersion() >= 1437) {
      value = Foundation1437::__NSSetMSize(*process_sp, valobj_addr, error);
    } else {
      value = process_sp->ReadUnsignedIntegerFromMemory(valobj_addr + ptr_size,
                                                        ptr_size, 0, error);
      value &= (is_64bit ? ~0xFC00000000000000UL : ~0xFC000000U);
    }
    if (error.Fail())
      return false;
  } else if (class_name_ref == g_SetCF || class_name_ref == g_SetCFRef) {
    ExecutionContext exe_ctx(process_sp);
    CFBasicHash cfbh;
    if (!cfbh.Update(valobj_addr, exe_ctx))
      return false;
    value = cfbh.GetCount();
  } else {
    auto &map(NSSet_Additionals::GetAdditionalSummaries());
    auto iter = map.find(class_name), end = map.end();
    if (iter != end)
      return iter->second(valobj, stream, options);
    else
      return false;
  }

  llvm::StringRef prefix, suffix;
  if (Language *language = Language::FindPlugin(options.GetLanguage()))
    std::tie(prefix, suffix) = language->GetFormatterPrefixSuffix(g_TypeHint);

  stream << prefix;
  stream.Printf("%" PRIu64 " %s%s", value, "element", value == 1 ? "" : "s");
  stream << suffix;
  return true;
}

SyntheticChildrenFrontEnd *
lldb_private::formatters::NSSetSyntheticFrontEndCreator(
    CXXSyntheticChildren *synth, lldb::ValueObjectSP valobj_sp) {
  lldb::ProcessSP process_sp(valobj_sp->GetProcessSP());
  if (!process_sp)
    return nullptr;
  ObjCLanguageRuntime *runtime = ObjCLanguageRuntime::Get(*process_sp);
  if (!runtime)
    return nullptr;

  CompilerType valobj_type(valobj_sp->GetCompilerType());
  Flags flags(valobj_type.GetTypeInfo());

  if (flags.IsClear(eTypeIsPointer)) {
    Status error;
    valobj_sp = valobj_sp->AddressOf(error);
    if (error.Fail() || !valobj_sp)
      return nullptr;
  }

  ObjCLanguageRuntime::ClassDescriptorSP descriptor(
      runtime->GetClassDescriptor(*valobj_sp));

  if (!descriptor || !descriptor->IsValid())
    return nullptr;

  ConstString class_name = descriptor->GetClassName();
  llvm::StringRef class_name_ref(class_name.GetStringRef());

  static constexpr llvm::StringLiteral g_SetI("__NSSetI");
  static constexpr llvm::StringLiteral g_OrderedSetI("__NSOrderedSetI");
  static constexpr llvm::StringLiteral g_SetM("__NSSetM");
  static constexpr llvm::StringLiteral g_SetCF("__NSCFSet");
  static constexpr llvm::StringLiteral g_SetCFRef("CFSetRef");

  if (class_name_ref.empty())
    return nullptr;

  if (class_name_ref == g_SetI || class_name_ref == g_OrderedSetI) {
    return (new NSSetISyntheticFrontEnd(valobj_sp));
  } else if (class_name_ref == g_SetM) {
    AppleObjCRuntime *apple_runtime =
        llvm::dyn_cast_or_null<AppleObjCRuntime>(runtime);
    if (apple_runtime) {
      if (apple_runtime->GetFoundationVersion() >= 1437)
        return (new Foundation1437::NSSetMSyntheticFrontEnd(valobj_sp));
      else if (apple_runtime->GetFoundationVersion() >= 1428)
        return (new Foundation1428::NSSetMSyntheticFrontEnd(valobj_sp));
      else
        return (new Foundation1300::NSSetMSyntheticFrontEnd(valobj_sp));
    } else {
      return (new Foundation1300::NSSetMSyntheticFrontEnd(valobj_sp));
    }
  } else if (class_name_ref == g_SetCF || class_name_ref == g_SetCFRef) {
    return (new NSCFSetSyntheticFrontEnd(valobj_sp));
  } else {
    auto &map(NSSet_Additionals::GetAdditionalSynthetics());
    auto iter = map.find(class_name), end = map.end();
    if (iter != end)
      return iter->second(synth, valobj_sp);
    return nullptr;
  }
}

lldb_private::formatters::NSSetISyntheticFrontEnd::NSSetISyntheticFrontEnd(
    lldb::ValueObjectSP valobj_sp)
    : SyntheticChildrenFrontEnd(*valobj_sp), m_exe_ctx_ref() {
  if (valobj_sp)
    Update();
}

lldb_private::formatters::NSSetISyntheticFrontEnd::~NSSetISyntheticFrontEnd() {
  delete m_data_32;
  m_data_32 = nullptr;
  delete m_data_64;
  m_data_64 = nullptr;
}

llvm::Expected<uint32_t>
lldb_private::formatters::NSSetISyntheticFrontEnd::CalculateNumChildren() {
  if (!m_data_32 && !m_data_64)
    return 0;
  return (m_data_32 ? m_data_32->_used : m_data_64->_used);
}

lldb::ChildCacheState
lldb_private::formatters::NSSetISyntheticFrontEnd::Update() {
  m_children.clear();
  delete m_data_32;
  m_data_32 = nullptr;
  delete m_data_64;
  m_data_64 = nullptr;
  m_ptr_size = 0;
  ValueObjectSP valobj_sp = m_backend.GetSP();
  if (!valobj_sp)
    return lldb::ChildCacheState::eRefetch;
  m_exe_ctx_ref = valobj_sp->GetExecutionContextRef();
  lldb::ProcessSP process_sp(valobj_sp->GetProcessSP());
  if (!process_sp)
    return lldb::ChildCacheState::eRefetch;
  m_ptr_size = process_sp->GetAddressByteSize();
  uint64_t data_location = valobj_sp->GetValueAsUnsigned(0) + m_ptr_size;
  Status error;
  if (m_ptr_size == 4) {
    m_data_32 = new DataDescriptor_32();
    process_sp->ReadMemory(data_location, m_data_32, sizeof(DataDescriptor_32),
                           error);
  } else {
    m_data_64 = new DataDescriptor_64();
    process_sp->ReadMemory(data_location, m_data_64, sizeof(DataDescriptor_64),
                           error);
  }
  if (error.Fail())
    return lldb::ChildCacheState::eRefetch;
  m_data_ptr = data_location + m_ptr_size;
  return lldb::ChildCacheState::eReuse;
}

lldb::ValueObjectSP
lldb_private::formatters::NSSetISyntheticFrontEnd::GetChildAtIndex(
    uint32_t idx) {
  uint32_t num_children = CalculateNumChildrenIgnoringErrors();

  if (idx >= num_children)
    return lldb::ValueObjectSP();

  ProcessSP process_sp = m_exe_ctx_ref.GetProcessSP();
  if (!process_sp)
    return lldb::ValueObjectSP();

  if (m_children.empty()) {
    // do the scan phase
    lldb::addr_t obj_at_idx = 0;

    uint32_t tries = 0;
    uint32_t test_idx = 0;

    while (tries < num_children) {
      obj_at_idx = m_data_ptr + (test_idx * m_ptr_size);
      if (!process_sp)
        return lldb::ValueObjectSP();
      llvm::Expected<lldb::addr_t> obj_at_idx_or_err =
          process_sp->ReadPointerFromMemory(obj_at_idx);
      if (!obj_at_idx_or_err) {
        llvm::consumeError(obj_at_idx_or_err.takeError());
        return lldb::ValueObjectSP();
      }
      obj_at_idx = *obj_at_idx_or_err;

      test_idx++;

      if (!obj_at_idx)
        continue;
      tries++;

      SetItemDescriptor descriptor = {obj_at_idx, lldb::ValueObjectSP()};

      m_children.push_back(descriptor);
    }
  }

  if (idx >= m_children.size()) // should never happen
    return lldb::ValueObjectSP();

  SetItemDescriptor &set_item = m_children[idx];
  if (!set_item.valobj_sp) {
    auto ptr_size = process_sp->GetAddressByteSize();
    DataBufferHeap buffer(ptr_size, 0);
    switch (ptr_size) {
    case 0: // architecture has no clue - fail
      return lldb::ValueObjectSP();
    case 4:
      *reinterpret_cast<uint32_t *>(buffer.GetBytes()) =
          static_cast<uint32_t>(set_item.item_ptr);
      break;
    case 8:
      *reinterpret_cast<uint64_t *>(buffer.GetBytes()) =
          static_cast<uint64_t>(set_item.item_ptr);
      break;
    default:
      lldbassert(false && "pointer size is not 4 nor 8");
    }
    StreamString idx_name;
    idx_name.Printf("[%" PRIu64 "]", (uint64_t)idx);

    DataExtractor data(buffer.GetBytes(), buffer.GetByteSize(),
                       process_sp->GetByteOrder(),
                       process_sp->GetAddressByteSize());

    set_item.valobj_sp = CreateChildValueObjectFromData(
        idx_name.GetString(), data, m_exe_ctx_ref,
        m_backend.GetCompilerType().GetBasicTypeFromAST(
            lldb::eBasicTypeObjCID));
  }
  return set_item.valobj_sp;
}

lldb_private::formatters::NSCFSetSyntheticFrontEnd::NSCFSetSyntheticFrontEnd(
    lldb::ValueObjectSP valobj_sp)
    : SyntheticChildrenFrontEnd(*valobj_sp), m_exe_ctx_ref(), m_hashtable(),
      m_pair_type() {}

llvm::Expected<uint32_t>
lldb_private::formatters::NSCFSetSyntheticFrontEnd::CalculateNumChildren() {
  if (!m_hashtable.IsValid())
    return 0;
  return m_hashtable.GetCount();
}

lldb::ChildCacheState
lldb_private::formatters::NSCFSetSyntheticFrontEnd::Update() {
  m_children.clear();
  ValueObjectSP valobj_sp = m_backend.GetSP();
  m_ptr_size = 0;
  if (!valobj_sp)
    return lldb::ChildCacheState::eRefetch;
  m_exe_ctx_ref = valobj_sp->GetExecutionContextRef();

  lldb::ProcessSP process_sp(valobj_sp->GetProcessSP());
  if (!process_sp)
    return lldb::ChildCacheState::eRefetch;
  m_ptr_size = process_sp->GetAddressByteSize();
  m_order = process_sp->GetByteOrder();
  return m_hashtable.Update(valobj_sp->GetValueAsUnsigned(0), m_exe_ctx_ref)
             ? lldb::ChildCacheState::eReuse
             : lldb::ChildCacheState::eRefetch;
}

lldb::ValueObjectSP
lldb_private::formatters::NSCFSetSyntheticFrontEnd::GetChildAtIndex(
    uint32_t idx) {
  lldb::addr_t m_values_ptr = m_hashtable.GetValuePointer();

  const uint32_t num_children = CalculateNumChildrenIgnoringErrors();

  if (idx >= num_children)
    return lldb::ValueObjectSP();

  if (m_children.empty()) {
    ProcessSP process_sp = m_exe_ctx_ref.GetProcessSP();
    if (!process_sp)
      return lldb::ValueObjectSP();

    lldb::addr_t val_at_idx = 0;

    uint32_t tries = 0;
    uint32_t test_idx = 0;

    // Iterate over inferior memory, reading value pointers by shifting the
    // cursor by test_index * m_ptr_size. Returns an empty ValueObject if a read
    // fails, otherwise, continue until the number of tries matches the number
    // of childen.
    while (tries < num_children) {
      val_at_idx = m_values_ptr + (test_idx * m_ptr_size);

      llvm::Expected<lldb::addr_t> val_at_idx_or_err =
          process_sp->ReadPointerFromMemory(val_at_idx);
      if (!val_at_idx_or_err) {
        llvm::consumeError(val_at_idx_or_err.takeError());
        return lldb::ValueObjectSP();
      }
      val_at_idx = *val_at_idx_or_err;

      test_idx++;

      if (!val_at_idx)
        continue;
      tries++;

      SetItemDescriptor descriptor = {val_at_idx, lldb::ValueObjectSP()};

      m_children.push_back(descriptor);
    }
  }

  if (idx >= m_children.size()) // should never happen
    return lldb::ValueObjectSP();

  SetItemDescriptor &set_item = m_children[idx];
  if (!set_item.valobj_sp) {

    WritableDataBufferSP buffer_sp(new DataBufferHeap(m_ptr_size, 0));

    switch (m_ptr_size) {
    case 0: // architecture has no clue - fail
      return lldb::ValueObjectSP();
    case 4:
      *reinterpret_cast<uint32_t *>(buffer_sp->GetBytes()) =
          static_cast<uint32_t>(set_item.item_ptr);
      break;
    case 8:
      *reinterpret_cast<uint64_t *>(buffer_sp->GetBytes()) =
          static_cast<uint64_t>(set_item.item_ptr);
      break;
    default:
      lldbassert(false && "pointer size is not 4 nor 8");
    }
    StreamString idx_name;
    idx_name.Printf("[%" PRIu64 "]", (uint64_t)idx);

    DataExtractor data(buffer_sp, m_order, m_ptr_size);

    set_item.valobj_sp = CreateChildValueObjectFromData(
        idx_name.GetString(), data, m_exe_ctx_ref,
        m_backend.GetCompilerType().GetBasicTypeFromAST(
            lldb::eBasicTypeObjCID));
  }

  return set_item.valobj_sp;
}

template <typename D32, typename D64>
lldb_private::formatters::GenericNSSetMSyntheticFrontEnd<
    D32, D64>::GenericNSSetMSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
    : SyntheticChildrenFrontEnd(*valobj_sp), m_exe_ctx_ref(),
      m_data_32(nullptr), m_data_64(nullptr) {
  if (valobj_sp)
    Update();
}

template <typename D32, typename D64>
lldb_private::formatters::GenericNSSetMSyntheticFrontEnd<D32, D64>::
    GenericNSSetMSyntheticFrontEnd::~GenericNSSetMSyntheticFrontEnd() {
  delete m_data_32;
  m_data_32 = nullptr;
  delete m_data_64;
  m_data_64 = nullptr;
}

template <typename D32, typename D64>
llvm::Expected<uint32_t>
lldb_private::formatters::GenericNSSetMSyntheticFrontEnd<
    D32, D64>::CalculateNumChildren() {
  if (!m_data_32 && !m_data_64)
    return 0;
  return (m_data_32 ? (uint32_t)m_data_32->_used : (uint32_t)m_data_64->_used);
}

template <typename D32, typename D64>
lldb::ChildCacheState
lldb_private::formatters::GenericNSSetMSyntheticFrontEnd<D32, D64>::Update() {
  m_children.clear();
  ValueObjectSP valobj_sp = m_backend.GetSP();
  m_ptr_size = 0;
  delete m_data_32;
  m_data_32 = nullptr;
  delete m_data_64;
  m_data_64 = nullptr;
  if (!valobj_sp)
    return lldb::ChildCacheState::eRefetch;
  if (!valobj_sp)
    return lldb::ChildCacheState::eRefetch;
  m_exe_ctx_ref = valobj_sp->GetExecutionContextRef();
  lldb::ProcessSP process_sp(valobj_sp->GetProcessSP());
  if (!process_sp)
    return lldb::ChildCacheState::eRefetch;
  m_ptr_size = process_sp->GetAddressByteSize();
  uint64_t data_location = valobj_sp->GetValueAsUnsigned(0) + m_ptr_size;
  Status error;
  if (m_ptr_size == 4) {
    m_data_32 = new D32();
    process_sp->ReadMemory(data_location, m_data_32, sizeof(D32),
                           error);
  } else {
    m_data_64 = new D64();
    process_sp->ReadMemory(data_location, m_data_64, sizeof(D64),
                           error);
  }
  return error.Success() ? lldb::ChildCacheState::eReuse
                         : lldb::ChildCacheState::eRefetch;
}

template <typename D32, typename D64>
lldb::ValueObjectSP
lldb_private::formatters::
  GenericNSSetMSyntheticFrontEnd<D32, D64>::GetChildAtIndex(uint32_t idx) {
  lldb::addr_t m_objs_addr =
      (m_data_32 ? m_data_32->_objs_addr : m_data_64->_objs_addr);

  uint32_t num_children = CalculateNumChildrenIgnoringErrors();

  if (idx >= num_children)
    return lldb::ValueObjectSP();

  ProcessSP process_sp = m_exe_ctx_ref.GetProcessSP();
  if (!process_sp)
    return lldb::ValueObjectSP();

  if (m_children.empty()) {
    // do the scan phase
    lldb::addr_t obj_at_idx = 0;

    uint32_t tries = 0;
    uint32_t test_idx = 0;

    while (tries < num_children) {
      obj_at_idx = m_objs_addr + (test_idx * m_ptr_size);
      if (!process_sp)
        return lldb::ValueObjectSP();
      llvm::Expected<lldb::addr_t> obj_at_idx_or_err =
          process_sp->ReadPointerFromMemory(obj_at_idx);
      if (!obj_at_idx_or_err) {
        llvm::consumeError(obj_at_idx_or_err.takeError());
        return lldb::ValueObjectSP();
      }
      obj_at_idx = *obj_at_idx_or_err;

      test_idx++;

      if (!obj_at_idx)
        continue;
      tries++;

      SetItemDescriptor descriptor = {obj_at_idx, lldb::ValueObjectSP()};

      m_children.push_back(descriptor);
    }
  }

  if (idx >= m_children.size()) // should never happen
    return lldb::ValueObjectSP();

  SetItemDescriptor &set_item = m_children[idx];
  if (!set_item.valobj_sp) {
    auto ptr_size = process_sp->GetAddressByteSize();
    DataBufferHeap buffer(ptr_size, 0);
    switch (ptr_size) {
    case 0: // architecture has no clue?? - fail
      return lldb::ValueObjectSP();
    case 4:
      *((uint32_t *)buffer.GetBytes()) = (uint32_t)set_item.item_ptr;
      break;
    case 8:
      *((uint64_t *)buffer.GetBytes()) = (uint64_t)set_item.item_ptr;
      break;
    default:
      assert(false && "pointer size is not 4 nor 8 - get out of here ASAP");
    }
    StreamString idx_name;
    idx_name.Printf("[%" PRIu64 "]", (uint64_t)idx);

    DataExtractor data(buffer.GetBytes(), buffer.GetByteSize(),
                       process_sp->GetByteOrder(),
                       process_sp->GetAddressByteSize());

    set_item.valobj_sp = CreateChildValueObjectFromData(
        idx_name.GetString(), data, m_exe_ctx_ref,
        m_backend.GetCompilerType().GetBasicTypeFromAST(
            lldb::eBasicTypeObjCID));
  }
  return set_item.valobj_sp;
}

template bool lldb_private::formatters::NSSetSummaryProvider<true>(
    ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options);

template bool lldb_private::formatters::NSSetSummaryProvider<false>(
    ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options);