AppleObjCClassDescriptorV2.cpp

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//===-- AppleObjCClassDescriptorV2.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 "AppleObjCClassDescriptorV2.h"
 
#include "lldb/Expression/FunctionCaller.h"
#include "lldb/Target/ABI.h"
#include "lldb/Target/Language.h"
#include "lldb/Utility/LLDBLog.h"
#include "lldb/Utility/Log.h"
#include "lldb/lldb-enumerations.h"
 
using namespace lldb;
using namespace lldb_private;
 
bool ClassDescriptorV2::Read_objc_class(
    Process *process, std::unique_ptr<objc_class_t> &objc_class) const {
  objc_class = std::make_unique<objc_class_t>();
 
  bool ret = objc_class->Read(process, m_objc_class_ptr);
 
  if (!ret)
    objc_class.reset();
 
  return ret;
}
 
static lldb::addr_t GetClassDataMask(Process *process) {
  switch (process->GetAddressByteSize()) {
  case 4:
    return 0xfffffffcUL;
  case 8:
    return 0x00007ffffffffff8UL;
  default:
    break;
  }
 
  return LLDB_INVALID_ADDRESS;
}
 
bool ClassDescriptorV2::objc_class_t::Read(Process *process,
                                           lldb::addr_t addr) {
  size_t ptr_size = process->GetAddressByteSize();
 
  size_t objc_class_size = ptr_size    // uintptr_t isa;
                           + ptr_size  // Class superclass;
                           + ptr_size  // void *cache;
                           + ptr_size  // IMP *vtable;
                           + ptr_size; // uintptr_t data_NEVER_USE;
 
  DataBufferHeap objc_class_buf(objc_class_size, '\0');
  Status error;
 
  process->ReadMemory(addr, objc_class_buf.GetBytes(), objc_class_size, error);
  if (error.Fail()) {
    return false;
  }
 
  DataExtractor extractor(objc_class_buf.GetBytes(), objc_class_size,
                          process->GetByteOrder(),
                          process->GetAddressByteSize());
 
  lldb::offset_t cursor = 0;
 
  m_isa = extractor.GetAddress_unchecked(&cursor);        // uintptr_t isa;
  m_superclass = extractor.GetAddress_unchecked(&cursor); // Class superclass;
  m_cache_ptr = extractor.GetAddress_unchecked(&cursor);  // void *cache;
  m_vtable_ptr = extractor.GetAddress_unchecked(&cursor); // IMP *vtable;
  lldb::addr_t data_NEVER_USE =
      extractor.GetAddress_unchecked(&cursor); // uintptr_t data_NEVER_USE;
 
  m_flags = (uint8_t)(data_NEVER_USE & (lldb::addr_t)3);
  m_data_ptr = data_NEVER_USE & GetClassDataMask(process);
 
  if (ABISP abi_sp = process->GetABI()) {
    m_isa = abi_sp->FixCodeAddress(m_isa);
    m_superclass = abi_sp->FixCodeAddress(m_superclass);
    m_data_ptr = abi_sp->FixCodeAddress(m_data_ptr);
  }
  return true;
}
 
bool ClassDescriptorV2::class_rw_t::Read(Process *process, lldb::addr_t addr) {
  size_t ptr_size = process->GetAddressByteSize();
 
  size_t size = sizeof(uint32_t)   // uint32_t flags;
                + sizeof(uint32_t) // uint32_t version;
                + ptr_size         // const class_ro_t *ro;
                + ptr_size         // union { method_list_t **method_lists;
                                   // method_list_t *method_list; };
                + ptr_size         // struct chained_property_list *properties;
                + ptr_size         // const protocol_list_t **protocols;
                + ptr_size         // Class firstSubclass;
                + ptr_size;        // Class nextSiblingClass;
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  if (error.Fail()) {
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          process->GetAddressByteSize());
 
  lldb::offset_t cursor = 0;
 
  m_flags = extractor.GetU32_unchecked(&cursor);
  m_version = extractor.GetU32_unchecked(&cursor);
  m_ro_ptr = extractor.GetAddress_unchecked(&cursor);
  if (ABISP abi_sp = process->GetABI())
    m_ro_ptr = abi_sp->FixCodeAddress(m_ro_ptr);
  m_method_list_ptr = extractor.GetAddress_unchecked(&cursor);
  m_properties_ptr = extractor.GetAddress_unchecked(&cursor);
  m_firstSubclass = extractor.GetAddress_unchecked(&cursor);
  m_nextSiblingClass = extractor.GetAddress_unchecked(&cursor);
 
  if (m_ro_ptr & 1) {
    DataBufferHeap buffer(ptr_size, '\0');
    process->ReadMemory(m_ro_ptr ^ 1, buffer.GetBytes(), ptr_size, error);
    if (error.Fail())
      return false;
    cursor = 0;
    DataExtractor extractor(buffer.GetBytes(), ptr_size,
                            process->GetByteOrder(),
                            process->GetAddressByteSize());
    m_ro_ptr = extractor.GetAddress_unchecked(&cursor);
    if (ABISP abi_sp = process->GetABI())
      m_ro_ptr = abi_sp->FixCodeAddress(m_ro_ptr);
  }
 
  return true;
}
 
bool ClassDescriptorV2::class_ro_t::Read(Process *process, lldb::addr_t addr) {
  size_t ptr_size = process->GetAddressByteSize();
 
  size_t size = sizeof(uint32_t)   // uint32_t flags;
                + sizeof(uint32_t) // uint32_t instanceStart;
                + sizeof(uint32_t) // uint32_t instanceSize;
                + (ptr_size == 8 ? sizeof(uint32_t)
                                 : 0) // uint32_t reserved; // __LP64__ only
                + ptr_size            // const uint8_t *ivarLayout;
                + ptr_size            // const char *name;
                + ptr_size            // const method_list_t *baseMethods;
                + ptr_size            // const protocol_list_t *baseProtocols;
                + ptr_size            // const ivar_list_t *ivars;
                + ptr_size            // const uint8_t *weakIvarLayout;
                + ptr_size;           // const property_list_t *baseProperties;
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  if (error.Fail()) {
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          process->GetAddressByteSize());
 
  lldb::offset_t cursor = 0;
 
  m_flags = extractor.GetU32_unchecked(&cursor);
  m_instanceStart = extractor.GetU32_unchecked(&cursor);
  m_instanceSize = extractor.GetU32_unchecked(&cursor);
  if (ptr_size == 8)
    m_reserved = extractor.GetU32_unchecked(&cursor);
  else
    m_reserved = 0;
  m_ivarLayout_ptr = extractor.GetAddress_unchecked(&cursor);
  m_name_ptr = extractor.GetAddress_unchecked(&cursor);
  m_baseMethods_ptr = extractor.GetAddress_unchecked(&cursor);
  m_baseProtocols_ptr = extractor.GetAddress_unchecked(&cursor);
  m_ivars_ptr = extractor.GetAddress_unchecked(&cursor);
  m_weakIvarLayout_ptr = extractor.GetAddress_unchecked(&cursor);
  m_baseProperties_ptr = extractor.GetAddress_unchecked(&cursor);
 
  DataBufferHeap name_buf(1024, '\0');
 
  process->ReadCStringFromMemory(m_name_ptr, (char *)name_buf.GetBytes(),
                                 name_buf.GetByteSize(), error);
 
  if (error.Fail()) {
    return false;
  }
 
  m_name.assign((char *)name_buf.GetBytes());
 
  return true;
}
 
bool ClassDescriptorV2::Read_class_row(
    Process *process, const objc_class_t &objc_class,
    std::unique_ptr<class_ro_t> &class_ro,
    std::unique_ptr<class_rw_t> &class_rw) const {
  class_ro.reset();
  class_rw.reset();
 
  Status error;
  uint32_t class_row_t_flags = process->ReadUnsignedIntegerFromMemory(
      objc_class.m_data_ptr, sizeof(uint32_t), 0, error);
  if (!error.Success())
    return false;
 
  if (class_row_t_flags & RW_REALIZED) {
    class_rw = std::make_unique<class_rw_t>();
 
    if (!class_rw->Read(process, objc_class.m_data_ptr)) {
      class_rw.reset();
      return false;
    }
 
    class_ro = std::make_unique<class_ro_t>();
 
    if (!class_ro->Read(process, class_rw->m_ro_ptr)) {
      class_rw.reset();
      class_ro.reset();
      return false;
    }
  } else {
    class_ro = std::make_unique<class_ro_t>();
 
    if (!class_ro->Read(process, objc_class.m_data_ptr)) {
      class_ro.reset();
      return false;
    }
  }
 
  return true;
}
 
bool ClassDescriptorV2::method_list_t::Read(Process *process,
                                            lldb::addr_t addr) {
  size_t size = sizeof(uint32_t)    // uint32_t entsize_NEVER_USE;
                + sizeof(uint32_t); // uint32_t count;
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  if (ABISP abi_sp = process->GetABI())
    addr = abi_sp->FixCodeAddress(addr);
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  if (error.Fail()) {
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          process->GetAddressByteSize());
 
  lldb::offset_t cursor = 0;
 
  uint32_t entsize = extractor.GetU32_unchecked(&cursor);
  m_is_small = (entsize & 0x80000000) != 0;
  m_has_direct_selector = (entsize & 0x40000000) != 0;
  m_entsize = entsize & 0xfffc;
  m_count = extractor.GetU32_unchecked(&cursor);
  m_first_ptr = addr + cursor;
 
  return true;
}
 
bool ClassDescriptorV2::method_t::Read(Process *process, lldb::addr_t addr,
                                       lldb::addr_t relative_selector_base_addr,
                                       bool is_small, bool has_direct_sel) {
  size_t ptr_size = process->GetAddressByteSize();
  size_t size = GetSize(process, is_small);
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  if (error.Fail()) {
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          ptr_size);
  lldb::offset_t cursor = 0;
 
  if (is_small) {
    uint32_t nameref_offset = extractor.GetU32_unchecked(&cursor);
    uint32_t types_offset = extractor.GetU32_unchecked(&cursor);
    uint32_t imp_offset = extractor.GetU32_unchecked(&cursor);
 
    m_name_ptr = addr + nameref_offset;
 
    if (!has_direct_sel) {
      // The SEL offset points to a SELRef. We need to dereference twice.
      m_name_ptr = process->ReadUnsignedIntegerFromMemory(m_name_ptr, ptr_size,
                                                          0, error);
      if (!error.Success())
        return false;
    } else if (relative_selector_base_addr != LLDB_INVALID_ADDRESS) {
      m_name_ptr = relative_selector_base_addr + nameref_offset;
    }
    m_types_ptr = addr + 4 + types_offset;
    m_imp_ptr = addr + 8 + imp_offset;
  } else {
    m_name_ptr = extractor.GetAddress_unchecked(&cursor);
    m_types_ptr = extractor.GetAddress_unchecked(&cursor);
    m_imp_ptr = extractor.GetAddress_unchecked(&cursor);
  }
 
  process->ReadCStringFromMemory(m_name_ptr, m_name, error);
  if (error.Fail()) {
    return false;
  }
 
  process->ReadCStringFromMemory(m_types_ptr, m_types, error);
  return !error.Fail();
}
 
bool ClassDescriptorV2::ivar_list_t::Read(Process *process, lldb::addr_t addr) {
  size_t size = sizeof(uint32_t)    // uint32_t entsize;
                + sizeof(uint32_t); // uint32_t count;
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  if (error.Fail()) {
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          process->GetAddressByteSize());
 
  lldb::offset_t cursor = 0;
 
  m_entsize = extractor.GetU32_unchecked(&cursor);
  m_count = extractor.GetU32_unchecked(&cursor);
  m_first_ptr = addr + cursor;
 
  return true;
}
 
bool ClassDescriptorV2::ivar_t::Read(Process *process, lldb::addr_t addr) {
  size_t size = GetSize(process);
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  if (error.Fail()) {
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          process->GetAddressByteSize());
 
  lldb::offset_t cursor = 0;
 
  m_offset_ptr = extractor.GetAddress_unchecked(&cursor);
  m_name_ptr = extractor.GetAddress_unchecked(&cursor);
  m_type_ptr = extractor.GetAddress_unchecked(&cursor);
  m_alignment = extractor.GetU32_unchecked(&cursor);
  m_size = extractor.GetU32_unchecked(&cursor);
 
  process->ReadCStringFromMemory(m_name_ptr, m_name, error);
  if (error.Fail()) {
    return false;
  }
 
  process->ReadCStringFromMemory(m_type_ptr, m_type, error);
  return !error.Fail();
}
 
bool ClassDescriptorV2::relative_list_entry_t::Read(Process *process,
                                                    lldb::addr_t addr) {
  Log *log = GetLog(LLDBLog::Types);
  size_t size = sizeof(uint64_t); // m_image_index : 16
                                  // m_list_offset : 48
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  // FIXME: Propagate this error up
  if (error.Fail()) {
    LLDB_LOG(log, "Failed to read relative_list_entry_t at address {0:x}",
             addr);
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          process->GetAddressByteSize());
  lldb::offset_t cursor = 0;
  uint64_t raw_entry = extractor.GetU64_unchecked(&cursor);
  m_image_index = raw_entry & 0xFFFF;
  m_list_offset = llvm::SignExtend64<48>(raw_entry >> 16);
  return true;
}
 
bool ClassDescriptorV2::relative_list_list_t::Read(Process *process,
                                                   lldb::addr_t addr) {
  Log *log = GetLog(LLDBLog::Types);
  size_t size = sizeof(uint32_t)    // m_entsize
                + sizeof(uint32_t); // m_count
 
  DataBufferHeap buffer(size, '\0');
  Status error;
 
  // FIXME: Propagate this error up
  process->ReadMemory(addr, buffer.GetBytes(), size, error);
  if (error.Fail()) {
    LLDB_LOG(log, "Failed to read relative_list_list_t at address 0x" PRIx64,
             addr);
    return false;
  }
 
  DataExtractor extractor(buffer.GetBytes(), size, process->GetByteOrder(),
                          process->GetAddressByteSize());
  lldb::offset_t cursor = 0;
  m_entsize = extractor.GetU32_unchecked(&cursor);
  m_count = extractor.GetU32_unchecked(&cursor);
  m_first_ptr = addr + cursor;
  return true;
}
 
std::optional<ClassDescriptorV2::method_list_t>
ClassDescriptorV2::GetMethodList(Process *process,
                                 lldb::addr_t method_list_ptr) const {
  Log *log = GetLog(LLDBLog::Types);
  ClassDescriptorV2::method_list_t method_list;
  if (!method_list.Read(process, method_list_ptr))
    return std::nullopt;
 
  const size_t method_size = method_t::GetSize(process, method_list.m_is_small);
  if (method_list.m_entsize != method_size) {
    LLDB_LOG(log,
             "method_list_t at address 0x" PRIx64 " has an entsize of " PRIu16
             " but method size should be " PRIu64,
             method_list_ptr, method_list.m_entsize, method_size);
    return std::nullopt;
  }
 
  return method_list;
}
 
bool ClassDescriptorV2::ProcessMethodList(
    std::function<bool(const char *, const char *)> const &instance_method_func,
    ClassDescriptorV2::method_list_t &method_list) const {
  lldb_private::Process *process = m_runtime.GetProcess();
  auto method = std::make_unique<method_t>();
  lldb::addr_t relative_selector_base_addr =
      m_runtime.GetRelativeSelectorBaseAddr();
  for (uint32_t i = 0, e = method_list.m_count; i < e; ++i) {
    method->Read(process, method_list.m_first_ptr + (i * method_list.m_entsize),
                 relative_selector_base_addr, method_list.m_is_small,
                 method_list.m_has_direct_selector);
    if (instance_method_func(method->m_name.c_str(), method->m_types.c_str()))
      break;
  }
  return true;
}
 
// The relevant data structures:
//  - relative_list_list_t
//    - uint32_t count
//    - uint32_t entsize
//    - Followed by <count> number of relative_list_entry_t of size <entsize>
//
//  - relative_list_entry_t
//    - uint64_t image_index : 16
//    - int64_t list_offset : 48
//    - Note: The above 2 fit into 8 bytes always
//
//    image_index corresponds to an image in the shared cache
//    list_offset is used to calculate the address of the method_list_t we want
bool ClassDescriptorV2::ProcessRelativeMethodLists(
    std::function<bool(const char *, const char *)> const &instance_method_func,
    lldb::addr_t relative_method_list_ptr) const {
  lldb_private::Process *process = m_runtime.GetProcess();
  auto relative_method_lists = std::make_unique<relative_list_list_t>();
 
  // 1. Process the count and entsize of the relative_list_list_t
  if (!relative_method_lists->Read(process, relative_method_list_ptr))
    return false;
 
  auto entry = std::make_unique<relative_list_entry_t>();
  for (uint32_t i = 0; i < relative_method_lists->m_count; i++) {
    // 2. Extract the image index and the list offset from the
    // relative_list_entry_t
    const lldb::addr_t entry_addr = relative_method_lists->m_first_ptr +
                                    (i * relative_method_lists->m_entsize);
    if (!entry->Read(process, entry_addr))
      return false;
 
    // 3. Calculate the pointer to the method_list_t from the
    // relative_list_entry_t
    const lldb::addr_t method_list_addr = entry_addr + entry->m_list_offset;
 
    // 4. Get the method_list_t from the pointer
    std::optional<method_list_t> method_list =
        GetMethodList(process, method_list_addr);
    if (!method_list)
      return false;
 
    // 5. Cache the result so we don't need to reconstruct it later.
    m_image_to_method_lists[entry->m_image_index].emplace_back(*method_list);
 
    // 6. If the relevant image is loaded, add the methods to the Decl
    if (!m_runtime.IsSharedCacheImageLoaded(entry->m_image_index))
      continue;
 
    if (!ProcessMethodList(instance_method_func, *method_list))
      return false;
  }
 
  // We need to keep track of the last time we updated so we can re-update the
  // type information in the future
  m_last_version_updated = m_runtime.GetSharedCacheImageHeaderVersion();
 
  return true;
}
 
bool ClassDescriptorV2::Describe(
    std::function<void(ObjCLanguageRuntime::ObjCISA)> const &superclass_func,
    std::function<bool(const char *, const char *)> const &instance_method_func,
    std::function<bool(const char *, const char *)> const &class_method_func,
    std::function<bool(const char *, const char *, lldb::addr_t,
                       uint64_t)> const &ivar_func) const {
  lldb_private::Process *process = m_runtime.GetProcess();
 
  std::unique_ptr<objc_class_t> objc_class;
  std::unique_ptr<class_ro_t> class_ro;
  std::unique_ptr<class_rw_t> class_rw;
 
  if (!Read_objc_class(process, objc_class))
    return false;
  if (!Read_class_row(process, *objc_class, class_ro, class_rw))
    return false;
 
  static ConstString NSObject_name("NSObject");
 
  if (m_name != NSObject_name && superclass_func)
    superclass_func(objc_class->m_superclass);
 
  if (instance_method_func) {
    // This is a relative list of lists
    if (class_ro->m_baseMethods_ptr & 1) {
      if (!ProcessRelativeMethodLists(instance_method_func,
                                      class_ro->m_baseMethods_ptr ^ 1))
        return false;
    } else {
      std::optional<method_list_t> base_method_list =
          GetMethodList(process, class_ro->m_baseMethods_ptr);
      if (base_method_list &&
          !ProcessMethodList(instance_method_func, *base_method_list))
        return false;
    }
  }
 
  if (class_method_func) {
    AppleObjCRuntime::ClassDescriptorSP metaclass(GetMetaclass());
 
    // We don't care about the metaclass's superclass, or its class methods.
    // Its instance methods are our class methods.
 
    if (metaclass) {
      metaclass->Describe(
          std::function<void(ObjCLanguageRuntime::ObjCISA)>(nullptr),
          class_method_func,
          std::function<bool(const char *, const char *)>(nullptr),
          std::function<bool(const char *, const char *, lldb::addr_t,
                             uint64_t)>(nullptr));
    }
  }
 
  if (ivar_func) {
    if (class_ro->m_ivars_ptr != 0) {
      ivar_list_t ivar_list;
      if (!ivar_list.Read(process, class_ro->m_ivars_ptr))
        return false;
 
      if (ivar_list.m_entsize != ivar_t::GetSize(process))
        return false;
 
      ivar_t ivar;
 
      for (uint32_t i = 0, e = ivar_list.m_count; i < e; ++i) {
        ivar.Read(process, ivar_list.m_first_ptr + (i * ivar_list.m_entsize));
 
        if (ivar_func(ivar.m_name.c_str(), ivar.m_type.c_str(),
                      ivar.m_offset_ptr, ivar.m_size))
          break;
      }
    }
  }
 
  return true;
}
 
ConstString ClassDescriptorV2::GetClassName() {
  if (!m_name) {
    lldb_private::Process *process = m_runtime.GetProcess();
 
    if (process) {
      std::unique_ptr<objc_class_t> objc_class;
      std::unique_ptr<class_ro_t> class_ro;
      std::unique_ptr<class_rw_t> class_rw;
 
      if (!Read_objc_class(process, objc_class))
        return m_name;
      if (!Read_class_row(process, *objc_class, class_ro, class_rw))
        return m_name;
 
      m_name = ConstString(class_ro->m_name.c_str());
    }
  }
  return m_name;
}
 
ObjCLanguageRuntime::ClassDescriptorSP ClassDescriptorV2::GetSuperclass() {
  lldb_private::Process *process = m_runtime.GetProcess();
 
  if (!process)
    return ObjCLanguageRuntime::ClassDescriptorSP();
 
  std::unique_ptr<objc_class_t> objc_class;
 
  if (!Read_objc_class(process, objc_class))
    return ObjCLanguageRuntime::ClassDescriptorSP();
 
  return m_runtime.ObjCLanguageRuntime::GetClassDescriptorFromISA(
      objc_class->m_superclass);
}
 
ObjCLanguageRuntime::ClassDescriptorSP ClassDescriptorV2::GetMetaclass() const {
  lldb_private::Process *process = m_runtime.GetProcess();
 
  if (!process)
    return ObjCLanguageRuntime::ClassDescriptorSP();
 
  std::unique_ptr<objc_class_t> objc_class;
 
  if (!Read_objc_class(process, objc_class))
    return ObjCLanguageRuntime::ClassDescriptorSP();
 
  lldb::addr_t candidate_isa = m_runtime.GetPointerISA(objc_class->m_isa);
 
  return ObjCLanguageRuntime::ClassDescriptorSP(
      new ClassDescriptorV2(m_runtime, candidate_isa, nullptr));
}
 
uint64_t ClassDescriptorV2::GetInstanceSize() {
  lldb_private::Process *process = m_runtime.GetProcess();
 
  if (process) {
    std::unique_ptr<objc_class_t> objc_class;
    std::unique_ptr<class_ro_t> class_ro;
    std::unique_ptr<class_rw_t> class_rw;
 
    if (!Read_objc_class(process, objc_class))
      return 0;
    if (!Read_class_row(process, *objc_class, class_ro, class_rw))
      return 0;
 
    return class_ro->m_instanceSize;
  }
 
  return 0;
}
 
// From the ObjC runtime.
static uint8_t IS_SWIFT_STABLE = 1U << 1;
 
LanguageType ClassDescriptorV2::GetImplementationLanguage() const {
  std::unique_ptr<objc_class_t> objc_class;
  if (auto *process = m_runtime.GetProcess())
    if (Read_objc_class(process, objc_class))
      if (objc_class->m_flags & IS_SWIFT_STABLE)
        return lldb::eLanguageTypeSwift;
 
  return lldb::eLanguageTypeObjC;
}
 
ClassDescriptorV2::iVarsStorage::iVarsStorage() : m_ivars(), m_mutex() {}
 
size_t ClassDescriptorV2::iVarsStorage::size() { return m_ivars.size(); }
 
ClassDescriptorV2::iVarDescriptor &ClassDescriptorV2::iVarsStorage::
operator[](size_t idx) {
  return m_ivars[idx];
}
 
void ClassDescriptorV2::iVarsStorage::fill(AppleObjCRuntimeV2 &runtime,
                                           ClassDescriptorV2 &descriptor) {
  if (m_filled)
    return;
  std::lock_guard<std::recursive_mutex> guard(m_mutex);
  Log *log = GetLog(LLDBLog::Types);
  LLDB_LOGV(log, "class_name = {0}", descriptor.GetClassName());
  m_filled = true;
  ObjCLanguageRuntime::EncodingToTypeSP encoding_to_type_sp(
      runtime.GetEncodingToType());
  Process *process(runtime.GetProcess());
  if (!encoding_to_type_sp)
    return;
  descriptor.Describe(nullptr, nullptr, nullptr, [this, process,
                                                  encoding_to_type_sp,
                                                  log](const char *name,
                                                       const char *type,
                                                       lldb::addr_t offset_ptr,
                                                       uint64_t size) -> bool {
    const bool for_expression = false;
    const bool stop_loop = false;
    LLDB_LOGV(log, "name = {0}, encoding = {1}, offset_ptr = {2:x}, size = {3}",
              name, type, offset_ptr, size);
    CompilerType ivar_type =
        encoding_to_type_sp->RealizeType(type, for_expression);
    if (ivar_type) {
      LLDB_LOGV(log,
                "name = {0}, encoding = {1}, offset_ptr = {2:x}, size = "
                "{3}, type_size = {4}",
                name, type, offset_ptr, size,
                expectedToOptional(ivar_type.GetByteSize(nullptr)).value_or(0));
      Scalar offset_scalar;
      Status error;
      const int offset_ptr_size = 4;
      const bool is_signed = false;
      size_t read = process->ReadScalarIntegerFromMemory(
          offset_ptr, offset_ptr_size, is_signed, offset_scalar, error);
      if (error.Success() && 4 == read) {
        LLDB_LOGV(log, "offset_ptr = {0:x} --> {1}", offset_ptr,
                  offset_scalar.SInt());
        m_ivars.push_back(
            {ConstString(name), ivar_type, size, offset_scalar.SInt()});
      } else
        LLDB_LOGV(log, "offset_ptr = {0:x} --> read fail, read = %{1}",
                  offset_ptr, read);
    }
    return stop_loop;
  });
}
 
void ClassDescriptorV2::GetIVarInformation() {
  m_ivars_storage.fill(m_runtime, *this);
}