ValueObjectConstResultImpl.cpp

//===-- ValueObjectConstResultImpl.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 "lldb/ValueObject/ValueObjectConstResultImpl.h"

#include "lldb/Core/Value.h"
#include "lldb/Symbol/CompilerType.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Utility/DataBufferHeap.h"
#include "lldb/Utility/Endian.h"
#include "lldb/Utility/LLDBLog.h"
#include "lldb/Utility/Log.h"
#include "lldb/Utility/Scalar.h"
#include "lldb/ValueObject/ValueObject.h"
#include "lldb/ValueObject/ValueObjectConstResult.h"
#include "lldb/ValueObject/ValueObjectConstResultCast.h"
#include "lldb/ValueObject/ValueObjectConstResultChild.h"

#include <string>

namespace lldb_private {
class DataExtractor;
}
namespace lldb_private {
class Status;
}

using namespace lldb;
using namespace lldb_private;

ValueObjectConstResultImpl::ValueObjectConstResultImpl(
    ValueObject *valobj, lldb::addr_t live_address)
    : m_impl_backend(valobj), m_live_address(live_address),
      m_live_address_type(eAddressTypeLoad), m_address_of_backend() {}

lldb::ValueObjectSP ValueObjectConstResultImpl::Dereference(Status &error) {
  if (m_impl_backend == nullptr)
    return lldb::ValueObjectSP();

  return m_impl_backend->ValueObject::Dereference(error);
}

ValueObject *ValueObjectConstResultImpl::CreateChildAtIndex(size_t idx) {
  if (m_impl_backend == nullptr)
    return nullptr;

  m_impl_backend->UpdateValueIfNeeded(false);

  bool omit_empty_base_classes = true;
  bool ignore_array_bounds = false;
  std::string child_name;
  uint32_t child_byte_size = 0;
  int32_t child_byte_offset = 0;
  uint32_t child_bitfield_bit_size = 0;
  uint32_t child_bitfield_bit_offset = 0;
  bool child_is_base_class = false;
  bool child_is_deref_of_parent = false;
  uint64_t language_flags;
  const bool transparent_pointers = true;
  CompilerType compiler_type = m_impl_backend->GetCompilerType();

  ExecutionContext exe_ctx(m_impl_backend->GetExecutionContextRef());

  auto child_compiler_type_or_err = compiler_type.GetChildCompilerTypeAtIndex(
      &exe_ctx, idx, transparent_pointers, omit_empty_base_classes,
      ignore_array_bounds, child_name, child_byte_size, child_byte_offset,
      child_bitfield_bit_size, child_bitfield_bit_offset, child_is_base_class,
      child_is_deref_of_parent, m_impl_backend, language_flags);

  // One might think we should check that the size of the children
  // is always strictly positive, hence we could avoid creating a
  // ValueObject if that's not the case, but it turns out there
  // are languages out there which allow zero-size types with
  // children (e.g. Swift).
  if (!child_compiler_type_or_err || !child_compiler_type_or_err->IsValid()) {
    LLDB_LOG_ERROR(GetLog(LLDBLog::Types),
                   child_compiler_type_or_err.takeError(),
                   "could not find child: {0}");
    return nullptr;
  }

  lldb::addr_t child_live_addr = LLDB_INVALID_ADDRESS;
  // Transfer the live address (with offset) to the child.  But if
  // the parent is a pointer, the live address is where that pointer
  // value lives in memory, so the children live addresses aren't
  // offsets from that value, they are just other load addresses that
  // are recorded in the Value of the child ValueObjects.
  if (m_live_address != LLDB_INVALID_ADDRESS && !compiler_type.IsPointerType())
    child_live_addr = m_live_address + child_byte_offset;

  return new ValueObjectConstResultChild(
      *m_impl_backend, *child_compiler_type_or_err, ConstString(child_name),
      child_byte_size, child_byte_offset, child_bitfield_bit_size,
      child_bitfield_bit_offset, child_is_base_class, child_is_deref_of_parent,
      child_live_addr, language_flags);
}

ValueObject *
ValueObjectConstResultImpl::CreateSyntheticArrayMember(size_t idx) {
  if (m_impl_backend == nullptr)
    return nullptr;

  m_impl_backend->UpdateValueIfNeeded(false);

  bool omit_empty_base_classes = true;
  bool ignore_array_bounds = true;
  std::string child_name;
  uint32_t child_byte_size = 0;
  int32_t child_byte_offset = 0;
  uint32_t child_bitfield_bit_size = 0;
  uint32_t child_bitfield_bit_offset = 0;
  bool child_is_base_class = false;
  bool child_is_deref_of_parent = false;
  uint64_t language_flags;

  const bool transparent_pointers = false;
  CompilerType compiler_type = m_impl_backend->GetCompilerType();

  ExecutionContext exe_ctx(m_impl_backend->GetExecutionContextRef());

  auto child_compiler_type_or_err = compiler_type.GetChildCompilerTypeAtIndex(
      &exe_ctx, 0, transparent_pointers, omit_empty_base_classes,
      ignore_array_bounds, child_name, child_byte_size, child_byte_offset,
      child_bitfield_bit_size, child_bitfield_bit_offset, child_is_base_class,
      child_is_deref_of_parent, m_impl_backend, language_flags);
  // One might think we should check that the size of the children
  // is always strictly positive, hence we could avoid creating a
  // ValueObject if that's not the case, but it turns out there
  // are languages out there which allow zero-size types with
  // children (e.g. Swift).
  if (!child_compiler_type_or_err || !child_compiler_type_or_err->IsValid()) {
    LLDB_LOG_ERROR(GetLog(LLDBLog::Types),
                   child_compiler_type_or_err.takeError(),
                   "could not find child: {0}");
    return nullptr;
  }

  child_byte_offset += child_byte_size * idx;

  lldb::addr_t child_live_addr = LLDB_INVALID_ADDRESS;
  // Transfer the live address (with offset) to the child.  But if
  // the parent is a pointer, the live address is where that pointer
  // value lives in memory, so the children live addresses aren't
  // offsets from that value, they are just other load addresses that
  // are recorded in the Value of the child ValueObjects.
  if (m_live_address != LLDB_INVALID_ADDRESS && !compiler_type.IsPointerType())
    child_live_addr = m_live_address + child_byte_offset;
  return new ValueObjectConstResultChild(
      *m_impl_backend, *child_compiler_type_or_err, ConstString(child_name),
      child_byte_size, child_byte_offset, child_bitfield_bit_size,
      child_bitfield_bit_offset, child_is_base_class, child_is_deref_of_parent,
      child_live_addr, language_flags);
}

lldb::ValueObjectSP ValueObjectConstResultImpl::GetSyntheticChildAtOffset(
    uint32_t offset, const CompilerType &type, bool can_create,
    ConstString name_const_str) {
  if (m_impl_backend == nullptr)
    return lldb::ValueObjectSP();

  return m_impl_backend->ValueObject::GetSyntheticChildAtOffset(
      offset, type, can_create, name_const_str);
}

lldb::ValueObjectSP ValueObjectConstResultImpl::AddressOf(Status &error) {
  if (m_address_of_backend.get() != nullptr)
    return m_address_of_backend;

  if (m_impl_backend == nullptr)
    return lldb::ValueObjectSP();
  if (m_live_address != LLDB_INVALID_ADDRESS) {
    CompilerType compiler_type(m_impl_backend->GetCompilerType());

    lldb::DataBufferSP buffer(new lldb_private::DataBufferHeap(
        &m_live_address, sizeof(lldb::addr_t)));

    std::string new_name("&");
    new_name.append(m_impl_backend->GetName().AsCString(""));
    ExecutionContext exe_ctx(m_impl_backend->GetExecutionContextRef());
    m_address_of_backend = ValueObjectConstResult::Create(
        exe_ctx.GetBestExecutionContextScope(), compiler_type.GetPointerType(),
        ConstString(new_name.c_str()), buffer, endian::InlHostByteOrder(),
        exe_ctx.GetAddressByteSize());

    m_address_of_backend->GetValue().SetValueType(Value::ValueType::Scalar);
    m_address_of_backend->GetValue().GetScalar() = m_live_address;

    return m_address_of_backend;
  } else
    return m_impl_backend->ValueObject::AddressOf(error);
}

lldb::ValueObjectSP
ValueObjectConstResultImpl::Cast(const CompilerType &compiler_type) {
  if (m_impl_backend == nullptr)
    return lldb::ValueObjectSP();

  ValueObjectConstResultCast *result_cast =
      new ValueObjectConstResultCast(*m_impl_backend, m_impl_backend->GetName(),
                                     compiler_type, m_live_address);
  return result_cast->GetSP();
}

ValueObject::AddrAndType
ValueObjectConstResultImpl::GetAddressOf(bool scalar_is_load_address) {

  if (m_impl_backend == nullptr)
    return {0, eAddressTypeInvalid};

  if (m_live_address == LLDB_INVALID_ADDRESS)
    return m_impl_backend->ValueObject::GetAddressOf(scalar_is_load_address);

  return {m_live_address, m_live_address_type};
}

size_t ValueObjectConstResultImpl::GetPointeeData(DataExtractor &data,
                                                  uint32_t item_idx,
                                                  uint32_t item_count) {
  if (m_impl_backend == nullptr)
    return 0;
  return m_impl_backend->ValueObject::GetPointeeData(data, item_idx,
                                                     item_count);
}