ValueObjectChild.cpp

//===-- ValueObjectChild.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/ValueObjectChild.h"

#include "lldb/Core/Value.h"
#include "lldb/Symbol/CompilerType.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Utility/Flags.h"
#include "lldb/Utility/Scalar.h"
#include "lldb/Utility/Status.h"
#include "lldb/lldb-forward.h"

#include <functional>
#include <memory>
#include <vector>

#include <cstdio>
#include <cstring>

using namespace lldb_private;

ValueObjectChild::ValueObjectChild(
    ValueObject &parent, const CompilerType &compiler_type, ConstString name,
    uint64_t byte_size, int32_t byte_offset, uint32_t bitfield_bit_size,
    uint32_t bitfield_bit_offset, bool is_base_class, bool is_deref_of_parent,
    AddressType child_ptr_or_ref_addr_type, uint64_t language_flags)
    : ValueObject(parent), m_compiler_type(compiler_type),
      m_byte_size(byte_size), m_byte_offset(byte_offset),
      m_bitfield_bit_size(bitfield_bit_size),
      m_bitfield_bit_offset(bitfield_bit_offset),
      m_is_base_class(is_base_class), m_is_deref_of_parent(is_deref_of_parent),
      m_can_update_with_invalid_exe_ctx() {
  m_name = name;
  SetAddressTypeOfChildren(child_ptr_or_ref_addr_type);
  SetLanguageFlags(language_flags);
}

ValueObjectChild::~ValueObjectChild() = default;

lldb::ValueType ValueObjectChild::GetValueType() const {
  return m_parent->GetValueType();
}

llvm::Expected<uint32_t> ValueObjectChild::CalculateNumChildren(uint32_t max) {
  ExecutionContext exe_ctx(GetExecutionContextRef());
  auto children_count = GetCompilerType().GetNumChildren(true, &exe_ctx);
  if (!children_count)
    return children_count;
  return *children_count <= max ? *children_count : max;
}

static void AdjustForBitfieldness(ConstString &name,
                                  uint8_t bitfield_bit_size) {
  if (name && bitfield_bit_size)
    name.SetString(llvm::formatv("{0}:{1}", name, bitfield_bit_size).str());
}

ConstString ValueObjectChild::GetTypeName() {
  if (m_type_name.IsEmpty()) {
    m_type_name = GetCompilerType().GetTypeName();
    AdjustForBitfieldness(m_type_name, m_bitfield_bit_size);
  }
  return m_type_name;
}

ConstString ValueObjectChild::GetQualifiedTypeName() {
  ConstString qualified_name = GetCompilerType().GetTypeName();
  AdjustForBitfieldness(qualified_name, m_bitfield_bit_size);
  return qualified_name;
}

ConstString ValueObjectChild::GetDisplayTypeName() {
  ConstString display_name = GetCompilerType().GetDisplayTypeName();
  AdjustForBitfieldness(display_name, m_bitfield_bit_size);
  return display_name;
}

LazyBool ValueObjectChild::CanUpdateWithInvalidExecutionContext() {
  if (m_can_update_with_invalid_exe_ctx)
    return *m_can_update_with_invalid_exe_ctx;
  if (m_parent) {
    ValueObject *opinionated_parent =
        m_parent->FollowParentChain([](ValueObject *valobj) -> bool {
          return (valobj->CanUpdateWithInvalidExecutionContext() ==
                  eLazyBoolCalculate);
        });
    if (opinionated_parent)
      return *(m_can_update_with_invalid_exe_ctx =
                   opinionated_parent->CanUpdateWithInvalidExecutionContext());
  }
  return *(m_can_update_with_invalid_exe_ctx =
               this->ValueObject::CanUpdateWithInvalidExecutionContext());
}

bool ValueObjectChild::UpdateValue() {
  m_error.Clear();
  SetValueIsValid(false);
  ValueObject *parent = m_parent;
  if (parent) {
    if (parent->UpdateValueIfNeeded(false)) {
      m_value.SetCompilerType(GetCompilerType());

      CompilerType parent_type(parent->GetCompilerType());
      // Copy the parent scalar value and the scalar value type
      m_value.GetScalar() = parent->GetValue().GetScalar();
      m_value.SetValueType(parent->GetValue().GetValueType());

      Flags parent_type_flags(parent_type.GetTypeInfo());
      const bool is_instance_ptr_base =
          ((m_is_base_class) &&
           (parent_type_flags.AnySet(lldb::eTypeInstanceIsPointer)));

      if (parent->GetCompilerType().ShouldTreatScalarValueAsAddress()) {
        m_value.GetScalar() = parent->GetPointerValue().address;

        switch (parent->GetAddressTypeOfChildren()) {
        case eAddressTypeFile: {
          lldb::ProcessSP process_sp(GetProcessSP());
          if (process_sp && process_sp->IsAlive())
            m_value.SetValueType(Value::ValueType::LoadAddress);
          else
            m_value.SetValueType(Value::ValueType::FileAddress);
        } break;
        case eAddressTypeLoad:
          m_value.SetValueType(is_instance_ptr_base
                                   ? Value::ValueType::Scalar
                                   : Value::ValueType::LoadAddress);
          break;
        case eAddressTypeHost:
          m_value.SetValueType(Value::ValueType::HostAddress);
          break;
        case eAddressTypeInvalid:
          // TODO: does this make sense?
          m_value.SetValueType(Value::ValueType::Scalar);
          break;
        }
      }
      switch (m_value.GetValueType()) {
      case Value::ValueType::Invalid:
        break;
      case Value::ValueType::LoadAddress:
      case Value::ValueType::FileAddress:
      case Value::ValueType::HostAddress: {
        lldb::addr_t addr = m_value.GetScalar().ULongLong(LLDB_INVALID_ADDRESS);
        if (addr == LLDB_INVALID_ADDRESS) {
          m_error = Status::FromErrorString("parent address is invalid.");
        } else if (addr == 0) {
          m_error = Status::FromErrorString("parent is NULL");
        } else {
          // If a bitfield doesn't fit into the child_byte_size'd window at
          // child_byte_offset, move the window forward until it fits.  The
          // problem here is that Value has no notion of bitfields and thus the
          // Value's DataExtractor is sized like the bitfields CompilerType; a
          // sequence of bitfields, however, can be larger than their underlying
          // type.
          if (m_bitfield_bit_offset) {
            const bool thread_and_frame_only_if_stopped = true;
            ExecutionContext exe_ctx(GetExecutionContextRef().Lock(
                thread_and_frame_only_if_stopped));
            if (auto type_bit_size =
                    llvm::expectedToOptional(GetCompilerType().GetBitSize(
                        exe_ctx.GetBestExecutionContextScope()))) {
              uint64_t bitfield_end =
                  m_bitfield_bit_size + m_bitfield_bit_offset;
              if (bitfield_end > *type_bit_size) {
                uint64_t overhang_bytes =
                    (bitfield_end - *type_bit_size + 7) / 8;
                m_byte_offset += overhang_bytes;
                m_bitfield_bit_offset -= overhang_bytes * 8;
              }
            }
          }

          // Set this object's scalar value to the address of its value by
          // adding its byte offset to the parent address
          m_value.GetScalar() += m_byte_offset;
        }
      } break;

      case Value::ValueType::Scalar:
        // try to extract the child value from the parent's scalar value
        {
          Scalar scalar(m_value.GetScalar());
          scalar.ExtractBitfield(8 * m_byte_size, 8 * m_byte_offset);
          m_value.GetScalar() = scalar;
        }
        break;
      }

      if (m_error.Success()) {
        const bool thread_and_frame_only_if_stopped = true;
        ExecutionContext exe_ctx(
            GetExecutionContextRef().Lock(thread_and_frame_only_if_stopped));
        if (GetCompilerType().GetTypeInfo() & lldb::eTypeHasValue) {
          Value &value = is_instance_ptr_base ? m_parent->GetValue() : m_value;
          m_error = value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
        } else {
          m_error.Clear(); // No value so nothing to read...
        }
      }

    } else {
      m_error = Status::FromErrorStringWithFormat(
          "parent failed to evaluate: %s", parent->GetError().AsCString());
    }
  } else {
    m_error = Status::FromErrorString(
        "ValueObjectChild has a NULL parent ValueObject.");
  }

  return m_error.Success();
}

bool ValueObjectChild::IsInScope() {
  ValueObject *root(GetRoot());
  if (root)
    return root->IsInScope();
  return false;
}