llvm-project/lldb/source/Plugins/Language/CPlusPlus/LibStdcppUniquePointer.cpp

//===-- LibStdcppUniquePointer.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 "LibStdcpp.h"

#include "lldb/DataFormatters/FormattersHelpers.h"
#include "lldb/DataFormatters/TypeSynthetic.h"
#include "lldb/Utility/ConstString.h"
#include "lldb/ValueObject/ValueObject.h"
#include "llvm/Support/ErrorExtras.h"

#include <memory>
#include <vector>

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

namespace {

class LibStdcppUniquePtrSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
public:
  explicit LibStdcppUniquePtrSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);

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

  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;

  lldb::ChildCacheState Update() override;

  llvm::Expected<size_t> GetIndexOfChildWithName(ConstString name) override;

  bool GetSummary(Stream &stream, const TypeSummaryOptions &options);

private:
  // The lifetime of a ValueObject and all its derivative ValueObjects
  // (children, clones, etc.) is managed by a ClusterManager. These
  // objects are only destroyed when every shared pointer to any of them
  // is destroyed, so we must not store a shared pointer to any ValueObject
  // derived from our backend ValueObject (since we're in the same cluster).
  ValueObject *m_ptr_obj = nullptr;
  ValueObject* m_del_obj = nullptr;

  ValueObjectSP GetTuple();
};

} // end of anonymous namespace

LibStdcppUniquePtrSyntheticFrontEnd::LibStdcppUniquePtrSyntheticFrontEnd(
    lldb::ValueObjectSP valobj_sp)
    : SyntheticChildrenFrontEnd(*valobj_sp) {
  Update();
}

ValueObjectSP LibStdcppUniquePtrSyntheticFrontEnd::GetTuple() {
  ValueObjectSP valobj_backend_sp = m_backend.GetSP();

  if (!valobj_backend_sp)
    return nullptr;

  ValueObjectSP valobj_sp = valobj_backend_sp->GetNonSyntheticValue();
  if (!valobj_sp)
    return nullptr;

  ValueObjectSP obj_child_sp = valobj_sp->GetChildMemberWithName("_M_t");
  if (!obj_child_sp)
      return nullptr;

  ValueObjectSP obj_subchild_sp = obj_child_sp->GetChildMemberWithName("_M_t");

  // if there is a _M_t subchild, the tuple is found in the obj_subchild_sp
  // (for libstdc++ 6.0.23).
  if (obj_subchild_sp) {
    return obj_subchild_sp;
  }

  return obj_child_sp;
}

lldb::ChildCacheState LibStdcppUniquePtrSyntheticFrontEnd::Update() {
  ValueObjectSP tuple_sp = GetTuple();

  if (!tuple_sp)
    return lldb::ChildCacheState::eRefetch;

  std::unique_ptr<SyntheticChildrenFrontEnd> tuple_frontend(
      LibStdcppTupleSyntheticFrontEndCreator(nullptr, tuple_sp));

  ValueObjectSP ptr_obj = tuple_frontend->GetChildAtIndex(0);
  if (!ptr_obj)
    return lldb::ChildCacheState::eRefetch;

  m_ptr_obj = ptr_obj->Clone(ConstString("pointer")).get();

  // Add a 'deleter' child if there was a non-empty deleter type specified.
  //
  // The object might have size=1 in the TypeSystem but occupies no dedicated
  // storage due to no_unique_address, so infer the actual size from the total
  // size of the unique_ptr class. If sizeof(unique_ptr) == sizeof(void*) then
  // the deleter is empty and should be hidden.
  if (llvm::expectedToOptional(tuple_sp->GetByteSize()).value_or(0) >
      llvm::expectedToOptional(ptr_obj->GetByteSize()).value_or(0)) {
    ValueObjectSP del_obj = tuple_frontend->GetChildAtIndex(1);
    if (del_obj)
      m_del_obj = del_obj->Clone(ConstString("deleter")).get();
  }

  return lldb::ChildCacheState::eRefetch;
}

lldb::ValueObjectSP
LibStdcppUniquePtrSyntheticFrontEnd::GetChildAtIndex(uint32_t idx) {
  if (idx == 0 && m_ptr_obj)
    return m_ptr_obj->GetSP();
  if (idx == 1 && m_del_obj)
    return m_del_obj->GetSP();
  if (idx == 2) {
    if (m_ptr_obj) {
      Status status;
      auto value_sp = m_ptr_obj->Dereference(status);
      if (status.Success()) {
        return value_sp;
      }
    }
  }
  return lldb::ValueObjectSP();
}

llvm::Expected<uint32_t>
LibStdcppUniquePtrSyntheticFrontEnd::CalculateNumChildren() {
  if (m_del_obj)
    return 2;
  return 1;
}

llvm::Expected<size_t>
LibStdcppUniquePtrSyntheticFrontEnd::GetIndexOfChildWithName(ConstString name) {
  if (name == "ptr" || name == "pointer")
    return 0;
  if (name == "del" || name == "deleter")
    return 1;
  if (name == "obj" || name == "object" || name == "$$dereference$$")
    return 2;
  return llvm::createStringErrorV("type has no child named '{0}'", name);
}

bool LibStdcppUniquePtrSyntheticFrontEnd::GetSummary(
    Stream &stream, const TypeSummaryOptions &options) {
  if (!m_ptr_obj)
    return false;

  DumpCxxSmartPtrPointerSummary(stream, *m_ptr_obj, options);

  return true;
}

SyntheticChildrenFrontEnd *
lldb_private::formatters::LibStdcppUniquePtrSyntheticFrontEndCreator(
    CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
  return (valobj_sp ? new LibStdcppUniquePtrSyntheticFrontEnd(valobj_sp)
                    : nullptr);
}

bool lldb_private::formatters::LibStdcppUniquePointerSummaryProvider(
    ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
  LibStdcppUniquePtrSyntheticFrontEnd formatter(valobj.GetSP());
  return formatter.GetSummary(stream, options);
}