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

//===-- NSException.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 "clang/AST/DeclCXX.h"

#include "Cocoa.h"

#include "llvm/Support/ErrorExtras.h"

#include "lldb/DataFormatters/FormattersHelpers.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 "Plugins/Language/ObjC/NSString.h"
#include "Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h"
#include "Plugins/TypeSystem/Clang/TypeSystemClang.h"

#include <optional>

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

static bool ExtractFields(ValueObject &valobj, ValueObjectSP *name_sp,
                          ValueObjectSP *reason_sp, ValueObjectSP *userinfo_sp,
                          ValueObjectSP *reserved_sp, bool owned_by_valobj) {
  ProcessSP process_sp(valobj.GetProcessSP());
  if (!process_sp)
    return false;

  lldb::addr_t ptr = LLDB_INVALID_ADDRESS;

  CompilerType valobj_type(valobj.GetCompilerType());
  Flags type_flags(valobj_type.GetTypeInfo());
  if (type_flags.AllClear(eTypeHasValue)) {
    if (valobj.IsBaseClass() && valobj.GetParent())
      ptr = valobj.GetParent()->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
  } else {
    ptr = valobj.GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
  }

  if (ptr == LLDB_INVALID_ADDRESS)
    return false;
  size_t ptr_size = process_sp->GetAddressByteSize();

  // Read the ivar at the given pointer-sized slot in the NSException object.
  // Returns std::nullopt if the read fails.
  auto read_field = [&](size_t slot) {
    return llvm::expectedToOptional(
        process_sp->ReadPointerFromMemory(ptr + slot * ptr_size));
  };

  std::optional<lldb::addr_t> name = read_field(1);
  if (!name)
    return false;
  std::optional<lldb::addr_t> reason = read_field(2);
  if (!reason)
    return false;
  std::optional<lldb::addr_t> userinfo = read_field(3);
  if (!userinfo)
    return false;
  std::optional<lldb::addr_t> reserved = read_field(4);
  if (!reserved)
    return false;

  InferiorSizedWord name_isw(*name, *process_sp);
  InferiorSizedWord reason_isw(*reason, *process_sp);
  InferiorSizedWord userinfo_isw(*userinfo, *process_sp);
  InferiorSizedWord reserved_isw(*reserved, *process_sp);

  TypeSystemClangSP scratch_ts_sp =
      ScratchTypeSystemClang::GetForTarget(process_sp->GetTarget());
  if (!scratch_ts_sp)
    return false;

  CompilerType voidstar =
      scratch_ts_sp->GetBasicType(lldb::eBasicTypeVoid).GetPointerType();
  ExecutionContextRef exe_ref = valobj.GetExecutionContextRef();
  ByteOrder byte_order = process_sp->GetByteOrder();

  auto set_sp = [&](llvm::StringRef name, InferiorSizedWord &data_source,
                    ValueObjectSP *set_me_sp) {
    if (!set_me_sp)
      return;
    if (owned_by_valobj)
      *set_me_sp = valobj.CreateChildValueObjectFromData(
          name, data_source.GetAsData(byte_order), exe_ref, voidstar);
    else
      *set_me_sp = valobj.CreateValueObjectFromData(
          name, data_source.GetAsData(byte_order), exe_ref, voidstar);
  };

  set_sp("name", name_isw, name_sp);
  set_sp("reason", reason_isw, reason_sp);
  set_sp("userInfo", userinfo_isw, userinfo_sp);
  set_sp("reserved", reserved_isw, reserved_sp);

  return true;
}

bool lldb_private::formatters::NSException_SummaryProvider(
    ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
  lldb::ValueObjectSP reason_sp;
  if (!ExtractFields(valobj, nullptr, &reason_sp, nullptr, nullptr,
                     /*owned_by_valobj=*/false))
    return false;

  if (!reason_sp) {
    stream.Printf("No reason");
    return false;
  }

  StreamString reason_str_summary;
  if (NSStringSummaryProvider(*reason_sp, reason_str_summary, options) &&
      !reason_str_summary.Empty()) {
    stream.Printf("%s", reason_str_summary.GetData());
    return true;
  } else
    return false;
}

class NSExceptionSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
public:
  NSExceptionSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
      : SyntheticChildrenFrontEnd(*valobj_sp) {}

  ~NSExceptionSyntheticFrontEnd() override = default;

  llvm::Expected<uint32_t> CalculateNumChildren() override { return 4; }

  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override {
    switch (idx) {
      case 0: return m_name_sp;
      case 1: return m_reason_sp;
      case 2: return m_userinfo_sp;
      case 3: return m_reserved_sp;
    }
    return lldb::ValueObjectSP();
  }

  lldb::ChildCacheState Update() override {
    m_name_sp.reset();
    m_reason_sp.reset();
    m_userinfo_sp.reset();
    m_reserved_sp.reset();

    const auto ret = ExtractFields(m_backend, &m_name_sp, &m_reason_sp,
                                   &m_userinfo_sp, &m_reserved_sp,
                                   /*owned_by_valobj=*/true);

    return ret ? lldb::ChildCacheState::eReuse
               : lldb::ChildCacheState::eRefetch;
  }

  llvm::Expected<size_t> GetIndexOfChildWithName(ConstString name) override {
    // NSException has 4 members:
    //   NSString *name;
    //   NSString *reason;
    //   NSDictionary *userInfo;
    //   id reserved;
    static constexpr llvm::StringLiteral g_name("name");
    static constexpr llvm::StringLiteral g_reason("reason");
    static constexpr llvm::StringLiteral g_userInfo("userInfo");
    static constexpr llvm::StringLiteral g_reserved("reserved");
    if (name == g_name) return 0;
    if (name == g_reason) return 1;
    if (name == g_userInfo) return 2;
    if (name == g_reserved) return 3;
    return llvm::createStringErrorV("type has no child named '{0}'", name);
  }

private:
  ValueObjectSP m_name_sp;
  ValueObjectSP m_reason_sp;
  ValueObjectSP m_userinfo_sp;
  ValueObjectSP m_reserved_sp;
};

SyntheticChildrenFrontEnd *
lldb_private::formatters::NSExceptionSyntheticFrontEndCreator(
    CXXSyntheticChildren *, 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;

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

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

  const char *class_name = descriptor->GetClassName().GetCString();

  if (!class_name || !*class_name)
    return nullptr;

  if (!strcmp(class_name, "NSException"))
    return (new NSExceptionSyntheticFrontEnd(valobj_sp));
  else if (!strcmp(class_name, "NSCFException"))
    return (new NSExceptionSyntheticFrontEnd(valobj_sp));
  else if (!strcmp(class_name, "__NSCFException"))
    return (new NSExceptionSyntheticFrontEnd(valobj_sp));

  return nullptr;
}