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1// Copyright 2020 the V8 project authors. All rights reserved.2// Use of this source code is governed by a BSD-style license that can be3// found in the LICENSE file.4 5#ifndef INCLUDE_CPPGC_INTERNAL_NAME_TRAIT_H_6#define INCLUDE_CPPGC_INTERNAL_NAME_TRAIT_H_7 8#include <cstddef>9#include <cstdint>10#include <type_traits>11 12#include "cppgc/name-provider.h"13#include "v8config.h"  // NOLINT(build/include_directory)14 15namespace cppgc {16namespace internal {17 18#if CPPGC_SUPPORTS_OBJECT_NAMES && defined(__clang__)19#define CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME 120 21// Provides constexpr c-string storage for a name of fixed |Size| characters.22// Automatically appends terminating 0 byte.23template <size_t Size>24struct NameBuffer {25  char name[Size + 1]{};26 27  static constexpr NameBuffer FromCString(const char* str) {28    NameBuffer result;29    for (size_t i = 0; i < Size; ++i) result.name[i] = str[i];30    result.name[Size] = 0;31    return result;32  }33};34 35template <typename T>36const char* GetTypename() {37  static constexpr char kSelfPrefix[] =38      "const char *cppgc::internal::GetTypename() [T =";39  static_assert(__builtin_strncmp(__PRETTY_FUNCTION__, kSelfPrefix,40                                  sizeof(kSelfPrefix) - 1) == 0,41                "The prefix must match");42  static constexpr const char* kTypenameStart =43      __PRETTY_FUNCTION__ + sizeof(kSelfPrefix);44  static constexpr size_t kTypenameSize =45      __builtin_strlen(__PRETTY_FUNCTION__) - sizeof(kSelfPrefix) - 1;46  // NameBuffer is an indirection that is needed to make sure that only a47  // substring of __PRETTY_FUNCTION__ gets materialized in the binary.48  static constexpr auto buffer =49      NameBuffer<kTypenameSize>::FromCString(kTypenameStart);50  return buffer.name;51}52 53#else54#define CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME 055#endif56 57struct HeapObjectName {58  const char* value;59  bool name_was_hidden;60};61 62enum class HeapObjectNameForUnnamedObject : uint8_t {63  kUseClassNameIfSupported,64  kUseHiddenName,65};66 67class V8_EXPORT NameTraitBase {68 protected:69  static HeapObjectName GetNameFromTypeSignature(const char*);70};71 72// Trait that specifies how the garbage collector retrieves the name for a73// given object.74template <typename T>75class NameTrait final : public NameTraitBase {76 public:77  static constexpr bool HasNonHiddenName() {78#if CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME79    return true;80#elif CPPGC_SUPPORTS_OBJECT_NAMES81    return true;82#else   // !CPPGC_SUPPORTS_OBJECT_NAMES83    return std::is_base_of<NameProvider, T>::value;84#endif  // !CPPGC_SUPPORTS_OBJECT_NAMES85  }86 87  static HeapObjectName GetName(88      const void* obj, HeapObjectNameForUnnamedObject name_retrieval_mode) {89    return GetNameFor(static_cast<const T*>(obj), name_retrieval_mode);90  }91 92 private:93  static HeapObjectName GetNameFor(const NameProvider* name_provider,94                                   HeapObjectNameForUnnamedObject) {95    // Objects inheriting from `NameProvider` are not considered unnamed as96    // users already provided a name for them.97    return {name_provider->GetHumanReadableName(), false};98  }99 100  static HeapObjectName GetNameFor(101      const void*, HeapObjectNameForUnnamedObject name_retrieval_mode) {102    if (name_retrieval_mode == HeapObjectNameForUnnamedObject::kUseHiddenName)103      return {NameProvider::kHiddenName, true};104 105#if CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME106    return {GetTypename<T>(), false};107#elif CPPGC_SUPPORTS_OBJECT_NAMES108 109#if defined(V8_CC_GNU)110#define PRETTY_FUNCTION_VALUE __PRETTY_FUNCTION__111#elif defined(V8_CC_MSVC)112#define PRETTY_FUNCTION_VALUE __FUNCSIG__113#else114#define PRETTY_FUNCTION_VALUE nullptr115#endif116 117    static const HeapObjectName leaky_name =118        GetNameFromTypeSignature(PRETTY_FUNCTION_VALUE);119    return leaky_name;120 121#undef PRETTY_FUNCTION_VALUE122 123#else   // !CPPGC_SUPPORTS_OBJECT_NAMES124    // We wanted to use a class name but were unable to provide one due to125    // compiler limitations or build configuration. As such, return the hidden126    // name with name_was_hidden=false, which will cause this object to be127    // visible in the snapshot.128    return {NameProvider::kHiddenName, false};129#endif  // !CPPGC_SUPPORTS_OBJECT_NAMES130  }131};132 133using NameCallback = HeapObjectName (*)(const void*,134                                        HeapObjectNameForUnnamedObject);135 136}  // namespace internal137}  // namespace cppgc138 139#undef CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME140 141#endif  // INCLUDE_CPPGC_INTERNAL_NAME_TRAIT_H_142