folly/folly/lang/TypeInfo.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <typeinfo>

#include <folly/CppAttributes.h>
#include <folly/Portability.h>

//  FOLLY_TYPE_INFO_OF
//
//  Returns &typeid(...) if RTTI is available, nullptr otherwise. In either
//  case, has type std::type_info const*.
#if FOLLY_HAS_RTTI
#define FOLLY_TYPE_INFO_OF(...) …
#else
#define FOLLY_TYPE_INFO_OF …
#endif

namespace folly {

//  type_info_of
//
//  Returns &typeid(T) if RTTI is available, nullptr otherwise.
//
//  This overload works on the static type of the template parameter.
template <typename T>
FOLLY_ERASE constexpr std::type_info const* type_info_of() { … }

//  type_info_of
//
//  Returns &typeid(t) if RTTI is available, nullptr otherwise.
//
//  This overload works on the dynamic type of the non-template parameter.
template <typename T>
FOLLY_ERASE constexpr std::type_info const* type_info_of(
    [[maybe_unused]] T const& t) { … }

} // namespace folly