stdlib/include/llvm/Support/AlignOf.h

//===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file defines the AlignedCharArrayUnion class.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_ALIGNOF_H
#define LLVM_SUPPORT_ALIGNOF_H

#include "llvm/Support/Compiler.h"
#include <cstddef>

inline namespace __swift { inline namespace __runtime {
namespace llvm {

namespace detail {

template <typename T, typename... Ts> class AlignerImpl {
  T t;
  AlignerImpl<Ts...> rest;
  AlignerImpl() = delete;
};

template <typename T> class AlignerImpl<T> {
  T t;
  AlignerImpl() = delete;
};

template <typename T, typename... Ts> union SizerImpl {
  char arr[sizeof(T)];
  SizerImpl<Ts...> rest;
};

template <typename T> union SizerImpl<T> { char arr[sizeof(T)]; };
} // end namespace detail

/// A suitably aligned and sized character array member which can hold elements
/// of any type.
///
/// These types may be arrays, structs, or any other types. This exposes a
/// `buffer` member which can be used as suitable storage for a placement new of
/// any of these types.
template <typename T, typename... Ts> struct AlignedCharArrayUnion {
  alignas(__swift::__runtime::llvm::detail::AlignerImpl<T, Ts...>)
  char buffer[sizeof(llvm::detail::SizerImpl<T, Ts...>)];
};

} // end namespace llvm
}} // namespace swift::runtime

#endif // LLVM_SUPPORT_ALIGNOF_H