include/llvm/Support/AlignOf.h

   1 //===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file defines the AlignedCharArrayUnion class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_SUPPORT_ALIGNOF_H
  14 #define LLVM_SUPPORT_ALIGNOF_H
  15
  16 #include "llvm/Support/Compiler.h"
  17 #include <cstddef>
  18
  19 namespace llvm {
  20
  21 namespace detail {
  22
  23 template <typename T, typename... Ts> class AlignerImpl {
  24   T t;
  25   AlignerImpl<Ts...> rest;
  26   AlignerImpl() = delete;
  27 };
  28
  29 template <typename T> class AlignerImpl<T> {
  30   T t;
  31   AlignerImpl() = delete;
  32 };
  33
  34 template <typename T, typename... Ts> union SizerImpl {
  35   char arr[sizeof(T)];
  36   SizerImpl<Ts...> rest;
  37 };
  38
  39 template <typename T> union SizerImpl<T> { char arr[sizeof(T)]; };
  40 } // end namespace detail
  41
  42 /// A suitably aligned and sized character array member which can hold elements
  43 /// of any type.
  44 ///
  45 /// These types may be arrays, structs, or any other types. This exposes a
  46 /// `buffer` member which can be used as suitable storage for a placement new of
  47 /// any of these types.
  48 template <typename T, typename... Ts> struct AlignedCharArrayUnion {
  49   alignas(::llvm::detail::AlignerImpl<T, Ts...>) char buffer[sizeof(
  50       llvm::detail::SizerImpl<T, Ts...>)];
  51 };
  52
  53 } // end namespace llvm
  54
  55 #endif // LLVM_SUPPORT_ALIGNOF_H