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  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 <type_traits>
  17.  
  18. namespace llvm {
  19.  
  20. /// A suitably aligned and sized character array member which can hold elements
  21. /// of any type.
  22. ///
  23. /// This template is equivalent to std::aligned_union_t<1, ...>, but we cannot
  24. /// use it due to a bug in the MSVC x86 compiler:
  25. /// https://github.com/microsoft/STL/issues/1533
  26. /// Using `alignas` here works around the bug.
  27. template <typename T, typename... Ts> struct AlignedCharArrayUnion {
  28.   using AlignedUnion = std::aligned_union_t<1, T, Ts...>;
  29.   alignas(alignof(AlignedUnion)) char buffer[sizeof(AlignedUnion)];
  30. };
  31.  
  32. } // end namespace llvm
  33.  
  34. #endif // LLVM_SUPPORT_ALIGNOF_H
  35.