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