Author: Reid Kleckner Date: 2020-12-15T16:01:55-08:00 New Revision: b0b5d389635a54c5aeb490b1b067f3a38e038235
URL: https://github.com/llvm/llvm-project/commit/b0b5d389635a54c5aeb490b1b067f3a38e038235 DIFF: https://github.com/llvm/llvm-project/commit/b0b5d389635a54c5aeb490b1b067f3a38e038235.diff LOG: Document that AlignedCharArrayUnion exists to work around an MSVC bug Differential Revision: https://reviews.llvm.org/D93355 Added: Modified: llvm/include/llvm/Support/AlignOf.h Removed: ################################################################################ diff --git a/llvm/include/llvm/Support/AlignOf.h b/llvm/include/llvm/Support/AlignOf.h index f9dcde4d4ff1..f586d7f182aa 100644 --- a/llvm/include/llvm/Support/AlignOf.h +++ b/llvm/include/llvm/Support/AlignOf.h @@ -20,9 +20,10 @@ namespace llvm { /// 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. +/// This template is equivalent to std::aligned_union_t<1, ...>, but we cannot +/// use it due to a bug in the MSVC x86 compiler: +/// https://github.com/microsoft/STL/issues/1533 +/// Using `alignas` here works around the bug. template <typename T, typename... Ts> struct AlignedCharArrayUnion { using AlignedUnion = std::aligned_union_t<1, T, Ts...>; alignas(alignof(AlignedUnion)) char buffer[sizeof(AlignedUnion)]; _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
