From 2f7bb0ceae436c56d0e88c7a0215e6b072d86576 Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Mon, 5 Feb 2018 08:56:25 +0000 Subject: Merging r324134: ------------------------------------------------------------------------ r324134 | ericwf | 2018-02-02 21:30:39 +0100 (Fri, 02 Feb 2018) | 14 lines Make __has_unique_object_representations reject empty union types. Summary: Clang incorrectly reports empty unions as having a unique object representation. However, this is not correct since `sizeof(EmptyUnion) == 1` AKA it has 8 bits of padding. Therefore it should be treated the same as an empty struct and report `false`. @erichkeane also suggested this fix should be merged into the 6.0 release branch, so the initial release of `__has_unique_object_representations` is as bug-free as possible. Reviewers: erichkeane, rsmith, aaron.ballman, majnemer Reviewed By: erichkeane Subscribers: cfe-commits, erichkeane Differential Revision: https://reviews.llvm.org/D42863 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_60@324213 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/AST/ASTContext.cpp | 2 +- test/SemaCXX/type-traits.cpp | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp index 3dc961d4f1..c73ae9efe1 100644 --- a/lib/AST/ASTContext.cpp +++ b/lib/AST/ASTContext.cpp @@ -2145,7 +2145,7 @@ static bool unionHasUniqueObjectRepresentations(const ASTContext &Context, if (FieldSize != UnionSize) return false; } - return true; + return !RD->field_empty(); } static bool isStructEmpty(QualType Ty) { diff --git a/test/SemaCXX/type-traits.cpp b/test/SemaCXX/type-traits.cpp index b334e50755..3c2f9c7f0f 100644 --- a/test/SemaCXX/type-traits.cpp +++ b/test/SemaCXX/type-traits.cpp @@ -2524,6 +2524,7 @@ static_assert(!has_unique_object_representations::value, "No refere static_assert(!has_unique_object_representations::value, "No references!"); static_assert(!has_unique_object_representations::value, "No references!"); static_assert(!has_unique_object_representations::value, "No empty types!"); +static_assert(!has_unique_object_representations::value, "No empty types!"); class Compressed : Empty { int x; -- cgit v1.2.3