[PATCH] D145852: [Clang][AST] Fix __has_unique_object_representations computation for unnamed bitfields.

[Roy Jacobson via Phabricator via cfe-commits]

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As pointed out in https://github.com/llvm/llvm-project/issues/61336, objects with
unnamed bitfields aren't be uniquely representable.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145852

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/AST/ASTContext.cpp
  clang/test/SemaCXX/type-traits.cpp


Index: clang/test/SemaCXX/type-traits.cpp
===================================================================
--- clang/test/SemaCXX/type-traits.cpp
+++ clang/test/SemaCXX/type-traits.cpp
@@ -2878,9 +2878,15 @@
   char d : 2;
 };
 
+struct UnnamedBitfield {
+  int named : 8;
+  int : 24;
+};
+
 static_assert(!has_unique_object_representations<PaddedBitfield>::value, "Bitfield padding");
 static_assert(has_unique_object_representations<UnPaddedBitfield>::value, "Bitfield padding");
 static_assert(!has_unique_object_representations<AlignedPaddedBitfield>::value, "Bitfield padding");
+static_assert(!has_unique_object_representations<UnnamedBitfield>::value, "Bitfield padding");
 
 struct BoolBitfield {
   bool b : 8;
Index: clang/lib/AST/ASTContext.cpp
===================================================================
--- clang/lib/AST/ASTContext.cpp
+++ clang/lib/AST/ASTContext.cpp
@@ -2831,13 +2831,17 @@
   return structHasUniqueObjectRepresentations(Context, RD);
 }
 
-template <typename RangeT>
+template <bool CheckUnnamedBitFields, typename RangeT>
 static std::optional<int64_t> structSubobjectsHaveUniqueObjectRepresentations(
     const RangeT &Subobjects, int64_t CurOffsetInBits,
     const ASTContext &Context, const clang::ASTRecordLayout &Layout) {
   for (const auto *Subobject : Subobjects) {
     std::optional<int64_t> SizeInBits =
         getSubobjectSizeInBits(Subobject, Context);
+    if constexpr (CheckUnnamedBitFields) {
+      if (Subobject->isUnnamedBitfield())
+        return std::nullopt;
+    }
     if (!SizeInBits)
       return std::nullopt;
     if (*SizeInBits != 0) {
@@ -2873,15 +2877,15 @@
     });
 
     std::optional<int64_t> OffsetAfterBases =
-        structSubobjectsHaveUniqueObjectRepresentations(Bases, CurOffsetInBits,
-                                                        Context, Layout);
+        structSubobjectsHaveUniqueObjectRepresentations<false>(
+            Bases, CurOffsetInBits, Context, Layout);
     if (!OffsetAfterBases)
       return std::nullopt;
     CurOffsetInBits = *OffsetAfterBases;
   }
 
   std::optional<int64_t> OffsetAfterFields =
-      structSubobjectsHaveUniqueObjectRepresentations(
+      structSubobjectsHaveUniqueObjectRepresentations<true>(
           RD->fields(), CurOffsetInBits, Context, Layout);
   if (!OffsetAfterFields)
     return std::nullopt;
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -202,6 +202,9 @@
 - Fix crash when evaluating consteval constructor of derived class whose base
   has more than one field.
   (`#60166 <https://github.com/llvm/llvm-project/issues/60166>`_)
+- Fix bug in the computation of the ``__has_unique_object_representations``
+  builtin for types with unnamed bitfields.
+  (`#61336 <https://github.com/llvm/llvm-project/issues/61336>`_)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^


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