[clang] [clang][Interp] Ignore unnamed bitfields when zeroing records (PR #102749)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/102749

Including unions, where this is more important.

>From e2a9a796b2beb2dcee0f8ec974cc548427091af4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Sat, 10 Aug 2024 15:19:55 +0200
Subject: [PATCH] [clang][Interp] Ignore unnamed bitfields when zeroing records

Including unions, where this is more important.
---
 clang/lib/AST/Interp/Compiler.cpp | 3 +++
 clang/test/AST/Interp/unions.cpp  | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/clang/lib/AST/Interp/Compiler.cpp b/clang/lib/AST/Interp/Compiler.cpp
index 6c4d607706c6b..1fa7a944448fb 100644
--- a/clang/lib/AST/Interp/Compiler.cpp
+++ b/clang/lib/AST/Interp/Compiler.cpp
@@ -3356,6 +3356,9 @@ bool Compiler<Emitter>::visitZeroRecordInitializer(const Record *R,
   assert(R);
   // Fields
   for (const Record::Field &Field : R->fields()) {
+    if (Field.Decl->isUnnamedBitField())
+      continue;
+
     const Descriptor *D = Field.Desc;
     if (D->isPrimitive()) {
       QualType QT = D->getType();
diff --git a/clang/test/AST/Interp/unions.cpp b/clang/test/AST/Interp/unions.cpp
index 6f6bc3d6891b4..1f52950b1e09b 100644
--- a/clang/test/AST/Interp/unions.cpp
+++ b/clang/test/AST/Interp/unions.cpp
@@ -297,5 +297,13 @@ namespace Zeroing {
   static_assert(u6.a[4] == 0, "");
   static_assert(u6.b == 0, ""); // both-error {{not an integral constant expression}} \
                                 // both-note {{read of member 'b' of union with active member 'a'}}
+
+  union UnionWithUnnamedBitfield {
+    int : 3;
+    int n;
+  };
+  static_assert(UnionWithUnnamedBitfield().n == 0, "");
+  static_assert(UnionWithUnnamedBitfield{}.n == 0, "");
+  static_assert(UnionWithUnnamedBitfield{1}.n == 1, "");
 }
 #endif