[clang] 32ba045 - [clang][bytecode] Fix comparing pointers to union members (#154342)

[via cfe-commits]

Author: Timm Baeder
Date: 2025-08-20T07:09:20+02:00
New Revision: 32ba045bea95442e37302c17b344f7695b6520e7

URL: https://github.com/llvm/llvm-project/commit/32ba045bea95442e37302c17b344f7695b6520e7
DIFF: https://github.com/llvm/llvm-project/commit/32ba045bea95442e37302c17b344f7695b6520e7.diff

LOG: [clang][bytecode] Fix comparing pointers to union members (#154342)

If one of them is a one-past-end pointer.

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/Pointer.cpp
    clang/test/AST/ByteCode/unions.cpp

Removed: 
    


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diff  --git a/clang/lib/AST/ByteCode/Pointer.cpp b/clang/lib/AST/ByteCode/Pointer.cpp
index 7c6eb74da205c..89d9829399302 100644
--- a/clang/lib/AST/ByteCode/Pointer.cpp
+++ b/clang/lib/AST/ByteCode/Pointer.cpp
@@ -375,6 +375,8 @@ size_t Pointer::computeOffsetForComparison() const {
     }
 
     if (const Record *R = P.getBase().getRecord(); R && R->isUnion()) {
+      if (P.isOnePastEnd())
+        ++Result;
       // Direct child of a union - all have offset 0.
       P = P.getBase();
       continue;

diff  --git a/clang/test/AST/ByteCode/unions.cpp b/clang/test/AST/ByteCode/unions.cpp
index 8ed76258b879a..6bccbda23f468 100644
--- a/clang/test/AST/ByteCode/unions.cpp
+++ b/clang/test/AST/ByteCode/unions.cpp
@@ -966,3 +966,15 @@ namespace AddressComparison {
   static_assert(&U2.a[0] != &U2.b[1]);
   static_assert(&U2.a[0] == &U2.b[1]); // both-error {{failed}}
 }
+
+#if __cplusplus >= 202002L
+namespace UnionMemberOnePastEnd {
+  constexpr bool b() {
+    union  {
+      int p;
+    };
+    return &p == (&p + 1);
+  }
+  static_assert(!b());
+}
+#endif