[clang][bytecode] Fix comparing pointers to union members #154342
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@llvm/pr-subscribers-clang Author: Timm Baeder (tbaederr) ChangesIf one of them is a one-past-end pointer. Full diff: https://github.com/llvm/llvm-project/pull/154342.diff 2 Files Affected:
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..f9bc05110acf9 100644
--- a/clang/test/AST/ByteCode/unions.cpp
+++ b/clang/test/AST/ByteCode/unions.cpp
@@ -966,3 +966,13 @@ namespace AddressComparison {
static_assert(&U2.a[0] != &U2.b[1]);
static_assert(&U2.a[0] == &U2.b[1]); // both-error {{failed}}
}
+
+namespace UnionMemberOnePastEnd {
+ constexpr bool b() {
+ union {
+ int p;
+ };
+ return &p == (&p + 1);
+ }
+ static_assert(!b());
+}
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This was referenced Aug 19, 2025
If one of them is a one-past-end pointer.
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shafik
reviewed
Aug 23, 2025
| union { | ||
| int p; | ||
| }; | ||
| return &p == (&p + 1); |
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Do we have a test that shows it fails for return &p == (&p + 2);?
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Not in this specific configuration I think, but we have plenty of tests for the "cannot refer to element 2 of non-array object" diagnostic.
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If one of them is a one-past-end pointer.