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[clang][bytecode] Fix comparing pointers to union members #154342

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Merged
merged 1 commit into from
Aug 20, 2025
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[clang][bytecode] Fix comparing pointers to union members #154342

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2 changes: 2 additions & 0 deletions clang/lib/AST/ByteCode/Pointer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
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12 changes: 12 additions & 0 deletions clang/test/AST/ByteCode/unions.cpp
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Expand Up @@ -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);
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@shafik shafik Aug 23, 2025

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Do we have a test that shows it fails for return &p == (&p + 2);?

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@tbaederr tbaederr Aug 24, 2025

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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.

}
static_assert(!b());
}
#endif