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[Clang] __has_unique_object_representations should not accept Incomplete[] #138291

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Merged
merged 1 commit into from
May 2, 2025
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[Clang] __has_unique_object_representations should not accept Incomplete[] #138291

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3 changes: 3 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -547,6 +547,9 @@ Bug Fixes to Compiler Builtins
``void(char *, char *)`` to ``void(void *, void *)`` to match GCC's signature
for the same builtin. (#GH47833)

- ``__has_unique_object_representations(Incomplete[])`` is no longer accepted, per
`LWG4113 <https://cplusplus.github.io/LWG/issue4113>`_.

Bug Fixes to Attribute Support
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed crash when a parameter to the ``clang::annotate`` attribute evaluates to ``void``. See #GH119125
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14 changes: 9 additions & 5 deletions clang/lib/Sema/SemaExprCXX.cpp
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Expand Up @@ -5418,6 +5418,15 @@ static bool CheckUnaryTypeTraitTypeCompleteness(Sema &S, TypeTrait UTT,
return !S.RequireCompleteType(
Loc, ArgTy, diag::err_incomplete_type_used_in_type_trait_expr);

// has_unique_object_representations<T>
// remove_all_extents_t<T> shall be a complete type or cv void (LWG4113).
case UTT_HasUniqueObjectRepresentations:
ArgTy = QualType(ArgTy->getBaseElementTypeUnsafe(), 0);
if (ArgTy->isVoidType())
return true;
return !S.RequireCompleteType(
Loc, ArgTy, diag::err_incomplete_type_used_in_type_trait_expr);

// C++1z [meta.unary.prop]:
// remove_all_extents_t<T> shall be a complete type or cv void.
case UTT_IsTrivial:
Expand Down Expand Up @@ -5445,13 +5454,8 @@ static bool CheckUnaryTypeTraitTypeCompleteness(Sema &S, TypeTrait UTT,
case UTT_HasTrivialCopy:
case UTT_HasTrivialDestructor:
case UTT_HasVirtualDestructor:
// has_unique_object_representations<T> when T is an array is defined in terms
// of has_unique_object_representations<remove_all_extents_t<T>>, so the base
// type needs to be complete even if the type is an incomplete array type.
case UTT_HasUniqueObjectRepresentations:
ArgTy = QualType(ArgTy->getBaseElementTypeUnsafe(), 0);
[[fallthrough]];

// C++1z [meta.unary.prop]:
// T shall be a complete type, cv void, or an array of unknown bound.
case UTT_IsDestructible:
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10 changes: 10 additions & 0 deletions clang/test/SemaCXX/type-traits.cpp
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Expand Up @@ -3383,6 +3383,16 @@ static_assert(!__has_unique_object_representations(float), "definitely not Float
static_assert(!__has_unique_object_representations(double), "definitely not Floating Point");
static_assert(!__has_unique_object_representations(long double), "definitely not Floating Point");


static_assert(!__has_unique_object_representations(AnIncompleteType[]));
//expected-error@-1 {{incomplete type 'AnIncompleteType' used in type trait expression}}
static_assert(!__has_unique_object_representations(AnIncompleteType[][1]));
//expected-error@-1 {{incomplete type 'AnIncompleteType' used in type trait expression}}
static_assert(!__has_unique_object_representations(AnIncompleteType[1]));
//expected-error@-1 {{incomplete type 'AnIncompleteType' used in type trait expression}}
static_assert(!__has_unique_object_representations(AnIncompleteType));
//expected-error@-1 {{incomplete type 'AnIncompleteType' used in type trait expression}}

struct NoPadding {
int a;
int b;
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