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[libc++] Use __reference_constructs_from_temporary if eligible #141916

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Merged
merged 7 commits into from
Jun 3, 2025
Merged

[libc++] Use __reference_constructs_from_temporary if eligible #141916

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417b08a
[libc++] Use `__reference_constructs_from_temporary` if eligible
frederick-vs-ja May 29, 2025
4bfddda
Switch to use internal type trait
frederick-vs-ja Jun 1, 2025
4369c4a
Merge branch 'main' into tuple-no-__reference_binds_to_temporary
frederick-vs-ja Jun 1, 2025
8af4623
Remove inactive code branches
frederick-vs-ja Jun 2, 2025
7fdb5e5
Merge branch 'main' into tuple-no-__reference_binds_to_temporary
frederick-vs-ja Jun 2, 2025
e72fc82
Adopt @philnik777's review comment for comments
frederick-vs-ja Jun 2, 2025
ffcee98
Merge branch 'main' into tuple-no-__reference_binds_to_temporary
frederick-vs-ja Jun 2, 2025
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8 changes: 2 additions & 6 deletions libcxx/include/__type_traits/reference_constructs_from_temporary.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,14 +33,10 @@ _LIBCPP_NO_SPECIALIZATIONS inline constexpr bool reference_constructs_from_tempo
#if __has_builtin(__reference_constructs_from_temporary)
template <class _Tp, class _Up>
inline const bool __reference_constructs_from_temporary_v = __reference_constructs_from_temporary(_Tp, _Up);
#elif __has_builtin(__reference_binds_to_temporary)
// TODO: Remove this once all support compilers have __reference_constructs_from_temporary implemented.
template <class _Tp, class _Up>
inline const bool __reference_constructs_from_temporary_v = __reference_binds_to_temporary(_Tp, _Up);
#else
// TODO: Remove this once https://github.com/llvm/llvm-project/issues/111477 no longer affects supported compilers.
// TODO(LLVM 22): Remove this as all support compilers should have __reference_constructs_from_temporary implemented.
template <class _Tp, class _Up>
inline const bool __reference_constructs_from_temporary_v = false;
inline const bool __reference_constructs_from_temporary_v = __reference_binds_to_temporary(_Tp, _Up);
#endif

_LIBCPP_END_NAMESPACE_STD
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13 changes: 0 additions & 13 deletions .../utilities/tuple/tuple.tuple/tuple.cnstr/PR20855_tuple_ref_binding_diagnostics.verify.cpp
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Expand Up @@ -38,16 +38,7 @@ template <class T> struct CannotDeduce {
template <class ...Args>
void F(typename CannotDeduce<std::tuple<Args...>>::type const&) {}

#if TEST_HAS_BUILTIN(__reference_constructs_from_temporary)
# define TEST_HAS_REFERENCE_BINDING_TRAIT 1
#elif TEST_HAS_BUILTIN(__reference_binds_to_temporary)
# define TEST_HAS_REFERENCE_BINDING_TRAIT 1
#else
# define TEST_HAS_REFERENCE_BINDING_TRAIT 0
#endif

void f() {
#if TEST_HAS_REFERENCE_BINDING_TRAIT
// Test that we emit our diagnostic from the library.
// expected-error@tuple:* 8 {{Attempted construction of reference element binds to a temporary whose lifetime has ended}}

Expand Down Expand Up @@ -80,8 +71,4 @@ void f() {
std::tuple<std::string &&> t2("hello"); // expected-note {{requested here}}
std::tuple<std::string &&> t3(std::allocator_arg, alloc, "hello"); // expected-note {{requested here}}
}
#else
#error force failure
// expected-error@-1 {{force failure}}
#endif
}
6 changes: 2 additions & 4 deletions ...td/utilities/tuple/tuple.tuple/tuple.cnstr/PR20855_tuple_ref_binding_diagnostics.pass.cpp
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Expand Up @@ -22,12 +22,10 @@
# define ASSERT_REFERENCE_BINDS_TEMPORARY(...) static_assert(__reference_constructs_from_temporary(__VA_ARGS__), "")
# define ASSERT_NOT_REFERENCE_BINDS_TEMPORARY(...) \
static_assert(!__reference_constructs_from_temporary(__VA_ARGS__), "")
#elif TEST_HAS_BUILTIN(__reference_binds_to_temporary)
#else
// TODO(LLVM 22): Remove this as all support compilers should have __reference_constructs_from_temporary implemented.
# define ASSERT_REFERENCE_BINDS_TEMPORARY(...) static_assert(__reference_binds_to_temporary(__VA_ARGS__), "")
# define ASSERT_NOT_REFERENCE_BINDS_TEMPORARY(...) static_assert(!__reference_binds_to_temporary(__VA_ARGS__), "")
#else
# define ASSERT_REFERENCE_BINDS_TEMPORARY(...) static_assert(true, "")
# define ASSERT_NOT_REFERENCE_BINDS_TEMPORARY(...) static_assert(true, "")
#endif

template <class Tp>
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