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Specially handle array<T, 0> for non-default-constructible T #2296

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 3 commits into from
Nov 13, 2021
Merged

Specially handle array<T, 0> for non-default-constructible T #2296

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d50e1c0
Specially handle `array<T, 0>` for non-default-constructible `T`
CaseyCarter Oct 22, 2021
a2607b2
Tim's review comments
CaseyCarter Oct 25, 2021
69b708e
Tim's repeated review comment =)
CaseyCarter Oct 25, 2021
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18 changes: 11 additions & 7 deletions stl/inc/array
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Original file line number Diff line number Diff line change
Expand Up @@ -615,6 +615,8 @@ template <class _First, class... _Rest>
array(_First, _Rest...) -> array<typename _Enforce_same<_First, _Rest...>::type, 1 + sizeof...(_Rest)>;
#endif // _HAS_CXX17

struct _Empty_array_element {};

template <class _Ty>
class array<_Ty, 0> {
public:
Expand Down Expand Up @@ -728,47 +730,47 @@ public:
_STL_REPORT_ERROR("array subscript out of range");
#endif // _CONTAINER_DEBUG_LEVEL > 0

return _Elems[0];
return *data();
}

_NODISCARD const_reference operator[](size_type) const noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_REPORT_ERROR("array subscript out of range");
#endif // _CONTAINER_DEBUG_LEVEL > 0

return _Elems[0];
return *data();
}

_NODISCARD reference front() noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_REPORT_ERROR("array<T, 0>::front() invalid");
#endif // _CONTAINER_DEBUG_LEVEL > 0

return _Elems[0];
return *data();
}

_NODISCARD const_reference front() const noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_REPORT_ERROR("array<T, 0>::front() invalid");
#endif // _CONTAINER_DEBUG_LEVEL > 0

return _Elems[0];
return *data();
}

_NODISCARD reference back() noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_REPORT_ERROR("array<T, 0>::back() invalid");
#endif // _CONTAINER_DEBUG_LEVEL > 0

return _Elems[0];
return *data();
}

_NODISCARD const_reference back() const noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_REPORT_ERROR("array<T, 0>::back() invalid");
#endif // _CONTAINER_DEBUG_LEVEL > 0

return _Elems[0];
return *data();
}

_NODISCARD _CONSTEXPR17 _Ty* data() noexcept {
Expand All @@ -783,7 +785,9 @@ public:
_Xout_of_range("invalid array<T, 0> subscript");
}

_Ty _Elems[1];
conditional_t<disjunction_v<is_default_constructible<_Ty>, _Is_implicitly_default_constructible<_Ty>>, _Ty,
_Empty_array_element>
_Elems[1];
};

template <class _Ty, size_t _Size, enable_if_t<_Size == 0 || _Is_swappable<_Ty>::value, int> = 0>
Expand Down
10 changes: 3 additions & 7 deletions tests/libcxx/expected_results.txt
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Expand Up @@ -69,6 +69,9 @@ std/language.support/support.limits/support.limits.general/concepts.version.pass
# Bogus test believes that optional<non_constexpr_destructor> cannot be a literal type
std/utilities/optional/optional.object/optional.object.dtor/dtor.pass.cpp:0 FAIL

# Bogus test believes that copyability of array<T, 0> must be the same as array<T, 1>
std/containers/sequences/array/array.cons/implicit_copy.pass.cpp FAIL


# *** INTERACTIONS WITH CONTEST / C1XX THAT UPSTREAM LIKELY WON'T FIX ***
# Tracked by VSO-593630 "<filesystem> Enable libcxx filesystem tests"
Expand Down Expand Up @@ -348,13 +351,6 @@ std/input.output/file.streams/fstreams/filebuf.virtuals/underflow.pass.cpp FAIL
std/containers/sequences/array/array.fill/fill.fail.cpp FAIL
std/containers/sequences/array/array.swap/swap.fail.cpp FAIL

# GH-942 <array>: std::array<T,0> doesn't compile - when type is not default constructible
std/containers/sequences/array/array.cons/implicit_copy.pass.cpp FAIL
std/containers/sequences/array/array.cons/initialization.pass.cpp FAIL
std/containers/sequences/array/array.data/data_const.pass.cpp FAIL
std/containers/sequences/array/array.data/data.pass.cpp FAIL
std/containers/sequences/array/iterators.pass.cpp FAIL

# GH-1006 <algorithm>: debug checks for predicates are observable
std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp FAIL
std/algorithms/alg.sorting/alg.min.max/minmax_init_list_comp.pass.cpp FAIL
Expand Down
10 changes: 3 additions & 7 deletions tests/libcxx/skipped_tests.txt
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Expand Up @@ -69,6 +69,9 @@ language.support\support.limits\support.limits.general\concepts.version.pass.cpp
# Bogus test believes that optional<non_constexpr_destructor> cannot be a literal type
utilities\optional\optional.object\optional.object.dtor\dtor.pass.cpp

# Bogus test believes that copyability of array<T, 0> must be the same as array<T, 1>
containers\sequences\array\array.cons\implicit_copy.pass.cpp


# *** INTERACTIONS WITH CONTEST / C1XX THAT UPSTREAM LIKELY WON'T FIX ***
# Tracked by VSO-593630 "<filesystem> Enable libcxx filesystem tests"
Expand Down Expand Up @@ -348,13 +351,6 @@ input.output\file.streams\fstreams\filebuf.virtuals\underflow.pass.cpp
containers\sequences\array\array.fill\fill.fail.cpp
containers\sequences\array\array.swap\swap.fail.cpp

# GH-942 <array>: std::array<T,0> doesn't compile - when type is not default constructible
containers\sequences\array\array.cons\implicit_copy.pass.cpp
containers\sequences\array\array.cons\initialization.pass.cpp
containers\sequences\array\array.data\data_const.pass.cpp
containers\sequences\array\array.data\data.pass.cpp
containers\sequences\array\iterators.pass.cpp

# GH-1006 <algorithm>: debug checks for predicates are observable
algorithms\alg.sorting\alg.merge\inplace_merge_comp.pass.cpp
algorithms\alg.sorting\alg.min.max\minmax_init_list_comp.pass.cpp
Expand Down