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[libc++] LWG4012: common_view::begin/end are missing the simple-view check #153674

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[libc++] LWG4012: common_view::begin/end are missing the simple-view check #153674

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06a6c61
initial commit
changkhothuychung Aug 14, 2025
31d0cef
clang format
changkhothuychung Aug 14, 2025
265621c
sfinae test
changkhothuychung Aug 18, 2025
476a5f3
fix test
changkhothuychung Aug 18, 2025
3576d9d
fix test and clang format
changkhothuychung Aug 18, 2025
c308942
fix test
changkhothuychung Aug 18, 2025
e48ab16
revert styling for file
changkhothuychung Aug 19, 2025
02f206a
update test
changkhothuychung Aug 19, 2025
5e38145
formatting
changkhothuychung Aug 19, 2025
a3de665
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changkhothuychung Aug 19, 2025
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8 changes: 6 additions & 2 deletions libcxx/include/__ranges/common_view.h
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,9 @@ class common_view : public view_interface<common_view<_View>> {

_LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }

_LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
_LIBCPP_HIDE_FROM_ABI constexpr auto begin()
requires(!__simple_view<_View>)
{
if constexpr (random_access_range<_View> && sized_range<_View>)
return ranges::begin(__base_);
else
Expand All @@ -74,7 +76,9 @@ class common_view : public view_interface<common_view<_View>> {
return common_iterator<iterator_t<const _View>, sentinel_t<const _View>>(ranges::begin(__base_));
}

_LIBCPP_HIDE_FROM_ABI constexpr auto end() {
_LIBCPP_HIDE_FROM_ABI constexpr auto end()
requires(!__simple_view<_View>)
{
if constexpr (random_access_range<_View> && sized_range<_View>)
return ranges::begin(__base_) + ranges::size(__base_);
else
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6 changes: 6 additions & 0 deletions libcxx/test/std/ranges/range.adaptors/range.common.view/begin.pass.cpp
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Expand Up @@ -51,6 +51,12 @@ constexpr bool test() {
assert(begin == std::ranges::begin(view));
}

{
NonSimpleNonCommonView view{buf, buf + 8};
std::ranges::common_view<NonSimpleNonCommonView> common(view);
static_assert(!std::is_same_v<decltype(common.begin()), decltype(std::as_const(common).begin())>);
}

return true;
}

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6 changes: 6 additions & 0 deletions libcxx/test/std/ranges/range.adaptors/range.common.view/end.pass.cpp
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Expand Up @@ -39,6 +39,12 @@ constexpr bool test() {
assert(base(end) == buf + 8);
}

{
NonSimpleNonCommonView view{buf, buf + 8};
std::ranges::common_view<NonSimpleNonCommonView> common(view);
static_assert(!std::is_same_v<decltype(common.end()), decltype(std::as_const(common).end())>);
}

return true;
}

Expand Down
83 changes: 64 additions & 19 deletions libcxx/test/std/ranges/range.adaptors/range.common.view/types.h
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Expand Up @@ -14,10 +14,10 @@
#include "test_iterators.h"

struct DefaultConstructibleView : std::ranges::view_base {
int* begin_ = nullptr;
int* end_ = nullptr;
int* begin_ = nullptr;
int* end_ = nullptr;
explicit DefaultConstructibleView() = default;
constexpr int *begin() const { return begin_; }
constexpr int* begin() const { return begin_; }
constexpr auto end() const { return sentinel_wrapper<int*>(end_); }
};
static_assert(std::ranges::view<DefaultConstructibleView>);
Expand All @@ -26,21 +26,21 @@ static_assert(std::default_initializable<DefaultConstructibleView>);
struct MoveOnlyView : std::ranges::view_base {
int* begin_;
int* end_;
constexpr explicit MoveOnlyView(int* b, int* e) : begin_(b), end_(e) { }
constexpr MoveOnlyView(MoveOnlyView&&) = default;
constexpr explicit MoveOnlyView(int* b, int* e) : begin_(b), end_(e) {}
constexpr MoveOnlyView(MoveOnlyView&&) = default;
constexpr MoveOnlyView& operator=(MoveOnlyView&&) = default;
constexpr int *begin() const { return begin_; }
constexpr int* begin() const { return begin_; }
constexpr auto end() const { return sentinel_wrapper<int*>(end_); }
};
static_assert( std::ranges::view<MoveOnlyView>);
static_assert( std::ranges::contiguous_range<MoveOnlyView>);
static_assert(std::ranges::view<MoveOnlyView>);
static_assert(std::ranges::contiguous_range<MoveOnlyView>);
static_assert(!std::copyable<MoveOnlyView>);

struct CopyableView : std::ranges::view_base {
int* begin_;
int* end_;
constexpr explicit CopyableView(int* b, int* e) : begin_(b), end_(e) { }
constexpr int *begin() const { return begin_; }
constexpr explicit CopyableView(int* b, int* e) : begin_(b), end_(e) {}
constexpr int* begin() const { return begin_; }
constexpr auto end() const { return sentinel_wrapper<int*>(end_); }
};
static_assert(std::ranges::view<CopyableView>);
Expand All @@ -50,7 +50,7 @@ using ForwardIter = forward_iterator<int*>;
struct SizedForwardView : std::ranges::view_base {
int* begin_;
int* end_;
constexpr explicit SizedForwardView(int* b, int* e) : begin_(b), end_(e) { }
constexpr explicit SizedForwardView(int* b, int* e) : begin_(b), end_(e) {}
constexpr auto begin() const { return forward_iterator<int*>(begin_); }
constexpr auto end() const { return sized_sentinel<forward_iterator<int*>>(forward_iterator<int*>(end_)); }
};
Expand All @@ -62,9 +62,11 @@ using RandomAccessIter = random_access_iterator<int*>;
struct SizedRandomAccessView : std::ranges::view_base {
int* begin_;
int* end_;
constexpr explicit SizedRandomAccessView(int* b, int* e) : begin_(b), end_(e) { }
constexpr explicit SizedRandomAccessView(int* b, int* e) : begin_(b), end_(e) {}
constexpr auto begin() const { return random_access_iterator<int*>(begin_); }
constexpr auto end() const { return sized_sentinel<random_access_iterator<int*>>(random_access_iterator<int*>(end_)); }
constexpr auto end() const {
return sized_sentinel<random_access_iterator<int*>>(random_access_iterator<int*>(end_));
}
};
static_assert(std::ranges::view<SizedRandomAccessView>);
static_assert(std::ranges::random_access_range<SizedRandomAccessView>);
Expand All @@ -73,21 +75,64 @@ static_assert(std::ranges::sized_range<SizedRandomAccessView>);
struct CommonView : std::ranges::view_base {
int* begin_;
int* end_;
constexpr explicit CommonView(int* b, int* e) : begin_(b), end_(e) { }
constexpr int *begin() const { return begin_; }
constexpr int *end() const { return end_; }
constexpr explicit CommonView(int* b, int* e) : begin_(b), end_(e) {}
constexpr int* begin() const { return begin_; }
constexpr int* end() const { return end_; }
};
static_assert(std::ranges::view<CommonView>);
static_assert(std::ranges::common_range<CommonView>);

struct NonCommonView : std::ranges::view_base {
int* begin_;
int* end_;
constexpr explicit NonCommonView(int* b, int* e) : begin_(b), end_(e) { }
constexpr int *begin() const { return begin_; }
constexpr explicit NonCommonView(int* b, int* e) : begin_(b), end_(e) {}
constexpr int* begin() const { return begin_; }
constexpr auto end() const { return sentinel_wrapper<int*>(end_); }
};
static_assert( std::ranges::view<NonCommonView>);
static_assert(std::ranges::view<NonCommonView>);
static_assert(!std::ranges::common_range<NonCommonView>);

template <class T>
concept HasConstBegin = requires(const T& ct) { ct.begin(); };

template <class T>
concept HasBegin = requires(T& t) { t.begin(); };

template <class T>
concept HasConstAndNonConstBegin = HasConstBegin<T> && requires(T& t, const T& ct) {
requires !std::same_as<decltype(t.begin()), decltype(ct.begin())>;
};

template <class T>
concept HasOnlyNonConstBegin = HasBegin<T> && !HasConstBegin<T>;

template <class T>
concept HasOnlyConstBegin = HasConstBegin<T> && !HasConstAndNonConstBegin<T>;

template <bool Simple>
struct NonCommonBaseView : std::ranges::view_base {
int* begin_;
int* end_;
constexpr explicit NonCommonBaseView(int* b, int* e) : begin_(b), end_(e) {}
constexpr auto begin() const { return static_cast<const int*>(begin_); }
constexpr auto end() const { return sentinel_wrapper<const int*>(end_); }
constexpr int* begin()
requires(!Simple)
{
return begin_;
}
constexpr auto end()
requires(!Simple)
{
return sentinel_wrapper<int*>(end_);
}
};
using NonSimpleNonCommonView = NonCommonBaseView<false>;

static_assert(!HasOnlyNonConstBegin<std::ranges::common_view<NonSimpleNonCommonView>>);
static_assert(!HasOnlyConstBegin<std::ranges::common_view<NonSimpleNonCommonView>>);
static_assert(HasConstAndNonConstBegin<std::ranges::common_view<NonSimpleNonCommonView>>);
static_assert(HasConstBegin<std::ranges::common_view<NonSimpleNonCommonView> const>);
static_assert(HasOnlyConstBegin<std::ranges::common_view<NonSimpleNonCommonView> const>);

#endif // TEST_STD_RANGES_RANGE_ADAPTORS_RANGE_COMMON_VIEW_TYPES_H
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