NB: This backport of r12-1606 to the 11 branch deliberately omits parts
of P2325R3 so as to maximize backward compatibility with pre-P2325R3 code.
In particular, we don't remove the default ctors for back_insert_iterator,
front_insert_iterator, ostream_iterator, ref_view and basic_istream_view.
===
This implements the wording changes of P2325R3 "Views should not be
required to be default constructible". Changes are relatively
straightforward, besides perhaps those to __box (which now stands
for copyable-box instead of semiregular-box) and __non_propagating_cache.
For __box, this patch implements the recommended practice to also avoid
std::optional when the boxed type is nothrow_move/copy_constructible.
For __non_propagating_cache, now that it's used by split_view::_M_current,
we need to add assignment from a value of the underlying type to the
subset of the std::optional API implemented for the cache (needed by
split_view::begin()). Hence the new __non_propagating_cache::operator=
overload.
In passing, this fixes the undesirable list-init in the constructors of
the partial specialization of __box as reported in PR100475 comment #7.
PR libstdc++/103904
libstdc++-v3/ChangeLog:
* include/bits/iterator_concepts.h (weakly_incrementable): Remove
default_initializable requirement.
* include/bits/ranges_base.h (ranges::view): Likewise.
* include/bits/ranges_util.h (subrange): Constrain the default
ctor.
* include/bits/stl_iterator.h (common_iterator): Constrain the
default ctor.
(counted_iterator): Likewise.
* include/std/ranges (__detail::__box::operator=): Handle
self-assignment in the primary template.
(__detail::__box): In the partial specialization: adjust
constraints as per P2325. Add specialized operator= for the
case when the wrapped type is not copyable. Constrain the
default ctor. Avoid list-initialization.
(single_view): Constraint the default ctor.
(iota_view): Relax semiregular constraint to copyable.
Constrain the default ctor.
(iota_view::_Iterator): Constraint the default ctor.
(ref_view): Remove the default ctor. Remove NSDMIs.
(ref_view::_Iterator): Constrain the default ctor.
(__detail::__non_propagating_cache::operator=): Define overload
for assigning from a value of the underlying type.
(filter_view): Likewise.
(filter_view::_Iterator): Likewise.
(transform_view): Likewise.
(transform_view::_Iterator): Likewise.
(take_view): Likewise.
(take_view::_Iterator): Likewise.
(take_while_view): Likewise.
(take_while_view::_Iterator): Likewise.
(drop_while_view): Likewise.
(drop_while_view::_Iterator): Likewise.
(join_view): Likewise.
(split_view::_OuterIter::__current): Adjust after changing the
type of _M_current.
(split_view::_M_current): Wrap it in a __non_propagating_cache.
(split_view::split_view): Constrain the default ctor.
(common_view): Constrain the default ctor.
(reverse_view): Likewise.
(elements_view): Likewise.
* include/std/span (enable_view<span<_ElementType, _Extent>>):
Define this partial specialization to true unconditionally.
* include/std/version (__cpp_lib_ranges): Adjust value.
* testsuite/std/ranges/adaptors/detail/semiregular_box.cc:
Rename to ...
* testsuite/std/ranges/adaptors/detail/copyable_box.cc: ... this.
(test02): Adjust now that __box is copyable-box not
semiregular-box.
(test03): New test.
* testsuite/std/ranges/p2325.cc: New test.
* testsuite/std/ranges/single_view.cc (test06): New test.
* testsuite/std/ranges/view.cc: Adjust now that view doesn't
require default_initializable.
(cherry picked from commit
4b4f5666b4c2f3aab2a9f3d53d394e390b9b682d)
/// Requirements on types that can be incremented with ++.
template<typename _Iter>
- concept weakly_incrementable = default_initializable<_Iter>
- && movable<_Iter>
+ concept weakly_incrementable = movable<_Iter>
&& requires(_Iter __i)
{
typename iter_difference_t<_Iter>;
/// [range.view] The ranges::view concept.
template<typename _Tp>
concept view
- = range<_Tp> && movable<_Tp> && default_initializable<_Tp>
- && enable_view<_Tp>;
+ = range<_Tp> && movable<_Tp> && enable_view<_Tp>;
// [range.refinements]
[[no_unique_address]] _Size<__size_type> _M_size = {};
public:
- subrange() = default;
+ subrange() requires default_initializable<_It> = default;
constexpr
subrange(__detail::__convertible_to_non_slicing<_It> auto __i, _Sent __s)
constexpr
common_iterator()
noexcept(is_nothrow_default_constructible_v<_It>)
+ requires default_initializable<_It>
: _M_it(), _M_index(0)
{ }
// iterator_concept defined in __counted_iter_concept
// iterator_category defined in __counted_iter_cat
- constexpr counted_iterator() = default;
+ constexpr counted_iterator() requires default_initializable<_It> = default;
constexpr
counted_iterator(_It __i, iter_difference_t<_It> __n)
noexcept(is_nothrow_copy_constructible_v<_Tp>)
requires (!copyable<_Tp>)
{
- if ((bool)__that)
- this->emplace(*__that);
- else
- this->reset();
+ if (this != std::__addressof(__that))
+ {
+ if ((bool)__that)
+ this->emplace(*__that);
+ else
+ this->reset();
+ }
return *this;
}
noexcept(is_nothrow_move_constructible_v<_Tp>)
requires (!movable<_Tp>)
{
- if ((bool)__that)
- this->emplace(std::move(*__that));
- else
- this->reset();
+ if (this != std::__addressof(__that))
+ {
+ if ((bool)__that)
+ this->emplace(std::move(*__that));
+ else
+ this->reset();
+ }
return *this;
}
};
- // For types which are already semiregular, this specialization of the
- // semiregular wrapper stores the object directly without going through
+ // For types which are already copyable, this specialization of the
+ // copyable wrapper stores the object directly without going through
// std::optional. It provides just the subset of the primary template's
// API that we currently use.
- template<__boxable _Tp> requires semiregular<_Tp>
+ template<__boxable _Tp>
+ requires copyable<_Tp> || (is_nothrow_move_constructible_v<_Tp>
+ && is_nothrow_copy_constructible_v<_Tp>)
struct __box<_Tp>
{
private:
[[no_unique_address]] _Tp _M_value = _Tp();
public:
- __box() = default;
+ __box() requires default_initializable<_Tp> = default;
constexpr explicit
__box(const _Tp& __t)
noexcept(is_nothrow_copy_constructible_v<_Tp>)
- : _M_value{__t}
+ : _M_value(__t)
{ }
constexpr explicit
__box(_Tp&& __t)
noexcept(is_nothrow_move_constructible_v<_Tp>)
- : _M_value{std::move(__t)}
+ : _M_value(std::move(__t))
{ }
template<typename... _Args>
: _M_value(std::forward<_Args>(__args)...)
{ }
+ __box(const __box&) = default;
+ __box(__box&&) = default;
+ __box& operator=(const __box&) requires copyable<_Tp> = default;
+ __box& operator=(__box&&) requires copyable<_Tp> = default;
+
+ // When _Tp is nothrow_copy_constructible but not copy_assignable,
+ // copy assignment is implemented via destroy-then-copy-construct.
+ constexpr __box&
+ operator=(const __box& __that) noexcept
+ {
+ static_assert(is_nothrow_copy_constructible_v<_Tp>);
+ if (this != std::__addressof(__that))
+ {
+ _M_value.~_Tp();
+ std::construct_at(std::__addressof(_M_value), *__that);
+ }
+ return *this;
+ }
+
+ // Likewise for move assignment.
+ constexpr __box&
+ operator=(__box&& __that) noexcept
+ {
+ static_assert(is_nothrow_move_constructible_v<_Tp>);
+ if (this != std::__addressof(__that))
+ {
+ _M_value.~_Tp();
+ std::construct_at(std::__addressof(_M_value), std::move(*__that));
+ }
+ return *this;
+ }
+
constexpr bool
has_value() const noexcept
{ return true; };
class single_view : public view_interface<single_view<_Tp>>
{
public:
- single_view() = default;
+ single_view() requires default_initializable<_Tp> = default;
constexpr explicit
single_view(const _Tp& __t)
template<weakly_incrementable _Winc,
semiregular _Bound = unreachable_sentinel_t>
requires std::__detail::__weakly_eq_cmp_with<_Winc, _Bound>
- && semiregular<_Winc>
+ && copyable<_Winc>
class iota_view : public view_interface<iota_view<_Winc, _Bound>>
{
private:
using value_type = _Winc;
using difference_type = __detail::__iota_diff_t<_Winc>;
- _Iterator() = default;
+ _Iterator() requires default_initializable<_Winc> = default;
constexpr explicit
_Iterator(_Winc __value)
[[no_unique_address]] _Bound _M_bound = _Bound();
public:
- iota_view() = default;
+ iota_view() requires default_initializable<_Winc> = default;
constexpr explicit
iota_view(_Winc __value)
return *this;
}
+ constexpr __non_propagating_cache&
+ operator=(_Tp __val)
+ {
+ this->_M_reset();
+ std::construct_at(std::__addressof(this->_M_payload._M_payload),
+ std::in_place, std::move(__val));
+ this->_M_payload._M_engaged = true;
+ return *this;
+ }
+
constexpr _Tp&
operator*() noexcept
{ return this->_M_get(); }
using value_type = range_value_t<_Vp>;
using difference_type = range_difference_t<_Vp>;
- _Iterator() = default;
+ _Iterator() requires default_initializable<_Vp_iter> = default;
constexpr
_Iterator(filter_view* __parent, _Vp_iter __current)
_Vp _M_base = _Vp();
public:
- filter_view() = default;
+ filter_view() requires (default_initializable<_Vp>
+ && default_initializable<_Pred>)
+ = default;
constexpr
filter_view(_Vp __base, _Pred __pred)
= remove_cvref_t<invoke_result_t<_Fp&, range_reference_t<_Base>>>;
using difference_type = range_difference_t<_Base>;
- _Iterator() = default;
+ _Iterator() requires default_initializable<_Base_iter> = default;
constexpr
_Iterator(_Parent* __parent, _Base_iter __current)
_Vp _M_base = _Vp();
public:
- transform_view() = default;
+ transform_view() requires (default_initializable<_Vp>
+ && default_initializable<_Fp>)
+ = default;
constexpr
transform_view(_Vp __base, _Fp __fun)
_Vp _M_base = _Vp();
public:
- take_view() = default;
+ take_view() requires default_initializable<_Vp> = default;
constexpr
take_view(_Vp base, range_difference_t<_Vp> __count)
_Vp _M_base = _Vp();
public:
- take_while_view() = default;
+ take_while_view() requires (default_initializable<_Vp>
+ && default_initializable<_Pred>)
+ = default;
constexpr
take_while_view(_Vp base, _Pred __pred)
_M_cached_begin;
public:
- drop_view() = default;
+ drop_view() requires default_initializable<_Vp> = default;
constexpr
drop_view(_Vp __base, range_difference_t<_Vp> __count)
_Vp _M_base = _Vp();
public:
- drop_while_view() = default;
+ drop_while_view() requires (default_initializable<_Vp>
+ && default_initializable<_Pred>)
+ = default;
constexpr
drop_while_view(_Vp __base, _Pred __pred)
= common_type_t<range_difference_t<_Base>,
range_difference_t<range_reference_t<_Base>>>;
- _Iterator() = default;
+ _Iterator() requires (default_initializable<_Outer_iter>
+ && default_initializable<_Inner_iter>)
+ = default;
constexpr
_Iterator(_Parent* __parent, _Outer_iter __outer)
_Vp _M_base = _Vp();
public:
- join_view() = default;
+ join_view() requires default_initializable<_Vp> = default;
constexpr explicit
join_view(_Vp __base)
if constexpr (forward_range<_Vp>)
return _M_current;
else
- return _M_parent->_M_current;
+ return *_M_parent->_M_current;
}
constexpr auto&
if constexpr (forward_range<_Vp>)
return _M_current;
else
- return _M_parent->_M_current;
+ return *_M_parent->_M_current;
}
_Parent* _M_parent = nullptr;
// XXX: _M_current is "present only if !forward_range<V>"
[[no_unique_address]]
__detail::__maybe_present_t<!forward_range<_Vp>,
- iterator_t<_Vp>> _M_current;
+ __detail::__non_propagating_cache<iterator_t<_Vp>>> _M_current;
_Vp _M_base = _Vp();
public:
- split_view() = default;
+ split_view() requires (default_initializable<_Vp>
+ && default_initializable<_Pattern>)
+ = default;
constexpr
split_view(_Vp __base, _Pattern __pattern)
_Vp _M_base = _Vp();
public:
- common_view() = default;
+ common_view() requires default_initializable<_Vp> = default;
constexpr explicit
common_view(_Vp __r)
_Vp _M_base = _Vp();
public:
- reverse_view() = default;
+ reverse_view() requires default_initializable<_Vp> = default;
constexpr explicit
reverse_view(_Vp __r)
class elements_view : public view_interface<elements_view<_Vp, _Nm>>
{
public:
- elements_view() = default;
+ elements_view() requires default_initializable<_Vp> = default;
constexpr explicit
elements_view(_Vp base)
= remove_cvref_t<tuple_element_t<_Nm, range_value_t<_Base>>>;
using difference_type = range_difference_t<_Base>;
- _Iterator() = default;
+ _Iterator() requires default_initializable<iterator_t<_Base>> = default;
constexpr explicit
_Iterator(iterator_t<_Base> current)
// Opt-in to view concept
template<typename _ElementType, size_t _Extent>
inline constexpr bool
- enable_view<span<_ElementType, _Extent>>
- = _Extent == 0 || _Extent == dynamic_extent;
+ enable_view<span<_ElementType, _Extent>> = true;
}
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#define __cpp_lib_optional 202106L
#define __cpp_lib_polymorphic_allocator 201902L
#if __cpp_lib_concepts
-# define __cpp_lib_ranges 201911L
+# define __cpp_lib_ranges 202106L
#endif
#if __cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE
# define __cpp_lib_semaphore 201907L
}
static_assert(test01());
-template<bool make_semiregular>
+template<bool make_copyable>
struct A {
- A() requires make_semiregular;
+ A(const A&) = default;
+ A& operator=(const A&) requires make_copyable;
A(int, int);
A(std::initializer_list<int>) = delete;
};
test02()
{
// PR libstdc++/100475
- static_assert(std::
semiregular<A<true>>);
+ static_assert(std::
copyable<A<true>>);
__box<A<true>> x2(std::in_place, 0, 0);
- static_assert(!std::
semiregular<A<false>>);
+ static_assert(!std::
copyable<A<false>>);
__box<A<false>> x1(std::in_place, 0, 0);
}
+
+constexpr bool
+test03()
+{
+ // Verify correctness of the non-defaulted operator= for the partial
+ // specialization of __box.
+ struct B {
+ constexpr B(int* p) : p(p) { }
+ constexpr ~B() { ++*p; };
+ B(const B&) = default;
+ B& operator=(const B&) = delete;
+ int* p;
+ };
+ static_assert(!std::copyable<B>);
+ static_assert(std::is_nothrow_copy_constructible_v<B>);
+ static_assert(sizeof(__box<B>) == sizeof(B));
+
+ int m = 0;
+ __box<B> x(std::in_place, &m);
+ __glibcxx_assert(m == 0);
+ x = x;
+ __glibcxx_assert(m == 0);
+ x = std::move(x);
+ __glibcxx_assert(m == 0);
+
+ int n = 0;
+ __box<B> y(std::in_place, &n);
+ auto z = x;
+ x = y;
+ __glibcxx_assert(m == 1);
+ __glibcxx_assert(n == 0);
+ __glibcxx_assert(x->p == &n);
+ __glibcxx_assert(y->p == &n);
+ y = std::move(z);
+ __glibcxx_assert(m == 1);
+ __glibcxx_assert(n == 1);
+ __glibcxx_assert(y->p == &m);
+ __glibcxx_assert(z->p == &m);
+
+ return true;
+}
+static_assert(test03());
--- /dev/null
+// { dg-options "-std=gnu++20" }
+// { dg-do compile { target c++20 } }
+// P2325R3 "Views should not be required to be default constructible"
+
+// Parts of P2325R3 are deliberately omitted in libstdc++ 11, in particular the
+// removal of default ctors for back_/front_insert_iterator, ostream_iterator,
+// ref_view and basic_istream_view/::iterator, so as to maximize backward
+// compatibility with pre-P2325R3 code. So most static_asserts in this test fail,
+// see the xfails at the end of this file.
+
+#include <ranges>
+#include <iterator>
+#include <span>
+#include <sstream>
+#include <vector>
+#include <testsuite_iterators.h>
+
+using namespace std;
+
+template<default_initializable T> void f();
+template<typename T> requires weakly_incrementable<T> || ranges::view<T> void f();
+
+void
+test01()
+{
+ // Verify neither std::weakly_incrementable nor ranges::view require
+ // default_initializable.
+ f<int>(); // { dg-error "ambiguous" }
+}
+
+void
+test02()
+{
+ // Verify these iterators are not default constructible.
+ static_assert(!default_initializable<insert_iterator<vector<int>>>);
+ static_assert(!default_initializable<front_insert_iterator<vector<int>>>);
+ static_assert(!default_initializable<back_insert_iterator<vector<int>>>);
+ static_assert(!default_initializable<ostream_iterator<int>>);
+
+ using iter = ostream_iterator<int>;
+
+ // Verify common_iterator is conditionally default constructible.
+ static_assert(!default_initializable<common_iterator<iter, unreachable_sentinel_t>>);
+ static_assert(default_initializable<common_iterator<int*, unreachable_sentinel_t>>);
+
+ // Verify counted_iterator is conditionally default constructible.
+ static_assert(!default_initializable<counted_iterator<iter>>);
+ static_assert(default_initializable<counted_iterator<int*>>);
+}
+
+void
+test03()
+{
+ using iter = ostream_iterator<int>;
+
+ // Verify iota_view is conditionally default constructible.
+ static_assert(!default_initializable<ranges::iota_view<iter>>);
+ static_assert(!default_initializable<decltype(declval<ranges::iota_view<iter>>().begin())>);
+ static_assert(default_initializable<ranges::iota_view<int>>);
+ static_assert(default_initializable<decltype(declval<ranges::iota_view<int>>().begin())>);
+
+ // Verify subrange is conditionally default constructible.
+ static_assert(!default_initializable<ranges::subrange<iter, unreachable_sentinel_t>>);
+ static_assert(default_initializable<ranges::subrange<int*, unreachable_sentinel_t>>);
+
+ // Verify single_view is conditionally default constructible.
+ static_assert(!default_initializable<ranges::single_view<iter>>);
+ static_assert(default_initializable<ranges::single_view<int*>>);
+}
+
+void
+test04()
+{
+ // Verify basic_istream_view is not default constructible.
+ using type = ranges::basic_istream_view<int, char, char_traits<char>>;
+ static_assert(!default_initializable<type>);
+ static_assert(!default_initializable<decltype(declval<type>().begin())>);
+}
+
+void
+test05()
+{
+ // Verify ref_view is not default constructible.
+ static_assert(!default_initializable<ranges::ref_view<int[5]>>);
+}
+
+template<auto adaptor>
+void
+test06()
+{
+ auto f1 = [] (auto) { return true; };
+ auto f2 = [i=0] (auto) { return true; };
+ static_assert(default_initializable<decltype(views::single(0) | adaptor(f1))>);
+ static_assert(!default_initializable<decltype(views::single(0) | adaptor(f2))>);
+
+ struct S { S() = delete; };
+ static_assert(!default_initializable<decltype(views::single(declval<S>()) | adaptor(f1))>);
+ static_assert(!default_initializable<decltype(views::single(declval<S>()) | adaptor(f2))>);
+}
+
+// Verify filter_view, transform_view, take_while_view and drop_while_view are
+// conditionally default constructible.
+template void test06<views::filter>();
+template void test06<views::transform>();
+template void test06<views::take_while>();
+template void test06<views::drop_while>();
+
+void
+test07()
+{
+ // Verify join_view is conditionally default constructible.
+ struct S { S() = delete; };
+ using type1 = ranges::join_view<ranges::single_view<ranges::single_view<S>>>;
+ static_assert(!default_initializable<type1>);
+ using type2 = ranges::join_view<ranges::single_view<ranges::single_view<int>>>;
+ static_assert(default_initializable<type2>);
+}
+
+void
+test08()
+{
+ // Verify split_view is conditionally default constructible.
+ using type1 = ranges::split_view<ranges::ref_view<int[2]>, ranges::single_view<int>>;
+ static_assert(!default_initializable<type1>);
+ using type2 = ranges::split_view<ranges::single_view<int>, ranges::ref_view<int[2]>>;
+ static_assert(!default_initializable<type2>);
+ using type3 = ranges::split_view<ranges::ref_view<int[2]>, ranges::ref_view<int[2]>>;
+ static_assert(!default_initializable<type3>);
+ using type4 = ranges::split_view<ranges::single_view<int>, ranges::single_view<int>>;
+ static_assert(default_initializable<type4>);
+}
+
+void
+test09()
+{
+ // Verify common_view is conditionally default constructible.
+ using type1 = ranges::common_view<ranges::iota_view<ostream_iterator<int>>>;
+ static_assert(!default_initializable<type1>);
+ using type2 = ranges::common_view<ranges::iota_view<int*>>;
+ static_assert(default_initializable<type2>);
+}
+
+void
+test10()
+{
+ // Verify reverse_view is conditionally default constructible.
+ using type1 = ranges::reverse_view<ranges::ref_view<int[2]>>;
+ static_assert(!default_initializable<type1>);
+ using type2 = ranges::reverse_view<ranges::single_view<int>>;
+ static_assert(default_initializable<type2>);
+}
+
+void
+test11()
+{
+ // Verify elements_view is conditionally default constructible.
+ using type1 = ranges::elements_view<ranges::ref_view<pair<int,int>[2]>, 0>;
+ static_assert(!default_initializable<type1>);
+ using type2 = ranges::elements_view<ranges::single_view<pair<int,int>>, 0>;
+ static_assert(default_initializable<type2>);
+}
+
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 35 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 36 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 37 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 38 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 43 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 47 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 57 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 58 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 63 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 67 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 76 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 77 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 84 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 124 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 126 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 128 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 138 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 148 }
+// { dg-bogus "static assertion failed" "" { xfail *-*-* } 158 }
std::as_const(s).data();
}
+void
+test06()
+{
+ // PR libstdc++/100475 comment #7
+ struct S {
+ S() = default;
+ S(std::initializer_list<S>) = delete;
+ S(const S&) {}
+ };
+ S obj;
+ auto x = std::views::single(obj);
+ auto y = std::views::single(std::move(obj));
+}
+
int main()
{
test01();
test02();
test03();
test04();
+ test06();
}
static_assert(std::ranges::view<std::span<int>>);
static_assert(std::ranges::view<std::span<int, 0>>);
-static_assert(!std::ranges::view<std::span<int, 1>>);
+static_assert(std::ranges::view<std::span<int, 1>>); // Changed with P2325R3
static_assert(std::ranges::view<std::string_view>);
static_assert(std::ranges::view<std::experimental::string_view>);
projects / people / ms / gcc.git / commitdiff
