From 4a6f3676e7dd9e73a822f4da634b037299f0d482 Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Thu, 17 Aug 2023 12:40:04 -0400
Subject: [PATCH] libstdc++: Convert _RangeAdaptorClosure into a CRTP base
[PR108827]
Using the CRTP idiom for this base class avoids bloating the size of a
pipeline when adding distinct empty range adaptor closure objects to it,
as detailed in section 4.1 of P2387R3.
But it means we can no longer define its operator| overloads as hidden
friends, since it'd mean each instantiation of _RangeAdaptorClosure
introduces its own distinct set of hidden friends. So e.g. for the
outer | in
x | (views::reverse | views::join)
ADL would find 6 distinct hidden operator| friends:
two from _RangeAdaptorClosure<_Reverse>
two from _RangeAdaptorClosure<_Join>
two from _RangeAdaptorClosure<_Pipe<_Reverse, _Join>>
but we really only want to consider the last two.
We avoid this issue by instead defining the operator| overloads at
namespace scope alongside _RangeAdaptorClosure. This should be fine
because the only types defined in this namespace are _RangeAdaptorClosure,
_RangeAdaptor, _Pipe and _Partial, so we don't have to worry about
unintentional ADL.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/108827
libstdc++-v3/ChangeLog:
* include/std/ranges (__adaptor::_RangeAdaptorClosure):
Convert into a CRTP class template. Move hidden operator|
friends into namespace scope and adjust their constraints.
(__closure::__is_range_adaptor_closure_fn): Define.
(__closure::__is_range_adaptor_closure): Define.
(__adaptor::_Partial): Adjust use of _RangeAdaptorClosure.
(__adaptor::_Pipe): Likewise.
(views::_All): Likewise.
(views::_Join): Likewise.
(views::_Common): Likewise.
(views::_Reverse): Likewise.
(views::_Elements): Likewise.
(views::_Adjacent): Likewise.
(views::_AsRvalue): Likewise.
(views::_Enumerate): Likewise.
(views::_AsConst): Likewise.
* testsuite/std/ranges/adaptors/all.cc: Reinstate assertion
expecting that adding empty range adaptor closure objects to a
pipeline doesn't increase the size of a pipeline.
---
libstdc++-v3/include/std/ranges | 80 +++++++++++--------
.../testsuite/std/ranges/adaptors/all.cc | 7 --
2 files changed, 45 insertions(+), 42 deletions(-)
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index fb4a6a8b9d7d..ffa3e97ef944 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -892,25 +892,35 @@ namespace views::__adaptor
// The derived class should define the optional static data member
// _S_has_simple_call_op to true if the behavior of this adaptor is
// independent of the constness/value category of the adaptor object.
- struct _RangeAdaptorClosure
- {
- // range | adaptor is equivalent to adaptor(range).
- template<typename _Self, typename _Range>
- requires derived_from<remove_cvref_t<_Self>, _RangeAdaptorClosure>
- && __adaptor_invocable<_Self, _Range>
- friend constexpr auto
- operator|(_Range&& __r, _Self&& __self)
- { return std::forward<_Self>(__self)(std::forward<_Range>(__r)); }
-
- // Compose the adaptors __lhs and __rhs into a pipeline, returning
- // another range adaptor closure object.
- template<typename _Lhs, typename _Rhs>
- requires derived_from<_Lhs, _RangeAdaptorClosure>
- && derived_from<_Rhs, _RangeAdaptorClosure>
- friend constexpr auto
- operator|(_Lhs __lhs, _Rhs __rhs)
- { return _Pipe<_Lhs, _Rhs>{std::move(__lhs), std::move(__rhs)}; }
- };
+ template<typename _Derived>
+ struct _RangeAdaptorClosure
+ { };
+
+ template<typename _Tp, typename _Up>
+ requires (!same_as<_Tp, _RangeAdaptorClosure<_Up>>)
+ void __is_range_adaptor_closure_fn
+ (const _Tp&, const _RangeAdaptorClosure<_Up>&); // not defined
+
+ template<typename _Tp>
+ concept __is_range_adaptor_closure
+ = requires (_Tp __t) { __adaptor::__is_range_adaptor_closure_fn(__t, __t); };
+
+ // range | adaptor is equivalent to adaptor(range).
+ template<typename _Self, typename _Range>
+ requires __is_range_adaptor_closure<_Self>
+ && __adaptor_invocable<_Self, _Range>
+ constexpr auto
+ operator|(_Range&& __r, _Self&& __self)
+ { return std::forward<_Self>(__self)(std::forward<_Range>(__r)); }
+
+ // Compose the adaptors __lhs and __rhs into a pipeline, returning
+ // another range adaptor closure object.
+ template<typename _Lhs, typename _Rhs>
+ requires __is_range_adaptor_closure<_Lhs>
+ && __is_range_adaptor_closure<_Rhs>
+ constexpr auto
+ operator|(_Lhs __lhs, _Rhs __rhs)
+ { return _Pipe<_Lhs, _Rhs>{std::move(__lhs), std::move(__rhs)}; }
// The base class of every range adaptor non-closure.
//
@@ -952,7 +962,7 @@ namespace views::__adaptor
// A range adaptor closure that represents partial application of
// the range adaptor _Adaptor with arguments _Args.
template<typename _Adaptor, typename... _Args>
- struct _Partial : _RangeAdaptorClosure
+ struct _Partial : _RangeAdaptorClosure<_Partial<_Adaptor, _Args...>>
{
tuple<_Args...> _M_args;
@@ -993,7 +1003,7 @@ namespace views::__adaptor
// A lightweight specialization of the above primary template for
// the common case where _Adaptor accepts a single extra argument.
template<typename _Adaptor, typename _Arg>
- struct _Partial<_Adaptor, _Arg> : _RangeAdaptorClosure
+ struct _Partial<_Adaptor, _Arg> : _RangeAdaptorClosure<_Partial<_Adaptor, _Arg>>
{
_Arg _M_arg;
@@ -1026,7 +1036,7 @@ namespace views::__adaptor
template<typename _Adaptor, typename... _Args>
requires __adaptor_has_simple_extra_args<_Adaptor, _Args...>
&& (is_trivially_copyable_v<_Args> && ...)
- struct _Partial<_Adaptor, _Args...> : _RangeAdaptorClosure
+ struct _Partial<_Adaptor, _Args...> : _RangeAdaptorClosure<_Partial<_Adaptor, _Args...>>
{
tuple<_Args...> _M_args;
@@ -1056,7 +1066,7 @@ namespace views::__adaptor
template<typename _Adaptor, typename _Arg>
requires __adaptor_has_simple_extra_args<_Adaptor, _Arg>
&& is_trivially_copyable_v<_Arg>
- struct _Partial<_Adaptor, _Arg> : _RangeAdaptorClosure
+ struct _Partial<_Adaptor, _Arg> : _RangeAdaptorClosure<_Partial<_Adaptor, _Arg>>
{
_Arg _M_arg;
@@ -1081,7 +1091,7 @@ namespace views::__adaptor
// A range adaptor closure that represents composition of the range
// adaptor closures _Lhs and _Rhs.
template<typename _Lhs, typename _Rhs>
- struct _Pipe : _RangeAdaptorClosure
+ struct _Pipe : _RangeAdaptorClosure<_Pipe<_Lhs, _Rhs>>
{
[[no_unique_address]] _Lhs _M_lhs;
[[no_unique_address]] _Rhs _M_rhs;
@@ -1117,7 +1127,7 @@ namespace views::__adaptor
template<typename _Lhs, typename _Rhs>
requires __closure_has_simple_call_op<_Lhs>
&& __closure_has_simple_call_op<_Rhs>
- struct _Pipe<_Lhs, _Rhs> : _RangeAdaptorClosure
+ struct _Pipe<_Lhs, _Rhs> : _RangeAdaptorClosure<_Pipe<_Lhs, _Rhs>>
{
[[no_unique_address]] _Lhs _M_lhs;
[[no_unique_address]] _Rhs _M_rhs;
@@ -1141,7 +1151,7 @@ namespace views::__adaptor
template<typename _Derived>
requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
class range_adaptor_closure
- : public views::__adaptor::_RangeAdaptorClosure
+ : public views::__adaptor::_RangeAdaptorClosure<_Derived>
{ };
#endif
@@ -1287,7 +1297,7 @@ namespace views::__adaptor
concept __can_owning_view = requires { owning_view{std::declval<_Range>()}; };
} // namespace __detail
- struct _All : __adaptor::_RangeAdaptorClosure
+ struct _All : __adaptor::_RangeAdaptorClosure<_All>
{
template<typename _Range>
static constexpr bool
@@ -3071,7 +3081,7 @@ namespace views::__adaptor
= requires { join_view<all_t<_Range>>{std::declval<_Range>()}; };
} // namespace __detail
- struct _Join : __adaptor::_RangeAdaptorClosure
+ struct _Join : __adaptor::_RangeAdaptorClosure<_Join>
{
template<viewable_range _Range>
requires __detail::__can_join_view<_Range>
@@ -3865,7 +3875,7 @@ namespace views::__adaptor
= requires { common_view{std::declval<_Range>()}; };
} // namespace __detail
- struct _Common : __adaptor::_RangeAdaptorClosure
+ struct _Common : __adaptor::_RangeAdaptorClosure<_Common>
{
template<viewable_range _Range>
requires __detail::__already_common<_Range>
@@ -3986,7 +3996,7 @@ namespace views::__adaptor
= requires { reverse_view{std::declval<_Range>()}; };
} // namespace __detail
- struct _Reverse : __adaptor::_RangeAdaptorClosure
+ struct _Reverse : __adaptor::_RangeAdaptorClosure<_Reverse>
{
template<viewable_range _Range>
requires __detail::__is_reverse_view<remove_cvref_t<_Range>>
@@ -4386,7 +4396,7 @@ namespace views::__adaptor
} // namespace __detail
template<size_t _Nm>
- struct _Elements : __adaptor::_RangeAdaptorClosure
+ struct _Elements : __adaptor::_RangeAdaptorClosure<_Elements<_Nm>>
{
template<viewable_range _Range>
requires __detail::__can_elements_view<_Nm, _Range>
@@ -5504,7 +5514,7 @@ namespace views::__adaptor
}
template<size_t _Nm>
- struct _Adjacent : __adaptor::_RangeAdaptorClosure
+ struct _Adjacent : __adaptor::_RangeAdaptorClosure<_Adjacent<_Nm>>
{
template<viewable_range _Range>
requires (_Nm == 0) || __detail::__can_adjacent_view<_Nm, _Range>
@@ -8629,7 +8639,7 @@ namespace views::__adaptor
concept __can_as_rvalue_view = requires { as_rvalue_view(std::declval<_Tp>()); };
}
- struct _AsRvalue : __adaptor::_RangeAdaptorClosure
+ struct _AsRvalue : __adaptor::_RangeAdaptorClosure<_AsRvalue>
{
template<viewable_range _Range>
requires __detail::__can_as_rvalue_view<_Range>
@@ -8938,7 +8948,7 @@ namespace views::__adaptor
= requires { enumerate_view<all_t<_Tp>>(std::declval<_Tp>()); };
}
- struct _Enumerate : __adaptor::_RangeAdaptorClosure
+ struct _Enumerate : __adaptor::_RangeAdaptorClosure<_Enumerate>
{
template<viewable_range _Range>
requires __detail::__can_enumerate_view<_Range>
@@ -9024,7 +9034,7 @@ namespace views::__adaptor
concept __can_as_const_view = requires { as_const_view(std::declval<_Range>()); };
}
- struct _AsConst : __adaptor::_RangeAdaptorClosure
+ struct _AsConst : __adaptor::_RangeAdaptorClosure<_AsConst>
{
template<viewable_range _Range>
constexpr auto
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc
index 57cb542174b1..6bbaf73a20a9 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc
@@ -105,12 +105,6 @@ static_assert(std::is_empty_v<decltype(views::common
| views::common
| views::keys
| views::reverse)>);
-#if 0
-// Adding empty range adaptor closure objects to a pipeline used to not
-// increase the size of the pipeline, but now that our range adaptor closure
-// objects derive from a common empty base class, [[no_unique_address]] can no
-// longer make two empty adjacent range adaptor closure objects occupy the same
-// data member address.
static_assert(sizeof(decltype(views::take(5) | views::drop(5)))
== sizeof(decltype(views::take(5)
| views::join
@@ -119,7 +113,6 @@ static_assert(sizeof(decltype(views::take(5) | views::drop(5)))
| views::keys
| views::drop(5)
| views::reverse)));
-#endif
template<auto all = views::all>
void
--
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