Tested on x86_64-pc-linux-gnu, does this look OK for trunk/14?
-- >8 --
This case was incorrectly failing in C++23 mode even after P2492R2
because the perfect forwarding simplification mechanism assumed bound
arguments are copy-constructible which is no longer necessarily true
after that paper. It'd be easy enough to fix the mechanism, but in
C++23 mode the mechanism is no longer useful since we can just rely on
deducing 'this' to implement perfect forwarding with a single overload
(and done in r14-7150-gd2cb4693a0b383). So this patch just disables
the mechanism in C++23 mode so that the generic implementation is always
used.
PR libstdc++/118413
libstdc++-v3/ChangeLog:
* include/std/ranges
(_GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING): New.
(__closure_has_simple_call_op): Only define in C++20 mode.
(__closure_has_simple_extra_args): Likewise.
(_Partial, _Pipe): Likewise, for the "simple" partial
specializations.
(*::_S_has_simple_call_op): Likewise.
(*::_S_has_simple_extra_args): Likewise.
* testsuite/std/ranges/adaptors/100577.cc: Disable some
implementation detail checks in C++23 mode.
* testsuite/std/ranges/adaptors/transform.cc (test09): Also test
partially applying the move-only function.
---
libstdc++-v3/include/std/ranges | 53 +++++++++++++++++++
.../testsuite/std/ranges/adaptors/100577.cc | 4 +-
.../std/ranges/adaptors/transform.cc | 2 +
3 files changed, 58 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index ad69a94b21f..a2b8748bea6 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -1028,6 +1028,16 @@ namespace views::__adaptor
}
};
+#if __cplusplus <= 202003L
+ // In C++20 mode we simplify perfect forwarding of a range adaptor closure's
+ // bound arguments when possible (according to their types), for sake of
compile
+ // times and diagnostic quality. In C++23 mode we instead rely on deducing
'this'
+ // to idiomatically implement perfect forwarding. Note that this means the
+ // simplification logic doesn't consider C++23 <ranges> changes such as
P2492R2.
+# define _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING 1
+#endif
+
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
// True if the range adaptor closure _Adaptor has a simple operator(), i.e.
// one that's not overloaded according to constness or value category of the
// _Adaptor object.
@@ -1039,6 +1049,7 @@ namespace views::__adaptor
template<typename _Adaptor, typename... _Args>
concept __adaptor_has_simple_extra_args =
_Adaptor::_S_has_simple_extra_args
|| _Adaptor::template _S_has_simple_extra_args<_Args...>;
+#endif
// A range adaptor closure that represents partial application of
// the range adaptor _Adaptor with arguments _Args.
@@ -1139,6 +1150,7 @@ namespace views::__adaptor
#endif
};
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
// Partial specialization of the primary template for the case where the
extra
// arguments of the adaptor can always be safely and efficiently forwarded by
// const reference. This lets us get away with a single operator() overload,
@@ -1195,6 +1207,7 @@ namespace views::__adaptor
static constexpr bool _S_has_simple_call_op = true;
};
+#endif // _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
template<typename _Lhs, typename _Rhs, typename _Range>
concept __pipe_invocable
@@ -1245,6 +1258,7 @@ namespace views::__adaptor
#endif
};
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
// A partial specialization of the above primary template for the case where
// both adaptor operands have a simple operator(). This in turn lets us
// implement composition using a single simple operator(), which makes
@@ -1271,6 +1285,7 @@ namespace views::__adaptor
static constexpr bool _S_has_simple_call_op = true;
};
+#endif // _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
} // namespace views::__adaptor
#if __cpp_lib_ranges >= 202202L
@@ -1454,7 +1469,9 @@ namespace views::__adaptor
return owning_view{std::forward<_Range>(__r)};
}
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_call_op = true;
+#endif
};
inline constexpr _All all;
@@ -1872,7 +1889,9 @@ namespace views::__adaptor
using _RangeAdaptor<_Filter>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _Filter filter;
@@ -2260,7 +2279,9 @@ namespace views::__adaptor
using _RangeAdaptor<_Transform>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _Transform transform;
@@ -2494,12 +2515,14 @@ namespace views::__adaptor
using _RangeAdaptor<_Take>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
// The count argument of views::take is not always simple -- it can be
// e.g. a move-only class that's implicitly convertible to the difference
// type. But an integer-like count argument is surely simple.
template<typename _Tp>
static constexpr bool _S_has_simple_extra_args
= ranges::__detail::__is_integer_like<_Tp>;
+#endif
};
inline constexpr _Take take;
@@ -2621,7 +2644,9 @@ namespace views::__adaptor
using _RangeAdaptor<_TakeWhile>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _TakeWhile take_while;
@@ -2777,9 +2802,11 @@ namespace views::__adaptor
using _RangeAdaptor<_Drop>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
template<typename _Tp>
static constexpr bool _S_has_simple_extra_args
= _Take::_S_has_simple_extra_args<_Tp>;
+#endif
};
inline constexpr _Drop drop;
@@ -2866,7 +2893,9 @@ namespace views::__adaptor
using _RangeAdaptor<_DropWhile>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _DropWhile drop_while;
@@ -3273,7 +3302,9 @@ namespace views::__adaptor
return join_view<all_t<_Range>>{std::forward<_Range>(__r)};
}
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_call_op = true;
+#endif
};
inline constexpr _Join join;
@@ -3730,6 +3761,7 @@ namespace views::__adaptor
using _RangeAdaptor<_LazySplit>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
// The pattern argument of views::lazy_split is not always simple -- it
can be
// a non-view range, the value category of which affects whether the call
// is well-formed. But a scalar or a view pattern argument is surely
@@ -3738,6 +3770,7 @@ namespace views::__adaptor
static constexpr bool _S_has_simple_extra_args
= is_scalar_v<_Pattern> || (view<_Pattern>
&& copy_constructible<_Pattern>);
+#endif
};
inline constexpr _LazySplit lazy_split;
@@ -3937,9 +3970,11 @@ namespace views::__adaptor
using _RangeAdaptor<_Split>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
template<typename _Pattern>
static constexpr bool _S_has_simple_extra_args
= _LazySplit::_S_has_simple_extra_args<_Pattern>;
+#endif
};
inline constexpr _Split split;
@@ -4074,7 +4109,9 @@ namespace views::__adaptor
return common_view{std::forward<_Range>(__r)};
}
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_call_op = true;
+#endif
};
inline constexpr _Common common;
@@ -4207,7 +4244,9 @@ namespace views::__adaptor
return reverse_view{std::forward<_Range>(__r)};
}
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_call_op = true;
+#endif
};
inline constexpr _Reverse reverse;
@@ -4598,7 +4637,9 @@ namespace views::__adaptor
return elements_view<all_t<_Range>, _Nm>{std::forward<_Range>(__r)};
}
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_call_op = true;
+#endif
};
template<size_t _Nm>
@@ -6061,7 +6102,9 @@ namespace views::__adaptor
using __adaptor::_RangeAdaptor<_AdjacentTransform>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
template<size_t _Nm>
@@ -6617,7 +6660,9 @@ namespace views::__adaptor
using __adaptor::_RangeAdaptor<_Chunk>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _Chunk chunk;
@@ -6992,7 +7037,9 @@ namespace views::__adaptor
using __adaptor::_RangeAdaptor<_Slide>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _Slide slide;
@@ -7187,7 +7234,9 @@ namespace views::__adaptor
using __adaptor::_RangeAdaptor<_ChunkBy>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _ChunkBy chunk_by;
@@ -7715,9 +7764,11 @@ namespace views::__adaptor
using _RangeAdaptor<_JoinWith>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
template<typename _Pattern>
static constexpr bool _S_has_simple_extra_args
= _LazySplit::_S_has_simple_extra_args<_Pattern>;
+#endif
};
inline constexpr _JoinWith join_with;
@@ -8333,7 +8384,9 @@ namespace views::__adaptor
using __adaptor::_RangeAdaptor<_Stride>::operator();
static constexpr int _S_arity = 2;
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
static constexpr bool _S_has_simple_extra_args = true;
+#endif
};
inline constexpr _Stride stride;
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
index 53c81be7f02..eaa8454b318 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
@@ -31,6 +31,7 @@ namespace views = std::ranges::views;
void
test01()
{
+#ifdef _GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING
// Verify adaptors are deemed to have simple extra arguments when
appropriate.
using views::__adaptor::__adaptor_has_simple_extra_args;
using std::identity;
@@ -78,6 +79,7 @@ test01()
static_assert(!__closure_has_simple_call_op<decltype(a12a | a00)>);
static_assert(!__closure_has_simple_call_op<decltype(a00 | a12a)>);
#endif
+#endif
}
void
@@ -135,7 +137,7 @@ test03()
void
test04()
{
-#if __STDC_HOSTED__
+#if defined(_GLIBCXX_RANGES_SIMPLIFY_ADAPTOR_FORWARDING) && __STDC_HOSTED__
// Non-trivially-copyable extra arguments make a closure not simple.
using F = std::function<bool(bool)>;
static_assert(!std::is_trivially_copyable_v<F>);
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
index dfc91fb5e1f..934d2f65dcf 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
@@ -191,8 +191,10 @@ test09()
#if __cpp_lib_ranges >= 202207L
// P2494R2 Relaxing range adaptors to allow for move only types
static_assert( requires { transform(x, move_only{}); } );
+ static_assert( requires { x | transform(move_only{}); } ); // PR
libstdc++/118413
#else
static_assert( ! requires { transform(x, move_only{}); } );
+ static_assert( ! requires { x | transform(move_only{}); } );
#endif
}
--
2.48.1.91.g5f8f7081f7
