On 04/08/21 12:55 +0100, Jonathan Wakely wrote:
This adds [[nodiscard]] throughout <iterator>, as proposed by P2377R0
(with some minor corrections).
The attribute is added for all modes from C++11 up, using
[[__nodiscard__]] or _GLIBCXX_NODISCARD where C++17 [[nodiscard]] can't
be used directly.
This change causes errors when -fconcepts-ts is used. Fixed like so.
Tested powerpc64le-linux, committed to trunk.
commit 7b1de3eb9ed3f8dde54732d88520292c5ad1157d
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Thu Aug 5 13:34:00 2021
libstdc++: Move attributes that follow requires-clauses [PR101782]
As explained in the PR, the grammar in the Concepts TS means that a [
token following a requires-clause is parsed as part of the
logical-or-expression rather than the start of an attribute. That makes
the following ill-formed when using -fconcepts-ts:
template<typename T> requires foo<T> [[nodiscard]] int f(T);
This change moves all attributes that follow a requires-clause to the
end of the function declarator.
Signed-off-by: Jonathan Wakely <jwak...@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/101782
* include/bits/ranges_base.h (ranges::begin, ranges::end)
(ranges::rbegin, ranges::rend, ranges::size, ranges::ssize)
(ranges::empty, ranges::data): Move attribute to the end of
the declarator.
* include/bits/stl_iterator.h (__gnu_cxx::__normal_iterator)
(common_iterator): Likewise for non-member operator functions.
* include/std/ranges (views::all, views::filter)
(views::transform, views::take, views::take_while, views::drop)
(views::drop_while, views::join, views::lazy_split)
(views::split, views::counted, views::common, views::reverse)
(views::elements): Likewise.
* testsuite/std/ranges/access/101782.cc: New test.
diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h
index 614b6edf9df..1dac9680b4f 100644
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -110,9 +110,9 @@ namespace ranges
template<__maybe_borrowed_range _Tp>
requires is_array_v<remove_reference_t<_Tp>> || __member_begin<_Tp>
|| __adl_begin<_Tp>
- [[nodiscard]]
constexpr auto
operator()(_Tp&& __t) const noexcept(_S_noexcept<_Tp&>())
+ [[nodiscard]]
{
if constexpr (is_array_v<remove_reference_t<_Tp>>)
{
@@ -162,9 +162,9 @@ namespace ranges
template<__maybe_borrowed_range _Tp>
requires is_bounded_array_v<remove_reference_t<_Tp>>
|| __member_end<_Tp> || __adl_end<_Tp>
- [[nodiscard]]
constexpr auto
operator()(_Tp&& __t) const noexcept(_S_noexcept<_Tp&>())
+ [[nodiscard]]
{
if constexpr (is_bounded_array_v<remove_reference_t<_Tp>>)
{
@@ -267,10 +267,10 @@ namespace ranges
public:
template<__maybe_borrowed_range _Tp>
requires __member_rbegin<_Tp> || __adl_rbegin<_Tp> || __reversable<_Tp>
- [[nodiscard]]
constexpr auto
operator()(_Tp&& __t) const
noexcept(_S_noexcept<_Tp&>())
+ [[nodiscard]]
{
if constexpr (__member_rbegin<_Tp>)
return __t.rbegin();
@@ -326,10 +326,10 @@ namespace ranges
public:
template<__maybe_borrowed_range _Tp>
requires __member_rend<_Tp> || __adl_rend<_Tp> || __reversable<_Tp>
- [[nodiscard]]
constexpr auto
operator()(_Tp&& __t) const
noexcept(_S_noexcept<_Tp&>())
+ [[nodiscard]]
{
if constexpr (__member_rend<_Tp>)
return __t.rend();
@@ -416,9 +416,9 @@ namespace ranges
template<typename _Tp>
requires is_bounded_array_v<remove_reference_t<_Tp>>
|| __member_size<_Tp> || __adl_size<_Tp> || __sentinel_size<_Tp>
- [[nodiscard]]
constexpr auto
operator()(_Tp&& __t) const noexcept(_S_noexcept<_Tp&>())
+ [[nodiscard]]
{
if constexpr (is_bounded_array_v<remove_reference_t<_Tp>>)
return extent_v<remove_reference_t<_Tp>>;
@@ -437,9 +437,9 @@ namespace ranges
// 3403. Domain of ranges::ssize(E) doesn't match ranges::size(E)
template<typename _Tp>
requires requires (_Tp& __t) { _Size{}(__t); }
- [[nodiscard]]
constexpr auto
operator()(_Tp&& __t) const noexcept(noexcept(_Size{}(__t)))
+ [[nodiscard]]
{
auto __size = _Size{}(__t);
using __size_type = decltype(__size);
@@ -497,9 +497,9 @@ namespace ranges
template<typename _Tp>
requires __member_empty<_Tp> || __size0_empty<_Tp>
|| __eq_iter_empty<_Tp>
- [[nodiscard]]
constexpr bool
operator()(_Tp&& __t) const noexcept(_S_noexcept<_Tp&>())
+ [[nodiscard]]
{
if constexpr (__member_empty<_Tp>)
return bool(__t.empty());
@@ -539,9 +539,9 @@ namespace ranges
public:
template<__maybe_borrowed_range _Tp>
requires __member_data<_Tp> || __begin_data<_Tp>
- [[nodiscard]]
constexpr auto
operator()(_Tp&& __t) const noexcept(_S_noexcept<_Tp>())
+ [[nodiscard]]
{
if constexpr (__member_data<_Tp>)
return __t.data();
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index 3773d600b8f..053ae41e9c3 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -1120,19 +1120,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _IteratorL, typename _IteratorR, typename _Container>
requires requires (_IteratorL __lhs, _IteratorR __rhs)
{ { __lhs == __rhs } -> std::convertible_to<bool>; }
- [[nodiscard]]
constexpr bool
operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
noexcept(noexcept(__lhs.base() == __rhs.base()))
+ [[nodiscard]]
{ return __lhs.base() == __rhs.base(); }
template<typename _IteratorL, typename _IteratorR, typename _Container>
- [[nodiscard]]
constexpr std::__detail::__synth3way_t<_IteratorR, _IteratorL>
operator<=>(const __normal_iterator<_IteratorL, _Container>& __lhs,
const __normal_iterator<_IteratorR, _Container>& __rhs)
noexcept(noexcept(std::__detail::__synth3way(__lhs.base(), __rhs.base())))
+ [[nodiscard]]
{ return std::__detail::__synth3way(__lhs.base(), __rhs.base()); }
#else
// Forward iterator requirements
@@ -1984,10 +1984,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _It2, sentinel_for<_It> _Sent2>
requires sentinel_for<_Sent, _It2>
- [[nodiscard]]
friend bool
operator==(const common_iterator& __x,
const common_iterator<_It2, _Sent2>& __y)
+ [[nodiscard]]
{
switch(__x._M_index << 2 | __y._M_index)
{
@@ -2007,10 +2007,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _It2, sentinel_for<_It> _Sent2>
requires sentinel_for<_Sent, _It2> && equality_comparable_with<_It, _It2>
- [[nodiscard]]
friend bool
operator==(const common_iterator& __x,
const common_iterator<_It2, _Sent2>& __y)
+ [[nodiscard]]
{
switch(__x._M_index << 2 | __y._M_index)
{
@@ -2031,10 +2031,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<sized_sentinel_for<_It> _It2, sized_sentinel_for<_It> _Sent2>
requires sized_sentinel_for<_Sent, _It2>
- [[nodiscard]]
friend iter_difference_t<_It2>
operator-(const common_iterator& __x,
const common_iterator<_It2, _Sent2>& __y)
+ [[nodiscard]]
{
switch(__x._M_index << 2 | __y._M_index)
{
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 03a3778bb52..71b7dc7d295 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -1126,10 +1126,10 @@ namespace views::__adaptor
requires view<decay_t<_Range>>
|| __detail::__can_ref_view<_Range>
|| __detail::__can_subrange<_Range>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r) const
noexcept(_S_noexcept<_Range>())
+ [[nodiscard]]
{
if constexpr (view<decay_t<_Range>>)
return std::forward<_Range>(__r);
@@ -1553,9 +1553,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Pred>
requires __detail::__can_filter_view<_Range, _Pred>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Pred&& __p) const
+ [[nodiscard]]
{
return filter_view(std::forward<_Range>(__r), std::forward<_Pred>(__p));
}
@@ -1931,9 +1931,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Fp>
requires __detail::__can_transform_view<_Range, _Fp>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Fp&& __f) const
+ [[nodiscard]]
{
return transform_view(std::forward<_Range>(__r), std::forward<_Fp>(__f));
}
@@ -2113,9 +2113,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Tp>
requires __detail::__can_take_view<_Range, _Tp>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Tp&& __n) const
+ [[nodiscard]]
{
return take_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
}
@@ -2241,9 +2241,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Pred>
requires __detail::__can_take_while_view<_Range, _Pred>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Pred&& __p) const
+ [[nodiscard]]
{
return take_while_view(std::forward<_Range>(__r), std::forward<_Pred>(__p));
}
@@ -2362,9 +2362,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Tp>
requires __detail::__can_drop_view<_Range, _Tp>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Tp&& __n) const
+ [[nodiscard]]
{
return drop_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
}
@@ -2451,9 +2451,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Pred>
requires __detail::__can_drop_while_view<_Range, _Pred>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Pred&& __p) const
+ [[nodiscard]]
{
return drop_while_view(std::forward<_Range>(__r),
std::forward<_Pred>(__p));
@@ -2814,9 +2814,9 @@ namespace views::__adaptor
{
template<viewable_range _Range>
requires __detail::__can_join_view<_Range>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r) const
+ [[nodiscard]]
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3474. Nesting join_views is broken because of CTAD
@@ -3266,9 +3266,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Pattern>
requires __detail::__can_lazy_split_view<_Range, _Pattern>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Pattern&& __f) const
+ [[nodiscard]]
{
return lazy_split_view(std::forward<_Range>(__r), std::forward<_Pattern>(__f));
}
@@ -3475,9 +3475,9 @@ namespace views::__adaptor
{
template<viewable_range _Range, typename _Pattern>
requires __detail::__can_split_view<_Range, _Pattern>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r, _Pattern&& __f) const
+ [[nodiscard]]
{
return split_view(std::forward<_Range>(__r), std::forward<_Pattern>(__f));
}
@@ -3497,9 +3497,9 @@ namespace views::__adaptor
struct _Counted
{
template<input_or_output_iterator _Iter>
- [[nodiscard]]
constexpr auto
operator()(_Iter __i, iter_difference_t<_Iter> __n) const
+ [[nodiscard]]
{
if constexpr (random_access_iterator<_Iter>)
return subrange(__i, __i + __n);
@@ -3619,9 +3619,9 @@ namespace views::__adaptor
template<viewable_range _Range>
requires __detail::__already_common<_Range>
|| __detail::__can_common_view<_Range>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r) const
+ [[nodiscard]]
{
if constexpr (__detail::__already_common<_Range>)
return views::all(std::forward<_Range>(__r));
@@ -3742,9 +3742,9 @@ namespace views::__adaptor
requires __detail::__is_reverse_view<remove_cvref_t<_Range>>
|| __detail::__is_reversible_subrange<remove_cvref_t<_Range>>
|| __detail::__can_reverse_view<_Range>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r) const
+ [[nodiscard]]
{
using _Tp = remove_cvref_t<_Range>;
if constexpr (__detail::__is_reverse_view<_Tp>)
@@ -4141,9 +4141,9 @@ namespace views::__adaptor
{
template<viewable_range _Range>
requires __detail::__can_elements_view<_Nm, _Range>
- [[nodiscard]]
constexpr auto
operator()(_Range&& __r) const
+ [[nodiscard]]
{
return elements_view<all_t<_Range>, _Nm>{std::forward<_Range>(__r)};
}
diff --git a/libstdc++-v3/testsuite/std/ranges/access/101782.cc b/libstdc++-v3/testsuite/std/ranges/access/101782.cc
new file mode 100644
index 00000000000..abb0c8dab0f
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/access/101782.cc
@@ -0,0 +1,9 @@
+// { dg-options "-std=gnu++20 -fconcepts-ts" }
+// { dg-do compile { target c++20 } }
+
+// PR testsuite/101782
+// attribute-specifier-seq cannot follow requires-clause with -fconcepts-ts
+
+#include <algorithm>
+#include <iterator>
+#include <ranges>
