On Thu, 17 Oct 2024, 03:33 Patrick Palka, <ppa...@redhat.com> wrote:
> On Tue, 15 Oct 2024, Jonathan Wakely wrote:
>
> > Tested x86_64-linux.
> >
> > -- >8 --
> >
> > The __gnu_cxx::__normal_iterator type we use for std::vector::iterator
> > is not specified by the standard, it's an implementation detail. This
> > means it's not constrained by the rule that forbids strengthening
> > constexpr. We can make it meet the constexpr iterator requirements for
> > older standards, not only when it's required to be for C++20.
> >
> > For the non-const member functions they can't be constexpr in C++11, so
> > use _GLIBCXX14_CONSTEXPR for those. For all constructors, const members
> > and non-member operator overloads, use _GLIBCXX_CONSTEXPR or just
> > constexpr.
> >
> > We can also liberally add [[nodiscard]] and [[gnu::always_inline]]
> > attributes to those functions.
> >
> > Also change some internal helpers for std::move_iterator which can be
> > unconditionally constexpr and marked nodiscard.
> >
> > libstdc++-v3/ChangeLog:
> >
> > * include/bits/stl_iterator.h (__normal_iterator): Make all
> > members and overloaded operators constexpr before C++20.
> > (__niter_base, __niter_wrap, __to_address): Add nodiscard
> > and always_inline attributes.
> > (__make_move_if_noexcept_iterator, __miter_base): Add nodiscard
> > and make unconditionally constexpr.
> > ---
> > libstdc++-v3/include/bits/stl_iterator.h | 125 ++++++++++++++---------
> > 1 file changed, 76 insertions(+), 49 deletions(-)
> >
> > diff --git a/libstdc++-v3/include/bits/stl_iterator.h
> b/libstdc++-v3/include/bits/stl_iterator.h
> > index 85b98ffff61..3cc10a160bd 100644
> > --- a/libstdc++-v3/include/bits/stl_iterator.h
> > +++ b/libstdc++-v3/include/bits/stl_iterator.h
> > @@ -656,7 +656,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >
> > template<typename _Iterator>
> > _GLIBCXX20_CONSTEXPR
> > - auto
> > + inline auto
> > __niter_base(reverse_iterator<_Iterator> __it)
> > -> decltype(__make_reverse_iterator(__niter_base(__it.base())))
> > { return __make_reverse_iterator(__niter_base(__it.base())); }
> > @@ -668,7 +668,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >
> > template<typename _Iterator>
> > _GLIBCXX20_CONSTEXPR
> > - auto
> > + inline auto
>
> These 'inline' additions aren't mentioned in the ChangeLog it seems.
Good point.
Is
> the intent of these inlines solely as a compiler hint?
>
Yes, but they do a little more work than the really trivial ones, and are
less important, less frequently used, so I didn't think always_inline was
justified.
> > __miter_base(reverse_iterator<_Iterator> __it)
> > -> decltype(__make_reverse_iterator(__miter_base(__it.base())))
> > { return __make_reverse_iterator(__miter_base(__it.base())); }
> > @@ -1060,23 +1060,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > using iterator_concept = std::__detail::__iter_concept<_Iterator>;
> > #endif
> >
> > - _GLIBCXX_CONSTEXPR __normal_iterator() _GLIBCXX_NOEXCEPT
> > - : _M_current(_Iterator()) { }
> > + __attribute__((__always_inline__))
> > + _GLIBCXX_CONSTEXPR
> > + __normal_iterator() _GLIBCXX_NOEXCEPT
> > + : _M_current() { }
> >
> > - explicit _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__))
> > + explicit _GLIBCXX_CONSTEXPR
> > __normal_iterator(const _Iterator& __i) _GLIBCXX_NOEXCEPT
> > : _M_current(__i) { }
> >
> > // Allow iterator to const_iterator conversion
> > #if __cplusplus >= 201103L
> > template<typename _Iter, typename = __convertible_from<_Iter>>
> > - _GLIBCXX20_CONSTEXPR
> > + [[__gnu__::__always_inline__]]
> > + constexpr
> > __normal_iterator(const __normal_iterator<_Iter, _Container>& __i)
> > noexcept
> > #else
> > // N.B. _Container::pointer is not actually in container
> requirements,
> > // but is present in std::vector and std::basic_string.
> > template<typename _Iter>
> > + __attribute__((__always_inline__))
> > __normal_iterator(const __normal_iterator<_Iter,
> > typename __enable_if<
> > (std::__are_same<_Iter, typename
> _Container::pointer>::__value),
> > @@ -1085,17 +1090,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > : _M_current(__i.base()) { }
> >
> > // Forward iterator requirements
> > - _GLIBCXX20_CONSTEXPR
> > +
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > + _GLIBCXX_CONSTEXPR
> > reference
> > operator*() const _GLIBCXX_NOEXCEPT
> > { return *_M_current; }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > + _GLIBCXX_CONSTEXPR
> > pointer
> > operator->() const _GLIBCXX_NOEXCEPT
> > { return _M_current; }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__))
> > + _GLIBCXX14_CONSTEXPR
> > __normal_iterator&
> > operator++() _GLIBCXX_NOEXCEPT
> > {
> > @@ -1103,13 +1112,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > return *this;
> > }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__))
> > + _GLIBCXX14_CONSTEXPR
> > __normal_iterator
> > operator++(int) _GLIBCXX_NOEXCEPT
> > { return __normal_iterator(_M_current++); }
> >
> > // Bidirectional iterator requirements
> > - _GLIBCXX20_CONSTEXPR
> > +
> > + __attribute__((__always_inline__))
> > + _GLIBCXX14_CONSTEXPR
> > __normal_iterator&
> > operator--() _GLIBCXX_NOEXCEPT
> > {
> > @@ -1117,38 +1129,46 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > return *this;
> > }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__))
> > + _GLIBCXX14_CONSTEXPR
> > __normal_iterator
> > operator--(int) _GLIBCXX_NOEXCEPT
> > { return __normal_iterator(_M_current--); }
> >
> > // Random access iterator requirements
> > - _GLIBCXX20_CONSTEXPR
> > +
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > + _GLIBCXX_CONSTEXPR
> > reference
> > operator[](difference_type __n) const _GLIBCXX_NOEXCEPT
> > { return _M_current[__n]; }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__))
> > + _GLIBCXX14_CONSTEXPR
> > __normal_iterator&
> > operator+=(difference_type __n) _GLIBCXX_NOEXCEPT
> > { _M_current += __n; return *this; }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > + _GLIBCXX_CONSTEXPR
> > __normal_iterator
> > operator+(difference_type __n) const _GLIBCXX_NOEXCEPT
> > { return __normal_iterator(_M_current + __n); }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__))
> > + _GLIBCXX14_CONSTEXPR
> > __normal_iterator&
> > operator-=(difference_type __n) _GLIBCXX_NOEXCEPT
> > { _M_current -= __n; return *this; }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > + _GLIBCXX_CONSTEXPR
> > __normal_iterator
> > operator-(difference_type __n) const _GLIBCXX_NOEXCEPT
> > { return __normal_iterator(_M_current - __n); }
> >
> > - _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > + _GLIBCXX_CONSTEXPR
> > const _Iterator&
> > base() const _GLIBCXX_NOEXCEPT
> > { return _M_current; }
> > @@ -1164,7 +1184,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >
> > #if __cpp_lib_three_way_comparison
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - [[nodiscard]]
> > + [[nodiscard, __gnu__::__always_inline__]]
> > constexpr bool
> > operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1175,7 +1195,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() == __rhs.base(); }
> >
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - [[nodiscard]]
> > + [[nodiscard, __gnu__::__always_inline__]]
> > constexpr std::__detail::__synth3way_t<_IteratorR, _IteratorL>
> > operator<=>(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1183,7 +1203,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return std::__detail::__synth3way(__lhs.base(), __rhs.base()); }
> >
> > template<typename _Iterator, typename _Container>
> > - [[nodiscard]]
> > + [[nodiscard, __gnu__::__always_inline__]]
> > constexpr bool
> > operator==(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1194,7 +1214,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() == __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - [[nodiscard]]
> > + [[nodiscard, __gnu__::__always_inline__]]
> > constexpr std::__detail::__synth3way_t<_Iterator>
> > operator<=>(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1203,7 +1223,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > #else
> > // Forward iterator requirements
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1211,7 +1231,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() == __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator==(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1219,7 +1239,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() == __rhs.base(); }
> >
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator!=(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1227,7 +1247,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() != __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator!=(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1236,7 +1256,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >
> > // Random access iterator requirements
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - _GLIBCXX_NODISCARD
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator<(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1244,7 +1264,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() < __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX20_CONSTEXPR
> > inline bool
> > operator<(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1252,7 +1272,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() < __rhs.base(); }
> >
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - _GLIBCXX_NODISCARD
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator>(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1260,7 +1280,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() > __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator>(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1268,7 +1288,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() > __rhs.base(); }
> >
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - _GLIBCXX_NODISCARD
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator<=(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1276,7 +1296,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() <= __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator<=(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1284,7 +1304,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() <= __rhs.base(); }
> >
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > - _GLIBCXX_NODISCARD
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator>=(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> > @@ -1292,7 +1312,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() >= __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline bool
> > operator>=(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1307,8 +1327,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > template<typename _IteratorL, typename _IteratorR, typename
> _Container>
> > #if __cplusplus >= 201103L
> > // DR 685.
> > - [[__nodiscard__]] _GLIBCXX20_CONSTEXPR
> > - inline auto
> > + [[__nodiscard__, __gnu__::__always_inline__]]
> > + constexpr auto
> > operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
> > const __normal_iterator<_IteratorR, _Container>& __rhs)
> noexcept
> > -> decltype(__lhs.base() - __rhs.base())
> > @@ -1320,7 +1340,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() - __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline typename __normal_iterator<_Iterator,
> _Container>::difference_type
> > operator-(const __normal_iterator<_Iterator, _Container>& __lhs,
> > const __normal_iterator<_Iterator, _Container>& __rhs)
> > @@ -1328,7 +1348,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { return __lhs.base() - __rhs.base(); }
> >
> > template<typename _Iterator, typename _Container>
> > - _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> > inline __normal_iterator<_Iterator, _Container>
> > operator+(typename __normal_iterator<_Iterator,
> _Container>::difference_type
> > __n, const __normal_iterator<_Iterator, _Container>& __i)
> > @@ -1349,24 +1369,26 @@ namespace std _GLIBCXX_VISIBILITY(default)
> > _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >
> > // Unwrap a __normal_iterator to get the underlying iterator
> > - // (usually a pointer)
> > + // (usually a pointer). See uses in std::copy, std::fill, etc.
> > template<typename _Iterator, typename _Container>
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > _GLIBCXX20_CONSTEXPR
> > - _Iterator
> > + inline _Iterator
> > __niter_base(__gnu_cxx::__normal_iterator<_Iterator, _Container>
> __it)
> >
> _GLIBCXX_NOEXCEPT_IF(std::is_nothrow_copy_constructible<_Iterator>::value)
> > { return __it.base(); }
> >
> > - // Fallback implementation of the function in bits/stl_iterator.h
> used to
> > - // remove the __normal_iterator wrapper. See std::copy, std::fill,
> etc.
> > + // Fallback implementation used for iterators that can't be unwrapped.
> > template<typename _Iterator>
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > _GLIBCXX20_CONSTEXPR
> > inline _Iterator
> > __niter_base(_Iterator __it)
> >
> _GLIBCXX_NOEXCEPT_IF(std::is_nothrow_copy_constructible<_Iterator>::value)
> > { return __it; }
> >
> > - // Overload for _Safe_iterator needs to be declared before
> __niter_base uses.
> > + // Overload for _Safe_iterator needs to be declared before uses of
> > + // std::__niter_base because we call it qualified so isn't found by
> ADL.
>
> I guess this comment adjustment could be part of the first patch?
>
Could be, yup.
> LGTM otherwise. Patches 5,6,7 LGTM too.
>
Thanks.
> > #if __cplusplus < 201103L
> > template<typename _Ite, typename _Seq>
> > _Ite
> > @@ -1391,6 +1413,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > // __normal_iterator back again (this assumes that __normal_iterator
> > // is only used to wrap random access iterators, like pointers).
> > template<typename _From, typename _To>
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > _GLIBCXX20_CONSTEXPR
> > inline _From
> > __niter_wrap(_From __from, _To __res)
> > @@ -1398,6 +1421,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >
> > // No need to wrap, iterator already has the right type.
> > template<typename _Iterator>
> > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> > _GLIBCXX20_CONSTEXPR
> > inline _Iterator
> > __niter_wrap(const _Iterator&, _Iterator __res)
> > @@ -1407,6 +1431,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > // Need to overload __to_address because the pointer_traits primary
> template
> > // will deduce element_type of __normal_iterator<T*, C> as T* rather
> than T.
> > template<typename _Iterator, typename _Container>
> > + [[__gnu__::__always_inline__]] _GLIBCXX_NODISCARD
> > constexpr auto
> > __to_address(const __gnu_cxx::__normal_iterator<_Iterator,
> > _Container>& __it)
> noexcept
> > @@ -1861,7 +1886,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > = __conditional_t<__move_if_noexcept_cond
> > <typename iterator_traits<_Iterator>::value_type>::value,
> > _Iterator, move_iterator<_Iterator>>>
> > - inline _GLIBCXX17_CONSTEXPR _ReturnType
> > + [[__nodiscard__]]
> > + constexpr _ReturnType
> > __make_move_if_noexcept_iterator(_Iterator __i)
> > { return _ReturnType(__i); }
> >
> > @@ -1870,13 +1896,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > template<typename _Tp, typename _ReturnType
> > = __conditional_t<__move_if_noexcept_cond<_Tp>::value,
> > const _Tp*, move_iterator<_Tp*>>>
> > - inline _GLIBCXX17_CONSTEXPR _ReturnType
> > + [[__nodiscard__]]
> > + constexpr _ReturnType
> > __make_move_if_noexcept_iterator(_Tp* __i)
> > { return _ReturnType(__i); }
> >
> > template<typename _Iterator>
> > - _GLIBCXX20_CONSTEXPR
> > - auto
> > + [[__nodiscard__]]
> > + constexpr auto
> > __niter_base(move_iterator<_Iterator> __it)
> > -> decltype(make_move_iterator(__niter_base(__it.base())))
> > { return make_move_iterator(__niter_base(__it.base())); }
> > @@ -1889,8 +1916,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > };
> >
> > template<typename _Iterator>
> > - _GLIBCXX20_CONSTEXPR
> > - auto
> > + [[__nodiscard__]]
> > + constexpr auto
> > __miter_base(move_iterator<_Iterator> __it)
> > -> decltype(__miter_base(__it.base()))
> > { return __miter_base(__it.base()); }
> > --
> > 2.46.2
> >
> >
>
>
