From: Jonathan Wakely Date: Thu, 17 Oct 2024 20:02:03 +0000 (+0100) Subject: libstdc++: Make __normal_iterator constexpr, always_inline, nodiscard X-Git-Tag: basepoints/gcc-16~5079 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4020ee77186d1544e8565ae5786af99b8e56543a;p=thirdparty%2Fgcc.git libstdc++: Make __normal_iterator constexpr, always_inline, nodiscard 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, and add always_inline attribute (__to_address): Add nodiscard and always_inline attributes. (__make_move_if_noexcept_iterator): Add nodiscard and make unconditionally constexpr. (__niter_base(__normal_iterator), __niter_base(Iter)): Add nodiscard and always_inline attributes. (__niter_base(reverse_iterator), __niter_base(move_iterator)) (__miter_base): Add inline. (__niter_wrap(From, To)): Add nodiscard attribute. (__niter_wrap(const Iter&, Iter)): Add nodiscard and always_inline attributes. Reviewed-by: Patrick Palka --- diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h index be3fa6f7a34..26c5eab4b4e 100644 --- a/libstdc++-v3/include/bits/stl_iterator.h +++ b/libstdc++-v3/include/bits/stl_iterator.h @@ -1046,24 +1046,29 @@ _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> - _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 - __normal_iterator(const __normal_iterator<_Iter, + __attribute__((__always_inline__)) + __normal_iterator(const __normal_iterator<_Iter, typename __enable_if< (std::__are_same<_Iter, typename _Container::pointer>::__value), _Container>::__type>& __i) @@ -1071,17 +1076,21 @@ _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 { @@ -1089,13 +1098,16 @@ _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 { @@ -1103,38 +1115,46 @@ _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; } @@ -1150,7 +1170,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #if __cpp_lib_three_way_comparison template - [[nodiscard]] + [[nodiscard, __gnu__::__always_inline__]] constexpr bool operator==(const __normal_iterator<_IteratorL, _Container>& __lhs, const __normal_iterator<_IteratorR, _Container>& __rhs) @@ -1161,7 +1181,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() == __rhs.base(); } template - [[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) @@ -1169,7 +1189,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return std::__detail::__synth3way(__lhs.base(), __rhs.base()); } template - [[nodiscard]] + [[nodiscard, __gnu__::__always_inline__]] constexpr bool operator==(const __normal_iterator<_Iterator, _Container>& __lhs, const __normal_iterator<_Iterator, _Container>& __rhs) @@ -1180,7 +1200,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() == __rhs.base(); } template - [[nodiscard]] + [[nodiscard, __gnu__::__always_inline__]] constexpr std::__detail::__synth3way_t<_Iterator> operator<=>(const __normal_iterator<_Iterator, _Container>& __lhs, const __normal_iterator<_Iterator, _Container>& __rhs) @@ -1189,7 +1209,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #else // Forward iterator requirements template - _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) @@ -1197,7 +1217,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() == __rhs.base(); } template - _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) @@ -1205,7 +1225,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() == __rhs.base(); } template - _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) @@ -1213,7 +1233,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() != __rhs.base(); } template - _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) @@ -1222,7 +1242,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Random access iterator requirements template - _GLIBCXX_NODISCARD + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD _GLIBCXX_CONSTEXPR inline bool operator<(const __normal_iterator<_IteratorL, _Container>& __lhs, const __normal_iterator<_IteratorR, _Container>& __rhs) @@ -1230,7 +1250,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() < __rhs.base(); } template - _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) @@ -1238,7 +1258,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() < __rhs.base(); } template - _GLIBCXX_NODISCARD + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD _GLIBCXX_CONSTEXPR inline bool operator>(const __normal_iterator<_IteratorL, _Container>& __lhs, const __normal_iterator<_IteratorR, _Container>& __rhs) @@ -1246,7 +1266,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() > __rhs.base(); } template - _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) @@ -1254,7 +1274,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() > __rhs.base(); } template - _GLIBCXX_NODISCARD + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD _GLIBCXX_CONSTEXPR inline bool operator<=(const __normal_iterator<_IteratorL, _Container>& __lhs, const __normal_iterator<_IteratorR, _Container>& __rhs) @@ -1262,7 +1282,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() <= __rhs.base(); } template - _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) @@ -1270,7 +1290,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() <= __rhs.base(); } template - _GLIBCXX_NODISCARD + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD _GLIBCXX_CONSTEXPR inline bool operator>=(const __normal_iterator<_IteratorL, _Container>& __lhs, const __normal_iterator<_IteratorR, _Container>& __rhs) @@ -1278,7 +1298,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() >= __rhs.base(); } template - _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) @@ -1293,8 +1313,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template #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()) @@ -1306,7 +1326,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() - __rhs.base(); } template - _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) @@ -1314,7 +1334,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { return __lhs.base() - __rhs.base(); } template - _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) @@ -1332,6 +1352,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Need to overload __to_address because the pointer_traits primary template // will deduce element_type of __normal_iterator as T* rather than T. template + [[__gnu__::__always_inline__]] _GLIBCXX_NODISCARD constexpr auto __to_address(const __gnu_cxx::__normal_iterator<_Iterator, _Container>& __it) noexcept @@ -1786,7 +1807,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION = __conditional_t<__move_if_noexcept_cond ::value_type>::value, _Iterator, move_iterator<_Iterator>>> - inline _GLIBCXX17_CONSTEXPR _ReturnType + [[__nodiscard__]] + constexpr _ReturnType __make_move_if_noexcept_iterator(_Iterator __i) { return _ReturnType(__i); } @@ -1795,7 +1817,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template::value, const _Tp*, move_iterator<_Tp*>>> - inline _GLIBCXX17_CONSTEXPR _ReturnType + [[__nodiscard__]] + constexpr _ReturnType __make_move_if_noexcept_iterator(_Tp* __i) { return _ReturnType(__i); } @@ -1806,7 +1829,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION typedef __true_type __type; }; - #define _GLIBCXX_MAKE_MOVE_ITERATOR(_Iter) std::make_move_iterator(_Iter) #define _GLIBCXX_MAKE_MOVE_IF_NOEXCEPT_ITERATOR(_Iter) \ std::__make_move_if_noexcept_iterator(_Iter) @@ -2968,14 +2990,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Unwrap a __normal_iterator to get the underlying iterator // (usually a pointer). See uses in std::copy, std::fill, etc. template + __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 used for iterators that can't be unwrapped. template + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR inline _Iterator __niter_base(_Iterator __it) @@ -3007,28 +3031,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #if __cplusplus >= 201103L template _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())); } template _GLIBCXX20_CONSTEXPR - auto + inline auto __niter_base(move_iterator<_Iterator> __it) -> decltype(make_move_iterator(__niter_base(__it.base()))) { return make_move_iterator(__niter_base(__it.base())); } template _GLIBCXX20_CONSTEXPR - auto + inline auto __miter_base(reverse_iterator<_Iterator> __it) -> decltype(__make_reverse_iterator(__miter_base(__it.base()))) { return __make_reverse_iterator(__miter_base(__it.base())); } template _GLIBCXX20_CONSTEXPR - auto + inline auto __miter_base(move_iterator<_Iterator> __it) -> decltype(__miter_base(__it.base())) { return __miter_base(__it.base()); } @@ -3039,6 +3063,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // random access iterators, like pointers). // All overloads of std::__niter_base must be declared before this. template + _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR inline _From __niter_wrap(_From __from, _To __res) @@ -3046,6 +3071,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // No need to wrap, iterator already has the right type. template + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR inline _Iterator __niter_wrap(const _Iterator&, _Iterator __res)