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
__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.
#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
