mirrors/gcc
0
0
Fork 0
mirror of https://gcc.gnu.org/git/gcc.git synced 2024-12-20 09:35:05 +08:00
Code Issues Actions Packages Projects Releases Wiki Activity

libstdc++: Simplify __normal_iterator converting constructor

Browse Source 
This uses C++11 features to simplify the definition of the
__normal_iterator constructor that allows converting from iterator to
const_iterator. The previous definition relied on _Container::pointer
which is present in std::vector and std::basic_string, but is not
actually part of the container requirements.

Removing the use of _Container::pointer and defining it in terms of
is_convertible allows __normal_iterator to be used with new container
types which do not define a pointer member. Specifically, this will
allow it to be used in std::basic_stacktrace.

In theory this will enable some conversions which were not previously
permitted, for example __normal_iterator<volatile T*, vector<T>> can
now be converted to __normal_iterator<const volatile T*, vector<T>>.
In practice this doesn't matter because the library never uses such
types.  In any case, allowing those conversions is consistent with
the corresponding constructors of std::reverse_iterator and
std::move_iterator.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* include/bits/stl_iterator.h (__normal_iterator): Simplify
	converting constructor and do not require _Container::pointer.
This commit is contained in:
Jonathan Wakely 2021-05-06 13:44:36 +01:00
parent 10b6d89bad
commit fb4d55ef61
1 changed files with 17 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
libstdc++-v3/include/bits/stl_iterator.h
View File

@ -1022,6 +1022,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
typedef std::iterator_traits<_Iterator> __traits_type;
#if __cplusplus >= 201103L
template<typename _Iter>
using __convertible_from
= std::__enable_if_t<std::is_convertible<_Iter, _Iterator>::value>;
#endif
public:
typedef _Iterator iterator_type;
typedef typename __traits_type::iterator_category iterator_category;
@ -1042,12 +1048,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: _M_current(__i) { }
// Allow iterator to const_iterator conversion
#if __cplusplus >= 201103L
template<typename _Iter, typename = __convertible_from<_Iter>>
_GLIBCXX20_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>
_GLIBCXX20_CONSTEXPR
__normal_iterator(const __normal_iterator<_Iter,
typename __enable_if<
(std::__are_same<_Iter, typename _Container::pointer>::__value),
_Container>::__type>& __i) _GLIBCXX_NOEXCEPT
(std::__are_same<_Iter, typename _Container::pointer>::__value),
_Container>::__type>& __i)
#endif
: _M_current(__i.base()) { }
// Forward iterator requirements