Here is another proposal with the __to_address overload.
I preferred to let it open to any kind of __normal_iterator
instantiation cause afaics std::vector supports fancy pointer types. It
is better if __to_address works fine also in this case, no ?
libstdc++: Overload std::__to_address for __gnu_cxx::__normal_iterator.
Prefer to overload __to_address to partially specialize
std::pointer_traits because
std::pointer_traits would be mostly useless. In the case of
__gnu_debug::_Safe_iterator
the to_pointer method is even impossible to implement correctly
because we are missing
the parent container to associate the iterator to.
libstdc++-v3/ChangeLog:
* include/bits/stl_iterator.h
(std::pointer_traits<__gnu_cxx::__normal_iterator<>>): Remove.
(std::__to_address(const __gnu_cxx::__normal_iterator<>&)):
New.
* include/debug/safe_iterator.h
(std::__to_address(const
__gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<>, _Sequence>&)):
New.
* testsuite/24_iterators/normal_iterator/to_address.cc: Add
check on std::vector::iterator
to validate both __gnu_cxx::__normal_iterator<>
__to_address overload in normal mode and the
Tested under Linux x86_64.
Ok to commit ?
François
On 04/10/21 10:30 pm, Jonathan Wakely wrote:
On Mon, 4 Oct 2021 at 21:28, François Dumont via Libstdc++
<libstd...@gcc.gnu.org> wrote:
On 04/10/21 10:05 pm, François Dumont wrote:
On 02/10/21 10:24 pm, Jonathan Wakely wrote:
On Sat, 2 Oct 2021 at 18:27, François Dumont wrote:
I would like to propose this alternative approach.
In this patch I make __normal_iterator and random iterator
_Safe_iterator compatible for pointer_traits primary template.
Regarding pointer_traits I wonder if it shouldn't check for the
to_pointer method availability and use per default: return {
std::addressof(__e) }; otherwise. This way we wouldn't have to
provide a
pointer_to method on __normal_iterator.
But I would rather not have these members present in vector::iterator
and string::iterator, in case users accidentally start to rely on them
being present.
Making pointer_traits friends would help but I do not like it neither.
Another option would be to overload std::__to_address so it knows how
to get the address from __normal_iterator and _Safe_iterator.
.
I start thinking that rather than proposing not-useful and even
incorrect code in the case of the _Safe_iterator<> it might be a
better approach.
Even the rebind for __normal_iterator is a little strange because when
doing rebind on std::vector<int>::iterator for long it produces
__normal_iterator<long*, std::vector<int>>, quite inconsistent even if
useless.
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index 8afd6756613..6b915ec011c 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -1312,32 +1312,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cplusplus >= 201103L
- // Need to specialize pointer_traits because the primary template will
- // deduce element_type of __normal_iterator<T*, C> as T* rather than T.
+ // 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>
- struct pointer_traits<__gnu_cxx::__normal_iterator<_Iterator, _Container>>
- {
- private:
- using _Base = pointer_traits<_Iterator>;
-
- public:
- using element_type = typename _Base::element_type;
- using pointer = __gnu_cxx::__normal_iterator<_Iterator, _Container>;
- using difference_type = typename _Base::difference_type;
-
- template<typename _Tp>
- using rebind = __gnu_cxx::__normal_iterator<_Tp, _Container>;
-
- static pointer
- pointer_to(element_type& __e) noexcept
- { return pointer(_Base::pointer_to(__e)); }
-
-#if __cplusplus >= 202002L
- static element_type*
- to_address(pointer __p) noexcept
- { return __p.base(); }
-#endif
- };
+ constexpr auto
+ __to_address(const __gnu_cxx::__normal_iterator<_Iterator,
+ _Container>& __it) noexcept
+ -> decltype(std::__to_address(__it.base()))
+ { return std::__to_address(__it.base()); }
/**
* @addtogroup iterators
diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index 5584d06de5a..09e35f79067 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -1018,6 +1018,23 @@ namespace __gnu_debug
#undef _GLIBCXX_DEBUG_VERIFY_EQ_OPERANDS
#undef _GLIBCXX_DEBUG_VERIFY_OPERANDS
+#if __cplusplus >= 201103L
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+ template<typename _Iterator, typename _Container, typename _Sequence>
+ constexpr auto
+ __to_address(const __gnu_debug::_Safe_iterator<
+ __gnu_cxx::__normal_iterator<_Iterator, _Container>,
+ _Sequence>& __it) noexcept
+ -> decltype(std::__to_address(__it.base()))
+ { return std::__to_address(__it.base()); }
+
+_GLIBCXX_END_NAMESPACE_VERSION
+}
+#endif
+
#include <debug/safe_iterator.tcc>
#endif
diff --git a/libstdc++-v3/testsuite/24_iterators/normal_iterator/to_address.cc b/libstdc++-v3/testsuite/24_iterators/normal_iterator/to_address.cc
index 510d627435f..433c803beb1 100644
--- a/libstdc++-v3/testsuite/24_iterators/normal_iterator/to_address.cc
+++ b/libstdc++-v3/testsuite/24_iterators/normal_iterator/to_address.cc
@@ -1,6 +1,9 @@
// { dg-do compile { target { c++11 } } }
#include <string>
+#include <vector>
#include <memory>
char* p = std::__to_address(std::string("1").begin());
const char* q = std::__to_address(std::string("2").cbegin());
+int* r = std::__to_address(std::vector<int>(1, 1).begin());
+const int* s = std::__to_address(std::vector<int>(1, 1).cbegin());
