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* [gcc r12-3935] libstdc++: Specialize std::pointer_traits<__normal_iterator<I, C>>
@ 2021-09-28 19:24 Jonathan Wakely
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From: Jonathan Wakely @ 2021-09-28 19:24 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:82626be2d633a9802a8b08727ef51c627e37fee5
commit r12-3935-g82626be2d633a9802a8b08727ef51c627e37fee5
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue Sep 28 15:26:46 2021 +0100
libstdc++: Specialize std::pointer_traits<__normal_iterator<I,C>>
This allows std::__to_address to be used with __normal_iterator in
C++11/14/17 modes. Without the partial specialization the deduced
pointer_traits::element_type is incorrect, and so the return type of
__to_address is wrong.
A similar partial specialization is probably needed for
__gnu_debug::_Safe_iterator.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/stl_iterator.h (pointer_traits): Define partial
specialization for __normal_iterator.
* testsuite/24_iterators/normal_iterator/to_address.cc: New test.
Diff:
---
libstdc++-v3/include/bits/stl_iterator.h | 28 ++++++++++++++++++++++
.../24_iterators/normal_iterator/to_address.cc | 6 +++++
2 files changed, 34 insertions(+)
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index c5b02408c1c..004d767224d 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -1285,6 +1285,34 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return __it.base(); }
#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.
+ 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
+ };
+
/**
* @addtogroup iterators
* @{
diff --git a/libstdc++-v3/testsuite/24_iterators/normal_iterator/to_address.cc b/libstdc++-v3/testsuite/24_iterators/normal_iterator/to_address.cc
new file mode 100644
index 00000000000..510d627435f
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/normal_iterator/to_address.cc
@@ -0,0 +1,6 @@
+// { dg-do compile { target { c++11 } } }
+#include <string>
+#include <memory>
+
+char* p = std::__to_address(std::string("1").begin());
+const char* q = std::__to_address(std::string("2").cbegin());
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