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. Moreover partial specialization of
pointer_traits<__normal_iterator<P, C>> fails to rebind C, so you get incorrect types
like __normal_iterator<long*, vector<int>>. In the case of __gnu_debug::_Safe_iterator
the to_pointer method is 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 for C++11 to C++17.
	* include/debug/safe_iterator.h
	(std::__to_address(const __gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<>,
	_Sequence>&)): New for C++11 to C++17.
	* 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
	__gnu_debug::_Safe_iterator in _GLIBCXX_DEBUG mode.

1 files changed, 15 insertions, 2 deletions

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..6afc6540609 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 +1,19 @@
 // { 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());
+#include <testsuite_allocator.h>
+
+char* p __attribute__((unused))
+  = std::__to_address(std::string("1").begin());
+const char* q __attribute__((unused))
+  = std::__to_address(std::string("2").cbegin());
+int* r __attribute__((unused))
+  = std::__to_address(std::vector<int>(1, 1).begin());
+const int* s __attribute__((unused))
+  = std::__to_address(std::vector<int>(1, 1).cbegin());
+int* t __attribute__((unused))
+  = std::__to_address(std::vector<int, __gnu_test::CustomPointerAlloc<int>>(1, 1).begin());
+const int* u __attribute__((unused))
+  = std::__to_address(std::vector<int, __gnu_test::CustomPointerAlloc<int>>(1, 1).cbegin());