[patch] Limit operations on vector::pointer to NullablePointer requirements.

[Jonathan Wakely]

This patch makes std::vector work with fancy pointer types that cannot
be initialized or assigned from a literal zero. Currently we don't
have any tests that fail under such cases, but I'll be adding some
later in stage 1 as part of other changes. This fix stands alone and
doesn't rely on those larger changes.

Tested x86_64-linux, committed to trunk.



commit d78a65207d27b0994f6bd29ca54e3b84e4be1981
Author: Jonathan Wakely <a...@kayari.org>
Date:   Mon Apr 14 15:24:35 2014 +0100

    Limit operations on vector::pointer to NullablePointer requirements.
    
        * include/bits/stl_vector.h (_Vector_base::_Vector_impl,
        _Vector_base::_M_allocate): NullablePointer requirements do not
        include initialization from literal zero, use value-initialization.
        * include/bits/vector.tcc (vector::_M_insert_aux,
        vector::_M_explace_back_aux): Likewise for assignment.

diff --git a/libstdc++-v3/include/bits/stl_vector.h 
b/libstdc++-v3/include/bits/stl_vector.h
index 7e52fde..3d3a2cf 100644
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -84,17 +84,17 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
        pointer _M_end_of_storage;
 
        _Vector_impl()
-       : _Tp_alloc_type(), _M_start(0), _M_finish(0), _M_end_of_storage(0)
+       : _Tp_alloc_type(), _M_start(), _M_finish(), _M_end_of_storage()
        { }
 
        _Vector_impl(_Tp_alloc_type const& __a) _GLIBCXX_NOEXCEPT
-       : _Tp_alloc_type(__a), _M_start(0), _M_finish(0), _M_end_of_storage(0)
+       : _Tp_alloc_type(__a), _M_start(), _M_finish(), _M_end_of_storage()
        { }
 
 #if __cplusplus >= 201103L
        _Vector_impl(_Tp_alloc_type&& __a) noexcept
        : _Tp_alloc_type(std::move(__a)),
-         _M_start(0), _M_finish(0), _M_end_of_storage(0)
+         _M_start(), _M_finish(), _M_end_of_storage()
        { }
 #endif
 
@@ -167,7 +167,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       _M_allocate(size_t __n)
       {
        typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Tr;
-       return __n != 0 ? _Tr::allocate(_M_impl, __n) : 0;
+       return __n != 0 ? _Tr::allocate(_M_impl, __n) : pointer();
       }
 
       void
diff --git a/libstdc++-v3/include/bits/vector.tcc 
b/libstdc++-v3/include/bits/vector.tcc
index 1eff514..299e614 100644
--- a/libstdc++-v3/include/bits/vector.tcc
+++ b/libstdc++-v3/include/bits/vector.tcc
@@ -362,7 +362,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #else
                                       __x);
 #endif
-             __new_finish = 0;
+             __new_finish = pointer();
 
              __new_finish
                = std::__uninitialized_move_if_noexcept_a
@@ -412,7 +412,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
          {
            _Alloc_traits::construct(this->_M_impl, __new_start + size(),
                                     std::forward<_Args>(__args)...);
-           __new_finish = 0;
+           __new_finish = pointer();
 
            __new_finish
              = std::__uninitialized_move_if_noexcept_a
@@ -493,7 +493,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                  std::__uninitialized_fill_n_a(__new_start + __elems_before,
                                                __n, __x,
                                                _M_get_Tp_allocator());
-                 __new_finish = 0;
+                 __new_finish = pointer();
 
                  __new_finish
                    = std::__uninitialized_move_if_noexcept_a