[Bug libstdc++/72792] allocator_traits is too strict about rebinding

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72792

--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue Feb 14 20:08:12 2017
New Revision: 245452

URL: https://gcc.gnu.org/viewcvs?rev=245452&root=gcc&view=rev
Log:
PR72792 PR72793 relax requirements on rebind members

Backport from mainline
2017-01-20  Jonathan Wakely  <jwakely@redhat.com>

        PR libstdc++/72792
        * include/bits/alloc_traits.h (__allocator_traits_base::__diff_type)
        (__allocator_traits_base::__size_type): Remove.
        (allocator_traits::_Ptr): New class template to detect const and void
        pointer types without instantiating pointer_traits::rebind
        unnecessarily.
        (allocator_traits::_Diff): Likewise for detecting difference_type.
        (allocator_traits::_Size): New class template to detect size_type
        without instantiating make_unsigned unnecessarily.
        * include/bits/ptr_traits.h (pointer_traits::element_type): Use
        __detected_or_t instead of __detected_or_t_.
        * include/std/type_traits (__detected_or_t_): Remove.
        * testsuite/20_util/allocator_traits/members/pointers.cc: New test.

        PR libstdc++/72792
        PR libstdc++/72793
        * include/bits/alloc_traits.h (__allocator_traits_base::__rebind):
        Replace with class template using void_t.
        (__alloc_rebind): Define in terms of
        __allocator_traits_base::__rebind.
        (allocator_traits): Remove unconditional static_assert for
        rebind_alloc.
        * include/bits/ptr_traits.h (__replace_first_arg): Remove type member.
        (pointer_traits::__rebind): Replace with class template using void_t.
        (pointer_traits::rebind): Define in terms of __rebind.
        (pointer_traits): Remove unconditional static_assert for rebind.
        * testsuite/20_util/allocator_traits/members/rebind_alloc.cc: New test.
        * testsuite/20_util/pointer_traits/rebind.cc: New test.

Added:
   
branches/gcc-6-branch/libstdc++-v3/testsuite/20_util/allocator_traits/members/pointers.cc
   
branches/gcc-6-branch/libstdc++-v3/testsuite/20_util/allocator_traits/members/rebind_alloc.cc
   
branches/gcc-6-branch/libstdc++-v3/testsuite/20_util/pointer_traits/rebind.cc
Modified:
    branches/gcc-6-branch/libstdc++-v3/ChangeLog
    branches/gcc-6-branch/libstdc++-v3/include/bits/alloc_traits.h
    branches/gcc-6-branch/libstdc++-v3/include/bits/ptr_traits.h
    branches/gcc-6-branch/libstdc++-v3/include/std/type_traits