libstdc++-v3/testsuite/20_util/allocator_traits/members/rebind_alloc.cc

   1 // Copyright (C) 2017-2024 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-do compile { target c++11 } }
  19
  20 #include <memory>
  21
  22 using std::is_same;
  23
  24 template<typename T, typename U>
  25   using Rebind = typename std::allocator_traits<T>::template rebind_alloc<U>;
  26
  27 template<typename T, typename = T>
  28   struct HasRebind {
  29     using value_type = T;
  30     template<typename U> struct rebind { using other = HasRebind<U>; };
  31   };
  32
  33 // Would get HasRebind<long, int> here if the first template argument is
  34 // replaced instead of using the nested rebind.
  35 static_assert(is_same<Rebind<HasRebind<int>, long>, HasRebind<long>>::value,
  36               "nested alias template is used");
  37
  38 template<typename T>
  39   struct NoRebind0 {
  40     using value_type = T;
  41   };
  42
  43 static_assert(is_same<Rebind<NoRebind0<int>, long>,
  44                       NoRebind0<long>>::value,
  45               "first template argument is replaced");
  46
  47 template<typename T, typename>
  48   struct NoRebind1 {
  49     using value_type = T;
  50   };
  51
  52 static_assert(is_same<Rebind<NoRebind1<int, void>, long>,
  53                       NoRebind1<long, void>>::value,
  54               "first template argument is replaced");
  55
  56 template<typename T, typename, typename>
  57   struct NoRebind2 {
  58     using value_type = T;
  59   };
  60
  61 static_assert(is_same<Rebind<NoRebind2<int, void, void>, long>,
  62                       NoRebind2<long, void, void>>::value,
  63               "first template argument is replaced");
  64
  65 template<typename T, typename...>
  66   struct NoRebindN {
  67     using value_type = T;
  68   };
  69
  70 static_assert(is_same<Rebind<NoRebindN<int>, long>,
  71                       NoRebindN<long>>::value,
  72               "first template argument is replaced");
  73 static_assert(is_same<Rebind<NoRebindN<int, void>, long>,
  74                       NoRebindN<long, void>>::value,
  75               "first template argument is replaced");
  76
  77 template<typename T, int = 0>
  78   struct CannotRebind {
  79     using value_type = T;
  80   };
  81 // PR libstdc++/72792 specialization of allocator_traits is still well-formed:
  82 std::allocator_traits<CannotRebind<int>>::value_type v;