libstdc++-v3/testsuite/20_util/shared_ptr/modifiers/reset_sfinae.cc

   1 // Copyright (C) 2016-2023 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 // { dg-require-effective-target hosted }
  20
  21 #include <memory>
  22
  23 template<typename T, typename Args, typename = void>
  24   struct resettable
  25   : std::false_type
  26   { };
  27
  28 template<typename... T> struct type_list { };
  29
  30 template<typename T, typename... Args>
  31   using reset_result
  32     = decltype(std::shared_ptr<T>{}.reset(std::declval<Args>()...));
  33
  34 template<typename T, typename... Args>
  35   struct resettable<T, type_list<Args...>, reset_result<T, Args...>>
  36   : std::true_type
  37   { };
  38
  39 template<typename T, typename... Args>
  40 constexpr bool can_reset()
  41 { return resettable<T, type_list<Args...>>::value; }
  42
  43 template<typename T>
  44 struct Deleter {
  45   void operator()(T*) const;
  46 };
  47
  48 template<typename T>
  49 using Alloc = std::allocator<T>;
  50
  51 struct Base { };
  52 struct Derived : Base { };
  53
  54 // Positive cases:
  55
  56 static_assert( can_reset<const void, void*>(),
  57     "void* convertible to const void*");
  58 static_assert( can_reset<const int, int*>(),
  59     "int* convertible to const int*");
  60 static_assert( can_reset<Base, Derived*>(),
  61     "Derived* convertible to Base*");
  62 static_assert( can_reset<const Base, Derived*>(),
  63     "Derived* convertible to const Base*");
  64
  65 // Negative cases:
  66
  67 static_assert( !can_reset<int, void*>(),
  68     "void* not convertible to int*");
  69 static_assert( !can_reset<int, void*, Deleter<int>>(),
  70     "void* not convertible to int*");
  71 static_assert( !can_reset<int, void*, Deleter<int>, Alloc<int>>(),
  72     "void* not convertible to int*");
  73
  74 static_assert( !can_reset<int, const int*>(),
  75     "const int* not convertible to int*");
  76 static_assert( !can_reset<int, const int*, Deleter<int>>(),
  77     "const int* not convertible to int*");
  78 static_assert( !can_reset<int, const int*, Deleter<int>, Alloc<int>>(),
  79     "const int* not convertible to int*");
  80
  81 static_assert( !can_reset<int, long*>(),
  82     "long* not convertible to int*");
  83 static_assert( !can_reset<int, long*, Deleter<int>>(),
  84     "long* not convertible to int*");
  85 static_assert( !can_reset<int, long*, Deleter<int>, Alloc<int>>(),
  86     "long* not convertible to int*");
  87
  88 static_assert( !can_reset<Derived, Base*>(),
  89     "Base* not convertible to Derived*");
  90 static_assert( !can_reset<Derived, Base*, Deleter<int>>(),
  91     "Base* not convertible to Derived*");
  92 static_assert( !can_reset<Derived, Base*, Deleter<int>, Alloc<int>>(),
  93     "Base* not convertible to Derived*");