libcxx/include/__memory/uses_allocator.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___MEMORY_USES_ALLOCATOR_H
  11 #define _LIBCPP___MEMORY_USES_ALLOCATOR_H
  12
  13 #include <__config>
  14 #include <__type_traits/is_convertible.h>
  15 #include <cstddef>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #  pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 template <class _Tp>
  24 struct __has_allocator_type
  25 {
  26 private:
  27     template <class _Up> static false_type __test(...);
  28     template <class _Up> static true_type __test(typename _Up::allocator_type* = 0);
  29 public:
  30     static const bool value = decltype(__test<_Tp>(0))::value;
  31 };
  32
  33 template <class _Tp, class _Alloc, bool = __has_allocator_type<_Tp>::value>
  34 struct __uses_allocator
  35     : public integral_constant<bool,
  36         is_convertible<_Alloc, typename _Tp::allocator_type>::value>
  37 {
  38 };
  39
  40 template <class _Tp, class _Alloc>
  41 struct __uses_allocator<_Tp, _Alloc, false>
  42     : public false_type
  43 {
  44 };
  45
  46 template <class _Tp, class _Alloc>
  47 struct _LIBCPP_TEMPLATE_VIS uses_allocator
  48     : public __uses_allocator<_Tp, _Alloc>
  49 {
  50 };
  51
  52 #if _LIBCPP_STD_VER >= 17
  53 template <class _Tp, class _Alloc>
  54 inline constexpr bool uses_allocator_v = uses_allocator<_Tp, _Alloc>::value;
  55 #endif
  56
  57 _LIBCPP_END_NAMESPACE_STD
  58
  59 #endif // _LIBCPP___MEMORY_USES_ALLOCATOR_H