text: // Concept-checking control -*- C++ -*-
  
  // Copyright (C) 2001-2017 Free Software Foundation, Inc.
  //
  // This file is part of the GNU ISO C++ Library.  This library is free
  // software; you can redistribute it and/or modify it under the
  // terms of the GNU General Public License as published by the
  // Free Software Foundation; either version 3, or (at your option)
  // any later version.
  
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  // GNU General Public License for more details.
  
  // Under Section 7 of GPL version 3, you are granted additional
  // permissions described in the GCC Runtime Library Exception, version
  // 3.1, as published by the Free Software Foundation.
  
  // You should have received a copy of the GNU General Public License and
  // a copy of the GCC Runtime Library Exception along with this program;
  // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  // <http://www.gnu.org/licenses/>.
  
  /** @file bits/concept_check.h
   *  This is an internal header file, included by other library headers.
   *  Do not attempt to use it directly. @headername{iterator}
   */
  
  #ifndef _CONCEPT_CHECK_H
  #define _CONCEPT_CHECK_H 1
  
  #pragma GCC system_header
  
  #include <bits/c++config.h>
  
  // All places in libstdc++-v3 where these are used, or /might/ be used, or
  // don't need to be used, or perhaps /should/ be used, are commented with
  // "concept requirements" (and maybe some more text).  So grep like crazy
  // if you're looking for additional places to use these.
  
  // Concept-checking code is off by default unless users turn it on via
  // configure options or editing c++config.h.
  // It is not supported for freestanding implementations.
  
  #if !defined(_GLIBCXX_CONCEPT_CHECKS) || !_GLIBCXX_HOSTED
  
  #define __glibcxx_function_requires(...)
  #define __glibcxx_class_requires(_a,_b)
  #define __glibcxx_class_requires2(_a,_b,_c)
  #define __glibcxx_class_requires3(_a,_b,_c,_d)
  #define __glibcxx_class_requires4(_a,_b,_c,_d,_e)
  
  #else // the checks are on
  
  #include <bits/boost_concept_check.h>
  
  // Note that the obvious and elegant approach of
  //
  //#define glibcxx_function_requires(C) debug::function_requires< debug::C >()
  //
  // won't work due to concept templates with more than one parameter, e.g.,
  // BinaryPredicateConcept.  The preprocessor tries to split things up on
  // the commas in the template argument list.  We can't use an inner pair of
  // parenthesis to hide the commas, because "debug::(Temp<Foo,Bar>)" isn't
  // a valid instantiation pattern.  Thus, we steal a feature from C99.
  
  #define __glibcxx_function_requires(...)                                 \
              __gnu_cxx::__function_requires< __gnu_cxx::__VA_ARGS__ >();
  #define __glibcxx_class_requires(_a,_C)                                  \
              _GLIBCXX_CLASS_REQUIRES(_a, __gnu_cxx, _C);
  #define __glibcxx_class_requires2(_a,_b,_C)                              \
              _GLIBCXX_CLASS_REQUIRES2(_a, _b, __gnu_cxx, _C);
  #define __glibcxx_class_requires3(_a,_b,_c,_C)                           \
              _GLIBCXX_CLASS_REQUIRES3(_a, _b, _c, __gnu_cxx, _C);
  #define __glibcxx_class_requires4(_a,_b,_c,_d,_C)                        \
              _GLIBCXX_CLASS_REQUIRES4(_a, _b, _c, _d, __gnu_cxx, _C);
  
  #endif // enable/disable
  
  #endif // _GLIBCXX_CONCEPT_CHECK
  