libstdc++
concept_check.h
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1 // Concept-checking control -*- C++ -*-
2 
3 // Copyright (C) 2001-2021 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file bits/concept_check.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{iterator}
28  */
29 
30 #ifndef _CONCEPT_CHECK_H
31 #define _CONCEPT_CHECK_H 1
32 
33 #pragma GCC system_header
34 
35 #include <bits/c++config.h>
36 
37 // All places in libstdc++-v3 where these are used, or /might/ be used, or
38 // don't need to be used, or perhaps /should/ be used, are commented with
39 // "concept requirements" (and maybe some more text). So grep like crazy
40 // if you're looking for additional places to use these.
41 
42 // Concept-checking code is off by default unless users turn it on via
43 // configure options or editing c++config.h.
44 // It is not supported for freestanding implementations.
45 
46 #if !defined(_GLIBCXX_CONCEPT_CHECKS) || !_GLIBCXX_HOSTED
47 
48 #define __glibcxx_function_requires(...)
49 #define __glibcxx_class_requires(_a,_b)
50 #define __glibcxx_class_requires2(_a,_b,_c)
51 #define __glibcxx_class_requires3(_a,_b,_c,_d)
52 #define __glibcxx_class_requires4(_a,_b,_c,_d,_e)
53 
54 #else // the checks are on
55 
57 
58 // Note that the obvious and elegant approach of
59 //
60 //#define glibcxx_function_requires(C) debug::function_requires< debug::C >()
61 //
62 // won't work due to concept templates with more than one parameter, e.g.,
63 // BinaryPredicateConcept. The preprocessor tries to split things up on
64 // the commas in the template argument list. We can't use an inner pair of
65 // parenthesis to hide the commas, because "debug::(Temp<Foo,Bar>)" isn't
66 // a valid instantiation pattern. Thus, we steal a feature from C99.
67 
68 #define __glibcxx_function_requires(...) \
69  __gnu_cxx::__function_requires< __gnu_cxx::__VA_ARGS__ >();
70 #define __glibcxx_class_requires(_a,_C) \
71  _GLIBCXX_CLASS_REQUIRES(_a, __gnu_cxx, _C);
72 #define __glibcxx_class_requires2(_a,_b,_C) \
73  _GLIBCXX_CLASS_REQUIRES2(_a, _b, __gnu_cxx, _C);
74 #define __glibcxx_class_requires3(_a,_b,_c,_C) \
75  _GLIBCXX_CLASS_REQUIRES3(_a, _b, _c, __gnu_cxx, _C);
76 #define __glibcxx_class_requires4(_a,_b,_c,_d,_C) \
77  _GLIBCXX_CLASS_REQUIRES4(_a, _b, _c, _d, __gnu_cxx, _C);
78 
79 #endif // enable/disable
80 
81 #endif // _GLIBCXX_CONCEPT_CHECK