dhcpd-pools  2.28
ISC dhcpd lease usage analyser
stdalign.in.h
Go to the documentation of this file.
1 /* A substitute for ISO C11 <stdalign.h>.
2 
3  Copyright 2011-2015 Free Software Foundation, Inc.
4 
5  This program is free software; you can redistribute it and/or modify
6  it under the terms of the GNU General Public License as published by
7  the Free Software Foundation; either version 3, or (at your option)
8  any later version.
9 
10  This program is distributed in the hope that it will be useful,
11  but WITHOUT ANY WARRANTY; without even the implied warranty of
12  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  GNU General Public License for more details.
14 
15  You should have received a copy of the GNU General Public License
16  along with this program; if not, see <http://www.gnu.org/licenses/>. */
17 
18 /* Written by Paul Eggert and Bruno Haible. */
19 
20 #ifndef _GL_STDALIGN_H
21 #define _GL_STDALIGN_H
22 
23 /* ISO C11 <stdalign.h> for platforms that lack it.
24 
25  References:
26  ISO C11 (latest free draft
27  <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf>)
28  sections 6.5.3.4, 6.7.5, 7.15.
29  C++11 (latest free draft
30  <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf>)
31  section 18.10. */
32 
33 /* alignof (TYPE), also known as _Alignof (TYPE), yields the alignment
34  requirement of a structure member (i.e., slot or field) that is of
35  type TYPE, as an integer constant expression.
36 
37  This differs from GCC's __alignof__ operator, which can yield a
38  better-performing alignment for an object of that type. For
39  example, on x86 with GCC, __alignof__ (double) and __alignof__
40  (long long) are 8, whereas alignof (double) and alignof (long long)
41  are 4 unless the option '-malign-double' is used.
42 
43  The result cannot be used as a value for an 'enum' constant, if you
44  want to be portable to HP-UX 10.20 cc and AIX 3.2.5 xlc.
45 
46  Include <stddef.h> for offsetof. */
47 #include <stddef.h>
48 
49 /* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other
50  standard headers, defines conflicting implementations of _Alignas
51  and _Alignof that are no better than ours; override them. */
52 #undef _Alignas
53 #undef _Alignof
54 
55 /* GCC releases before GCC 4.9 had a bug in _Alignof. See GCC bug 52023
56  <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */
57 #if (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 \
58  || (defined __GNUC__ && __GNUC__ < 4 + (__GNUC_MINOR__ < 9)))
59 # ifdef __cplusplus
60 # if 201103 <= __cplusplus
61 # define _Alignof(type) alignof (type)
62 # else
63  template <class __t> struct __alignof_helper { char __a; __t __b; };
64 # define _Alignof(type) offsetof (__alignof_helper<type>, __b)
65 # endif
66 # else
67 # define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
68 # endif
69 #endif
70 #if ! (defined __cplusplus && 201103 <= __cplusplus)
71 # define alignof _Alignof
72 #endif
73 #define __alignof_is_defined 1
74 
75 /* alignas (A), also known as _Alignas (A), aligns a variable or type
76  to the alignment A, where A is an integer constant expression. For
77  example:
78 
79  int alignas (8) foo;
80  struct s { int a; int alignas (8) bar; };
81 
82  aligns the address of FOO and the offset of BAR to be multiples of 8.
83 
84  A should be a power of two that is at least the type's alignment
85  and at most the implementation's alignment limit. This limit is
86  2**28 on typical GNUish hosts, and 2**13 on MSVC. To be portable
87  to MSVC through at least version 10.0, A should be an integer
88  constant, as MSVC does not support expressions such as 1 << 3.
89  To be portable to Sun C 5.11, do not align auto variables to
90  anything stricter than their default alignment.
91 
92  The following C11 requirements are not supported here:
93 
94  - If A is zero, alignas has no effect.
95  - alignas can be used multiple times; the strictest one wins.
96  - alignas (TYPE) is equivalent to alignas (alignof (TYPE)).
97 
98  */
99 
100 #if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
101 # if defined __cplusplus && 201103 <= __cplusplus
102 # define _Alignas(a) alignas (a)
103 # elif ((defined __APPLE__ && defined __MACH__ \
104  ? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
105  : __GNUC__) \
106  || __HP_cc || __HP_aCC || __IBMC__ || __IBMCPP__ \
107  || __ICC || 0x590 <= __SUNPRO_C)
108 # define _Alignas(a) __attribute__ ((__aligned__ (a)))
109 # elif 1300 <= _MSC_VER
110 # define _Alignas(a) __declspec (align (a))
111 # endif
112 #endif
113 #if ((defined _Alignas && ! (defined __cplusplus && 201103 <= __cplusplus)) \
114  || (defined __STDC_VERSION && 201112 <= __STDC_VERSION__))
115 # define alignas _Alignas
116 #endif
117 #if defined alignas || (defined __cplusplus && 201103 <= __cplusplus)
118 # define __alignas_is_defined 1
119 #endif
120 
121 #endif /* _GL_STDALIGN_H */