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1 | /* A substitute for ISO C11 <stdalign.h>. | ||
2 | |||
3 | Copyright 2011-2013 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 | #if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 | ||
56 | # ifdef __cplusplus | ||
57 | # if 201103 <= __cplusplus | ||
58 | # define _Alignof(type) alignof (type) | ||
59 | # else | ||
60 | template <class __t> struct __alignof_helper { char __a; __t __b; }; | ||
61 | # define _Alignof(type) offsetof (__alignof_helper<type>, __b) | ||
62 | # endif | ||
63 | # else | ||
64 | # define _Alignof(type) offsetof (struct { char __a; type __b; }, __b) | ||
65 | # endif | ||
66 | #endif | ||
67 | #define alignof _Alignof | ||
68 | #define __alignof_is_defined 1 | ||
69 | |||
70 | /* alignas (A), also known as _Alignas (A), aligns a variable or type | ||
71 | to the alignment A, where A is an integer constant expression. For | ||
72 | example: | ||
73 | |||
74 | int alignas (8) foo; | ||
75 | struct s { int a; int alignas (8) bar; }; | ||
76 | |||
77 | aligns the address of FOO and the offset of BAR to be multiples of 8. | ||
78 | |||
79 | A should be a power of two that is at least the type's alignment | ||
80 | and at most the implementation's alignment limit. This limit is | ||
81 | 2**28 on typical GNUish hosts, and 2**13 on MSVC. To be portable | ||
82 | to MSVC through at least version 10.0, A should be an integer | ||
83 | constant, as MSVC does not support expressions such as 1 << 3. | ||
84 | To be portable to Sun C 5.11, do not align auto variables to | ||
85 | anything stricter than their default alignment. | ||
86 | |||
87 | The following C11 requirements are not supported here: | ||
88 | |||
89 | - If A is zero, alignas has no effect. | ||
90 | - alignas can be used multiple times; the strictest one wins. | ||
91 | - alignas (TYPE) is equivalent to alignas (alignof (TYPE)). | ||
92 | |||
93 | */ | ||
94 | |||
95 | #if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 | ||
96 | # if defined __cplusplus && 201103 <= __cplusplus | ||
97 | # define _Alignas(a) alignas (a) | ||
98 | # elif __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC || 0x5110 <= __SUNPRO_C | ||
99 | # define _Alignas(a) __attribute__ ((__aligned__ (a))) | ||
100 | # elif 1300 <= _MSC_VER | ||
101 | # define _Alignas(a) __declspec (align (a)) | ||
102 | # endif | ||
103 | #endif | ||
104 | #if defined _Alignas || (defined __STDC_VERSION && 201112 <= __STDC_VERSION__) | ||
105 | # define alignas _Alignas | ||
106 | # define __alignas_is_defined 1 | ||
107 | #endif | ||
108 | |||
109 | #endif /* _GL_STDALIGN_H */ | ||