Commit | Line | Data |
---|---|---|
725e2999 JB |
1 | /* A substitute for ISO C11 <stdalign.h>. |
2 | ||
5df4cba6 | 3 | Copyright 2011-2020 Free Software Foundation, Inc. |
725e2999 JB |
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 | |
c0c3707f | 16 | along with this program; if not, see <https://www.gnu.org/licenses/>. */ |
725e2999 JB |
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 | |
c0c3707f | 56 | <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */ |
725e2999 JB |
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__) \ | |
c0c3707f CB |
105 | : __GNUC__ && !defined __ibmxl__) \ |
106 | || (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \ | |
725e2999 JB |
107 | || __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__) |
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 */ |