1 /* -*- buffer-read-only: t -*- vi: set ro: */
2 /* DO NOT EDIT! GENERATED AUTOMATICALLY! */
3 /* A substitute for ISO C11 <stdalign.h>.
5 Copyright 2011-2013 Free Software Foundation, Inc.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, see <http://www.gnu.org/licenses/>. */
20 /* Written by Paul Eggert and Bruno Haible. */
22 #ifndef _GL_STDALIGN_H
23 #define _GL_STDALIGN_H
25 /* ISO C11 <stdalign.h> for platforms that lack it.
28 ISO C11 (latest free draft
29 <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf>)
30 sections 6.5.3.4, 6.7.5, 7.15.
31 C++11 (latest free draft
32 <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf>)
35 /* alignof (TYPE), also known as _Alignof (TYPE), yields the alignment
36 requirement of a structure member (i.e., slot or field) that is of
37 type TYPE, as an integer constant expression.
39 This differs from GCC's __alignof__ operator, which can yield a
40 better-performing alignment for an object of that type. For
41 example, on x86 with GCC, __alignof__ (double) and __alignof__
42 (long long) are 8, whereas alignof (double) and alignof (long long)
43 are 4 unless the option '-malign-double' is used.
45 The result cannot be used as a value for an 'enum' constant, if you
46 want to be portable to HP-UX 10.20 cc and AIX 3.2.5 xlc. */
48 #if defined __cplusplus
49 template <class __t> struct __alignof_helper { char __a; __t __b; };
50 # define _Alignof(type) offsetof (__alignof_helper<type>, __b)
52 # define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
54 #define alignof _Alignof
55 #define __alignof_is_defined 1
57 /* alignas (A), also known as _Alignas (A), aligns a variable or type
58 to the alignment A, where A is an integer constant expression. For
62 struct s { int a; int alignas (8) bar; };
64 aligns the address of FOO and the offset of BAR to be multiples of 8.
66 A should be a power of two that is at least the type's alignment
67 and at most the implementation's alignment limit. This limit is
68 2**28 on typical GNUish hosts, and 2**13 on MSVC. To be portable
69 to MSVC through at least version 10.0, A should be an integer
70 constant, as MSVC does not support expressions such as 1 << 3.
71 To be portable to Sun C 5.11, do not align auto variables to
72 anything stricter than their default alignment.
74 The following C11 requirements are not supported here:
76 - If A is zero, alignas has no effect.
77 - alignas can be used multiple times; the strictest one wins.
78 - alignas (TYPE) is equivalent to alignas (alignof (TYPE)).
82 #if __GNUC__ || __IBMC__ || __IBMCPP__ || 0x5110 <= __SUNPRO_C
83 # define _Alignas(a) __attribute__ ((__aligned__ (a)))
84 #elif 1300 <= _MSC_VER
85 # define _Alignas(a) __declspec (align (a))
88 # define alignas _Alignas
89 # define __alignas_is_defined 1
92 #endif /* _GL_STDALIGN_H */