1/* A substitute for ISO C11 <stdalign.h>.
2
3   Copyright 2011-2014 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__ || __HP_cc || __HP_aCC || __IBMC__ || __IBMCPP__ \
99        || __ICC || 0x5110 <= __SUNPRO_C)
100#  define _Alignas(a) __attribute__ ((__aligned__ (a)))
101# elif 1300 <= _MSC_VER
102#  define _Alignas(a) __declspec (align (a))
103# endif
104#endif
105#if defined _Alignas || (defined __STDC_VERSION && 201112 <= __STDC_VERSION__)
106# define alignas _Alignas
107# define __alignas_is_defined 1
108#endif
109
110#endif /* _GL_STDALIGN_H */
111