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/* A substitute for ISO C11 <stdalign.h>.
Copyright 2011-2013 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <http://www.gnu.org/licenses/>. */
/* Written by Paul Eggert and Bruno Haible. */
#ifndef _GL_STDALIGN_H
#define _GL_STDALIGN_H
/* ISO C11 <stdalign.h> for platforms that lack it.
References:
ISO C11 (latest free draft
<http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf>)
sections 6.5.3.4, 6.7.5, 7.15.
C++11 (latest free draft
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf>)
section 18.10. */
/* alignof (TYPE), also known as _Alignof (TYPE), yields the alignment
requirement of a structure member (i.e., slot or field) that is of
type TYPE, as an integer constant expression.
This differs from GCC's __alignof__ operator, which can yield a
better-performing alignment for an object of that type. For
example, on x86 with GCC, __alignof__ (double) and __alignof__
(long long) are 8, whereas alignof (double) and alignof (long long)
are 4 unless the option '-malign-double' is used.
The result cannot be used as a value for an 'enum' constant, if you
want to be portable to HP-UX 10.20 cc and AIX 3.2.5 xlc.
Include <stddef.h> for offsetof. */
#include <stddef.h>
/* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other
standard headers, defines conflicting implementations of _Alignas
and _Alignof that are no better than ours; override them. */
#undef _Alignas
#undef _Alignof
#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
# ifdef __cplusplus
# if 201103 <= __cplusplus
# define _Alignof(type) alignof (type)
# else
template <class __t> struct __alignof_helper { char __a; __t __b; };
# define _Alignof(type) offsetof (__alignof_helper<type>, __b)
# endif
# else
# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
# endif
#endif
#define alignof _Alignof
#define __alignof_is_defined 1
/* alignas (A), also known as _Alignas (A), aligns a variable or type
to the alignment A, where A is an integer constant expression. For
example:
int alignas (8) foo;
struct s { int a; int alignas (8) bar; };
aligns the address of FOO and the offset of BAR to be multiples of 8.
A should be a power of two that is at least the type's alignment
and at most the implementation's alignment limit. This limit is
2**28 on typical GNUish hosts, and 2**13 on MSVC. To be portable
to MSVC through at least version 10.0, A should be an integer
constant, as MSVC does not support expressions such as 1 << 3.
To be portable to Sun C 5.11, do not align auto variables to
anything stricter than their default alignment.
The following C11 requirements are not supported here:
- If A is zero, alignas has no effect.
- alignas can be used multiple times; the strictest one wins.
- alignas (TYPE) is equivalent to alignas (alignof (TYPE)).
*/
#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
# if defined __cplusplus && 201103 <= __cplusplus
# define _Alignas(a) alignas (a)
# elif __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC || 0x5110 <= __SUNPRO_C
# define _Alignas(a) __attribute__ ((__aligned__ (a)))
# elif 1300 <= _MSC_VER
# define _Alignas(a) __declspec (align (a))
# endif
#endif
#if defined _Alignas || (defined __STDC_VERSION && 201112 <= __STDC_VERSION__)
# define alignas _Alignas
# define __alignas_is_defined 1
#endif
#endif /* _GL_STDALIGN_H */
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