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/* A substitute for ISO C11 <stdalign.h>.
Copyright 2011-2023 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://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 and clang's __alignof__ operator, which can
yield a better-performing alignment for an object of that type. For
example, on x86 with GCC and on Linux/x86 with clang,
__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. */
/* 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
/* GCC releases before GCC 4.9 had a bug in _Alignof. See GCC bug 52023
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>.
clang versions < 8.0.0 have the same bug. */
#if (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 \
|| (defined __GNUC__ && __GNUC__ < 4 + (__GNUC_MINOR__ < 9) \
&& !defined __clang__) \
|| (defined __clang__ && __clang_major__ < 8))
# ifdef __cplusplus
# if (201103 <= __cplusplus || defined _MSC_VER)
# define _Alignof(type) alignof (type)
# else
template <class __t> struct __alignof_helper { char __a; __t __b; };
# define _Alignof(type) offsetof (__alignof_helper<type>, __b)
# define _GL_STDALIGN_NEEDS_STDDEF 1
# endif
# else
# if (defined __GNUC__ && 4 <= __GNUC__) || defined __clang__
# define _Alignof(type) __builtin_offsetof (struct { char __a; type __b; }, __b)
# else
# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
# define _GL_STDALIGN_NEEDS_STDDEF 1
# endif
# endif
#endif
#if ! (defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER))
# define alignof _Alignof
#endif
#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 || defined _MSC_VER)
# define _Alignas(a) alignas (a)
# elif (!defined __attribute__ \
&& ((defined __APPLE__ && defined __MACH__ \
? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
: __GNUC__ && !defined __ibmxl__) \
|| (4 <= __clang_major__) \
|| (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
|| __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__))
# define _Alignas(a) __attribute__ ((__aligned__ (a)))
# elif 1300 <= _MSC_VER
# define _Alignas(a) __declspec (align (a))
# endif
#endif
#if ((defined _Alignas \
&& !(defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER))) \
|| (defined __STDC_VERSION__ && 201112 <= __STDC_VERSION__))
# define alignas _Alignas
#endif
#if (defined alignas \
|| (defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER)))
# define __alignas_is_defined 1
#endif
/* Include <stddef.h> if needed for offsetof. */
#if _GL_STDALIGN_NEEDS_STDDEF
# include <stddef.h>
#endif
#endif /* _GL_STDALIGN_H */
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