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/* Determine alignment of types.
Copyright (C) 2003-2004, 2006, 2009-2021 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/>. */
#ifndef _ALIGNOF_H
#define _ALIGNOF_H
#include <stddef.h>
/* alignof_slot (TYPE)
Determine the alignment of a structure slot (field) of a given type,
at compile time. Note that the result depends on the ABI.
This is the same as alignof (TYPE) and _Alignof (TYPE), defined in
<stdalign.h> if __alignof_is_defined is 1.
Note: The result cannot be used as a value for an 'enum' constant,
due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */
#if defined __cplusplus
template <class type> struct alignof_helper { char __slot1; type __slot2; };
# define alignof_slot(type) offsetof (alignof_helper<type>, __slot2)
#else
# define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
#endif
/* alignof_type (TYPE)
Determine the good alignment of an object of the given type at compile time.
Note that this is not necessarily the same as alignof_slot(type).
For example, with GNU C on x86 platforms and with clang on Linux/x86:
alignof_type(long long) = 8, but alignof_slot(long long) = 4.
And alignof_type(double) = 8, but
- when -malign-double is not specified: alignof_slot(double) = 4,
- when -malign-double is specified: alignof_slot(double) = 8.
Note: The result cannot be used as a value for an 'enum' constant,
due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */
#if defined __GNUC__ || defined __clang__ || defined __IBM__ALIGNOF__
# define alignof_type __alignof__
#else
# define alignof_type alignof_slot
#endif
#endif /* _ALIGNOF_H */
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