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/* Sizes of structs with flexible array members.
Copyright 2016-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library 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.
The GNU C Library 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 the GNU C Library; if not, see
<https://www.gnu.org/licenses/>.
Written by Paul Eggert. */
#include <stddef.h>
/* Nonzero multiple of alignment of TYPE, suitable for FLEXSIZEOF below.
On older platforms without _Alignof, use a pessimistic bound that is
safe in practice even if FLEXIBLE_ARRAY_MEMBER is 1.
On newer platforms, use _Alignof to get a tighter bound. */
#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
# define FLEXALIGNOF(type) (sizeof (type) & ~ (sizeof (type) - 1))
#else
# define FLEXALIGNOF(type) _Alignof (type)
#endif
/* Upper bound on the size of a struct of type TYPE with a flexible
array member named MEMBER that is followed by N bytes of other data.
This is not simply sizeof (TYPE) + N, since it may require
alignment on unusually picky C11 platforms, and
FLEXIBLE_ARRAY_MEMBER may be 1 on pre-C11 platforms.
Yield a value less than N if and only if arithmetic overflow occurs. */
#define FLEXSIZEOF(type, member, n) \
((offsetof (type, member) + FLEXALIGNOF (type) - 1 + (n)) \
& ~ (FLEXALIGNOF (type) - 1))
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