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emacs/lib/flexmember.h
Paul Eggert 5a59e28dec Merge from gnulib
This incorporates:
2016-12-19 stdint: Fix WINT_MAX to match wint_t on mingw
2016-12-18 getopt: Fix link error for users of getopt() in <unistd.h>
2016-12-17 getlogin: Port to newer mingw
2016-12-17 stdint: Fix WINT_MAX to match wint_t on MSVC
2016-12-17 Avoid redefinition errors on MSVC
* lib/getopt.in.h, lib/stdint.in.h, lib/stdio.in.h, lib/unistd.in.h:
* m4/stdint.m4, m4/unistd_h.m4:
Copy from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
Plus, this commit updates the indenting on copyright notices to
match that of gnulib.
2017-01-01 01:32:56 -08:00

43 lines
1.7 KiB
C

/* Sizes of structs with flexible array members.
Copyright 2016-2017 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 of the License, 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. */
#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))