1 /* Determine alignment of types.
2 Copyright (C) 2003-2004, 2006, 2009-2020 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, see <https://www.gnu.org/licenses/>. */
22 /* alignof_slot (TYPE)
23 Determine the alignment of a structure slot (field) of a given type,
24 at compile time. Note that the result depends on the ABI.
25 This is the same as alignof (TYPE) and _Alignof (TYPE), defined in
26 <stdalign.h> if __alignof_is_defined is 1.
27 Note: The result cannot be used as a value for an 'enum' constant,
28 due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */
29 #if defined __cplusplus
30 template <class type
> struct alignof_helper
{ char __slot1
; type __slot2
; };
31 # define alignof_slot(type) offsetof (alignof_helper<type>, __slot2)
33 # define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
36 /* alignof_type (TYPE)
37 Determine the good alignment of an object of the given type at compile time.
38 Note that this is not necessarily the same as alignof_slot(type).
39 For example, with GNU C on x86 platforms: alignof_type(double) = 8, but
40 - when -malign-double is not specified: alignof_slot(double) = 4,
41 - when -malign-double is specified: alignof_slot(double) = 8.
42 Note: The result cannot be used as a value for an 'enum' constant,
43 due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */
44 #if defined __GNUC__ || defined __IBM__ALIGNOF__
45 # define alignof_type __alignof__
47 # define alignof_type alignof_slot
50 #endif /* _ALIGNOF_H */