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8912421c | 1 | /* Determine alignment of types. |
f0007cad | 2 | Copyright (C) 2003-2004, 2006, 2009-2012 Free Software Foundation, Inc. |
8912421c LC |
3 | |
4 | This program is free software; you can redistribute it and/or modify | |
5 | it under the terms of the GNU Lesser General Public License as published by | |
6 | the Free Software Foundation; either version 2, or (at your option) | |
7 | any later version. | |
8 | ||
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 Lesser General Public License for more details. | |
13 | ||
14 | You should have received a copy of the GNU Lesser General Public License | |
15 | along with this program; if not, write to the Free Software Foundation, | |
16 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ | |
17 | ||
18 | #ifndef _ALIGNOF_H | |
19 | #define _ALIGNOF_H | |
20 | ||
21 | #include <stddef.h> | |
22 | ||
7f1ea859 LC |
23 | /* alignof_slot (TYPE) |
24 | Determine the alignment of a structure slot (field) of a given type, | |
8912421c | 25 | at compile time. Note that the result depends on the ABI. |
7f1ea859 LC |
26 | This is the same as alignof (TYPE) and _Alignof (TYPE), defined in |
27 | <stdalign.h> if __alignof_is_defined is 1. | |
8912421c LC |
28 | Note: The result cannot be used as a value for an 'enum' constant, |
29 | due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ | |
30 | #if defined __cplusplus | |
31 | template <class type> struct alignof_helper { char __slot1; type __slot2; }; | |
32 | # define alignof_slot(type) offsetof (alignof_helper<type>, __slot2) | |
33 | #else | |
34 | # define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2) | |
35 | #endif | |
36 | ||
7f1ea859 LC |
37 | /* alignof_type (TYPE) |
38 | Determine the good alignment of an object of the given type at compile time. | |
8912421c LC |
39 | Note that this is not necessarily the same as alignof_slot(type). |
40 | For example, with GNU C on x86 platforms: alignof_type(double) = 8, but | |
41 | - when -malign-double is not specified: alignof_slot(double) = 4, | |
42 | - when -malign-double is specified: alignof_slot(double) = 8. | |
43 | Note: The result cannot be used as a value for an 'enum' constant, | |
44 | due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ | |
45 | #if defined __GNUC__ | |
46 | # define alignof_type __alignof__ | |
47 | #else | |
48 | # define alignof_type alignof_slot | |
49 | #endif | |
50 | ||
8912421c | 51 | #endif /* _ALIGNOF_H */ |