| 1 | /* Determine alignment of types. |
| 2 | Copyright (C) 2003-2004, 2006, 2009-2010 Free Software Foundation, Inc. |
| 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 | |
| 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 | Note: The result cannot be used as a value for an 'enum' constant, |
| 26 | due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ |
| 27 | #if defined __cplusplus |
| 28 | template <class type> struct alignof_helper { char __slot1; type __slot2; }; |
| 29 | # define alignof_slot(type) offsetof (alignof_helper<type>, __slot2) |
| 30 | #else |
| 31 | # define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2) |
| 32 | #endif |
| 33 | |
| 34 | /* Determine the good alignment of a object of the given type at compile time. |
| 35 | Note that this is not necessarily the same as alignof_slot(type). |
| 36 | For example, with GNU C on x86 platforms: alignof_type(double) = 8, but |
| 37 | - when -malign-double is not specified: alignof_slot(double) = 4, |
| 38 | - when -malign-double is specified: alignof_slot(double) = 8. |
| 39 | Note: The result cannot be used as a value for an 'enum' constant, |
| 40 | due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ |
| 41 | #if defined __GNUC__ |
| 42 | # define alignof_type __alignof__ |
| 43 | #else |
| 44 | # define alignof_type alignof_slot |
| 45 | #endif |
| 46 | |
| 47 | /* alignof is an alias for alignof_slot semantics, since that's what most |
| 48 | callers need. |
| 49 | Note: The result cannot be used as a value for an 'enum' constant, |
| 50 | due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ |
| 51 | #define alignof alignof_slot |
| 52 | |
| 53 | #endif /* _ALIGNOF_H */ |