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Diffstat (limited to 'lib/alignof.h')
-rw-r--r-- | lib/alignof.h | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/lib/alignof.h b/lib/alignof.h new file mode 100644 index 000000000..28ce79c48 --- /dev/null +++ b/lib/alignof.h @@ -0,0 +1,53 @@ +/* Determine alignment of types. + Copyright (C) 2003-2004, 2006, 2009 Free Software Foundation, Inc. + + This program 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, 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 Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program; if not, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +#ifndef _ALIGNOF_H +#define _ALIGNOF_H + +#include <stddef.h> + +/* Determine the alignment of a structure slot (field) of a given type, + at compile time. Note that the result depends on the ABI. + Note: The result cannot be used as a value for an 'enum' constant, + due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ +#if defined __cplusplus + template <class type> struct alignof_helper { char __slot1; type __slot2; }; +# define alignof_slot(type) offsetof (alignof_helper<type>, __slot2) +#else +# define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2) +#endif + +/* Determine the good alignment of a object of the given type at compile time. + Note that this is not necessarily the same as alignof_slot(type). + For example, with GNU C on x86 platforms: alignof_type(double) = 8, but + - when -malign-double is not specified: alignof_slot(double) = 4, + - when -malign-double is specified: alignof_slot(double) = 8. + Note: The result cannot be used as a value for an 'enum' constant, + due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ +#if defined __GNUC__ +# define alignof_type __alignof__ +#else +# define alignof_type alignof_slot +#endif + +/* alignof is an alias for alignof_slot semantics, since that's what most + callers need. + Note: The result cannot be used as a value for an 'enum' constant, + due to bugs in HP-UX 10.20 cc and AIX 3.2.5 xlc. */ +#define alignof alignof_slot + +#endif /* _ALIGNOF_H */ |