diff options
Diffstat (limited to 'gl/alignof.h')
| -rw-r--r-- | gl/alignof.h | 34 |
1 files changed, 27 insertions, 7 deletions
diff --git a/gl/alignof.h b/gl/alignof.h index 896382b0..240468c6 100644 --- a/gl/alignof.h +++ b/gl/alignof.h @@ -1,5 +1,5 @@ /* Determine alignment of types. - Copyright (C) 2003-2004, 2006, 2009 Free Software Foundation, Inc. + Copyright (C) 2003-2004, 2006, 2009-2010 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 @@ -20,14 +20,34 @@ #include <stddef.h> -/* Determine the alignment of a type at compile time. */ -#if defined __GNUC__ -# define alignof __alignof__ -#elif defined __cplusplus +/* 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(type) offsetof (alignof_helper<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) offsetof (struct { char __slot1; type __slot2; }, __slot2) +# 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 */ |