X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Falignof.h;h=74e35aa9d122ca548a86903e0e08844a254f97f2;hb=72983fb6b5bd6c7de54465eea29464bb9c0276cf;hp=49e7757a0e28e3a590a353486f44123f0fad77d2;hpb=23d767ba41eea6f9e38db321332b447891f2e416;p=gnulib.git

diff --git a/lib/alignof.h b/lib/alignof.h
index 49e7757a0..74e35aa9d 100644
--- a/lib/alignof.h
+++ b/lib/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, 2009-2012 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
@@ -12,30 +12,39 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU 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.  */
+   along with this program; if not, see <http://www.gnu.org/licenses/>.  */
 
 #ifndef _ALIGNOF_H
 #define _ALIGNOF_H
 
 #include <stddef.h>
 
-/* Determine the alignment of a type at compile time.  */
-#if defined __GNUC__
-# define alignof __alignof__
-#elif defined __cplusplus
+/* alignof_slot (TYPE)
+   Determine the alignment of a structure slot (field) of a given type,
+   at compile time.  Note that the result depends on the ABI.
+   This is the same as alignof (TYPE) and _Alignof (TYPE), defined in
+   <stdalign.h> if __alignof_is_defined is 1.
+   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)
-#elif defined __hpux
-  /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof
-     values.  */
-# define alignof(type) (sizeof (type) <= 4 ? 4 : 8)
-#elif defined _AIX
-  /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof
-     values.  */
-# define alignof(type) (sizeof (type) <= 4 ? 4 : 8)
+# define alignof_slot(type) offsetof (alignof_helper<type>, __slot2)
+#else
+# define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
+#endif
+
+/* alignof_type (TYPE)
+   Determine the good alignment of an 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
 
 #endif /* _ALIGNOF_H */