maint: update copyright

[gnulib.git] / lib / alignof.h

diff --git a/lib/alignof.h b/lib/alignof.h
index 3752ef3..2d26a5a 100644 (file)
--- 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, 2009-2014 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
@@ -12,22 +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)
+# define alignof_slot(type) offsetof (alignof_helper<type>, __slot2)
 #else
-# define alignof(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
+# 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__ || defined __IBM__ALIGNOF__
+# define alignof_type __alignof__
+#else
+# define alignof_type alignof_slot
 #endif
 
 #endif /* _ALIGNOF_H */