svn commit: r250578 - head/sys/sys

[Jeff Roberson]

Author: jeff
Date: Sun May 12 20:44:28 2013
New Revision: 250578
URL: http://svnweb.freebsd.org/changeset/base/250578

Log:
   - pctrie really only requires two byte alignment so that there is a single
     bit available for a flag in the pointer.  However, it felt more correct
     to enforce natural alignment of the key pointer.  Unfortunately on
     32bit architectures 64bit integers are not always naturally aligned.
     Change the assert to enforce only 32bit alignment of the 64bit key for
     now to fix the build.  A more correct fix would be to properly sort
     the struct buf fields which definitely suffer from bloat due to padding.

Modified:
  head/sys/sys/pctrie.h

Modified: head/sys/sys/pctrie.h
==============================================================================
--- head/sys/sys/pctrie.h	Sun May 12 16:50:18 2013	(r250577)
+++ head/sys/sys/pctrie.h	Sun May 12 20:44:28 2013	(r250578)
@@ -38,7 +38,11 @@
 #define	PCTRIE_DEFINE(name, type, field, allocfn, freefn)		\
 									\
 CTASSERT(sizeof(((struct type *)0)->field) == sizeof(uint64_t));	\
-CTASSERT((__offsetof(struct type, field) & (sizeof(uint64_t) - 1)) == 0); \
+/*									\
+ * XXX This assert protects flag bits, it does not enforce natural	\
+ * alignment.  32bit architectures do not naturally align 64bit fields.	\
+ */									\
+CTASSERT((__offsetof(struct type, field) & (sizeof(uint32_t) - 1)) == 0); \
 									\
 static __inline struct type *						\
 name##_PCTRIE_VAL2PTR(uint64_t *val)					\