--- a/ChangeLog	Tue Nov 01 11:01:10 2011 +0100
+++ b/ChangeLog	Tue Nov 01 12:43:23 2011 +0100
@@ -1,3 +1,10 @@
+2011-11-01  Bruno Haible  <bruno@clisp.org>
+
+	alignof: Avoid collision with stdalign module.
+	* lib/alignof.h (alignof): Remove macro.
+	* NEWS: Mention the change.
+	Reported by Paul Eggert.
+
 2011-11-01  Bruno Haible  <bruno@clisp.org>
 
 	New module 'fchownat', split off from module 'openat'.

--- a/NEWS	Tue Nov 01 11:01:10 2011 +0100
+++ b/NEWS	Tue Nov 01 12:43:23 2011 +0100
@@ -12,6 +12,9 @@
 
 Date        Modules         Changes
 
+2011-11-01  alignof         This module no longer provides the alignof() macro.
+                            Use either alignof_slot() or alignof_type() instead.
+
 2011-11-01  openat          This module no longer provides the fchownat()
                             function. If you need this function, you now need
                             to request the 'fchownat' module.

--- a/lib/alignof.h	Tue Nov 01 11:01:10 2011 +0100
+++ b/lib/alignof.h	Tue Nov 01 12:43:23 2011 +0100
@@ -20,8 +20,11 @@
 
 #include <stddef.h>
 
-/* Determine the alignment of a structure slot (field) of a given type,
+/* 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
@@ -31,7 +34,8 @@
 # define alignof_slot(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
 #endif
 
-/* Determine the good alignment of an object of the given type at compile time.
+/* 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,
@@ -44,10 +48,4 @@
 # 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 */