c-typeck.c (c_alignof): Error on incomplete types.

        * c-typeck.c (c_alignof): Error on incomplete types.
        * extend.texi (Alignment): Document this.

From-SVN: r32522

gcc/ChangeLog

+2000-03-14  Stan Shebs  <shebs@apple.com>
+
+	* c-typeck.c (c_alignof): Error on incomplete types.
+	* extend.texi (Alignment): Document this.
+
 2000-03-13  Zack Weinberg  <zack@wolery.cumb.org>
 
 	* cppfiles.c: Include mkdeps.h.

gcc/c-typeck.c

@@ -781,6 +781,12 @@ c_alignof (type)
   if (code == VOID_TYPE || code == ERROR_MARK)
     return size_one_node;
 
+  if (TYPE_SIZE (type) == 0)
+    {
+      error ("__alignof__ applied to an incomplete type");
+      return size_zero_node;
+    }
+
   return size_int (TYPE_ALIGN (type) / BITS_PER_UNIT);
 }
 

gcc/extend.texi

@@ -1879,6 +1879,8 @@ the value of @code{__alignof__ (foo1.y)} is probably 2 or 4, the same as
 @code{__alignof__ (int)}, even though the data type of @code{foo1.y}
 does not itself demand any alignment.@refill
 
+It is an error to ask for the alignment of an incomplete type.
+
 A related feature which lets you specify the alignment of an object is
 @code{__attribute__ ((aligned (@var{alignment})))}; see the following
 section.