symcat.h: Honor autoconf macro HAVE_STRINGIZE.

        * symcat.h: Honor autoconf macro HAVE_STRINGIZE.  Add
        comments/caveats with regard to traditional C behavior.

From-SVN: r33209

include/ChangeLog

+2000-04-17  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
+
+	* symcat.h: Honor autoconf macro HAVE_STRINGIZE.  Add
+	comments/caveats with regard to traditional C behavior.
+
 2000-04-05  Richard Henderson  <rth@cygnus.com>
 
 	* splay-tree.h (splay_tree_remove): Declare.

include/symcat.h

@@ -19,12 +19,16 @@
 #ifndef SYM_CAT_H
 #define SYM_CAT_H
 
-#if defined (__STDC__) || defined (ALMOST_STDC)
+#if defined (__STDC__) || defined (ALMOST_STDC) || defined (HAVE_STRINGIZE)
 #define CONCAT2(a,b)	 a##b
 #define CONCAT3(a,b,c)	 a##b##c
 #define CONCAT4(a,b,c,d) a##b##c##d
 #define STRINGX(s) #s
 #else
+/* Note one should never pass extra whitespace to the CONCATn macros,
+   e.g. CONCAT2(foo, bar) because traditonal C will keep the space between
+   the two labels instead of concatenating them.  Instead, make sure to
+   write CONCAT2(foo,bar).  */
 #define CONCAT2(a,b)	 a/**/b
 #define CONCAT3(a,b,c)	 a/**/b/**/c
 #define CONCAT4(a,b,c,d) a/**/b/**/c/**/d
@@ -35,6 +39,11 @@
 #define XCONCAT3(a,b,c)   CONCAT3(a,b,c)
 #define XCONCAT4(a,b,c,d) CONCAT4(a,b,c,d)
 
+/* Note the layer of indirection here is typically used to allow
+   stringification of the expansion of macros.  I.e. "#define foo
+   bar", "XSTRING(foo)", to yield "bar".  Be aware that this only
+   works for __STDC__, not for traditional C which will still resolve
+   to "foo".  */
 #define XSTRING(s) STRINGX(s) 
 
 #endif SYM_CAT_H