make CAT2() portable for use as a macro argument with an extra

level of macros

p4raw-id: //depot/perl@5525

diff --git a/config_h.SH b/config_h.SH
index d452aa9..40b5b84 100644 (file)
--- a/config_h.SH
+++ b/config_h.SH
@@ -1204,15 +1204,19 @@ sed <<!GROK!THIS! >config.h -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un-
  *     This macro surrounds its token with double quotes.
  */
 #if $cpp_stuff == 1
-#define CAT2(a,b)a/**/b
-#define STRINGIFY(a)"a"
+#  define CAT2(a,b)    a/**/b
+#  define STRINGIFY(a) "a"
                /* If you can get stringification with catify, tell me how! */
 #endif
 #if $cpp_stuff == 42
-#define CAT2(a,b)a ## b
-#define StGiFy(a)# a
-#define STRINGIFY(a)StGiFy(a)
+#  define PeRl_CaTiFy(a,b)     a ## b
+#  define PeRl_StGiFy(a)       #a
+       /* the additional level of indirection enables these macros to be
+        * used as arguments to other macros.  See K&R 2nd ed., page 231. */
+#  define CAT2(a,b)    PeRl_CaTiFy(a,b)
+#  define STRINGIFY(a) PeRl_StGiFy(a)
 #endif
+
 #if $cpp_stuff != 1 && $cpp_stuff != 42
 #include "Bletch: How does this C preprocessor catenate tokens?"
 #endif