The following patch makes the tests pass, but please be cautioned that my XS-foo is *very* limited. The CvXSUB CvROOT stuff is stolen directly from dump.c of the 5.8.0 source, specifically the Perl_dump_sub routine at line 70.

Let me re-iterate. I'm no expert here. This just worked for me. 
--- CCC.xs~     2003-05-23 13:58:57.000000000 -0400
+++ CCC.xs      2003-05-23 13:58:46.000000000 -0400
@@ -2,15 +2,18 @@
 #include "perl.h"
 #include "XSUB.h"
  
-
 void inspect( char* name ) {
-  if( get_cv( name, (I32)0 ) != NULL ) {
-    printf( " &%s is defined\n", name );
+  GV *glob = CvGV(get_cv( name, (I32)0 ));
+  if ( (CvXSUB(GvCV(glob))) || CvROOT(GvCV(glob)) ) {
+    printf( " &%s has code\n", name );
     {
       dSP ;
       PUSHMARK(SP) ;
       call_pv( name, G_DISCARD | G_NOARGS );
     }
+  }
+  else {
+    printf( " &%s is undefined\n", name );
   }
 }

[download]
-- dug

In reply to Re: How to check for subroutine existence from within XS code by dug
in thread How to check for subroutine existence from within XS code by philou

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