skip T_IMEMO for VMDEBUG

* vm_dump.c (vm_stack_dump_each): skip T_IMEMO object to display
  for VMDEBUG=3. [Bug #13030]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57427 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

vm_dump.c

@@ -281,11 +281,16 @@ vm_stack_dump_each(rb_thread_t *th, rb_control_frame_t *cfp)
 
 	ptr = vm_base_ptr(cfp);
 	for (; ptr < sp; ptr++, i++) {
-	    if (*ptr == Qundef) {
+	    switch (TYPE(*ptr)) {
+	      case T_UNDEF:
 		rstr = rb_str_new2("undef");
-	    }
-	    else {
+		break;
+	      case T_IMEMO:
+		rstr = rb_str_new2("imemo"); /* TODO: can put mode detail information */
+		break;
+	      default:
 		rstr = rb_inspect(*ptr);
+		break;
 	    }
 	    fprintf(stderr, "  stack %2d: %8s (%"PRIdPTRDIFF")\n", i, StringValueCStr(rstr),
 		    (ptr - th->stack));