--- gforth/comp-i.fs	2002/01/14 08:40:23	1.9
+++ gforth/comp-i.fs	2007/09/29 22:20:02	1.17
@@ -1,6 +1,6 @@
 \ Compare nonrelocatable images and produce a relocatable image
 
-\ Copyright (C) 1996,1997,1998 Free Software Foundation, Inc.
+\ Copyright (C) 1996,1997,1998,2002,2003,2004 Free Software Foundation, Inc.
 
 \ This file is part of Gforth.
 
@@ -19,7 +19,7 @@
 \ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
 
 s" address-unit-bits" environment? drop constant bits/au
-6 constant dodoes-tag
+7 constant dodoes-tag
 
 : write-cell { w^ w  file-id -- ior }
     \ write a cell to the file
@@ -43,12 +43,19 @@ s" address-unit-bits" environment? drop
     if
 	." : images have the same base address; producing only a data-relocatable image" cr
     else
-	offset abs expected-offset <> abort" images produced by different engines"
+	\ the following sanity check produces false positices with exec-shield
+	\ offset abs expected-offset <> abort" images produced by different engines"
 	."  offset=" offset . cr
 	0 image1 i-field + ! 0 image2 i-field + !
     endif
     base offset ;
-    
+
+: >tag ( index -- tag )
+    dup dodoes-tag 2 + > IF
+	$21 1 DO  dup tag-offsets I cells + @ < IF
+		tag-offsets I 1- cells + @ - I 1- 9 lshift + negate
+		UNLOOP  EXIT  THEN  LOOP
+    THEN  -2 swap - ;
 
 : compare-images { image1 image2 reloc-bits size file-id -- }
     \G compares image1 and image2 (of size cells) and sets reloc-bits.
@@ -78,7 +85,7 @@ s" address-unit-bits" environment? drop
 		    dbase negate image1 i 1+ th +!
 		    dbase doffset + negate image2 i 1+ th +!
 		endif
-		-2 tag $4000 or - file-id write-cell throw
+		tag >tag $4000 xor file-id write-cell throw
 		i reloc-bits set-bit
 	    else
 		xoffset 0<> cell1 xoffset + cell2 = and
@@ -91,7 +98,7 @@ s" address-unit-bits" environment? drop
 			dbase negate image1 i 1+ th +!
 			dbase doffset + negate image2 i 1+ th +!
 		    endif
-		    -2 tag - file-id write-cell throw
+		    tag >tag file-id write-cell throw
 		    i reloc-bits set-bit
 		else
 		    cell1 file-id write-cell throw
@@ -106,7 +113,7 @@ s" address-unit-bits" environment? drop
 
 : comp-image ( "image-file1" "image-file2" "new-image" -- )
     name slurp-file { image1 size1 }
-    image1 size1 s" Gforth2" search 0= abort" not a Gforth image"
+    image1 size1 s" Gforth3" search 0= abort" not a Gforth image"
     drop 8 + image1 - { header-offset }
     size1 aligned size1 <> abort" unaligned image size"
     image1 header-offset + 2 cells + @ header-offset + size1 <> abort" header gives wrong size"