From 850952d612ad708d7952bc30b9a6c674fdc90f58 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Mon, 26 Sep 2022 21:28:12 -0500
Subject: [PATCH] Treat ORG records as giving a signed offset from the current
 location.

This is the way they are defined in the GS/OS Reference, as well as the way they seem to be used by all assemblers and all other linkers that I could check (ORCA/M, MPW AsmIIGS, Apple LinkIIGS, old ORCA/APW LINKED, 8-bit ORCA linker).

Previously, this linker treated ORG records as giving an absolute address to ORG to (but with a bug in the address computation). The OMF spec in appendix B of the ORCA/M manual defines them this way, but this is inconsistent with the spec in the GS/OS Reference and with the way ORG records are generated by ORCA/M itself (for an ORG *+expression directive). Therefore, I think this is just an error and the specification in the GS/OS Reference should be regarded as correct.

We still do not support going backward (using a negative ORG operand). Trying to do so will just give an error.
---
 linker.notes | 9 ++++++++-
 pass1.asm    | 9 ++++-----
 pass2.asm    | 7 +++----
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/linker.notes b/linker.notes
index dbd56c6..8ff8c4f 100644
--- a/linker.notes
+++ b/linker.notes
@@ -13,6 +13,11 @@ Updated 2022
 	    3.	Fixed bug that caused EQU or GEQU expressions with non-constant
 		operands to be evaluated incorrectly.
 
+	    4.	The numeric value in an ORG record is now treated as a signed
+		offset from the current location, consistent with its
+		definition in the GS/OS Reference.  However, negative offset
+		values are not supported and will produce an error.
+
 2.0.6       1.	The linker could give a spurious error about the relative
 		address calculation for a BRL instruction if it branched
 		forward or backward more than 32 KB.  Since the address
@@ -69,7 +74,9 @@ Updated 2022
 
 -- Documentation Update -----------------------------------------------------
 
-No changes.
+ORCA/M Manual, p. 492
+
+The operand in an ORG record is a signed offset from the current location, not an absolute address.  (This is consistent with the definition in the GS/OS Reference, and with the behavior of ORCA/M and other assemblers and linkers.)
 
 -- Changes introduced in ORCA/Linker 2.1.0 ----------------------------------
 
diff --git a/pass1.asm b/pass1.asm
index b18a290..24a5a34 100644
--- a/pass1.asm
+++ b/pass1.asm
@@ -137,13 +137,12 @@ DoOrg	private
 	sta	r0
 	ldy	#3
 	lda	[sp],Y
-	sta	r2+2
+	sta	r2
 	add4	sp,#5
 
-	sub4	r0,loadOrg	get the disp from the segment start
-	cmpl	pc,r0
-	bge	lb1	if the disp is greater than the pc then
-	move4 r0,pc	  update the pc
+	lda	r2
+	bmi	lb1	if the disp is positive
+	add4	pc,r0	  update the pc
 lb1	anop
 	rts
 	end
diff --git a/pass2.asm b/pass2.asm
index 07ad2ff..bae0513 100644
--- a/pass2.asm
+++ b/pass2.asm
@@ -643,13 +643,12 @@ DoOrg	private
 
 	ldy	#1	get the value
 	lda	[sp],Y
-	sta	r4
+	sta	r0
 	ldy	#3
 	lda	[sp],Y
-	sta	r6
+	sta	r2
 	add4	sp,#5	skip the op code & operand
-	sub4	pc,r4,r0	calculate the space to insert
-	lda	r2	if space < 0 then
+	lda	r2	if disp < 0 then
 	bpl	lb1
 	ph4	#0	  Error(NULL,3)
 	ph2	#3