From da13b94a4339b94b359076fb55d60303d43fdff8 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Sun, 25 Sep 2022 21:42:20 -0500
Subject: [PATCH] Properly evaluate non-constant expressions in EQU/GEQU
 records.

Previously, the values of such expressions were essentially ignored, resulting in incorrect output.

This affected code like the following example:

test1   start
        lda     >p
        rtl
        end

D1      data
p       gequ    val
        end

val     data
        dc      i'123'
        end

Note that the EQU/GEQU expression is evaluated within the context of the location that references it, not the location where it is defined. This affects the value of the location counter, as well as the symbol search behavior. The references for the OMF format do not clearly define which way this should be done, but the current behavior can cause problems with certain object files produced by ORCA/M.
---
 exp.asm      |  1 +
 linker.notes |  3 +++
 symbol.asm   | 14 ++------------
 3 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/exp.asm b/exp.asm
index a545482..73e4a6b 100644
--- a/exp.asm
+++ b/exp.asm
@@ -727,6 +727,7 @@ addr	dc	a'EndExp'	$00		End
 *	shiftFlag - 1 if the value is shifted, else 0
 *	shiftValue - expression result before shifting
 *	shiftCount - shift counter
+*	symbolRelocatable - non-zero if sym is relocatable
 *	returns the value of the expression
 *
 ****************************************************************
diff --git a/linker.notes b/linker.notes
index 9f2c539..dbd56c6 100644
--- a/linker.notes
+++ b/linker.notes
@@ -10,6 +10,9 @@ Updated 2022
 	    2.	A load segment is now flagged as position-independent only if
 		all the constituent object segments have that attribute set.
 
+	    3.	Fixed bug that caused EQU or GEQU expressions with non-constant
+		operands to be evaluated incorrectly.
+
 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
diff --git a/symbol.asm b/symbol.asm
index eccdb34..319f492 100644
--- a/symbol.asm
+++ b/symbol.asm
@@ -845,15 +845,10 @@ gb3	ldy	#symPriv	if sym^.symPriv then
 sv1	ldy	#symExp	if the value is an expression then
 	lda	[sym],Y
 	jeq	sv2
-	ph2	copiedExpression	  save volitile variables
+	ph2	copiedExpression	  save volatile variables
 	ph4	shiftCount
 	ph2	shiftFlag
 	ph4	shiftValue
-	ph2	symbolCount
-	ph2	symbolLength
-	ph2	symbolRelocatable
-	ph2	symbolType
-	ph4	symbolValue
 	ldy	#symVal+2	  evaluate the expression
 	lda	[sym],Y
 	pha
@@ -875,12 +870,7 @@ sv1a	lda	symbolRelocatable	  if the symbol is relocatable then
 	ldy	#symSeg	    set the expression file
 	lda	[sym],Y
 	sta	expSegment
-sv1c	pl4	symbolValue	  restore volitile variables
-	pl2	symbolType
-	pl2	symbolRelocatable
-	pl2	symbolLength
-	pl2	symbolCount
-	pl4	shiftValue
+sv1c	pl4	shiftValue	  restore volatile variables
 	pl2	shiftFlag
 	pl4	shiftCount
 	pl2	copiedExpression