From 6e714875dc56488b51f47672524b7abc6d44abbb Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Thu, 14 Nov 2019 21:16:36 -0500
Subject: [PATCH] zasm: Constants now override labels at all times

Will be important for a mega-commit I'm preparing.
---
 apps/zasm/README.md            | 12 +++++++-----
 apps/zasm/symbol.asm           | 14 +++++++-------
 tools/tests/unit/test_core.asm | 10 ++++++++++
 3 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/apps/zasm/README.md b/apps/zasm/README.md
index 0d880ae..1bc77b2 100644
--- a/apps/zasm/README.md
+++ b/apps/zasm/README.md
@@ -76,6 +76,12 @@ forward-reference labels.
 
 However, they *cannot* forward-reference other constants.
 
+When defining a constant, if the symbol specified has already been defined, no
+error occur and the first value defined stays intact. This allows for "user
+override" of programs.
+
+It's also important to note that constants always override labels, regardless
+of declaration order.
 
 ## Expressions
 
@@ -119,12 +125,8 @@ allowed. An included file cannot have an `.inc` directive.
 
 **.equ**: Binds a symbol named after the first parameter to the value of the
           expression written as the second parameter. Example:
-          `.equ foo 0x42+'A'`
+          `.equ foo 0x42+'A'`. See "Constants" above.
           
-If the symbol specified has already been defined, no error occur and
-the first value defined stays intact. This allows for "user override"
-of programs.
-
 **.fill**: Outputs the number of null bytes specified by its argument, an
            expression. Often used with `$` to fill our binary up to a certain
            offset. For example, if we want to place an instruction exactly at
diff --git a/apps/zasm/symbol.asm b/apps/zasm/symbol.asm
index 1504bd3..08f4312 100644
--- a/apps/zasm/symbol.asm
+++ b/apps/zasm/symbol.asm
@@ -112,11 +112,11 @@ symRegister:
 	push	de		; --> lvl 3
 	ld 	d, 0
 	ld 	e, c
-	add 	hl, de		; if carry set here, sbc will carry too	
+	add 	hl, de		; if carry set here, sbc will carry too
 	ld	e, (ix+2)	; DE --> pointer to record list, which is also
 	ld	d, (ix+3)	; the end of names pool
 	; DE --> names end
-	
+
 	sbc	hl, de		; compares hl and de destructively
 	pop	de		; <-- lvl 3
 	pop	hl		; <-- lvl 2
@@ -192,11 +192,11 @@ _symFind:
 	jr	z, .end		; match! Z already set, IY and HL placed.
 .skip:
 	; ok, next!
-	
+
 	push 	de		; --> lvl 1
 	ld 	de, 0x0003
 	add 	iy, de		; faster and shorter than three inc's
-	ld 	e, (iy-3)	; offset is also compulsory, so no extra bytes used	
+	ld 	e, (iy-3)	; offset is also compulsory, so no extra bytes used
 	; (iy-3) holds the name length of the string just processed
 	add 	hl, de	; advance HL by (iy-3) characters
 	pop	de		; <-- lvl 1
@@ -219,13 +219,13 @@ symFindVal:
 	push	ix
 	call	symIsLabelLocal
 	jr	z, .local
-	; global. Let's try labels first, then consts
+	; global. Let's try consts first, then symbols
 	push	hl		; --> lvl 1. we'll need it again if not found.
-	ld	ix, SYM_GLOBAL_REGISTRY
+	ld	ix, SYM_CONST_REGISTRY
 	call	_symFind
 	pop	hl		; <-- lvl 1
 	jr	z, .found
-	ld	ix, SYM_CONST_REGISTRY
+	ld	ix, SYM_GLOBAL_REGISTRY
 	call	_symFind
 	jr	nz, .end
 .found:
diff --git a/tools/tests/unit/test_core.asm b/tools/tests/unit/test_core.asm
index a0a7eba..0c4fcd0 100644
--- a/tools/tests/unit/test_core.asm
+++ b/tools/tests/unit/test_core.asm
@@ -2,8 +2,11 @@ jp	test
 
 .inc "core.asm"
 
+dummyLabel:
 testNum:	.db 1
 
+.equ	dummyLabel	0x42
+
 test:
 	ld	hl, 0xffff
 	ld	sp, hl
@@ -30,6 +33,13 @@ test:
 	jp	p, fail		; negative
 	call	nexttest
 
+	; Test that .equ can override label
+	ld	a, 0x42
+	ld	hl, dummyLabel
+	cp	l
+	jp	nz, fail
+	call	nexttest
+
 	; *** cpHLDE ***
 	ld	hl, 0x42
 	ld	de, 0x42