zasm: Constants now override labels at all times

Will be important for a mega-commit I'm preparing.
This commit is contained in:
Virgil Dupras 2019-11-14 21:16:36 -05:00
parent 7cf3ed38da
commit 6e714875dc
3 changed files with 24 additions and 12 deletions

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@ -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

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@ -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:

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@ -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