Tool z80asm preprocessor - marinus-lab/z88dk GitHub Wiki

Preprocessor

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z80asm runs a preprocessor on the input text and assembles the result output. The preprocessor understands the following statements:

#define

#define works like in the C preprocessor and allows the definition of assembly macros. The macro definition may include \ which is translated to a newline. The macro definition can be continued on a subsequent line if the previous line ends with \.

The macro name and the formal parameters names follow the rules of a C identifier.

Example:

#define pushall \
    push bc \ \
    push de \ \
    push hl
pushall                 ; pushes bc, de and hl

Note the double role of the backslash, as a line continuation, and as a line break.

The token pasting operator ## can be used to glue together two tokens into one:

#define cat(a, b) a ## b

cat(aa,bb)              ; expands to aabb

#undef

#undef works like in the C preprocessor and allows a macro definition to be deleted, if it exists.

DEFL

Define a text macro that can be redefined and that can refer to it's previous value. A pure text-substitution is done, i.e. the text of the previous value is pasted in place in the new value.

DEFL var = var+1    ; var is now "+1"
DEFL var = var+1    ; var is now "+1+1"

Alternative syntax:

var DEFL var+1

EXITM

Exits the current macro expansion. It is normally used inside a conditional.

MACRO m1 arg
if arg==1
  EXITM
endif
...
ENDM

LOCAL

Used inside macros to declare the following symbols as local to the macro invocation, i.e. they are replaced by a unique identifier on each invocation.

MACRO abc
LOCAL l1,l2
l1:                 ; replaced by l1__<n> unique identifier
l2:                 ; replaced by l2__<n> unique identifier
ENDM

MACRO

Define a new macro.

MACRO name [arg1,...]
text
ENDM

Creates a macro that is expanded when referred to in the opcode field of an instruction. The formal parameters are assigned to the actual arguments before the expansion.

Alternative syntax:

name MACRO [arg1,...]
text
ENDM

REPT

Repeat a block of code a predefined number of times. The count expression must be constant.

; output 10 spaces on a ZX Spectrum
REPT 10
ld  a, ' '
rst 10h
ENDR

REPTC

Repeat a block of code for each character of the given string, identifier or number

; output "hello" on a ZX Spectrum
REPTC var, "hello world"
ld  a, var
rst 10h
ENDR

; store the digits of the version
DEFL version=23
REPTC var, version
defb var
ENDR

REPTI

Repeat a block of code for each of the given expressions.

; push all registers
REPTI reg, bc, de, hl, af
push reg
ENDR