Exporting/Importing absolute expressions

[dissident]

Hi,

I use XREF/XDEF for bigger projects in conjunction with a linker. It seems that I can only use them for labels. It doesn't work with absolute expressions like in this example:

file.a

XDEF absolute_expression

absolute_expression EQU 5


file.b

XREF absolute_expression

move.w #absolute_expression*2,d0 ;Error: I can't use any computing on the importet absolute expression

Is there a way to export/import absolute expressions?

[Hedeon]

use an include (.i) file where you define absolute_expression?

Not really exporting/importing, though.

[dissident]

Originally Posted by Hedeon

use an include (.i) file where you define absolute_expression?

Not really exporting/importing, though.

Hmm, that's not my intention. The absolute expression in fila.a may change with the next assembling/linking. It's a little more complex.

[a/b]

That's not what XDEF/XREF are used for (EQUs&co).
You could see EQU/SET/RSSET/.. as "compile time" variables/constants. Now, if you would do something like:

QQQ EQU 123
varQQQ: DC.L QQQ

then you would use XDEF/XREF with varQQQ. To handle QQQ you simply include a header file (if they are in a separate file) and don't involve XREF/XDEF at all.

[meynaf]

Originally Posted by dissident

Hmm, that's not my intention. The absolute expression in fila.a may change with the next assembling/linking. It's a little more complex.

Can you provide an example that's indeed more complex and won't work with simple include file ?

[dissident]

Originally Posted by meynaf

Can you provide an example that's indeed more complex and won't work with simple include file ?

It's my example from above. I refered to Hedeon's answer.

file.a doesn't know the expression from file.b.

A more precise example;

file.a:

XDEF v_BPLCON4

BPLCON4    EQU $0011
v_BPLCON4 EQU BPLCON4

file.b has its own value which will be combined with the value of file.a:

XREF v_BPLCOBN4

BPLCON4 EQU 0

lea copperlist,a0

move.w #BPLCON4+v_BPLCON4,x(a0)

[meynaf]

Originally Posted by dissident

It's my example from above. I refered to Hedeon's answer.

file.a doesn't know the expression from file.b.

A more precise example;

This can still work with an include...

; file.i
v_BPLCON4 EQU $0011

; file.a
 include file.i
BPLCON4 EQU v_BPLCON4

; file.b
 include file.i
BPLCON4 EQU 0

 lea copperlist,a0
 move.w #BPLCON4+v_BPLCON4,x(a0)

[dissident]

Originally Posted by meynaf

This can still work with an include...

In most cases you are right, but not in my case. I need the different scopes for each file which represent separate effects.

file.a sets up a view with some sprites with the first copperlist. The first copperlist calls the second copperlist with a COPJMP2. You can see file.a as a wrapper for file.b.

file.b sets the viewport and uses the second copperlist. Now, if in the first copperlist the sprites colourbank is set, then the second copperlist should do the same. Otherwise the sprite colours would be weird, If I do only changes of the sprites colourbank in file.a, file.b has to know this after the linking.

Anyway, I found a solution which works. If the importet value is not part of any computing formula, it can look like this:

lea copperlist,a0

move.w #BPLCON4,d0
or.w   #v_BPLCON4,d0
move.w d0,x(a0)

[a/b]

1. Use SET instead of EQU so you can simply overwrite the symbol with a new value in file.b (EQU is for constants and can be used only once, while SET you can use multiple times)

; file.a:
QQ SET 123

; file.b:
  INCLUDE file.a
QQ SET 0

2. Use conditional assembly

; file.a:
 IFD IN_B
QQ EQU 0
 ELSE
QQ EQU 123
 ENDIF  ; or ENDC

; file.b:
IN_B EQU 1
  INCLUDE file.a

[dissident]

Thx for all your replies. I guess I found a solution for my case.

[phx]

Originally Posted by dissident

I use XREF/XDEF for bigger projects in conjunction with a linker. It seems that I can only use them for labels. It doesn't work with absolute expressions like in this example:

There is no difference between absolute symbols and relocatable symbols (labels). The only allowed operation is

symbol + addend

(where

addend

can also be negative or zero).

[dissident]

Originally Posted by phx

There is no difference between absolute symbols and relocatable symbols (labels). The only allowed operation is

symbol + addend

(where

addend

can also be negative or zero).

Well, there is a difference for O.M.A 2.04, otherwise it would work. An absolute value is not a relocatable symbol. That's the point why formulas dont't work with XREF/XDEF absolute values.

[phx]

Originally Posted by dissident

Well, there is a difference for O.M.A 2.04, otherwise it would work. An absolute value is not a relocatable symbol.

You are right, of course. Absolute and relocatable symbols are very different.
I should have been more precise: There is no difference for the operators allowed in expressions involving externally defined relocatable or absolute symbols.