#1 Relocation info

[Mads Orbesen Troest]

First: excellent work, k2asm is by far the best cross
assembler I've used. :)

One suggestion: I would really like k2asm to be able to
provide relocation for the code it generates (ideally
support an object code format including this). Fx, I've
written a C64 play routine and want to make a relocator
for it, so I need the indexes of all ORG-address
related data to be able to make the adjustments.

Regards

[Mads Orbesen Troest]

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Uhm, was supposed to read "... to provide relocation
INFORMATION for the code ..." ;)

[Zed Yago]

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Thanks for the kind words!

We have an ugly workaround for relocating code, I will post
an example later here (using a Makefile and c64la).
You are right, we need that relocation feature!

The actual Problem (relocate a routine at runtime) can be
done without assembler-relocation, if you use the *.hdr
files right (i think)

[Zed Yago]

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k2asm v1.1 does not have a .reorg

There are 2 types of relocation, assemble-time relocation
and run-time
relocation.

Assemble-Time is needed, when your Program should be loaded
into another
memory, then it will run.

Assemble-Time Relocation can be implemented with clever
Makefiles.
The main idea is to assemble the program into the
run-location with .org and
to use the c64la utility to change that address pefore
linking it.

Assemble-Time Relocation is also supported by many packers.

Run-Time Relocation is most often used for music-play routines.
The music-play routine is e.g. assembled and run at $1000.
But because of certain memory-requirements, inside an
Application, it should
rather run at $C000.

To implement this Feature i would suggest the following:

1. .export all to be changed adresses in the play-routine.
[code]
;player.src

.org $1000
.scope music {
.export high10_01=*+2
jmp init
.export high10_02=*+2
jmp play
.export high10_03=*+2
jmp exit
}
[/code]
2. Put these words into a table, which _must_ be assembled
after the
playroutine.
[code]
;reloctab.src

#include "player.hdr"

.org $0f00

.word high10_01

[/code]
3. To relocate the program to e.g. $9000, copy the
playroutine to $9000,
then add to all addresses+$8000, which are in the table at
$0f00, the value
$80.
This sounds more complicated then it is in 6502 :-)

[code]
;copy the playroutine to $9000
ldx#0
{
lda $1000,x
sta $9000,x
dex
bne _cont
}

;read address from reloctab and add $8000
lda $0f00
sta $fc
lda $0f01
clc
adc#$80
sta $fd

;change the playroutine at $9000
ldy#0
lda ($fc),y
clc
adc#$80
sta ($fc),y

;repeat until all words in reloctab are processed

[/code]

Proposal for new relocation-directive in k2asm
We can either use the standard 6502-Way, by assigning the
programcounter.

.org linktimeaddr
*=runtimeaddr

However, this breaks our internal styleguide, which looks
like this:
#include "local.inc"
.org org.main
That means that org.* is always the runtimeaddress, not the
linktimeaddress.
The linktimeaddress is assigned to reorg.*

.reorg linktimeaddr
.org runtimeaddr

Howkey suggested, that we shall use just the .org directive
several times:

.org linktimeaddr
.org runtimeaddr

Please note that each syntax is possible, but we are not
sure yet, which
fits best...