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Slammer
Registered: Feb 2004
Posts: 416 |
Kick Assembler Thread 2
The previous thread took a little long to load, so this is a new fresh one.. |
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soci
Registered: Sep 2003
Posts: 473 |
Works as designed, it seems. |
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chatGPZ
Registered: Dec 2001
Posts: 11092 |
i am not doubting that at all :) |
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Oswald
Registered: Apr 2002
Posts: 5017 |
"I got a plenty of SMC labels like Something=*-1 so my code looks like ANYTHING else but CLEAN because of this :)
How you would create that kind of label touching code? I spent just several hours just because of this..."
I guess its a matter of habit what's comfortable & clean to you. I usually do this:
smod lda #$00
sta $d020
inc smod+1
this keeps the label and the instruction on the same line *-x wont fuck up, since you cant insert extra instruction inbetween, furthermure its obvious where the label points no *+ fucking, and one label is enough to reach lo/hi / instruction.
if the branch is really close then just:
inc $d020
jmp *-3
lda #$03
adc $02
sta $02
bcc *+3
inc $03
but I only use it in very simple cases like this. if you insert an instruction and forget to update the * you're fucked. |
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soci
Registered: Sep 2003
Posts: 473 |
Oswald, that was a good example why using *+ and *- is really error prone:
bcc *+3
inc $03
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chatGPZ
Registered: Dec 2001
Posts: 11092 |
hey, that way debugging never becomes a bore! =) |
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Oswald
Registered: Apr 2002
Posts: 5017 |
Quote: Oswald, that was a good example why using *+ and *- is really error prone:
bcc *+3
inc $03
*+4, got me there. I use those without knowing what happens, now I got exposed. i never know if the * refers to the instruction or the operand... and just too lazy to think about it for a minute O:-) I only use them to avoid the 125th skip label. |
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soci
Registered: Sep 2003
Posts: 473 |
The current location symbol (*) is traditionally the location at the beginning of the line in many assemblers. That is before any bytes are output for opcodes and other stuff.
Unfortunately the handling of this is broken in this assembler (e.g. in v3.34), or at least it's hard to defend the way it works.
Simple stuff is fine, e.g.:
jmp *
results in (assembled to $2000):
00 20 4c 00 20
But let's see something else:
.word *, *
results in:
00 20 04 20 04 20
while the expected result is:
00 20 00 20 00 20
Yes, I also got this wrong too in some special cases in a different way just until 3 years ago.
For those hundreds of skip labels I use "anonymous" labels. Of course moderately, as copy-pasting skip label containing code in between is a sure way to get a long lasting debug session ;) |
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Oswald
Registered: Apr 2002
Posts: 5017 |
well, 16 bit addition like that sort of works like a macro from my head, unless I get rusty like now. Editing is a bit easyer if you dont have to carry around the anonymous label definition ("+") too, just have the *+. :) |
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Slammer
Registered: Feb 2004
Posts: 416 |
Soci: Interesting details about the *. I didn't know of the 'start of line' convension for all directives and never used * together with '.word'. Could you give an example of where this is usefull with the word/byte directive? Which assemblers use it, and which don't? Since KickAssembler, like languages as C# and Java, are throwing lineshifts away in the preprocess, it will be a 'start of directive'-convention instead of 'start of line' (In kickass, you can write several commands on one line). Seams like a good convention. |
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soci
Registered: Sep 2003
Posts: 473 |
Start of directive/opcode is fine instead of line start, then it's consistent at least.
It works like this in acme, dasm, dreamass, tasm/tass, xa, nasm and maybe some others. ca65 has it wrong just as old 64tass versions, but at least both give correct results for code like below.
A useful example which stores 7 at len instead of 6.
txt: .text "abcdef"
len: .byte *-txt
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