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Index > DOS > Error in compiled com image

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keyoke



Joined: 18 Jun 2003
Posts: 56
Location: London
keyoke
Hi Privalov,
this is a example of the code i compile.

Code:
SumProc:

some intructions

someloop:
call someotherproc
jne someloop

ret

text db "somtext",0

someotherproc:

someother instructions

ret

    
1

now when i debug this type of example the call to the someotherproc
function works fine but the first intructions of the someotherproc procedure are compiled incorrectly almost like the defined bytes interfere with the first instructions in the procedure.
is this a error is compiler or what?
thanks for your help in advance.
Post 25 Aug 2003, 07:50
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wanderer



Joined: 18 Jun 2003
Posts: 44
Location: Moldova, Kishinev
wanderer
keyoke wrote:
now when i debug this type of example the call to the someotherproc
function works fine but the first intructions of the someotherproc procedure are compiled incorrectly almost like the defined bytes interfere with the first instructions in the procedure.
is this a error is compiler or what?
thanks for your help in advance.


If you mean that a wrong offset is generated in this instruction, then it's because you didn't place org 100h in the beginning of code. As you know, com files are loaded on offset 100h from segment start. The procedure call was generated correctly as there's relative offset in it, however it won't work for global variables for example.

_________________
Best regards,
Antoch Victor
Post 25 Aug 2003, 09:30
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7802
Location: Kraków, Poland
Tomasz Grysztar
It's probably an error of debugger - if it treats your data string as instructions and disassemble them, it might happen (an often happens) that it'll end with treating first bytes or real instructions that you put after the data block as the additional bytes for some not-really-existing instruction discovered in your data, and so the disassembly will be wrong.
Post 25 Aug 2003, 09:40
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keyoke



Joined: 18 Jun 2003
Posts: 56
Location: London
keyoke
Privalov,
I do use
Code:
org 100h
use16
    


to debug i use the ms-dos debug command would this disassemble the code incorrectly?
i have also tried turbo debugger to debug the code...
it seems like the debugger isnt disassembling the code directly???
i dunno maybe ill try disassembling it with ida to check wat comes up..
Post 25 Aug 2003, 10:29
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Yawgmoth



Joined: 20 Aug 2003
Posts: 37
Yawgmoth
Speaking of debuggers, when can we expect a FASM debugger?
Post 25 Aug 2003, 11:44
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keyoke



Joined: 18 Jun 2003
Posts: 56
Location: London
keyoke
I think privalov has enough on his plate already.....with the fasm compiler, and all the documentation. So i think we should give him a bit of a break Wink maybe someone else will code a debugger for fasm. would be good Smile
Post 27 Aug 2003, 07:09
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