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Index > Compiler Internals > Minor flaw in fasm v1.50

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yazper



Joined: 20 Nov 2003
Posts: 4
Location: at home
yazper
Hi everyone

I was just playing around with some code after dwl version 1.5 and found that

Code:
        sbb     edx,0
    


gets assembled to

Code:
        sbb     edx,-1
    


I tried to assemble it in version 1.49 and it gave the correct result
So I think Privalov introduced a new bug

thanks

yazper

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Post 16 Dec 2003, 18:27
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7796
Location: Kraków, Poland
Tomasz Grysztar
Minor flaw? I would rather call it a "serious bug" if it was true (fasm itself wouldn't work correctly after such reassembly). But all it's OK in my test, if it happened to you in some special case, please post your source.
Post 16 Dec 2003, 19:41
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yazper



Joined: 20 Nov 2003
Posts: 4
Location: at home
yazper
Ok. sorry I didnt check it thouroghly.
I use Ollydebug for ...yes well...debugging a sinusgenerator made with a 2-pole filter.
Olly gives me "sbb edx,-1" when using 1.50 and "sbb edx,0" when using 1.49.

Here's the source

The culprit is line40 in "sinusgenerator.fasm"
Dont post about the generator not working, thats why I'm debugging Wink

Plz go easy on my coding...I'm somewhat new to assembler on PC, but I've programmed lots on the Amiga using the (in my opinion) best assembler environment ever made (AsmPro). Maybe you could use some of the ideas from AsmPro?

PS: I can give you screen shots of olly if you want?!

-yazper


Description:
Download
Filename: source.zip
Filesize: 2.23 KB
Downloaded: 454 Time(s)


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Light speed is faster then the speed of sound - that's why ppl look smart until they talk!
Post 16 Dec 2003, 20:34
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comrade



Joined: 16 Jun 2003
Posts: 1137
Location: Russian Federation
comrade
Assembled just fine here. I check disassembly and its all okay. Maybe you confuse two sbb's together?

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Post 16 Dec 2003, 20:45
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7796
Location: Kraków, Poland
Tomasz Grysztar
This is how that routine does look like in my OllyDbg - as you can see, the "sbb edx,0" is encoded correctly. Perhaps you have mistaken it with the instruction which is at address 4020A3h on this screen, this is "sbb edx,0ffffffffh" from your source.


Description:
Filesize: 6.52 KB
Viewed: 5324 Time(s)

ollydbg.gif


Post 16 Dec 2003, 20:49
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yazper



Joined: 20 Nov 2003
Posts: 4
Location: at home
yazper
Oops Embarassed
I did confuse it.... i'm just making a complete arse of myself Crying or Very sad
Sorry for wasting you time.

-yazper

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Light speed is faster then the speed of sound - that's why ppl look smart until they talk!
Post 16 Dec 2003, 20:55
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