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faser



Joined: 03 Oct 2010
Posts: 4
faser
Hello,

I've downloaded the DLL version of FASM and fired up the ASM demo program.
When I encode: "xor eax, eax" I get "66 31 C0" which is "xor ax, ax"!

Am I missing something or is this a major bug?

Thank you.
Post 03 Oct 2010, 13:18
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17279
Location: In your JS exploiting you and your system
revolution
Code:
use32
xor eax,eax ;31 C0
xor ax,ax ;66 31 C0
use16
xor eax,eax ;66 31 C0
xor ax,ax ;31 C0    
By default fasm starts in 16 bit mode. Which you will need to change to 32 bit mode if that is what you need.
Post 03 Oct 2010, 13:32
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
revolution wrote:
Code:
use32
xor eax,eax ;31 C0
xor ax,ax ;66 31 C0
use16
xor eax,eax ;66 31 C0
xor ax,ax ;31 C0    
By default fasm starts in 16 bit mode. Which you will need to change to 32 bit mode if that is what you need.


this is due to the PC compatible, it start by default in 16 bit mode, then, fasm too is in 16 bit mode by default.
Post 03 Oct 2010, 13:43
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faser



Joined: 03 Oct 2010
Posts: 4
faser
Thanks a lot for your help.
Post 03 Oct 2010, 13:46
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