the if macro/instruction

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hyperzap

Joined: 22 Apr 2011
Posts: 4

hyperzap 15 May 2012, 05:02

hi,

i have seen where people have written assembly like:

.if eax==2
inc eax
.endif

is this possible in FASM? if yes, how complex may the conditional expressions become? is this the correct syntax for the preprocessor?

thanks, hyperzap

15 May 2012, 05:02

typedef

Joined: 25 Jul 2010
Posts: 2909
Location: 0x77760000

typedef 15 May 2012, 05:24

Yes it's valid. It's more of a high-level syntax. But FASM will generate an appropriate J/MP/NE/S etc opcode.

15 May 2012, 05:24

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19250
Location: In your JS exploiting you and your system

revolution 15 May 2012, 05:32

hyperzap: See the documentation about these extensions macros:

http://flatassembler.net/docs.php?article=win32#2.2

15 May 2012, 05:32

hyperzap

Joined: 22 Apr 2011
Posts: 4

hyperzap 15 May 2012, 05:40

thanks. i didn't see that.

/solved.

15 May 2012, 05:40

AsmGuru62

Joined: 28 Jan 2004
Posts: 1509
Location: Toronto, Canada

AsmGuru62 15 May 2012, 12:51

It is better to avoid a jump in this case:

Code:

xor    ecx, ecx
cmp eax, 2
sete  cl
add       eax, ecx

That is if you do not need ECX.
Smile

Yeah... I am not in love with these IF (spaggheti-making) macros.

15 May 2012, 12:51

JohnFound

Joined: 16 Jun 2003
Posts: 3499
Location: Bulgaria

JohnFound 15 May 2012, 13:26

Quote:

Yeah... I am not in love with these IF (spaggheti-making) macros.

Me too. IMHO, these HLL style macros make asm programming unclear and not readable.

15 May 2012, 13:26

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