Assembly

Assembly RSS

Conditional assambly doesn't work! :(

•

Join Date: Jun 2008

Posts: 88

Reputation: Alex_ is an unknown quantity at this point

Solved Threads: 1

Alex_

Offline

Junior Poster in Training

Conditional assambly doesn't work! :(

May 2nd, 2009

Hello everyone.
I'm trying to do this in nasm under linux :

 Help with Code Tags 
 Assembly Syntax (Toggle Plain Text) 
 cmp eax,ebx
jng .loop
 cmp eax,ebx
jng .loop

and also

 Help with Code Tags 
 Assembly Syntax (Toggle Plain Text) 
 test eax,ebx
jng .loop
 test eax,ebx
jng .loop

and yet also

 Help with Code Tags 
 Assembly Syntax (Toggle Plain Text) 
 %if eax < ebx
jmp .loop
%endif
 %if eax < ebx
jmp .loop
%endif

I want to loop while eax is lesser than ebx and non of the 3 methods work!
First 2 execute once and then hit for the exit code
the last one gives error:
error: `<': operands differ by a non-scalar

Can someone help me? I've been banging my head against the wall for some hours now!

•

Join Date: Apr 2009

Posts: 39

Reputation: sysop_fb is an unknown quantity at this point

Solved Threads: 5

sysop_fb

Offline

Light Poster

Re: Conditional assambly doesn't work! :(

May 4th, 2009

Sorry for the late response been really busy lately.
From the code you've posted I don't really see a problem.

Here's the best and most useful time to open up gdb.
And I'll attempt to explain an easy way to do so!

so in my linux asm code I usually have a main label. So I would do this.

Help with Code Tags

Assembly Syntax (Toggle Plain Text)

gdb myprog
gdb> break main
breakpoint set
gdb> display /x $eax
gdb> display /x $ebx
gdb> display /x $eflags
gdb> run
breakpoint reached

Now here gdb is hanging out at the main label in myprog which happens for me to be the begging of my code!
So I do 'stepi' while watching my registers until I get to the instruction that I want to watch then I'll usually do a 'info all-reg'

If you're going to programming in assembly you're going to NEED to become familiar with a debugger. What do other languages do for you? By writing in assembly you're saying "I'm smart enough that I can get down into the hardware and interact with it directly". There's no type safety or any standard or a compiler to tell you that what you're doing is unsafe. Actually the only thing keeping your program in check from obliterating the machine is the O/S (assuming you're in a protected mode O/S such as linux).

•

Join Date: Jun 2008

Posts: 88

Reputation: Alex_ is an unknown quantity at this point

Solved Threads: 1

Alex_

Offline

Junior Poster in Training

Re: Conditional assambly doesn't work! :(

May 4th, 2009

Sorry i don't understand how to get it work...

I try running: gdb lab4a
it gives : (no debugging symbols found)
Then i try: - files lab4a
But it says:
exec No process In: Line: ?? PC: 0x0
Invalid window specified.
The window name specified must be valid and visible.

What am i doing wrong? Please bare with me. )

Fundamental law of life:
do{ ThingsToDo+=me.CompleteTask(ThingsToDo); }while(ThingsToDo); Die(me);
Law of the Spirit:
do{ Rebuke(me); }while(!me.Repented); LiveEternal(me);
PM me to know more why i wrote this or what it means.