[Question from a Newbie] : Proc

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flaith

Joined: 07 Feb 2005
Posts: 122
Location: $300:20 58 FC 60 N 300G => Vietnam

flaith 03 May 2005, 14:31

Hi everybody

i'm learning asm actually (well i try)
i found a little prog here about arrays and i decided to modify it with a procedure.

here it is

Code:

format PE GUI 4.0
entry start

include '%fasminc%\win32a.inc'

section '.data' data readable writeable

_caption db 'Test array',0

_simple_array:
cat     db 'cat',0
dog     db 'dog',0
dolphin db 'dolhpin',0
monkey  db 'monkey',0
donkey  db 'donkey',0
pig     db 'pig',0
end_array db 0,0

_pointer2array dd cat,dog,dolphin,monkey,donkey,pig  ;0->cat; 5->pig

section '.code' code readable executable
start:
    stdcall Aff_Element,0
    stdcall Aff_Element,5
    invoke  ExitProcess,0
ret

proc Aff_Element, numElement
    push    ebx esi edi
    mov     edi,[numElement]  ;  <---which element
    shl     edi,2
    invoke  MessageBox,0,[_pointer2array+edi],_caption,0      ; show me-> _simple_array[2]
    pop     ebx esi edi
endp

section '.idata' import data readable writeable

    library kernel32, 'KERNEL32.DLL',\
            user32,   'USER32.DLL'

    include '%fasminc%\apia\kernel32.inc'
    include '%fasminc%\apia\user32.inc'

Pb is, after the first call to aff_element, i've got a error message, i don't know why, help welcome Confused

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03 May 2005, 14:31

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 03 May 2005, 15:07

1) You forgot to return from your procedure, it should be done with the "return" macro.

2) When you restore registers from stack, you have to pop them in the reverse order, since you first get the register that is on the top of the stack and this is the last one you pushed there.

So the correct procedure should look like:

Code:

proc Aff_Element, numElement
    push    ebx esi edi
    mov     edi,[numElement]
    shl     edi,2
    invoke  MessageBox,0,[_pointer2array+edi],_caption,0
    pop     edi esi ebx
    return
endp

BTW, because of your problem I have realized it would be not bad thing to make "endp" macro generate return code on the end of procedure automatically when you forget to do it. I will think about it.

03 May 2005, 15:07

flaith

Joined: 07 Feb 2005
Posts: 122
Location: $300:20 58 FC 60 N 300G => Vietnam

flaith 03 May 2005, 15:55

thank you SO much Very Happy

03 May 2005, 15:55

Reverend

Joined: 24 Aug 2004
Posts: 408
Location: Poland

Reverend 03 May 2005, 20:28

Quote:

Code:

    mov     edi,[numElement]
    shl     edi,2
    invoke  MessageBox,0,[_pointer2array+edi],_caption,0

Actually it could be done like this:

Code:

    mov     edi,[numElement]
    invoke  MessageBox,0,[_pointer2array+edi*4],_caption,0

If you multiply by 2,4,8,16,... you can do like this

03 May 2005, 20:28

flaith

Joined: 07 Feb 2005
Posts: 122
Location: $300:20 58 FC 60 N 300G => Vietnam

flaith 03 May 2005, 21:12

thank you

03 May 2005, 21:12

mike.dld

Joined: 03 Oct 2003
Posts: 235
Location: Belarus, Minsk

mike.dld 04 May 2005, 22:06

Reverend wrote:

If you multiply by 2,4,8,16,... you can do like this

AFAIK, it can be only 1,2,3,4,5,8 and 9 Wink

like follows:

Code:

  [eax*1] = [eax]
  [eax*2] = [eax*2] = [eax+eax]
  [eax*3] = [eax*2+eax]
  [eax*4] = [eax*4]
  [eax*5] = [eax*4+eax]
  [eax*8] = [eax*8]
  [eax*9] = [eax*8+eax]

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04 May 2005, 22:06

madmatt

Joined: 07 Oct 2003
Posts: 1045
Location: Michigan, USA

madmatt 05 May 2005, 07:23

shouldn't you have an "enter" before the "proc" because of the parameter? Also someone made the "return" macro except a return-value, I can post the new macro if you like.
madmatt

05 May 2005, 07:23

mike.dld

Joined: 03 Oct 2003
Posts: 235
Location: Belarus, Minsk

mike.dld 05 May 2005, 07:53

ENTER as macro should be used only if you have some local variables, otherwise it doesn't generate any code.

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05 May 2005, 07:53

Reverend

Joined: 24 Aug 2004
Posts: 408
Location: Poland

Reverend 05 May 2005, 20:20

mike.dld wrote:

Reverend wrote:
If you multiply by 2,4,8,16,... you can do like this
AFAIK, it can be only 1,2,3,4,5,8 and 9 like follows:

Yes, you're right, sorry for my mistake Embarassed

05 May 2005, 20:20

madmatt

Joined: 07 Oct 2003
Posts: 1045
Location: Michigan, USA

madmatt 05 May 2005, 20:58

mike.dld: Didn't know you could do that. Tried it in a simple test and it seemed to work.
MadMatt

05 May 2005, 20:58

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