flat assembler - MessageBox without macros [MASM

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Izu1

Joined: 15 Feb 2010
Posts: 4

Izu1

Hello everyone, can somebody show how to convert this to fasm? I read that offsets are don't exist in fasm, so how would you pass string as an argument?

Code:

      jmp @F
      szDlgTitle    db "Minimum MASM",0
      szMsg         db "  --- Assembler Pure and Simple ---  ",0
    @@:

    push MB_OK
    push offset szDlgTitle
    push offset szMsg
    push 0
    call MessageBox

thanks for help.

15 Feb 2010, 12:01

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid

in FASM, name of label always stands for offset. Eg. if "szMsg" is at offset 403020, then "mov eax, szMsg" means "mov eax, 403020", and "mov eax, [szMsg]" means "mov eax, [403020]". First moves offset, second moves value at offset. BTW, this is same in NASM.

15 Feb 2010, 12:31

Izu1

Joined: 15 Feb 2010
Posts: 4

Izu1

This still doesnt compile, says write failed.

Code:

  
    push MB_OK
    push szDlgTitle
    push szMsg
    push 0
    call [MessageBox]

15 Feb 2010, 12:40

Picnic

Joined: 05 May 2007
Posts: 1292
Location: Paradise Falls

Picnic

Hi Izu1,

Perhaps an instance of the application keep running in the background?

15 Feb 2010, 12:48

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid

Write failed means the output file can't be (re)written. You probably didn't finish your application, and it is still running (so the EXE file is locked and can't be overwritten by FASM). Hit CTRL+ALT+DEL and kill it.

15 Feb 2010, 13:17

Izu1

Joined: 15 Feb 2010
Posts: 4

Izu1

Yes seems like the process did not terminate properly... Laughing

by the way should I adjust the stack after pushing parameters on it? or is it adjusted by api when it returns?

15 Feb 2010, 13:51

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17876
Location: In your JS exploiting you and your system

revolution

Standard call (stdcall) spec says that the stack is adjusted by the callee. So you don't have to adjust it.

15 Feb 2010, 13:56

Izu1

Joined: 15 Feb 2010
Posts: 4

Izu1

thanks for help everyone, I'm still kind of new to assembler programming and completely new to fasm.

15 Feb 2010, 14:21

Picnic

Joined: 05 May 2007
Posts: 1292
Location: Paradise Falls

Picnic

Hi everyone,

Why this code output is 321 in MASM and 123 in FASM?

Code:

.686
.model flat, stdcall

include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
include \masm32\include\user32.inc
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\user32.lib

.data
    msg  dd 0,0

.code
main:
       mov [msg], "123"
  invoke MessageBox, 0,  ADDR msg,  0, 0
      invoke ExitProcess, 0
end main

Code:

    format pe console 4.0
    include 'win32ax.inc'

.data
    msg  dd 0,0

.code
main:
    mov [msg], "123"
    invoke MessageBox, 0, addr msg,  0, 0
    invoke ExitProcess, 0
.end main

29 Apr 2010, 20:38

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7848
Location: Kraków, Poland

Tomasz Grysztar

See fasm's FAQ, third question.

29 Apr 2010, 20:55

Picnic

Joined: 05 May 2007
Posts: 1292
Location: Paradise Falls

Picnic

Thanks for response Tomasz Grysztar.

29 Apr 2010, 21:16

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