flat assembler

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shadowomf

Joined: 31 Mar 2010
Posts: 12
Location: Germany

shadowomf 19 Feb 2012, 17:27

Hello,

I have a small problem with the locals macro, not the macro itself but I don't know how to make the following example work:

Code:

    proc WinMain hInst, hPrevInst, CmdLine, CmdShow
        
        locals
            windowClassName TCHAR 'OPENGL64DUMMY', 0
            windowClass WNDCLASSEX sizeof.WNDCLASSEX, 0, DummyWindowProc, 0, 0, 0, 0, 0, 0, 0, windowClassName, 0
            message MSG
        endl
        
        ; new window class for dummy window
        mov [windowClass.hInstance], rcx
        invoke LoadIcon, rax, 17
        mov [windowClass.hIcon], rax
        invoke LoadCursor, 0, IDC_ARROW
        mov [windowClass.hCursor], rax
        invoke RegisterClassEx, addr windowClass

The above code does not assemble and results in an fasm error (invalid value in the line

Quote:

windowClass WNDCLASSEX sizeof.WNDCLASSEX, 0, DummyWindowProc, 0, 0, 0, 0, 0, 0, 0, windowClassName, 0

).
When I use a global variable as windowClassName it does work without problems. However I would like to keep things seperated.

Is there any way to make it work?

And one more Question, I am using the "w" (Unicode) header version, is TCHAR the right way to do it or would a "du" be better?

Thanks in advance.
-Christoph

19 Feb 2012, 17:27

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20430
Location: In your JS exploiting you and your system

revolution 19 Feb 2012, 20:33

The problem is you are trying to make the assembler do this:

Code:

mov [ebp+offset1],ebp+offset2

You could try this:

Code:

windowClass WNDCLASSEX sizeof.WNDCLASSEX, 0, DummyWindowProc, 0, 0, 0, 0, 0, 0, 0, 'OPENGL64DUMMY', 0

19 Feb 2012, 20:33

SFeLi

Joined: 03 Nov 2004
Posts: 138

SFeLi 19 Feb 2012, 21:39

shadowomf wrote:

windowClassName TCHAR 'OPENGL64DUMMY', 0

Do you really need this? Maybe:

Code:

proc foo ; Note that all local labels start with a dot.
    locals
        .pt     POINT
        .buffer rb 32
    endl

    .get:
        stdcall [GetCursorPos], addr .pt
        ccall   [wsprintf], addr .buffer, .fmt, [.pt.x], [.pt.y]
    .show:
        stdcall [MessageBox], 0, addr .buffer, .title, MB_ICONINFORMATION
  .exit: 
    ret 

  .fmt db 'Cursor at %u:%u',0
  .title db 'CursorPos',0
endp
; This way you can "keep things seperated" without initializing locals with the bunch of MOVs.

Last edited by SFeLi on 19 Feb 2012, 21:52; edited 2 times in total

19 Feb 2012, 21:39

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20430
Location: In your JS exploiting you and your system

revolution 19 Feb 2012, 21:49

SFeLi wrote:

every name/label in foo should start with a dot.

This is not a necessary condition. Labels inside locals can start with any non-numeric character. The macros use an equ to define the label and later it is released with restore.

19 Feb 2012, 21:49

SFeLi

Joined: 03 Nov 2004
Posts: 138

SFeLi 19 Feb 2012, 21:55

revolution, thank you for the correction. I don't use proc macros, but several years ago I had some problems with locals and I just remembered to use the dot for everything Smile

19 Feb 2012, 21:55

shadowomf

Joined: 31 Mar 2010
Posts: 12
Location: Germany

shadowomf 19 Feb 2012, 22:52

Thank you for your fast reply.

Quote:

The problem is you are trying to make the assembler do this:
Code:
mov [ebp+offset1],ebp+offset2    

Maybe I'm a bit slow but why doesn't the following work? (I also tried it without brackets.)

Code:

        mov rax, [windowClassName]
        mov [windowClass.lpszClassName], rax

Quote:

You could try this:

Code:

windowClass WNDCLASSEX sizeof.WNDCLASSEX, 0, DummyWindowProc, 0, 0, 0, 0, 0, 0, 0, 'OPENGL64DUMMY', 0

Sadly this doesn't work.

Quote:

Do you really need this? Maybe:

Code:

proc foo ; Note that all local labels start with a dot.
    locals
        .pt     POINT
        .buffer rb 32
    endl

    .get:
        stdcall [GetCursorPos], addr .pt
        ccall   [wsprintf], addr .buffer, .fmt, [.pt.x], [.pt.y]
    .show:
        stdcall [MessageBox], 0, addr .buffer, .title, MB_ICONINFORMATION
  .exit: 
    ret 

  .fmt db 'Cursor at %u:%u',0
  .title db 'CursorPos',0
endp

; This way you can "keep things seperated" without initializing locals with the bunch of MOVs.

Even thouggh it looks a bit strange, it does work, thank you.
Using the TCHAR thingy results in an error, but "du" doesn't, is there anything that TCHAR does that "du" doesn't?

Thanks.
-Christoph

19 Feb 2012, 22:52

yoshimitsu

Joined: 07 Jul 2011
Posts: 96

yoshimitsu 20 Feb 2012, 00:44

windowClassName is a byte array, means with your code you get 8 bytes out of it which would be 'OPENGL64' and move it into windowClass.lpszClassName which should actually contain an address of string.
To be more precise, windowClassName is a symbolic equation for ebp+8, so it's not an actual address and therefore to calculate its real address you have to use lea:

Code:

lea rax,[windowClassName] ;it gets substituted for lea rax,[ebp+xx]
mov [windowClass.lpszClassName],rax

PS: brackets are always needed when accessing memory.

20 Feb 2012, 00:44

shadowomf

Joined: 31 Mar 2010
Posts: 12
Location: Germany

shadowomf 20 Feb 2012, 10:12

Now I think I've got it.
Thank you all.

20 Feb 2012, 10:12

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