error: undefined symbol, are you sure?

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vbVeryBeginner

Joined: 15 Aug 2004
Posts: 884
Location: \\world\asia\malaysia

vbVeryBeginner 04 Nov 2004, 21:28

hi, i came with another weird situation, maybe it is my mistake, hopefully your guys could check with the following code.

Code:

format PE GUI 4.0
entry start

include '%fasminc%\win32a.inc'

section '.data' data readable writeable
 insH            dd ?
        
section '.code' code readable executable
start:
        invoke  GetModuleHandle,0
           mov  [insH],eax
     invoke  DialogBoxParam,eax,30,NULL,dialog_procedureA,NULL

proc dialog_procedureA,hDlg,uMsg,wParam,lParam
.test1       dd ?                                            ;define the symbol
enter
 cmp  [uMsg],WM_CLOSE
        je   wdmCLOSE
       cmp  [uMsg],WM_INITDIALOG
   je   wdmINITDIALOG
       return

     wdmCLOSE:
               invoke  EndDialog,[hDlg],0
          return

  wdmINITDIALOG:
                  ;lea  eax,[.test1]              ; error: undefined symbol?
              stdcall testing,2,4,6,8
             return
endp

proc testing,a,b,c,d
.test1    dd ?
enter
       lea  eax,[.test1]                               ; ok here
   mov  [.test1],eax
   return
endp

section '.idata' import data readable
       library kernel32, 'KERNEL32.DLL',\
               user32,   'USER32.DLL'

        include '%fasminc%\apia\Kernel32.inc'
   include '%fasminc%\apia\User32.inc'

section '.rsrc' resource data readable
     directory RT_DIALOG,appDialog

   resource appDialog,\
                30,LANG_NEUTRAL,dlgTest

        dialog dlgTest,'Test',0,0,170,50,\
               DS_MODALFRAME + WS_VISIBLE + WS_CAPTION + WS_POPUP + WS_SYSMENU
             dialogitem      'STATIC','On Test',0,17,14,40,10,SS_LEFT + WS_GROUP + WS_VISIBLE
        enddialog

04 Nov 2004, 21:28

Tommy

Joined: 17 Jun 2003
Posts: 489
Location: Norway

Tommy 04 Nov 2004, 21:54

that's because you're not using local labels inside the proc... you're using wdmINITDIALOG.test1... it's defined as dialog_procedureA.test1

04 Nov 2004, 21:54

vbVeryBeginner

Joined: 15 Aug 2004
Posts: 884
Location: \\world\asia\malaysia

vbVeryBeginner 04 Nov 2004, 23:19

thanks tommy,
i didn't realize that once we use a : we are in another scope!

Code:

  wdmINITDIALOG:
          jmp there
           .test1  dd ?
                there:
                  lea  eax,[wdmINITDIALOG.test1]
                      lea  eax,[dialog_procedureA.test1]
          stdcall testing,2,4,6,8
             return

this clear my confuse Smile

, thanks

04 Nov 2004, 23:19

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19876
Location: In your JS exploiting you and your system

revolution 05 Nov 2004, 01:22

It's not the : that makes a new scope, it is a label that does nos begin with a . that makes a new scope.

Try this with the four extra .'s instead.

Code:

proc dialog_procedureA,hDlg,uMsg,wParam,lParam 
.test1  dd ?                                            ;define the symbol 
enter 
        cmp  [uMsg],WM_CLOSE 
        je   .wdmCLOSE 
        cmp  [uMsg],WM_INITDIALOG 
        je   .wdmINITDIALOG 
             return 

        .wdmCLOSE: 
                invoke  EndDialog,[hDlg],0 
                return 

        .wdmINITDIALOG: 
                        lea  eax,[.test1]              ; Now it works. 
                stdcall testing,2,4,6,8 
                return 
endp

05 Nov 2004, 01:22

vbVeryBeginner

Joined: 15 Aug 2004
Posts: 884
Location: \\world\asia\malaysia

vbVeryBeginner 05 Nov 2004, 03:30

thanks revolution but ...

Code:

format PE GUI 4.0
entry start

include '%fasminc%\win32a.inc'

section '.data' data readable writeable
   insH            dd ?
        wndTitle        db 'On Test',0

        buf1    rb 0x30
     buf2    rb 0x30
     f1      db '.wdmINITDIALOG -> %lu',0
   f2      db '.wdmCTLCOLORSTATIC -> %lu',0
       
section '.code' code readable executable
start:
        invoke  GetModuleHandle,0
           mov  [insH],eax
     invoke  DialogBoxParam,eax,30,NULL,dialog_procedureA,NULL

proc dialog_procedureA,hDlg,uMsg,wParam,lParam
.t2  dd ?
enter
       cmp  [uMsg],WM_CLOSE
        je   .wdmCLOSE
      cmp  [uMsg],WM_INITDIALOG
   je   .wdmINITDIALOG
 cmp  [uMsg],WM_CTLCOLORSTATIC
       je   .wdmCTLCOLORSTATIC
          return

     .wdmCLOSE:
              invoke  EndDialog,[hDlg],0
          return

  .wdmINITDIALOG:
                 mov  [.t2],30                           ;<- so, we move 30 into it
                       mov  eax,[.t2]
              invoke  wsprintf,buf1,f1,eax
                invoke  MessageBox,NULL,buf1,wndTitle,MB_OK
                 return

  .wdmCTLCOLORSTATIC:
                     mov  eax,[.t2]                          ;<- now, do you have any idea
            invoke  wsprintf,buf2,f2,eax                    ;   why it shouldn't be 30?
                invoke  MessageBox,NULL,buf2,wndTitle,MB_OK
                 mov  eax,FALSE
                      return
endp

section '.idata' import data readable
       library kernel32, 'KERNEL32.DLL',\
               user32,   'USER32.DLL'

        include '%fasminc%\apia\Kernel32.inc'
   include '%fasminc%\apia\User32.inc'

section '.rsrc' resource data readable
     directory RT_DIALOG,appDialog

   resource appDialog,\
                30,LANG_NEUTRAL,dlgTest

        dialog dlgTest,'Test',0,0,170,50,\
               DS_MODALFRAME + WS_VISIBLE + WS_CAPTION + WS_POPUP + WS_SYSMENU
             dialogitem      'STATIC','',0,5,5,100,40,SS_LEFT + WS_VISIBLE
   enddialog

05 Nov 2004, 03:30

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19876
Location: In your JS exploiting you and your system

revolution 05 Nov 2004, 08:23

The variable ".t2" is not a static variable. It is on the stack. Each time dialog_procedureA is called a new space is allocated within the stack. More than likely the value will be changed by many other things happening on the stack between calls the dialog_procedureA

You need to put ".t2" in the same place as buf1 and the others for it to keep values between calls.

Try viewing the actual code generated in a debugger. It may help you to understand how the stack is used by the "proc" macro.

05 Nov 2004, 08:23

Matrix

Joined: 04 Sep 2004
Posts: 1166
Location: Overflow

Matrix 05 Nov 2004, 11:06

Code:

stackerproc:
.t1 ; this is interpreted as stackerproc.t1
jmp .t2 ; now you see what is the case?
cxz: 
.t2 ; this is interpreted as cxz.t2
.t4 ; this is interpreted as cxz..t4
.t3 ; this is interpreted as cxz.t3
ret

local labels are referenced to the nearest global label/procedure upwards.

05 Nov 2004, 11:06

vbVeryBeginner

Joined: 15 Aug 2004
Posts: 884
Location: \\world\asia\malaysia

vbVeryBeginner 07 Nov 2004, 14:43

arent the stack supposely cannot be modifed?

07 Nov 2004, 14:43

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19876
Location: In your JS exploiting you and your system

revolution 08 Nov 2004, 01:41

Stacks are always being modified. It is one of the most volitile places to store data. Once the routine returns (RET) it releases the stack for use by other code.

08 Nov 2004, 01:41

vbVeryBeginner

Joined: 15 Aug 2004
Posts: 884
Location: \\world\asia\malaysia

vbVeryBeginner 08 Nov 2004, 09:22

thanks you revolution, you RET clears my confuse Smile

ps: i am acutally quite new to assembly language, play with NASM before for a very short time, (no application produced!), any later on, i found FASM (which makes me stick until now) about 4 months already Smile

08 Nov 2004, 09:22

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19876
Location: In your JS exploiting you and your system

revolution 09 Nov 2004, 02:04

Kembali.

PS: Selamat Hari Raya. Anda balik kampung untuk minggu depan?

09 Nov 2004, 02:04

vbVeryBeginner

Joined: 15 Aug 2004
Posts: 884
Location: \\world\asia\malaysia

vbVeryBeginner 09 Nov 2004, 04:54

thank you revolution Smile

never know you could speak malay hah :p
are you from malaysia? anyway, i am chinese :p

希望您开斋节快乐!

i don't have kampung to balik lah :p

09 Nov 2004, 04:54

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19876
Location: In your JS exploiting you and your system

revolution 10 Nov 2004, 08:20

Saya tak cakap bahasa cina.

Saya cakap sedikit sahaja bahasa Melayu. Saya kerja dalam Malaysia sebelum ini. Suka berlatih bila-bila saya dapat peluang.

10 Nov 2004, 08:20

vbVeryBeginner

Joined: 15 Aug 2004
Posts: 884
Location: \\world\asia\malaysia

vbVeryBeginner 10 Nov 2004, 13:05

bagus lah, sedikit pun jadilah :p

chinese language is fun, if you got time, you could learn it Smile

maybe someday you would work in china ?

10 Nov 2004, 13:05

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