Define proc inside a struct

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M_H

Joined: 25 Feb 2017
Posts: 2

M_H 25 Feb 2017, 19:20

Hi eveyone
im new to asm language
i was woundering how can i define someting like a proc inside a struct

i use this code to define a struct but i need to pass some parameters to the print function

struct String DATA
jmp .x
.len dw .strend-.str
.str db DATA,' '
.strend db 0
.Print:
invoke MessageBox,HWND_DESKTOP,.str,"",MB_OK
ret
.x:
ends

_________________
Lets Learn Assembly

25 Feb 2017, 19:20

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20414
Location: In your JS exploiting you and your system

revolution 26 Feb 2017, 00:11

If you want to pass parameters to .Print then you can do it just as normal. Assuming you are using stdcall then:

Code:

struct String DATA
        jmp .x
        .len dw .strend-.str
        .str db DATA,' '
        .strend db 0
        .Print:
        ;access first parameter at [esp+8]
        invoke MessageBox,HWND_DESKTOP,.str,[esp+8],MB_OK
        ret
        .x:
ends
my_string String 'Title'
stdcall my_string.Print,'Text'  ;pass 'Text' as a parameter

26 Feb 2017, 00:11

M_H

Joined: 25 Feb 2017
Posts: 2

M_H 26 Feb 2017, 12:50

revolution wrote:

If you want to pass parameters to .Print then you can do it just as normal. Assuming you are using stdcall then:

Code:

struct String DATA
        jmp .x
        .len dw .strend-.str
        .str db DATA,' '
        .strend db 0
        .Print:
        ;access first parameter at [esp+8]
        invoke MessageBox,HWND_DESKTOP,.str,[esp+8],MB_OK
        ret
        .x:
ends
my_string String 'Title'
stdcall my_string.Print,'Text'  ;pass 'Text' as a parameter

i don't think its that easy
Im keeping recieving this error:
Operand size not specifing
push [ebp+8]

_________________
Lets Learn Assembly

26 Feb 2017, 12:50

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20414
Location: In your JS exploiting you and your system

revolution 26 Feb 2017, 12:54

Okay I forgot the dword override.

Code:

        invoke MessageBox,HWND_DESKTOP,.str,dword[esp+8],MB_OK

26 Feb 2017, 12:54

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