"Assuming" parameters

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alorent

Joined: 05 Dec 2005
Posts: 221

alorent 17 Nov 2010, 21:25

Hello!

I was wondering what's wrong with this assume in the "proc" parameter:

Code:

format PE GUI 4.0
entry start

include 'win32ax.inc'
include 'macro\if.inc'
include 'macro\masm.inc'

struct my_struct
   Member1   dd  ?
   Member2   dd  ?
ends


list_member dd 11111111h, 22222222h


.code

start:

    stdcall  MyProc, list_member    



MyProc proc pList

    assume pList:my_struct

    push   [pList.Member1]     ; FASM error here: "undefined symbol pList.Member1"

MyProc endp

I guess the problem is that "pList" is taken as [ebp + XXX] and the assume causes error there.

Or maybe is there an alternative macro "assume_ptr" that can deal with that type of "assuming"?

Thanks in advance!

17 Nov 2010, 21:25

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 17 Nov 2010, 23:03

alorent,

assume macro from MACRO\MASM.INC is limited to assume reg:struct syntax.

Let's see, pList is a pointer to structure? x86 doesn't support double indirection, you have to put pointer in register beforehand (then assume becomes useful).

17 Nov 2010, 23:03

alorent

Joined: 05 Dec 2005
Posts: 221

alorent 18 Nov 2010, 12:46

Thanks baldr.

Well, it seems that the following is accepted (at least with latest FASM):

Code:

assume list_member:my_struct
mov    eax, [list_member.Member1]

Thanks!

18 Nov 2010, 12:46

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 18 Nov 2010, 17:51

alorent,

list_member should be address of my_struct then, not address of pointer to it. You may think of assume as type cast.

That's my favorite part: there are ways thing is supposed to be used, and much more ways thing can be used (some of them are productive too). Wink

18 Nov 2010, 17:51

alorent

Joined: 05 Dec 2005
Posts: 221

alorent 19 Nov 2010, 05:49

Thanks for clarifying that baldr! Wink

19 Nov 2010, 05:49

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