offsetof MACRO

[habran]

I was googling the net to find something about the C macro offsetof and as usual MSDN is stingy to give some acceptable info and example
I was curious if someone ever translated it to ASM and I found nothing
so I decided to shad lights on it
In masm there is no need for that macro because it has it built in,
however I wrote one for those who were not clear what is it about
especially for C programmers who want to learn assembly language 

Code Select Expand

;defined in stddef.h
;#define offsetof(s,m)   (size_t)( (ptrdiff_t)&(((s *)0)->m) )
;s = struct
;m = member
;returns offset of a member in struct
;E.G.
;   mov edx, offsetof(MYFRAME,EditWindow)
;it is a same as
;   mov edx, MYFRAME.EditWindow

;struct MYFRAME
; rcFrame RECT <>
; FrameWindow HWND
; EditWindow  HWND
; rcEdit RECT <>
;ends

offsetof MACRO s,m
sm EQU <>   
    sm CATSTR sm,<s>,<.>,<m>
    EXITM<sm>
ENDM

 

[qWord]

offsetof MACRO s,m
    EXITM <s.&m>
ENDM

:t

[habran]

Cool  8)
You said more with less words :t
My intention was to show the steps what is actually happening

[Gunther]

Habran,

Cool  8)
You said more with less words :t
My intention was to show the steps what is actually happening

You should know that qWord is a really macro magician. Some of his tricks border on witchcraft.

Gunther

[dedndave]

qWord understands the syntax - a few other members do too, of course

that's the whole trick to macros
it's not clearly explained in the masm manual

maybe we can get qWord to write a macro tutorial   

[Gunther]

it's not clearly explained in the masm manual

maybe we can get qWord to write a macro tutorial   

That's an excellent idea. It would help a lot of members.

Gunther

[habran]

C'mon Gunther,  witchcraft!? that reminds me on witch-hunt in medieval history :icon_eek:
It is not flattering ;)
Sorcery maybe or Shamanism or Magic
Hey qWord maybe you should change your avatar to this:
                         

what do you say dedndave 8)

[jj2007]

include \masm32\include\masm32rt.inc

offsetof MACRO s,m
    EXITM <s.&m>
ENDM

.code
start:
   print str$(offsetof(RECT, top)), " = "
   print str$(RECT.top)
   exit
end start ;)

[qWord]

The trick with macros is to get around MASM's bugs 

[habran]

maybe this can help :P
                                                                               

[dedndave]

qWord is a macro wizard
however, that icon is already in use by Tom Bleeker   :P

http://www.madwizard.org/

[habran]

Damn!
What about this one:
                                 

[dedndave]

"Nothin' up my sleeve!"

[habran]

dedndave you are a real wizard

hey jj2007 :t

I have a suggestion for hutch:
why not devote a topic for macros where people can contribute they own macros

[hutch--]

> The trick with macros is to get around MASM's bugs

We generally call them undocumented features.  :icon_mrgreen: