Passing structs as parameters

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realcr

Joined: 02 Apr 2007
Posts: 39

realcr 07 Jul 2007, 11:53

Hey.

I was passing some structs pointers as arguments into my function.
things like:

Code:

struc point x,y
{
        .x        dd     x
        .y        dd     y
}

However when referring it from inside my functions it isn't that tidy , more like:

Code:

func:
      label          .pnt       at ebp+8
      enter          0,0
      
      mov           esi,[.pnt]
      add          esi,4
      mov           eax,[esi]  ; Got the y!

      leave
      ret

There's probably a nicer way to do it , I just can't find out how.

realcr.

07 Jul 2007, 11:53

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 07 Jul 2007, 15:13

You can use

Code:

virtual at esi
  .point point ?, ?
end virtual

Then, when you do some reference like "mov eax, [.point.y]" it gets translated into "mov eax, [esi+4]".

BTW, are you aware of the PROC macro that comes in the fasm package? I you are developing for Windows I suggest you a full read to http://flatassembler.net/docs.php?article=win32 which will simplify your code.

07 Jul 2007, 15:13

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 07 Jul 2007, 15:33

realcr: do it this way:

Code:

struc point x,y
{
        .x        dd     x
        .y        dd     y
}    
virtual at 0
  point point
  ;this declares point.x=0, and point.y=4
end virtual

func:
      label          .pnt       at ebp+8
      enter          0,0
      
      mov           esi,[.pnt]  ;esi = pointer to pnt structure
      mov           eax, [esi + point.x]
      mov           ebx, [esi + point.y]

      leave
      ret

07 Jul 2007, 15:33

realcr

Joined: 02 Apr 2007
Posts: 39

realcr 07 Jul 2007, 16:00

Great thanks loco and vid!

I get to learn something new about fasm every time you post a reply.

realcr.

07 Jul 2007, 16:00

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