Please help: JE ret

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wht36

Joined: 18 Sep 2005
Posts: 106

wht36 04 Sep 2006, 16:14

Sorry, I am new to macro programming... In the old days when I was using A86, I could put something like

Code:

         cmp al,0
         je   ret
         ...
         ret

and the assembler would automatically generate a jump to the nearest return. Now is it possible to use make a macro to do something similar in FASM?

The closest I've come to is

Code:

macro ret
{ if ~ defined .ret | defined @f
  .ret:
  @@: ret
  end if }
...
     cmp al,0
     je .ret
     ...
     ret

So is this the way to do it?

Going off on a tangent, must I use commas between the parameters of a macro e.g. push ax,bx,cx,dx instead of push ax bx cx dx?

04 Sep 2006, 16:14

okasvi

Joined: 18 Aug 2005
Posts: 382
Location: Finland

okasvi 04 Sep 2006, 16:52

Quote:

Going off on a tangent, must I use commas between the parameters of a macro e.g. push ax,bx,cx,dx instead of push ax bx cx dx?

No, push 0h esi 0h edi seems to be working

04 Sep 2006, 16:52

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 04 Sep 2006, 19:26

1. there is no "ret" isntruction, i believe you mean "retn". "ret" is pseudo-opcode (macro in FASM) to return from current context (eg. procedure)

to your problem: you may find way to solution here

04 Sep 2006, 19:26

UCM

Joined: 25 Feb 2005
Posts: 285
Location: Canada

UCM 04 Sep 2006, 23:54

Yes, there is the "ret" instruction. In fact, it is not an instruction, but not implemented as a macro.

04 Sep 2006, 23:54

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 05 Sep 2006, 01:36

But it's true that "ret" is implemented as a macro in PROC context.

05 Sep 2006, 01:36

wht36

Joined: 18 Sep 2005
Posts: 106

wht36 05 Sep 2006, 05:47

Hmm, so ret is not an instruction... does that mean if I try to implement my ret macro something nasty would happen and I should just use something like jmp @f instead of jmp .ret?

Sigh... what a pity, I thought something like JMP RET would be much clearer than JMP @F

05 Sep 2006, 05:47

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 05 Sep 2006, 07:33

i think tomasz explained it somewhere, that ret should be return from current context, it's not defined in manuals (not sure about this), and implemented "ret"="retn" for compatibility with other assemblers, and because people ought to use it.

those @@@/@@f/@@b macros showed you way how you can solve your problem with macros. analogy, overload "ret" with something like "@@@", and overload "jmp ret" with something that compares distance to neares preceding ret (@@b) and nearest following ret (@@f). Of course you need more checks (no preceding/following ret) etc.

05 Sep 2006, 07:33

wht36

Joined: 18 Sep 2005
Posts: 106

wht36 07 Dec 2010, 15:31

Not fully tested, but I think one can simulate JE ret, jb ret4 etc with the macros below

Code:

irp cond, mp, a, b, be, c, e, l, le, o, s, z, na, nb, nbe, nc, ne, nl, nle, no, ns, nz {
   macro j#cond addr { 
      j equ addr
      match =ret,addr { j equ ..ret \\}
      match =ret4,addr { j equ ..ret4 \\}
      match =ret8,addr { j equ ..ret8 \\}
      match =ret12,addr { j equ ..ret12 \\}
      j#cond j
   \}
}

macro ret n {                           ; macro to create a label for each ret instruction so one can use e.g. jmp .ret4 & je .ret
   match =..ret#n,..ret#n {..ret#n:\}  ; create the label .ret if .ret was not defined previously so that forward jumps to .ret will work
   local ..z                              ; create anonymous label ..z for each ret
   ..z: ret n                          ; make the anonymous label specific to n
   match ,n { ..ret equ ..z \}           ; assign the label to .ret if there is no n specified
   match x,n { ..ret\#x equ ..z \} ; else assign .retn to the label
}

07 Dec 2010, 15:31

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