Home » Forums » Assemblers » Functions with variable number of parameters

Functions with variable number of parameters
Hi Randy,

What *universal* prototype of function with variable number of parameters should be? For function like API's wsprintf.
Equivalent to MASM's VARARG.

Regards, GJ
Posted on 2003-05-09 17:26:08 by Green Joe
Re: Functions with variable number of parameters

Hi Randy,

What *universal* prototype of function with variable number of parameters should be? For function like API's wsprintf.
Equivalent to MASM's VARARG.

Regards, GJ


You would use a macro for this purpose.


Here's a simple example I've whipped out for this purpose: 



program t;

#include( "stdlib.hhf" )



procedure varparms_p( count:uns32 ); 

    @nodisplay; 

    @noframe; 

    @nostackalign;

    @cdecl;

begin varparms_p;



    push( ebp );

    mov( esp, ebp );

    mov( count, ecx );

    while( ecx > 0 ) do

    

        mov( count[ ecx*4 ], eax );

        stdout.put( "Parm #", (type uns32 ecx), "=", (type uns32 eax), nl );

        dec( ecx );

        

    endwhile;

    mov( ebp, esp );

    pop( ebp );

    ret();

    

end varparms_p;



#macro varparms( cnt, parms[] ):_parmCnt;



    #for( _parmCnt := @elements( parms )-1 downto 0 )

    

        pushd( @text( parms[ _parmCnt ] ) );

    

    #endfor

    varparms_p( cnt );



#endmacro





begin t;    





    // Manual calls:

    

    pushd( 1 );

    pushd( 2 );

    pushd( 3 );

    varparms_p(3);

    add( 16, esp );

    

    pushd( 4 );

    pushd( 5 );

    varparms_p(2);

    add( 12, esp );

    

    // Calls supporting a variable # of arguments:

    

    varparms( 1, 6 );

    add( 8, esp );



    varparms( 4, 7,8,9,10 );

    add( 20, esp );



end t;
Posted on 2003-05-09 23:28:27 by rhyde
Functions with variable number of parameters
Hi Randy,

Following your example I wrote this wrapper for wsprintf function: 



static

    wsprintfA : procedure(p0:dword;p1:dword);

	      @cdecl;

	      external("__imp__wsprintfA");



#macro wsprintf( lpOut, lpFmt, parms[] ):_parmCnt;

	

   ?_parmCnt : int32 := @elements( parms ) - 1;

    #while(_parmCnt >= 0)

    	pushd( @text( parms[ _parmCnt ] ) );

  	 	?_parmCnt := _parmCnt - 1;

    #endwhile



	pushd(lpFmt);

	pushd(lpOut);



	lea(eax,wsprintfA);

    call([eax]);

    add((@elements( parms )+8) * 4, esp);

#endmacro


I couldn't make for loop work as in your example above. I used while loop instead.
This macro seems to make his job fine, so I want to include it in user32.hhf and upload with Icz tutorial #28 that uses wsprintf. Maybe there is a better way to wrote this wrapper?

Reagards, GJ
Posted on 2003-05-12 16:24:06 by Green Joe
Functions with variable number of parameters

Hi Randy,

Following your example I wrote this wrapper for wsprintf function: 



static

    wsprintfA : procedure(p0:dword;p1:dword);

	      @cdecl;

	      external("__imp__wsprintfA");



#macro wsprintf( lpOut, lpFmt, parms[] ):_parmCnt;

	

   ?_parmCnt : int32 := @elements( parms ) - 1;

    #while(_parmCnt >= 0)

    	pushd( @text( parms[ _parmCnt ] ) );

  	 	?_parmCnt := _parmCnt - 1;

    #endwhile



	pushd(lpFmt);

	pushd(lpOut);



	lea(eax,wsprintfA);

    call([eax]);

    add((@elements( parms )+8) * 4, esp);

#endmacro


I couldn't make for loop work as in your example above. I used while loop instead.
This macro seems to make his job fine, so I want to include it in user32.hhf and upload with Icz tutorial #28 that uses wsprintf. Maybe there is a better way to wrote this wrapper?

Reagards, GJ


About the only change I would make is to call the indirect pointer directly rather than
first loading it into EAX, e.g.,

call( wsprintfA );

Cheers,
Randy Hyde
Posted on 2003-05-12 23:09:48 by rhyde