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flat assembler > Macroinstructions > Quick Question on Macros

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Imagist



Joined: 13 Jun 2004
Posts: 114
Location: Pennsylvania (USA)
How exactly are macros assembled? Does the assembler simply insert the code into the program like this?:

Code:
jmp code
label var1
db 10
label var2
db 11

code:
   switch var1, var2
   
macro switch a,b{
mov ax,[a]
mov bx,[b]
mov [b],ax
mov [a],bx
}
    


assembles to:

Code:
jmp code
label var1
db 10
label var2
db 11

code:
   mov ax,[var1]
   mov bx,[var2]
   mov [var2],ax
   mov [var1],bx
    


Or is the macro called from a different spot, like functions in C, allowing recursion?

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Many things are possible. Few things are likely.
Post 23 Aug 2004, 18:14
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7108
Location: Slovakia
you are right with your result, except one thing, macro has to be defined before it is used. Your example will be preprocessed to
Code:
jmp code 
label var1 
db 10 
label var2 
db 11 

code: 
   switch var1, var2
    

and then during assembly you will get error saying "switch" is not name of instruction or directive.
Post 23 Aug 2004, 19:49
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Imagist



Joined: 13 Jun 2004
Posts: 114
Location: Pennsylvania (USA)
So recursive macros are impossible. Darn. And I should do:

Code:
jmp code
label var1
db 10
label var2
db 11

macro switch a,b{
   mov ax,[a]
   mov bx,[b]
   mov [b],ax
   mov [a],bx
}

code:
   switch var1, var2
    


In my dk_lib (a library for using fasm as an HLL; school project) I have the following macro:

macro dk_setupGUI{
format PE GUI 4.0
entry start

include '%fasminc%\win32ax.inc'
};end macro dk_setupGUI

Will this work?

Also, do includes work in a similar way to macros, like:

Code:
;this is in a file called switch.asm
push ax
push bx
pop ax
pop bx
    


Code:
;this is in a file called very-bad-code.asm
mov ax, 10
mov bx, 11

include 'switch.asm'

;now ax should be 11 and bx 10
    


so that very-bad-code.asm assembles to:

Code:
mov ax, 10
mov bx, 11

push ax
push bx
pop ax
pop bx
    


I have many questions, and I am glad there are many here to help, becuase the library is due on next Monday!

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Many things are possible. Few things are likely.
Post 24 Aug 2004, 03:04
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pelaillo
Missing in inaction


Joined: 19 Jun 2003
Posts: 874
Location: Colombia
Imagist wrote:
Also, do includes work in a similar way to macros...

Yes, but macros are more flexible. They have arguments, so you could do many things you cannot with includes.

Think on macros as text search and replace, but advanced.

Includes are useful as a way to split source code in more files, either because is easier to manage smaller files or to use one part in different projects.

Code:
; Without using registers:
macro switch a,b{ 
   push [a] 
   push [b] 
   pop [a] 
   pop [b] 
}    

Quote:

Will this work?

If you are calling this macro from a source that have access to dk_setupGUI macro definition it will work. But if the definition is accessible only through 'win32ax.inc' it won't work.
i.e. this type of recursiveness does not work.
Code:
;filename: test.inc
macro dk_setupGUI{ 
format PE GUI 4.0 
entry start 

include 'test.inc' 
};end macro dk_setupGUI 
    
Post 24 Aug 2004, 03:38
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 7318
Location: Kraków, Poland
Quote:
So recursive macros are impossible.

This is not really true. The "invoke" nesting macros from WIN32AX.INC file in FASMW package demonstrate some kind of the macro recursion in action. A bit complicated, but possible.
Post 24 Aug 2004, 09:32
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halyavin



Joined: 21 Aug 2004
Posts: 42
And use recursion instead of cycles in compicated macros; it is often helps. You can't write program that sorts array at compilation time using 'repeat' macro.
Post 28 Aug 2004, 14:31
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