11.3: Macro Example

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The following example program demonstrates the definition and use of a simple macro.

; Example Program to demonstrate a simple macro

; ************************************************** 
; Define the macro
;   called with three arguments: 
;        aver    <1st>, <len>, <ave>

%macro     aver     3 
    mov    eax, 0
    mov ecx, dword [%2]                 ; length
    mov r12, 0
    lea rbx, [%1]
    
%%sumLoop:
    add     eax, dword [rbx+r12*4]      ; get list[n]
    inc     r12
    loop    %%sumLoop

    cdq
    idiv    dword [%2]
    mov     dword [%3], eax

%endmacro

; **************************************************
;  Data declarations

section .data

; -----
;  Define constants

EXIT_SUCCESS     equ     0                     ; success code
SYS_exit         equ     60                    ; code for terminate

; Define Data. 

section     .data
list1       dd     4, 5, 2, -3, 1
len1        dd     5
ave1        dd     0

list2       dd     2, 6, 3, -2, 1, 8, 19
len2        dd     7
ave2        dd     0
; **************************************************

section     .text 
global  _start 
_start:

; -----
;  Use the macro in the program

    aver list1, len1, ave1                    ; 1st, data set 1
    aver list2, len2, ave2                    ; 2nd, data set 2

; -----
;  Done, terminate program.

last:
    mov rax, SYS_exit                         ; exit
    mov rdi, EXIT_SUCCESS                     ; success
    syscall

In this example, the macro is invoked twice. Each time the macro is used, it is copied from the definition into the text section. As such, macros typically use more memory.