NASM - The Netwide Assembler
NASM Forum => Using NASM => Topic started by: c0dehunter on November 24, 2010, 03:26:56 PM
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Hello, it's been a week since I have started to write this program but still no success :(
I get "Access violation - cannot read memory at 0x000001" at the end of the program. Also, do not mind about comments, they're in my language.
Can anyone suggest what could be wrong?
Task:
In an assembler language, write recursive function that calculates the n-th term of a sequence in the series:
f(n) = f(n-3) + f(n-2), n > 2, f(0) = 1, f(1)=1, f(2) = 7
My program:
bits 32
extern _printf
global _main
section .data
izpis db "Rezultat za f(%d)= %d",10,0 ;za izpis zaporedja
n dd 0
section .text
_rekurz:
mov eax, [esp+4] ;trenutni argument shranimo v eax
cmp eax,0 ;primerjamo, ?e je argument 0 in v tem primeru v eax shranimo 1
je .vrni1
cmp eax,1
je .vrni1
cmp eax,2 ;primerjamo argument z 2
je .vrni7
sub eax,2 ;n=n-2
mov edx, eax ;eax (n) shranimo v drug register, saj se bo vrednost eax spremenila
push eax ;na sklad potisnemo eax (n-2)
call _rekurz ;klicemo funkcijo za trenutni (n-2) - rezultat bo v eax
add esp,4 ;pobrišemo argument
mov ecx,eax ;dobljeno vrednost shranimo v ecx, za?asno
mov eax,edx ;v eax nazaj shrani tisti trenutni n (n-2)
dec eax ;in se zmanjsamo za 1 (n-2 -1 = n-3)
push eax ;in to potisnemo na sklad na naslednji klic
call _rekurz ;klicemo funkcijo za trenutni (n-3) - rezultat bo v eax
add esp,4
add eax,ecx ;rezultata seštejemo
ret
.vrni1:
mov eax,1
ret
.vrni7:
mov eax,7
ret
.konec:
ret
_main:
pushad
; klic funkcije - rad bi izracunal 10. clen
push 10
call _rekurz
add esp,4
; izpis rezultata
push eax
push 10
push dword izpis
call _printf
add esp, 8
popad
ret
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You always find it the last place you look! :)
; izpis rezultata
push eax
push 10
push dword izpis
call _printf
add esp, 8
Best,
Frank
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Frank, thank you! I have also found a flaw that registers are changinh throughout the recursion, so i'll have to use the stack.