messagebox invokation problem on assembler-CodePudding

Here is the code (works with masm64)

include \masm64\include64\masm64rt.inc ; библиотеки
count PROTO arg_a:QWORD,arg_b:QWORD,arg_c:QWORD,arg_d:QWORD, arg_e:QWORD,arg_f:QWORD
.data
_a1 dq 2
_b1 dq 4
_c1 dq 2
_d1 dq 2
_e1 dq 2
_f1 dq 8
_res1 dq 0

_title db "Лаб.1-2. Процедуры. masm64",0
strbuf dq ?,0
_text db "Уравнение  f/e — b/d – a/c",0ah,"Результат: %d",10,"Адрес переменной в памяти: %p",0ah,0ah,
"Автор: Неопознанный пингвин",0

.code
count proc arg_a:QWORD, arg_b:QWORD,arg_c:QWORD, arg_d:QWORD, arg_e:QWORD, arg_f:QWORD ; переносим параметри, как аргументи функции

mov rax,arg_f     ; f->rax
div arg_c       ; f/e

mov rbx,rax     ; f/e->rbx 
xor rax,rax     ; rax=0 

mov rax,rdx     ; b->rax
div arg_d       ; b/d

sub rbx,rax     ; (f/e)-(b/d)
xor rax,rax     ; rax=0

mov rax,rcx     ; a->rax
div arg_c       ; a/c

sub rbx,rax     ; (f/e)-(b/d)-(a/c)

mov _res1,rbx   ; содержимое rax в _res1
ret 
count endp

entry_point proc
invoke count,_a1,_b1,_c1,_d1,_e1,_f1
invoke wsprintf,ADDR strbuf,ADDR _text,_res1,ADDR _res1
invoke MessageBox,0,addr strbuf, addr _title, MB_ICONINFORMATION
invoke ExitProcess,0
entry_point endp

The program works in a following way: it solves the mathematical problem f/e — b/d – a/c and sends the result into message box, but it doesn't work. it normally works without invoke count, but i need this part of code. how can i fix it?

CodePudding user response：

strbuf dq ?,0  ;only 8 byte long for output

Your destination buffer is too small. You need define large byte area for result of wsprint function. For example

strbuf db 512 dup(?)

CodePudding user response：

Your count proc has 6 args but the code only uses 3 of them! The comments don't match the instructions. You don't calculate f/e — b/d – a/c.

See if next code displays the result:

mov  rax, _f1  ; f -> rax
div  _e1       ; f/e
mov  rcx, rax  ; f/e -> rcx

mov  rax, _b1  ; b -> rax
div  _d1       ; b/d
sub  rcx, rax  ; (f/e)-(b/d)

mov  rax, _a1  ; a -> rax
div  _c1       ; a/c
sub  rcx, rax  ; (f/e)-(b/d)-(a/c)

mov  _res1, rcx

invoke wsprintf, ADDR strbuf, ADDR _text, _res1, ADDR _res1
invoke MessageBox, 0, addr strbuf, addr _title, MB_ICONINFORMATION
invoke ExitProcess, 0

Does invoke take care of cleaning the stack in invoke count, _a1, _b1, _c1, _d1, _e1, _f1 ? Or should you have written ret 48 ?