Thanks in advance for any assistance. This issue has been driving me crazy. So Ive got a little calculator application that asks for the users name, asks for 2 numbers, asks if they want to Add/Sub/Mul/Div, prints out the answer and then asks if they want to do it again. Well, everything works perfectly until I get to the part that asks if they want to do it again. When we get to this point, the system prints the question, but does not wait for a response. The code is pretty well the same for all user input, so Im incredibly confused as to what the issue is. Ive included the code below and highlighted the function that is the issue. Youll see that there are others that are pretty well exactly the same, and they have no issues. Anyway, here it is.
; "Hello World!" in 64 bit Linux NASM
global _start ; global entry point export for ld
section .text
_start:
; sys_write(stdout, message, length)
nop
mov rax, 4 ; sys_write syscall
mov rbx, 1 ; std_out
mov rcx, inputMsg ; message address
mov rdx, input_L ; message string length
int 80h
; grab user input
mov rax, 3 ; sys_read syscall
mov rbx, 0 ; std_in
mov rcx, userIn ; output to username
mov rdx, 16 ; accept 16 bytes
int 80h
; say hello
mov rax, 4 ; sys_write
mov rbx, 1 ; std_out
mov rcx, helloMsg
mov rdx, helloMsg_L
int 80h
; print users name
mov rax, 4
mov rbx, 1
mov rcx, userIn
mov rdx, 16
int 80h
_calc:
; ask for first number
mov rax, 4
mov rbx, 1
mov rcx, numMsg1
mov rdx, numMsg1_L
int 80h
; grab first number
mov rax, 3
mov rbx, 2
mov rcx, num1
mov rdx, 8
int 80h
; ask user for second number
mov rax, 4
mov rbx, 1
mov rcx, numMsg2
mov rdx, numMsg2_L
int 80h
; grab second number
mov rax, 3
mov rbx, 2
mov rcx, num2
mov rdx, 8
int 80h
; ask user what function they want to do 1=add, 2=sub, 3=mul, 4=div
mov rax, 4
mov rbx, 1
mov rcx, function
mov rdx, function_L
int 80h
; get what function user wants to do
mov rax, 3
mov rbx, 2
mov rcx, func
mov rdx, 1
int 80h
; go to appropriate label
mov rax, [func]
sub rax, '0'
cmp rax, 1
je _add
cmp rax, 2
je _sub
cmp rax, 3
je _mul
cmp rax, 4
je _div
_sum:
; display sum
mov rax, 4 ; sys_write
mov rbx, 1 ; std_out
mov rcx, sum
mov rdx, 16
int 80h
; ask user if they want to enter more numbers
mov rax, 4
mov rbx, 1
mov rcx, inMsg2
mov rdx, inMsg2_L
int 80h
;get answer
mov rax, 3
mov rbx, 2
mov rcx, response
mov rdx, 1
int 80h
mov rax, [response]
sub rax, '0'
cmp rax, 1
je _calc
jmp _end
_add:
; add numbers
mov rax, [num1] ; move first number into rax
sub rax, '0' ; sub '0' to convert ascii to decimal
mov rbx, [num2] ; move second number into rbx
sub rbx, '0' ; sub ascii '0' to convert to decimal
add rax, rbx ; add rbx to rax
add rax, '0' ; add ascii '0' to convert to ascii
mov [sum], rax ; move the sum to a temp variable
jmp _sum
_sub:
; subtract numbers
mov rax, [num1] ; move first number into rax
sub rax, '0' ; sub '0' to convert ascii to decimal
mov rbx, [num2] ; move second number into rbx
sub rbx, '0' ; sub ascii '0' to convert to decimal
sub rax, rbx ; add rbx to rax
add rax, '0' ; add ascii '0' to convert to ascii
mov [sum], rax ; move the sum to a temp variable
jmp _sum
_mul:
; multiply numbers
mov rax, [num1] ; move first number into rax
sub rax, '0' ; sub '0' to convert ascii to decimal
mov rbx, [num2] ; move second number into rbx
sub rbx, '0' ; sub ascii '0' to convert to decimal
imul rax, rbx ; multiply rbx to rax
add rax, '0' ; add ascii '0' to convert to ascii
mov [sum], rax ; move the sum to a temp variable
jmp _sum
_div:
; devide numbers
mov rax, [num1] ; move first number into rax
sub rax, '0' ; sub '0' to convert ascii to decimal
mov rbx, [num2] ; move second number into rbx
sub rbx, '0' ; sub ascii '0' to convert to decimal
idiv rbx ; divide rbx to rax
add rax, '0' ; add ascii '0' to convert to ascii
mov [sum], rax ; move the sum to a temp variable
jmp _sum
_end:
; sys_exit(return_code)
mov rax, 1 ; sys_exit syscall
mov rbx, 0 ; return 0 (success)
int 80h
section .data
helloMsg: db 'Hello, ' ; message and newline
helloMsg_L: equ $-helloMsg ;
inputMsg: db 'Enter your name: ' ; message telling user to input name
input_L: equ $-inputMsg
numMsg1: db 'Enter number 1: ' ; message telling user to inpt first number
numMsg1_L: equ $-numMsg1
numMsg2: db 'Enter number 2: ' ; message telling user to input second number
numMsg2_L: equ $-numMsg2
function: db 'Select function: ADD(1), SUB(2), MUL(3), DIV(4) '
function_L: equ $-function
inMsg2: db 'Run again? YES(1), NO(0) '
inMsg2_L: equ $-inMsg2
sumMsg: db 'The sum is: '
sumMsg_L: equ $-sumMsg
section .bss
userIn: resb 16
num1: resb 8
num2: resb 8
sum: resb 16
func: resb 2
response: resb 2
So the bolded section is where the issue is, at least where I think it is. Basically it just skips over this, or seems like its skipping over it. The previous function displays the question but then doesnt wait for a response and, because we cannot enter anything, it just ends.
Thanks again for any help,
Brad.
Oh, and I hope that it turns out to be something really stupid that Ive just overlooked.. I can deal with being stupid Lol, I just want this to work.
EDIT: When I debug this with GDB, there is no issue, so unfortunately debugging is no help..
EDIT2: Just realized that it didnt actually bold that section but rather just put ** before and after.. I guess to simplify, for those that dont want to read all the code, this is the function, or system call, that seems to be not functioning correctly.
; ask user if they want to enter more numbers
mov rax, 4
mov rbx, 1
mov rcx, inMsg2
mov rdx, inMsg2_L
int 80h
;get answer
mov rax, 3
mov rbx, 2
mov rcx, response
mov rdx, 1
int 80h
mov rax, [response]
sub rax, '0'
cmp rax, 1
je _calc
jmp _end
and then there is this one, that does function.
; ask user what function they want to do 1=add, 2=sub, 3=mul, 4=div
mov rax, 4
mov rbx, 1
mov rcx, function
mov rdx, function_L
int 80h
; get what function user wants to do
mov rax, 3
mov rbx, 2
mov rcx, func
mov rdx, 1
int 80h
; go to appropriate label
mov rax, [func]
sub rax, '0'
cmp rax, 1
je _add
cmp rax, 2
je _sub
cmp rax, 3
je _mul
cmp rax, 4
je _div
So again, why one works and the other doesnt escapes me at this point, and I have debugged the code, which unfortunately has not really given me any insite into what the issue is.
EDIT3:
This is what I get when I run it.
h**p@h**p-VirtualBox:~/Programming$ ./helloInput64
Enter your name: brad
Hello, brad
Enter number 1: 2
Enter number 2: 3
Select function: ADD(1), SUB(2), MUL(3), DIV(4) 1
The sum is: 5Run again? YES(1), NO(0) h**p@h**p-VirtualBox:~/Programming$
So after it prints the sum it just totally goes stupid. Prints the next string on the same line and just ends without grabbing user input..
response, and it applies tonumandnum2as well. I hope you can convince him. I was able to fix his entire program but there is no way I'm going to post it as an answer.So after it prints the sum it just totally goes stupid. Prints the next string on the same line and just ends without grabbing user input... It did grab the input. It grabbed the Newline (Linefeed=LF) character that was remaining in the buffer when you did theSelect functioninput. The leftover LF in the buffer was used as input to the next prompt. The LF character would then be the sole input on the next prompt (like you just hitENTERfor the response). You then compare the LF with 0 and 1, it doesn't match so it exits.mov rcx, funcmov rdx, 1int 80htomov rcx, funcmov rdx, 2int 80h. Then make a similar change for the code that getsresponse.