问题
My program(assembly tasm 16bit) supposed to print a bar graph represtion for an array.Right now its only supports specificarray but I will add support for general cases in the future.The code works fine in debugger and prints the bars as expcted.But in run the code gets stuck and dosent print anything. All the functions apart from PrintArr were working separately as expcted. I cant find my problam in debugging beacouse the problame dosent seem to exist in the debugger.
;
IDEAL
MODEL small
STACK 100h
DATASEG
; --------------------------
; Your variables here
; --------------------------
arr db 3,1,2
screen_width dw 300
screen_height dw 190
plo dw 0
var db ?
CODESEG
;works on tasm syntex 16 bit
proc FindWidthForColAndSpace
;finds the width for each col and space
;input:
;1.number of cols
;2.screen width
;ouput:
;1.space
;2.width
push bp
mov bp,sp
push ax
push bx
push cx
push dx
mov ax,[bp+4];sceen width
mov bx,[bp+6];number of cols
div bx
xor dx,dx
mov bx,ax
mov cx,5
mul cx
xor dx,dx
mov cx,100
div cx
xor dx,dx
sub bx,ax
mov [bp+4],ax
mov [bp+6],bx
pop dx
pop cx
pop bx
pop ax
pop bp
ret
endp FindWidthForColAndSpace
proc FindHeight
;finds the pixel repsention for
;input:
;1.screen height
;2.highest value
;3.lowest value
;ouput:
;1.height
push bp
mov bp,sp
push ax
push bx
push cx
push dx
xor dx,dx
mov cx,[bp+4];lowest value
mov bx,[bp+6];highest value
mov ax,[bp+8];screen height
div bx
mov [bp+8],ax
pop dx
pop cx
pop bx
pop ax
pop bp
ret 4
endp FindHeight
proc PrintLine
;prints a line
;1.length
;2.colour
;3.x
;4.y
push bp
mov bp,sp
push ax
push bx
push cx
push dx
push si
mov cx,[bp+10];leangth
mov dx,[bp+4];y
mov al,[bp+8];colour
mov si,[bp+6];x
mov ah,0ch
xor bx,bx
pl:
push cx
mov cx,si
int 10h
inc si
pop cx
loop pl
pop si
pop dx
pop cx
pop bx
pop ax
pop bp
ret 8
endp PrintLine
;clean screen
proc Cls
push ax
push cx
mov cx,200
xor ax,ax
Clean:
push 320
push 0
push 0
push ax
call PrintLine
inc ax
loop Clean
pop cx
pop ax
ret
endp cls
proc PrintSquare
;print a square
;input:
;1.height
;2.leangth
;3.colour
;4.x
;5.y
push bp
mov bp,sp
push ax
push bx
push cx
push dx
push di
push si
mov cx,[bp+12]
mov ax,[bp+10]
mov bx,[bp+8]
mov dx,[bp+6]
mov di,[bp+4]
xor si,si
print:
mov di,[bp+4]
push ax
push bx
push dx
sub di,si
push di
call PrintLine
inc si
loop print
pop si
pop di
pop dx
pop cx
pop bx
pop ax
pop bp
ret 10
endp PrintSquare
proc PrintArr
;prints a array
;1.strat of the array(offset)
;2.end of the array (offset)
;output
;none
push bp
mov bp,sp
push ax
push bx
push cx
push dx
push di
push si
mov bx,[bp+6];strat of the array(offset)
mov ax,[bp+4];end of the array (offset)
mov cx,[screen_width]
push 3
push cx
call FindWidthForColAndSpace
pop dx;space widfth
pop di;cooloum width
mov cx,[screen_height]
push cx
push 3
push 1
call FindHeight
pop si;height(dyamnic height *value =pixels)
mov cx,3
xor ax,ax
printar:
xor ax,ax
mov al,[byte ptr bx]
push dx
xor dx,dx
mul si
pop dx
push ax
push di
push 4
push [plo]
push [screen_height]
call PrintSquare
mov ah,1
int 21h
inc bx
push ax
mov ax,[plo]
add ax,dx
add ax,di
mov [plo],ax
pop ax
loop printar
pop si
pop di
pop dx
pop cx
pop bx
pop ax
pop bp
ret 4
endp PrintArr
start:
mov ax, @data
mov ds, ax
mov ax,13h
int 10h
call cls
push 0
push 2
call PrintArr
mov ah,1
int 21h
; push 10
; push 5
; push 4
; push 100
; push 100
; call PrintSquare
; mov ah,86h
; int 15h
;call cls
exit:
mov ax, 4c00h
int 21h
END start
回答1:
Turbo Debugger sets a bunch of registers to 0 when it loads the program. When MS-DOS starts these registers are not set to null. The information which register needs to be null you can achieve by adding
xor ax, ax
xor bx, bx
xor cx, cx
xor dx, dx
xor si, si
xor di, di
xor bp, bp
at the beginning of the start procedure and by commenting it out successively. It will turn out that the delinquent is DX. So search for the first function or instruction which expects a null in this register. I found it in the first div instruction in FindWidthForColAndSpace. This div performs DX:AX/BX and needs therefore a value in DX. Is it an accident that the line xor dx, dx follows the div? It must be in front of it.
来源：https://stackoverflow.com/questions/43819436/assemblytasm-program-crashes-in-run-but-works-fine-in-debuggerturbo-debugger