Assembly how can I compare a dword to an int

[Assembly] how can I compare a dword to an int - Printable Version

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how can I compare a dword to an int - c0mputer-fr0d - Oct 18, 2012

I want to do this

Code 
point      DD ? 

LBL:

cmp point,40;

add point,4;

* - K4Fr - Oct 18, 2012

(Oct 18, 2012 05:30 PM)c0mputer-fr0d Wrote: I want to do this

Code
point DD ? LBL: cmp point,40; add point,4;

Exactly like you did...Its comparing a dword to an int

* - notsteve - Oct 18, 2012

Why do you have semicolons after each instruction?

* - DaRkReD - Oct 18, 2012

Move them into registers and use atodw

Code 
.386

.model flat,stdcall

option casemap:none

include \masm32\include\windows.inc

include \masm32\include\kernel32.inc

include \masm32\include\user32.inc

include \masm32\include\masm32.inc

includelib \masm32\lib\kernel32.lib

includelib \masm32\lib\user32.lib

includelib \masm32\lib\masm32.lib

.data

string db '7546754',0

format db 'eax=%u',0

.data?

buffer db 12 dup(?)

.code

start:

invoke atodw,addr string ; eax=7546754

invoke wsprintf,addr buffer,addr format,eax

invoke StdOut,addr buffer

invoke ExitProcess,0

end start

* - D3vildog - Oct 18, 2012

(Oct 18, 2012 09:08 PM)DaRkReD Wrote: Move them into registers and use atodw

Code
.386 .model flat,stdcall option casemap:none include \masm32\include\windows.inc include \masm32\include\kernel32.inc include \masm32\include\user32.inc include \masm32\include\masm32.inc includelib \masm32\lib\kernel32.lib includelib \masm32\lib\user32.lib includelib \masm32\lib\masm32.lib .data string db '7546754',0 format db 'eax=%u',0 .data? buffer db 12 dup(?) .code start: invoke atodw,addr string ; eax=7546754 invoke wsprintf,addr buffer,addr format,eax invoke StdOut,addr buffer invoke ExitProcess,0 end start

Ooh Darkred, where'd you learn to do MASM? I've only found books on FASM and ROSM and some other ones.

* - Amokov - Oct 19, 2012

What is this DWORD being used for? If it's something numerical, like an address, you can just cmp, you don't need to call any function.

* - Feminist - Oct 19, 2012

(Oct 19, 2012 07:33 AM)Amokov Wrote: What is this DWORD being used for? If it's something numerical, like an address, you can just cmp, you don't need to call any function.

It depends on the IDE you are using (if any) and compiler. Real assembly cannot do

cmp value, 1

It has to use value as a pointer

i.e.

mov eax, dword ptr [value]

o

cmp dword ptr [value], 40

* - c0mputer-fr0d - Oct 19, 2012

Code 
mov ecx dword ptr [point]

    cmp dword ptr [point] ,40

this is what I tried but it doesn't work

* - K4Fr - Oct 19, 2012

(Oct 19, 2012 05:48 PM)c0mputer-fr0d Wrote:
Code
mov ecx dword ptr [point] cmp dword ptr [point] ,40

this is what I tried but it doesn't work

A dword is an int. Secondly cmp only sets flags you still need a branch instruction.
e.g for MASM:

Code 
cmp dword ptr [point], 40

40  jne @F   

add ecx, 40  

@@:   

add ecx, 20

@@ is just an unnamed label, @F is forward so it scans forward for @@: @B is back
just use what ever labels are valid in in your assembler

* - .SCHiM. - Oct 20, 2012

cmp dword ptr[ variable ], value is a perfectly valid instruction. That will work.

An int does not differ in size from a dword (on a 32bit machine), the only difference between the two is that an int is signed and a dword is unsigned. On a 64 bit machine an integer type might be 64 bits long, while a dword is always 32 bits long.

To test if both hold the same number (despite their signs) do this:

Code 
point dd -40h

mov eax, 40

neg eax     ; negate sign

cmp point, eax

je Equal

    ;; |point| != eax

Equal: 

     ;; |point| = eax

* - c0mputer-fr0d - Oct 20, 2012

Thanks everyone and especially schim