Buffer not filling correctly

[Magnum]

This is only filling the buffer with one A.

Andy

xor ecx,ecx

comp:

mov    ebx,offset Buffer
mov    [ebx],byte ptr 'A'

inc    ebx
inc    ecx
cmp    ecx,5
jne    comp

[MichaelW]

The code is setting EBX to the start of the buffer at the top of the loop... you  need to move your loop label.

[Gunner]

Code Select Expand

xor     ecx,ecx

mov     ebx,offset Buffer

comp:
mov     [ebx],byte ptr 'A'

inc     ebx
inc     ecx
cmp     ecx,5
jne     comp

See the difference?  Your code, each time the loop starts you reload the Buffer address into ebx, move an "A", then reload the address.  You keep resetting the pointer each iteration.

[Magnum]

Thanks.

Andy

[Magnum]

I know that buffer overruns are bad, but I wanted to see what happened if I did.

If I put another buffer after the 1st one, it writes into that.

Otherwise, I assume it is writing over my code.

Just for information, when does that become a problem ?

I could not see any ill effects writing 30 bytes over.

[dedndave]

it's a trick used for malware
we can't really discuss it any further on this forum   :P