Program can't assemble

[Kyoy]

This was an example i extracted from a book. This is basically just adding up the an array of dwords.

Code Select Expand


main PROC USES esi ecx
ptrArray:PTR DWORD
szArray:DWORD

mov esi,ptrArray
mov ecx,szArray
cmp ecx,0
je L2
mov eax,0

l1:add eax,[esi]
add esi,1
loop L1
L2:ret


it says error A2008 syntax error: ptr and
error A2008 syntax error:dword

It can't recognise ptr and dword. But i was just following the books example. Any idea what additional steps or codes i must put to get this to work?

[Titan]

Here, I edited your code and this compiles for me:

main PROC USES esi ecx
LOCAL ptrArray:DWORD
LOCAL szArray:DWORD
mov esi,ptrArray
mov ecx,szArray
cmp ecx,0
je L2
mov eax,0

L1:add eax,[esi]
add esi,1
loop L1
L2:ret
main endp

Your loop was simple, MASM is case sensative, so you have to have your "L1"'s both capitalized.  And you should have "LOCAL" before your variables to declare them as local.  This worked for me, hope it helps! ;)

[Ic3D4ne]

This was an example i extracted from a book. This is basically just adding up the an array of dwords.

Code Select Expand


main PROC USES esi ecx
ptrArray:PTR DWORD
szArray:DWORD

mov esi,ptrArray
mov ecx,szArray
cmp ecx,0
je L2
mov eax,0

l1:add eax,[esi]
add esi,1
loop L1
L2:ret


it says error A2008 syntax error: ptr and
error A2008 syntax error:dword

It can't recognise ptr and dword. But i was just following the books example. Any idea what additional steps or codes i must put to get this to work?

I'm also new to this, but should "PTR DWORD" be "DWORD PTR" ?

-Ic3D4ne

[thomasantony]

Hi IC3D4NE,
      You use dword ptr when you want to access a dword at an addess. For eg. if esi contains the pointer to a dword you use:
  mov dword ptr[esi],1 to set that variable to 1 etc. What he means with PTR DWORD is something like a data type which is not defined in MASM. Kyoy, you goota understand that everything is a dword in assembler. It doesn't matter whether it is HANDLE, HINSTANCE or any other data type of 32bits

Thomas Antony :U

[Kyoy]

That l1 was a typo :P
Titan, thanks. That compiled but the program keeps crashing whenever executed. Any further mistakes to fix up?

Code Select Expand


main PROC USES esi ecx
LOCAL ptrArray:DWORD
LOCAL szArray:DWORD
mov esi,ptrArray
mov ecx,szArray
cmp ecx,0
je L2
mov eax,0

L1:add eax,[esi]
add esi,1
loop L1
L2:ret
main endp


[thomasantony]

Hi,
    Yoiu must first set the variables to point to some arrays. Or else it will point to some bogus address. This may be why your prog is crashing.

Thomas Antony :U

[MichaelW]

See MSDN: IsBadReadPtr, and the related information.

[dsouza123]

Two problems:
What is the exit condition to stop the loop.
Since it is adding dwords it should increment by 4 bytes not 1.


L1:add eax,[esi]
add esi,4  <=  increase by 4 bytes, a dword, each time
=>some sort of check for exiting the loop should be here
loop L1
L2:ret
main endp

[P1]

Kyoy,

Please post the calling code, the error maybe there.

You have not programmed for an overflow condition for the adds.

How old is this book?   Is it a DOS MASM book?

Regards,  P1  :8)

[Titan]

Apparently MASM doesn't like your brackets.  I took away the brackets and I got no errors.

Code Select Expand


main PROC USES esi ecx

LOCAL ptrArray:DWORD
LOCAL szArray:DWORD

mov esi,ptrArray
mov ecx,szArray
cmp ecx,0
je L2
mov eax,0
L1:
add eax,esi
add esi,1
loop L1
L2:
ret

main endp


I came up with this after I ran your programming in OllyDbg.  It told me the error was here:

Code Select Expand


0040107A  |. B8 00000000    MOV EAX,0
0040107F  |> 0306           /ADD EAX,DWORD PTR DS:[ESI] <------- Error Here
00401081  |. 83C6 01        |ADD ESI,1


Looks like it's not doing exactly what you want it to do.  Hopefully this helps someone who is better than me, and can explain this to you better.  :P

[GregL]

PTR DWORD is perfectly acceptable in MASM. It means the variable is a pointer to a DWORD. I use it all the time, it makes things clearer if you ask me.

[tenkey]

That l1 was a typo :P
Titan, thanks. That compiled but the program keeps crashing whenever executed. Any further mistakes to fix up?

Code Select Expand


main PROC USES esi ecx
LOCAL ptrArray:DWORD
LOCAL szArray:DWORD
mov esi,ptrArray
mov ecx,szArray
cmp ecx,0
je L2
mov eax,0

L1:add eax,[esi]
add esi,1
loop L1
L2:ret
main endp


This is not a complete program. As thomasanthony says, the two critical pieces of data, ptrArray and szArray, do not start with known good values. Start with garbage data, get garbage results.

I suspect the original PROC line was coded this way:

Code Select Expand

main PROC USES esi ecx ptrArray:PTR DWORD, szArray:DWORD


This would clearly point up the need to create "calling" code that CALLs or INVOKEs this PROC. The calling code would provide the data in the form of an array to this snippet of code.