The MASM Forum

for this to work:
bt [eax][esi],0do i need to:
ASSUME eax,ptr BYTEand can I use ecx,edx as pointers the same way?
thanx

Your instruction won't work. It's one reg that points to memory, the other containing the bit's position:

  xor eax, eax
  bt [esi], eax

how about bt [esi+eax],0?
im trying to do indexed indirect addressing
actually i want to reference with an indexed pointer

How about testing instead of asking?
Or reading the documentation?
Or finding a workaround for illegal instructions?

QuoteError A2049: Invalid instruction operands

+im guessing now that i have to add the index to the pointer and then subtract the index from the pointer to preserve the pointer???

Quote from: dc on September 08, 2023, 08:48:22 AMhow about bt [esi+eax],0?

im trying to do indexed indirect addressing
actually i want to reference with an indexed pointer

I'll be a little more generous than JJ here. Yes, your addressing method ([esi+eax]) will work fine, just so long as you know what you're doing (meaning that you know where the result of this expression points to).

---

Aaaargh; your addressing mode is OK, but this does indeed give an "invalid instruction operands" error, and I'm not sure why. According to the instruction documentation (https://www.felixcloutier.com/x86/bt), you should be able to use the "BT r/m32, imm8" form of the instruction, where the data to be tested is an 8-bit immediate like you have. Maybe JJ can explain why this doesn't work. (I've never ever used this instruction myself, though it does look mighty handy.)

Quote from: NoCforMe on September 08, 2023, 10:37:58 AM

Quote from: dc on September 08, 2023, 08:48:22 AMYes, your addressing method ([esi+eax]) will work fine

Can you post an example with the bt instruction?

See reply above you. I edited mine after you posted yours.

Try this instead, as suggested:

BT [ESI+EAX], ECX

(bit to test in a register instead of coded as an immediate)
It at least assembles correctly ...

The problem here is a misleading error message (in Masm, UAsm and AsmC):

  int 3
  ; bt [esi+eax], 3 ; Error A2049: Invalid instruction operands
  bt dword ptr [esi+eax], 2
  bt word ptr [esi+eax], 2
  ; bt byte ptr [esi+eax], 2 ; Error A2049: invalid instruction operands
  bt [esi+eax], ecx0FBA2430 02   bt dword ptr [esi+eax], 2
66:0FBA2430 0 bt word ptr [esi+eax], 2
0FA30C30      bt [esi+eax], ecx
The instruction operands are absolutely valid, but for some reason the assembler needs the size, too. Besides, DWORD and WORD are legal but BYTE isn't.

Without specifying the size (word, dword or qword ptr) for a memory address the assembler assumes that the memory address points to a byte, and yes that's not possible for BT.
bt [esi+eax], ecx lets the assembler assume that the memory address points to a dword because of ecx as the second operand.

So, the error messages are correct.

EDIT:
bt [eax][esi],0 is the same as bt [eax+esi],0, so this syntax is valid.

include \masm32\include\masm32rt.inc

.data
MyArray dd 25, 18, 23, 17, 9, 2, 6

.code
start:
  mov esi, offset MyArray
  xor eax, eax
  mov [esi+eax], 123
  mov [esi+eax], 1234
  mov [esi+eax], 123456
  exit

end start
ml 6.14 ... 14.0 (dumb):
tmp_file.asm(10) : error A2070: invalid instruction operands
tmp_file.asm(11) : error A2070: invalid instruction operands
tmp_file.asm(12) : error A2070: invalid instruction operands

UAsm, AsmC (less dumb):
tmp_file.asm(10) : warning A8019: size not specified, assuming: BYTE
tmp_file.asm(11) : warning A8019: size not specified, assuming: WORD
tmp_file.asm(12) : warning A8019: size not specified, assuming: DWORD
The instruction operands are ok, but the assembler wants to know the size.

Btw bt dword ptr [esi+eax], 40 assembles fine with all three assemblers. Testing bit 40 of a DWORD works ;-)

Seriously:

QuoteSome assemblers support immediate bit offsets larger than 31 by using the immediate bit offset field in combination with the displacement field of the memory operand. In this case, the low-order 3 or 5 bits (3 for 16-bit operands, 5 for 32-bit operands) of the immediate bit offset are stored in the immediate bit offset field, and the high-order bits are shifted and combined with the byte displacement in the addressing mode by the assembler. The processor will ignore the high order bits if they are not zero.

Quote from: jj2007 on September 09, 2023, 04:04:00 AM

Code Select Expand

ml 6.14 ... 14.0 (dumb):
tmp_file.asm(10) : error A2070: invalid instruction operands
tmp_file.asm(11) : error A2070: invalid instruction operands
tmp_file.asm(12) : error A2070: invalid instruction operands

UAsm, AsmC (less dumb):
tmp_file.asm(10) : warning A8019: size not specified, assuming: BYTE
tmp_file.asm(11) : warning A8019: size not specified, assuming: WORD
tmp_file.asm(12) : warning A8019: size not specified, assuming: DWORD

Maybe kind of a fine point, but I now don't see that (ML's behavior) as "dumb". Why not? Because otherwise the assembler has to make assumptions about what the coder really meant, assumptions that could well be wrong. So probably the right thing to alert them to the ambiguity of their coding. (Lord knows I've been "helped" this way many times to fix my own mistakes.)

Quote from: NoCforMe on September 09, 2023, 06:15:51 AMBecause otherwise the assembler has to make assumptions about what the coder really meant, assumptions that could well be wrong

Fully agreed, but there are two options:
1. a warning, see UAsm and AsmC
2. an error saying "you need to specify the size"

"invalid instruction operands" is just plain wrong. Or, in other words, dumb :cool:

Yes, fully agree. My vote is for (2), an error saying "you need to specify the size".

So, what is the consensus, or simply the answer for the OP, dc?
Hard to tell, from the series of posts.  :smiley:

From what I understood from the posts, to avoid ambiguity and cryptic error messages, to always specify the size? (dword, word, or byte)  Is that correct?

No; you only need to specify the size (WORD, DWORD) if it's not clear otherwise from the context, specifically when you use an immediate constant for the bit number and an ambiguous memory-based first operand (like [EDX], which could be a pointer to anything, byte, word, doubleword, quadword ...):

    BT    DWORD PTR [EDX], 5

You don't need the size spec if you use a register for that operand, or a register or a sized variable for the first operand:

    BT    [EDX], EAX
    BT    EDX, 5
    BT    dwordSizedVar, 5


Thank you NoCforMe for the detailed response. I am certain that the OP, dc, will understand better from the examples shown as well.

Just to clarify and summarize, the fact that the ambiguous cases (like BT [reg], imm) are flagged as errors by ML is appropriate. What is dumb, as JJ pointed out, is the exact error message ("invalid instruction operand"). There's nothing "invalid" about it; it's just ambiguous.

Ambiguous code leads to ambiguous error messages?  :joking:
Sounds like an issue to be taken up with Microsoft.  :biggrin:

Quote from: zedd151 on September 09, 2023, 10:20:17 AMSounds like an issue to be taken up with Microsoft.  :biggrin:

Yes, I'm sure Micro$oft is very committed to making improvements to ml.exe:

Copyright (C) Microsoft Corp 1981-1997

We'll have to get Raymond Chen to weigh in on this.

oooooo....
preliminarily...this seems to be working!
xor dword ptr pbrd[esi],1crap.... got ahead of myself, it doesn't
NEVERMIND!!! IT DOES WORK.... WOOHOO!!!!

oooops it doesn't...
that way uses memory after the label... in tester
pbrd            dd ?
tester          dd 50 dup (?)


Hi dc, could you post some more code. Just a line or two isn't really telling us what it is, that you now are trying to do. With a more complete piece of code, we will be able to help you better. Full source preferred, but a more complete snippet may be enough. We don't know what is in pbrd or in esi, or how they got there, or the result that you are expecting. Help us to help you.
Describe at least, what you want to do, with the last code that you posted, preferably with more complete code.

Edit for completeness and clarity.

i want to access allocated memory with an index like an array
i don't see why nobody understands my question
is it just not done?
also:
if i just put it in the inc file like:
board  dd 0100000h dup (?)
it works fine but takes a while to assemble

Quote from: dc on September 12, 2023, 12:50:29 AMi don't see why nobody understands my question

Where is your code?

Quote from: HSE on September 12, 2023, 12:58:05 AM

Quote from: dc on September 12, 2023, 12:50:29 AMi don't see why nobody understands my question

Where is your code?

HSE, what's wrong with your crystal ball, it's not working?

dc, it's considered bad practice to post snippets, thus assuming that older members love spending their precious time adding headers, includes etc.

If you want help, zip all necessary files, especially the complete *.asm source, and attach it here. Otherwise all your questions will be happily ignored. Please confirm arrival of the message.

Quote from: dc on September 12, 2023, 12:50:29 AMif i just put it in the inc file like:
board  dd 0100000h dup (?)
it works fine but takes a while to assemble

That's a known MASM bug (https://masm32.com/board/index.php?topic=2412.0). You can use UAsm (http://www.terraspace.co.uk/uasm.html#p2) instead, it's a perfect MASM clone with less bugs.

Quote from: dc on September 11, 2023, 06:52:36 AMoooooo....
preliminarily...this seems to be working!

Code Select Expand

xor dword ptr pbrd[esi],1crap.... got ahead of myself, it doesn't
NEVERMIND!!! IT DOES WORK.... WOOHOO!!!!

Quote from: dc on September 11, 2023, 11:38:49 PMoooops it doesn't...
that way uses memory after the label... in tester

Code Select Expand

pbrd            dd ?
tester          dd 50 dup (?)


OK, trying to bring this discussion back down to earth (and Zedd, back off on your net-nanny politeness campaign, please: JJ was just expressing a little irritation back there. Remember: moderation in moderation.)

First thing: if you code

pbrd            dd ?

xor dword ptr pbrd[esi],1

you don't need the dword ptr precautionary label, because you've clearly defined that variable as a doubleword, which the assembler, as dumb as it may be, knows about. So just use

xor pbrd[esi],1

instead.

that's not using allocated memory...
can allocated memory be used as an array?

Hi dc

Yes, allocated memory can be used as an array.

Quote from: dc on September 12, 2023, 08:39:37 AMthat's not using allocated memory...
can allocated memory be used as an array?

Odd question: of course it can. Why would you think otherwise?

Another thing: why are you so all-fired focused on using xxxx ptr constructs, instead of just the ordinary MASM tools (use PTR only when you need to make an ambiguous reference like MOV [EDX], 0 explicit)?

Maybe tell us what you're trying to accomplish here?

ive tried all the suggested ways and some seem to work but i test it and it ALWAYS uses the pointer like a label instead, so i have to put space after the labeled pointer like this:

pbrd            dd ?
tester          dd 500000 dup (?)

it fills up tester instead of the allocated memory

Quote from: zedd151 on September 12, 2023, 12:09:11 AMHi dc, could you post some more code. Just a line or two isn't really telling us what it is, that you now are trying to do. With a more complete piece of code, we will be able to help you better. Full source preferred

Quote from: HSE on September 12, 2023, 12:58:05 AM

Quote from: dc on September 12, 2023, 12:50:29 AMi don't see why nobody understands my question

Where is your code?

Quote from: jj2007 on September 12, 2023, 01:06:29 AMdc, it's considered bad practice to post snippets, thus assuming that older members love spending their precious time adding headers, includes etc.

If you want help, zip all necessary files, especially the complete *.asm source, and attach it here. Otherwise all your questions will be happily ignored. Please confirm arrival of the message.

Quote from: dc on September 12, 2023, 11:08:25 PMive tried all the suggested ways and some seem to work but i test it and it ALWAYS uses the pointer like a label instead, so i have to put space after the labeled pointer like this:

pbrd            dd ?
tester          dd 500000 dup (?)

it fills up tester instead of the allocated memory

dc please understand, without seeing more of your code, no one here knows exactly what you are trying to do.
Many members had asked for your code.

So please, post your code. The entire source code.

Hi dc,

tester          dd 500000 dup (?)
Why not to use memory allocation functions? Probably, you notice that ml is slow while assembling this code portion.

i did... global and heap... the pointer always works as a label instead...

Quote from: dc on September 13, 2023, 12:02:14 AMi did... global and heap... the pointer always works as a label instead...

dc, do everyone that is trying to help you a favor, and post your source code.
Please read: https://masm32.com/board/index.php?msg=123503

It is highly likely that you are doing something wrong in the code, some kind of error, and probably something simple to fix.

So please post your code so we can help you resolve this ,,,
We are waiting...

As a hint, do a forum search for "indirect addressing" this might be what you are looking for, and trying to achieve. Thinking about this, it might just be the case that you did not know the proper terminology to explain  what you want to achieve. Let us know here, please.

But still wondering why you won't post your code. Are you doing something that you are not supposed to be doing? Prove that theory wrong by posting or attaching your code.

Edit for further clarification and add the 'search' hint above.

Yes, without seeing more of your code we really can't help you much here. (Not necessarily the whole project, but certainly the part where you're trying to use pbrd as a pointer.)

You're not the first person to be confused over the concepts of direct and indirect addressing; they're somewhat tricky ideas to wrap your head around, the difference between

MOV EDX, pbrd ;Get the CONTENTS of pbrd, a pointer
MOV EAX, [EDX] ;Get the CONTENTS of what it points to
MOV EAX, [EDX + array] ;Get the CONTENTS of what it points to in "array"
MOV EAX, [EDX + EBX + array] ;Get the CONTENTS of what it points to, indexed into "array"

and

LEA EAX, pbrd ;Get the ADDRESS of pbrd
INVOKE SomeFunction, EAX ;Pass the ADDRESS of pbrd to a function

(and these are only two examples out of many more), but you'll get it, I'm sure. (Hope these examples aren't confusing you.)

im not seeing a way to upload my zip
my project is too big for this site

You can make a little test with just problematic code. You don't have to show complete code at all.

Quote from: dc on September 13, 2023, 08:45:25 AMim not seeing a way to upload my zip
my project is too big for this site

How big is your zipped source code only? (In kilobytes) Without the executable!!! Less than 512 kilobytes, then attach the .zip file.

Otherwise try this:
Okay, do as HSE suggests and post the relevant portion of the code. Try posting that at least. More than one or two lines, that is not enough. At least a dozen lines before and a dozen lines after...

dc, everyone that is trying to help you are running out of patience. You are wasting our time if you cannot post more code so that we understand what your problems are, with the code that you have written.

Edit for clarity and typos

Quote from: dc on September 13, 2023, 08:45:25 AMim not seeing a way to upload my zip
my project is too big for this site

Just copy and paste part of your code here directly so we can see what's going on inside there, 'k? (You can use the Code button (2nd in the last group on the top line) to put the code into a nice window.)

Quote from: dc on September 13, 2023, 08:45:25 AMim not seeing a way to upload my zip
my project is too big for this site

Your project, zipped, exceeds 512kBytes, but you need help with basic addressing concepts? Come on, be serious...

@Zedd: I'd suggest to move this to the Soap Box, unless dc manages to zip his project.

Quite possible that dc is trying to mix disassembled code into his project as in this thread: https://masm32.com/board/index.php?topic=11204.0 that might be adding to his confusion.

That thread is related to using GlobalAlloc.  :wink2: 

Go back six years: fat exe but no source (https://masm32.com/board/index.php?msg=70729)

Quote from: jj2007 on September 13, 2023, 11:05:03 PMGo back six years: fat exe but no source (https://masm32.com/board/index.php?msg=70729)

Yes, I saw that also.

Still waiting for dc's reply. I will close this thread unless dc can furnish his source code.


Edit to add:  Thank you... for posting your project below.

qmaz.zip (http://www.bmath.net/bmath/qMaz.zip)
sorry about that... sent an admin link by mistake

Quote from: dc on September 14, 2023, 12:22:48 AMqmaz.zip (http://www.bmath.net/bmath/qMaz.zip)
sorry about that... sent an admin link by mistake

Ok. Thanks. Where in the code are you having the issues?
Post that snippet... now we know where it comes from. :smiley:

jj2007, dc, I have removed a couple posts above to tidy up

And dc, I apologize for all the scrutiny.

Quote from: dc on September 14, 2023, 12:22:48 AMqmaz.zip (http://www.bmath.net/bmath/qMaz.zip)
sorry about that... sent an admin link by mistake

We are almost there:
Cannot open file: "dxbase.def"

Assembling: maze.asm

***********
ASCII build
***********

dxfunc.inc(12) : fatal error A1000: cannot open file : dxbase.def
Press any key to continue . . .
where is dxbase.def -- ??
btw, the project looks pretty impressive.  :thumbsup:  A good candidate for the Game Development (https://masm32.com/board/index.php?board=62.0) board.
I will leave it to the assembly gurus to assist you from here.  Thank you for posting your code.  :azn:

ooops... it might need all the direct x defs to work. ill experiment and see... maybe only the one is needed

Quote from: dc on September 14, 2023, 01:22:03 AMooops... it might need all the direct x defs to work. ill experiment and see... maybe only the one is needed

You can just zip those and post them here. No need to reupload the entire project again.  :smiley:

include.zip

Hi dc,

When trying to build your project, I got many error messages. With minor modifications to four files, all attached, I got it running, though - with UAsm but not with ML:
cannot open file : oaidl.inc
cannot open file : olectl.inc
If your project built without errors on your machine, there are two possible reasons:
1. You have an old version of the Masm32 SDK
2. You changed include files of the Masm32 SDK

If the version is old, get the latest one (http://masm32.com/download.htm) (if \Masm32\include\windows.inc is of 10 Jan 2012 and has 977,412 bytes, you got the latest one).

Under no circumstances, never, should you change the original Masm32 SDK files, for a very simple reason: doing that, your code becomes incompatible with the SDK, and nobody can help you. It is a hundred times better to adapt your sources to the SDK than the other way round!

The exe works, it looks like a big game, compliments :thumbsup:

Now it's time to explain where you see problems to solve: file name, line number, and three lines of code, please, so that we can check what's needed.

im gonna have to assume that a pointer and an index are not used together at all in ml... please prove me wrong...
thanx

mov eax, somevar[ecx]

Proved wrong :thumbsup:

Hmm, JJ: not to split hairs here or anything but isn't

    MOV    EAX, somevar[ECX]

an example of an index (ECX) only? Where's the pointer? I'm assuming that somevar is an array, with ECX indexing into it, right?

How about this--would you say this shows both a pointer (EBX) and an index (ESI)?

LEA EBX, somevar
MOV ESI, indexVal
MOV EAX, [EBX + ESI]

Anyhow, to the OP: Why so much confusion in your mind between pointers and indices? Can you give us a better clue as to where exactly you're having trouble understanding this concept? I know it's not trivial, and trips up a lot of beginners, but at the same time it ain't rocket science ...

Quote from: NoCforMe on September 25, 2023, 07:07:59 AM

Code Select Expand

    LEA    EBX, somevar
    MOV    ESI, indexVal
    MOV    EAX, [EBX + ESI]


If you store dwords usually must be:

    LEA    EBX, somevar
    MOV    ESI, index
    MOV    EAX, [EBX + ESI*4]


i get pointer 'pArray' from globalAlocate
then try to access it like:
mov esi,index
shl esi,2
mov eax,pArray
bt [eax+esi],0
jc @f
i get errors in assembly
ive tried:
bt [eax][esi],0

bt dword ptr eax[esi],0

bt dword ptr pArray[esi]
if anything assembles without error it isn't the allocated memory being accessed...

Quote from: dc on September 25, 2023, 06:10:48 AMim gonna have to assume that a pointer and an index are not used together at all in ml...

Interesting

Quote from: dc on September 25, 2023, 08:24:34 AMbt [eax+esi],0
i get errors in assembly

You must indicate to assembler what have to retrieve in memory position:

bt word ptr [eax+esi],0

bt dword ptr [eax+esi],0
Always is the same in any instruccion when first you have a memory position.

You don't need to make any indication when first there is a known size operand:

mov al, [eax+esi]

mov ax, [eax+esi]

mov eax, [eax+esi]

Whoa. Stop. Everyone shut up for one minute!

One thing at a time: you said this gave an assembler error:

bt [eax+esi],0

Of course it did. It's ambiguous: do you want to bit-test a word or a double word? (those are your choices with this instruction)

Try

bt DWORD PTR [eax+esi],0

(or whatever size you're trying to access here)

Quote from: dc on September 25, 2023, 08:24:34 AMi get pointer 'pArray' from globalAlocate
then try to access it like:

Code Select Expand

mov esi,index
shl esi,2
mov eax,pArray
bt [eax+esi],0
jc @f


OK, you're very close here. What you're trying to do makes sense.

Seems to me if you just remove the ambiguity of the bt instruction (use DWORD PTR), this should work as written.

One thing bothers me: the Microsoft documentation for GlobalAlloc() states that it returns a handle to the allocated memory*. Not sure if that's the same thing as a pointer which you can use directly. I use HeapAlloc() instead, which definitely returns a pointer. Why don't you try that instead? Any special reason to use GlobalAlloc()?

p.s.: As someone above pointed out, you can eliminate the shl esi, 2 by using

bt dword ptr [eax + (esi * 4)]

which does that arithmetic for you.

* Of course this could just be an ambiguity in the Micro$oft documentation ...

i want to use this on allocated memory that can be any size depending...

You can certainly do that as easily with HeapAlloc() as with GlobalAlloc(). You specify the size of allocation you want.

Check alloc macro,in qe macro help file
Returns a pointer to allocated memory or null if it fails allocate

Macro, schmacro.
Just code it:

CALL GetProcessHeap ;Only need to do this once at program start:
MOV HeapHandle, EAX

INVOKE HeapAlloc, HeapHandle, 0, <how many bytes to allocate>
MOV <pointer to allocated memory>, EAX

Sheesh.

Quote from: dc on September 25, 2023, 06:10:48 AMim gonna have to assume that a pointer and an index are not used together at all in ml... please prove me wrong...
thanx

It's not our job to prove you wrong, it's your job to study the docs, play with code, and show in detail (i.e. with complete code) what's wrong, and what the error messages are.

Quote from: dc on September 25, 2023, 10:55:34 AMi want to use this on allocated memory that can be any size depending...

It really, really would help if you sat down, zipped your code and posted it here, instead of asking vague questions. Here is the demo that pointers and indexes can be combined. And guess what, it's complete code. Just copy & paste & build :biggrin:

include \masm32\include\masm32rt.inc

.data?
ThePointer    dd ?

.code
start:
  mov ThePointer, rv(GlobalAlloc, GPTR, 100)
  mov eax, ThePointer  ; not necessary because eax = ThePointer at this point
  bt word ptr [eax+4*esi], 3
  .if Carry?
    print "bit 3 is set", 13, 10
  .else
    print "bit 3 is clear", 13, 10
  .endif
  mov esi, 25
  mov eax, ThePointer
  mov byte ptr [eax+4*esi], -1
  bt word ptr [eax+4*esi], 3
  .if Carry?
    inkey "bit 3 is set"
  .else
    inkey "bit 3 is clear"
  .endif
  exit

end start
If you start asking what GPTR means, I'll contact your teacher :bgrin:

Quote from: jj2007 on September 25, 2023, 06:08:06 PMIt really, really would help if you sat down, zipped your code and posted it here, instead of asking vague questions.

Well, in fairness, JJ, I don't think they should be required necessarily to post all of their code, which might be long, complicated and confused. I'd be happy just seeing the relevant parts, a condensed version.

I agree, asking vague questions ain't gonna get anybody nowhere.

OP, please post something from your code so we can get a better idea of what's going on.