QWORD issue

[cozofdeath]

I'm sorry but I just cannot find the answer to this. I'm simple trying to use the qword (dq) type to declare a variable. But masm will allow the declaration but not the initialization. It keeps spitting out:  "error A2070: invalid instruction operands". For example,

.data?
qwAge    QWORD    ?

.code
mov qwAge, 0

But if I use the data type "LONG" it seems to work. Is qword and long the same size? And why isn't Masm supporting this? I tried using ml64 but it thinks almost every line of code is an error. Thanks for any help!

[dedndave]

you can override the operand size with "ptr"

Code Select Expand

        mov dword ptr qwAge,eax   ;initialize the low dword
        mov dword ptr qwAge+4,edx ;initialize the high dword

i dunno who that variable is for, but they must be pretty old   :P

[dedndave]

another way to go is to split it up

Code Select Expand

        .DATA?

qwAge   LABEL   QWORD
dwAgeLo dd ?
dwAgeHi dd ?

now, you can access it as a qword with qwAge
or seperate dwords as dwAgeLo and dwAgeHi

[jj2007]

You cannot move a qword into a reg32, but you can use the FPU or an xmm reg instead:

include \masm32\MasmBasic\MasmBasic.inc   ; download
MyQ   dq 123456789012345678
   Init
   movq xmm0, MyQ
   fild MyQ
   Print Str$("FPU, ST0=\t%i\n", ST(0))
   Inkey Str$("Xmm0=    \t%i", xmm0)
   Exit
end start

Code Select Expand

FPU, ST0=       123456789012345678
Xmm0=           123456789012345678

[cozofdeath]

Thanks dedndave! That was quick. I can't get over how I can't use it like a normal variable. That kinda sucks. Everything has gone smooth until I tried to fill a QWORD in a structure in an accompanied .inc file. It seemed there was no way to fill it until you helped me. I never had to mess with qwords before. :cheekygreen: Thanks again!

[cozofdeath]

Ahhh...jj2007 :U That seems like a creative way to do it as well. I would have never dreamed up something like that.  :dance: Thanks

[MichaelW]

For what it's worth, if you put the variable in the initialized data section you can initialize it like this:

Code Select Expand


.data
    qwAge QWORD 0ffffffffffffffffh


[GregL]

cozofdeath,

You understand why right?  In 64-bit MASM you can mov qwAge, 0, since 0 is assumed to be 64-bit and the sizes are equal.  In 32-bit MASM with mov qwAge, 0, 0 is assumed to be 32-bit so it is not allowed due to a size mismatch.  So,

    xor eax, eax
    mov dword ptr qwAge,eax      ;initialize the low dword
    mov dword ptr qwAge+4,eax ;initialize the high dword

works.

You can also fistp qwAge from the FPU in 32-bit MASM. As in:

    fldz                ; corrected
    fistp qwAge


Hope that made sense.

[raymond]

fld0

Just to make it clear, the proper mnemonic is: fldz

[GregL]

Raymond,

Sorry, it is fldz.  Corrected above.