help me about highword

[boydtbk]

I'm using MASM32 SDK verison 10, and I have a problem with highword:

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            val dd 10101011b
            mov val, HIGHWORD val


error A2105: HIGH and LOW require immediate operands
Can some body help me?

[dedndave]

i have never used HIGHWORD
but, you can't do memory to memory MOV that way
try getting the value into a register first

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        movzx   eax,word ptr val+2   ;same as HIGHWORD ?
        mov word ptr val,ax
i think that's what you are trying to do   :P

[boydtbk]

and about lowword ? I don't know exactly what I have to do. Can you show me ?

[jj2007]

movzx   eax, word ptr val is the low word
movzx   eax, word ptr val+2 is the high word

[GregL]

boydtbk,

I prefer to write it as

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movzx   eax, word ptr val+0  ;is the low word
movzx   eax, word ptr val+2  ;is the high word


just for clarity.

[clive]

The typical usage for LOWWORD/HIGHWORD is as follows

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= DEADBEEF val     EQU     0DEADBEEFh

0000  B8 BEEF         mov     ax,LOWWORD val
0003  BA DEAD         mov     dx,HIGHWORD val


They are designed to handle immediate values (ie EQU, or simple constants/math)

As for style, I'd prefer this if you are pulling high/low values from memory

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value  dd  0DEADBEEFh
;...
movzx   eax, word ptr value[0] ; is the low word
movzx   edx, word ptr value[2] ; is the high word