Virtual Word marker.

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Roman

Joined: 21 Apr 2012
Posts: 1766

Roman 20 Jun 2022, 09:06

Fasmw 1.73
How apply some marker name to virtual?
Expand opportunities virtual.

Code:


Virtual. ;I want apply Word df mean float data
  dd -45.887
  load dword .value at $ - 4
end virtual

This good to tell macro what type have this virtual.

Code:

Virtual.df
End virtual

I found in fasm docs this

Code:

GDTR dp ?
    virtual at GDTR; how macro might chek name GDTR? 
        GDT_limit dw ?
        GDT_address dd ?
    end virtual

20 Jun 2022, 09:06

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20299
Location: In your JS exploiting you and your system

revolution 20 Jun 2022, 10:39

Code:

macro Virtual.df value {
  virtual
    dd value
    load .value dword from $$
  end virtual
}
Virtual.df -45.887
mov eax,.value

20 Jun 2022, 10:39

macomics

Joined: 26 Jan 2021
Posts: 926
Location: Russia

macomics 20 Jun 2022, 11:34

Roman wrote:

I found in fasm docs this

Code:

GDTR dp ?
    virtual at GDTR; how macro might chek name GDTR? 
        GDT_limit dw ?
        GDT_address dd ?
    end virtual

Nothing. The programmer adjusts the block described by virtual to the size of the dp type.

Code:

srtruc uint64 val& { . dq val
 label .low dword at .
 label .high dword at . + 4 }
struc gdt_ptr off, lim { label . pword
 .lim dw lim
 .off dd off }

20 Jun 2022, 11:34

Roman

Joined: 21 Apr 2012
Posts: 1766

Roman 20 Jun 2022, 14:56

Quote:

macro Virtual.df value {
virtual
dd value
load .value dword from $$
end virtual
}
Virtual.df -45.887
mov eax,.value

What is the difference compared with equ ? In this macro.
I mean simple write .value EQU -45.887

20 Jun 2022, 14:56

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20299
Location: In your JS exploiting you and your system

revolution 20 Jun 2022, 15:00

EQU is just a textual replacement. It doesn't compute anything.

Code:

value equ -45.887
dd_value = dword value
dq_value = qword value
dt_value = tword value

You don't need virtual for your example. Just use:

Code:

.value = dword -45.887

20 Jun 2022, 15:00

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