define sized constant

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Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

Hi!
From manual:
c8 = byte -1
c32 = dword -1
deﬁnes two diﬀerent constants, the ﬁrst one ﬁts in 8 bits, the second one ﬁts
in 32 bits.

But real code don't work:
tchar0 = byte 0
cmp [esi], tchar0

Error: operand size not specified.

Where I wrong?

02 Sep 2010, 13:32

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17247
Location: In your JS exploiting you and your system

revolution

Use:

Code:

cmp byte[esi],tchar0

Also declaring a constant with '=' will not preserve the size. You might want to use 'equ' instead.

Code:

tchar0 equ byte 0

02 Sep 2010, 13:43

Tomasz Grysztar
Assembly Artist

Joined: 16 Jun 2003
Posts: 7709
Location: Kraków, Poland

Tomasz Grysztar

Dimas wrote:

Hi!
From manual:
c8 = byte -1
c32 = dword -1
deﬁnes two diﬀerent constants, the ﬁrst one ﬁts in 8 bits, the second one ﬁts
in 32 bits.

These size operators are meant only to apply to the way the values are defined. In the first case the result value will be 0FFh, in the second case it will be 0FFFFFFFFh. But they are still just ordinary numbers, so that when using them in other places, you still have to provide enough context so that the size of operation will be known.

02 Sep 2010, 13:52

Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

But on Unicode:
cmp word [esi], 0 (or cmp [esi], word 0)

if sizeof.TCHAR... like this:
macro stosc {
if sizeof.TCHAR = 1
stosb
else
stosw
end if
}
But on size prefics it's not work. Why?

02 Sep 2010, 13:54

Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

I wont make code universal for ANSI and Unicode, and include 'win32wx.inc' mast be enough for this. In this case I have numerical constant sizeof.TCHAR.
And this code wrong:
if sizeof.TCHAR = 1
tchar equ byte
else
tchar equ word
end if
cmp [esi], tchar 0

Good code:
if sizeof.TCHAR = 1
cmp [esi], byte 0
else
cmp [esi], word 0
end if

But size prefics may be present in thousand operands.
How make macro for this purpose?

02 Sep 2010, 14:20

Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

Main module:
...
eUnicode equ TRUE ;selector for Unicode _in one place_ !!!
include '..\_macro.asm'
...

macro.asm:
...
define eUnicode_ 0
match =FALSE, eUnicode {
tchar fix byte
include 'win32ax.inc'
define eUnicode_ 1
}
match =TRUE, eUnicode {
tchar fix word
include 'win32wx.inc'
include 'encoding\win1251.inc'
define eUnicode_ 1
}
match =0, eUnicode_ {display 'Define eUnicode constant'
err}
...

Thanks to all.

Last question. Why this code don't work for undefined constant:
match , eUnicode {err}

02 Sep 2010, 15:20

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17247
Location: In your JS exploiting you and your system

revolution

Dimas wrote:

Last question. Why this code don't work for undefined constant:
match , eUnicode {err}

Use this:

Code:

match eUnicode,eUnicode {err}

By definition undefined constants have no replacement so are simply text strings that match to themselves.

02 Sep 2010, 15:29

Tomasz Grysztar
Assembly Artist

Joined: 16 Jun 2003
Posts: 7709
Location: Kraków, Poland

Tomasz Grysztar

revolution wrote:

Use this:

Code:

match eUnicode,eUnicode {err}

Even better would be:

Code:

match =eUnicode,eUnicode {err}

02 Sep 2010, 15:47

Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

match eUnicode,eUnicode {err}

match TRUE always (then eUnicode defined or undefined).

02 Sep 2010, 15:50

Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

match =eUnicode,eUnicode {err}

Yes!!!

02 Sep 2010, 15:52

Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

from the foregoing it follows simple addon in macro.asm

Code:

match =FALSE, eUnicode {
        tchar fix byte
        include 'win32ax.inc'
        }
match =TRUE, eUnicode {
        tchar fix word
        include 'win32wx.inc'
        include 'encoding\win1251.inc'
        }
match =eUnicode, eUnicode {display 'Define eUnicode constant'
        err}

Thanks!

02 Sep 2010, 15:59

Tomasz Grysztar
Assembly Artist

Joined: 16 Jun 2003
Posts: 7709
Location: Kraków, Poland

Tomasz Grysztar

That's not the right way to use "fix" - it is interpreted with highest priority (before the actual preprocessing) and therefore is not affected by "match" directive.

02 Sep 2010, 16:06

Dimas

Joined: 02 Sep 2010
Posts: 17

Dimas

tchar equ byte
...
tchar equ word

That's right.

02 Sep 2010, 16:11

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr

Tomasz Grysztar wrote:

revolution wrote:
Use this:
Code:
match eUnicode,eUnicode {err}    
Even better would be:
Code:
match =eUnicode,eUnicode {err}    

Not simply "even better", probably "only true". This one can give unexpected result (yep, I'm pushing it to the limit, but match is so powerful ;-)

Code:

match 13, 10 { db "Hello, world!", 13, 10 }

02 Sep 2010, 18:06

Tomasz Grysztar
Assembly Artist

Joined: 16 Jun 2003
Posts: 7709
Location: Kraków, Poland

Tomasz Grysztar

baldr wrote:

Tomasz Grysztar wrote:
revolution wrote:
Use this:
Code:
match eUnicode,eUnicode {err}    
Even better would be:
Code:
match =eUnicode,eUnicode {err}    
Not simply "even better", probably "only true".

The one given by revolution would work if one wanted to check for variable defined with empty value, like:

Code:

match eUnicode,eUnicode { display 'A' } ; match
define eUnicode
match eUnicode,eUnicode { display 'B' } ; no match

I use this trick sometimes.

02 Sep 2010, 18:11

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr

Tomasz Grysztar,

I've meant side effect of such match:

Code:

match a, a { match anything, a \{ db "a defined" \} }

02 Sep 2010, 18:41

Tomasz Grysztar
Assembly Artist

Joined: 16 Jun 2003
Posts: 7709
Location: Kraków, Poland

Tomasz Grysztar

What side-effect? This nesting seems redundant.

The way of using the trick I mentioned is perhaps better seen when it is written this way:

Code:

match anything,a { display 'a not defined' }
define a
match anything,a { display 'a not defined' }; now it is "defined" (that is: empty)

The trick is to "define" something in sense of giving it an empty value.

02 Sep 2010, 18:48

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr

Tomasz Grysztar,

I've understood the trick first time, thanks. My example was bad indeed.

Code:

define c b
match b, a { match =b, c \{ display "matched" \} }

Looks like that inner match should succeed… but it doesn't. Proper backslashing all the way. Wink

02 Sep 2010, 19:35

Tomasz Grysztar
Assembly Artist

Joined: 16 Jun 2003
Posts: 7709
Location: Kraków, Poland

Tomasz Grysztar

baldr wrote:

Code:
define c b
match b, a { match =b, c \{ display "matched" \} }    
Looks like that inner match should succeed… but it doesn't. Proper backslashing all the way.

Oh yes, one should be careful when choosing names.

Or...

Code:

define c b
match b, a { match =\b, c \{ display "matched" \} }

Is that what you mean? Smile

02 Sep 2010, 19:49

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr

Tomasz Grysztar,

Almost. I mean that missing '=' can cause subtle errors:

Code:

match 1, UNICODE {
;...
  match 1, WIN32 \{

My first high-level programming language was FORTRAN-IV so I can easily adopt the idea of literal constant's value being accidentally redefined; can anybody else? Wink

03 Sep 2010, 04:51

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