struct + label with "dot" ... ?

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ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 13 Oct 2010, 18:30

Code:

struct mystruct
  .yop_1  dd ?   ; <--- with dot
  .yop_2  dd ?
ends

can one do this ?
What would be the use and meaning of this ?
thank you all Smile

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13 Oct 2010, 18:30

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 14 Oct 2010, 18:27

ouadji,

Of course one can. Nothing special though: .yop_1 is a valid field name (its size will be sizeof.mystruct..yop_1, for example).

14 Oct 2010, 18:27

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 14 Oct 2010, 19:18

Code:

struct mystruct
  .yop_1  dd ?
  .yop_2  dd ?
ends

AA mystruct

-----> AA..yop_1 is a global label or local label ? (global for me)

thank you baldr.

with a "struct" or with a "struc"
is it possible to have a local label ?
or ... a label defined in "struct" (or in "struc") is always a global label ?

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14 Oct 2010, 19:18

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 15 Oct 2010, 07:12

ouadji,

To have local label be defined inside struc-macro you'll need to protect leading dot with backslash(es). With struct / ends macroinstructions it's different: current implementation encloses structure body in virtual at 0 directive and collects individual data definitions/reservations in symbolic constant. Labels (as you may expect) are not handled, so they are defined inside that virtual block instead of at macro expansion.

15 Oct 2010, 07:12

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Oct 2010, 09:38

Quote:

To have local label be defined inside struc-macro you'll need to protect leading dot with backslash(es).

ok. it's possible with "struc", but not with "struct".
about "struC + local label", please, could you give me an example.
(thank you baldr for your replies and your help)

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15 Oct 2010, 09:38

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 15 Oct 2010, 09:46

Code:

struc point {
   \.localLabel:
  .x dw ?
     .y dw ?
}
abc point
jmp abc.localLabel

15 Oct 2010, 09:46

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8263
Location: Kraków, Poland

Tomasz Grysztar 15 Oct 2010, 09:50

Code:

struc mystruc
 {
   .yop_1 dd ?
   .yop_2 dd ?
 }


first:
 .local_struc mystruc ; all fields get local labels

second:
 .local_struc mystruc

        mov     eax,[.local_struc.yop_2] ; from second
        mov     eax,[first.local_struc.yop_2] ; from first

That's not what the baldr meant, however - he proposed how can you define local label from a global structure, I hope he is going to provide some example as well. Wink

15 Oct 2010, 09:50

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Oct 2010, 10:10

Code:

;and this ? (I guess not)

struc point {
       \.x dw ?
        .y dw ?
}
abc point
mov eax,dword[abc.x] ;abc.x == local label ???

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15 Oct 2010, 10:10

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8263
Location: Kraków, Poland

Tomasz Grysztar 15 Oct 2010, 10:20

Yes, in this case it will work just as it works in revolution's example - however it doesn't really make much sense to do it. You just move the moment at which "abc" is prepended to the ".x" label from preprocessor into parser - but this doesn't really affect the result. In both cases you have "abc.x" label in the end. To get any noticeable difference between the backslashed and non-backslashed one you would need a more sophisticated example.

Last edited by Tomasz Grysztar on 15 Oct 2010, 10:22; edited 2 times in total

15 Oct 2010, 10:20

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 15 Oct 2010, 10:20

Code:

struc point {
   \.localLabel:
  \.x dw ?
   \.y dw ?
}

func1 point
      jmp .localLabel
     mov eax,dword[.x]

func2:
 jmp func1.localLabel
        mov eax,dword[func1.x]

15 Oct 2010, 10:20

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Oct 2010, 10:33

Code:

;Can I write this in all cases: (??)

struc AA {
         .a dw ?
         .b:
        \.c:
        \.d dw ? ;db, dd, dw, .....
}
BB AA

BB.a ; global
BB.b ; global
BB.c ; local
BB.d ; local

;without "\" before == always global ?
;with "\" before    == always local ?

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15 Oct 2010, 10:33

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 15 Oct 2010, 23:02

ouadji,

Due to the way struc-macro expands, those local labels get slightly longer full names than you're expecting: BB.b.c and BB.b.d.

----8<----

Tomasz Grysztar wrote:

I hope he is going to provide some example aswell.

I don't have slightest idea right now. They're so local. Wink

15 Oct 2010, 23:02

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Oct 2010, 23:38

This is not a big problem.
I have a recursive function which parses very well this kind of case.

but you did not answer my question: (thank you)

Code:

struc AA {
         .a dw ?
         .b:
        \.c:
        \.d dw ? ;db, dd, dw, .....
}
BB AA

BB.a ; global
BB.b ; global
BB.c ; local
BB.d ; local

(can I write this in all cases)

within a "struc" definition :

A) without "\" before == always global ?
B) with "\" before == always local ?

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15 Oct 2010, 23:38

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 16 Oct 2010, 00:30

ouadji: If you manually expand the struc macro then you will see what happens.

BB AA expands to:

Code:

BB.a dw ? ;<--- a global label
BB.b:     ;<--- a new global label
.c:       ;<--- it is local to the previous global label, i.e. it is BB.b.c
.d dw ?   ;<--- BB.b.d

16 Oct 2010, 00:30

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 16 Oct 2010, 00:38

So if you want to make the labels BB.c and BB.d then change the struc:

Code:

struc AA {
         .a dw ?
         .b:
         .#c:
         .#d dw ?
}
BB AA

But you gain nothing over a normal struc:

Code:

struc AA {
         .a dw ?
         .b:
         .c:
         .d dw ?
}
BB AA

16 Oct 2010, 00:38

bitRAKE

Joined: 21 Jul 2003
Posts: 3884
Location: vpcmipstrm

bitRAKE 16 Oct 2010, 01:57

All labels are global, the dot scheme just allows shortcuts to be used:

Code:

XX.abc dw 5

XX:
  mov ax,[.abc]

@@ might be the only truly local label? (I haven't looked into how FASM handles it - maybe there is a way to get some pseudo-name and use it globally?)

16 Oct 2010, 01:57

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 16 Oct 2010, 03:03

bitRAKE wrote:

All labels are global, the dot scheme just allows shortcuts to be used:
Code:
XX.abc dw 5

XX:
  mov ax,[.abc]    

That is not the same as a "true" local label.

Consider:

Code:

XX: ;global. Changes the base name to XX
  .bcd dw 1 ;.bcd as local. XX.bcd as global

XX.abc dw 2 ;global. Changes the base name to XX.abc
  .bcd dw 3 ;.bcd as local. XX.abc.bcd as global

The difference being the local labels do not change the base global label name for the next local label.

16 Oct 2010, 03:03

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 16 Oct 2010, 09:53

ouadji,

Is this question related to Wink development? I'm asking just to be sure I'm not taking the wrong route: in general case you should preprocess/interpret source to be sure what does symbol exactly mean.

Code:

macro A.c x { struc b \{ x \} }
struc a {
  .b db 1
  .c db 2
  .d db 3
}
A a
B b
C a

16 Oct 2010, 09:53

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 16 Oct 2010, 10:01

Quote:

The difference being the local labels do not change the base global label name for the next local label.

ok, i understood, here is the key of this problem.

just for the fun, Razz

Code:

struc AA1 {
   .x:
  \.y:
}
.BB1 AA1
jmp .BB1.x.y   ;does not compile

;is ".BB1.x.y" unattainable ?

;---------------------------------------------

struc AA1 {
   .x:
  \.y:
}
BB1 AA1
jmp BB1.x.y   ;does compile

Tomasz,when will we have a true doc about macros ?
Why this must remain the gods secret !!
(thank you)

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16 Oct 2010, 10:01

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 16 Oct 2010, 10:09

Quote:

Is this question related to Wink development ?

yes, of course.

Code:

macro A.c x { struc b \{ x \} }
struc a {
  .b db 1
  .c db 2
  .d db 3
}
A a
B b
C a

my god, how horrible! Shocked

I will never have the time to parse this kind of complex case in real time.

Quote:

in general case you should preprocess/interpret source to be sure what does symbol exactly mean.

I think it is impossible to do that in real time.
I have only the time between two keystrokes on the keyboard,
(repeat keystrokes ... 0,1 sec... max 0,2 sec!)
I don't have time to do what I want. Sad

I have to make choices, it's inescapable !

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I am not young enough to know everything (Oscar Wilde)-

16 Oct 2010, 10:09

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