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flat assembler > Macroinstructions > [fasmg] Symbol is undefined or out of scope problem

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zhak



Joined: 12 Apr 2005
Posts: 489
Location: Belarus
Tomasz, please take a look at the small template below
Code:
macro datatypes types*& irp <n, type>, types macro type args:[?]& match [?], args emit n: ? else match [x], args emit n: x dup ? else match [x] value, args match =, v, value emit n: x dup ?, v else emit n: x dup value end match else irp arg, args if arg eqtype '' emit n: arg else local value value = +arg emit n: value end if end irp end match type.__size = n datatype.type equ ::type:: end macro struc (name) type args& label .: n type args name.__size = n name.__length = $ - . end struc end irp end macro datatypes 1,byte?, 2,word?, 4,dword?, 6,fword?, 8,qword?, 10,tbyte?, 16,oword? macro log.number num local n, s n = +num if n = 0 s = '0' else s = 0 while n > 0 s = s shl 8 + (n mod 10 + '0') n = n / 10 end while end if display string s,13,10 end macro ;------------ ^^ just helpers above to compile -------------- macro struct? structname macro end?.struct?! end namespace irp arg, args match p:v, arg log.number .p.__size end match end irp end struc virtual at 0 structname structname structname.__size = $ end virtual purge end?.struct? end macro struc (name) structname args& label .: structname.__size namespace . name.__size = structname.__size ;<<<<<<< problem line end macro struct POINT x word y byte end struct struct POINT2 z POINT end struct my POINT2 z.x:1, z:1


I'm trying to get the size of a variable defined as structure. Variable, not structure itself, because later it will be an array of structures.

The problem is when I add
Code:
name.__size = structname.__size

I start getting the following error:
Quote:

Processed: label .: POINT.__size
Error: symbol '__size' is undefined or out of scope.

However, both sizes are logged correctly. If line is removed, label .: POINT.__size doesn't generate the error any more.

I thought that it could be processing order, and structname.__size is not initialized yet, when name.__size appears in code, but I guess it would then fail on that very line. Thanks in advance for your assistance!
Post 03 Apr 2017, 11:44
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 6863
Location: Kraków, Poland
The problem is caused by the case when both "name" and "structname" are equal to "POINT", because then
Code:
name.__size = structname.__size
gets evaluated to:
Code:
POINT.__size = POINT.__size
Because you then have "POINT.__size" defined with the actual value, this symbols becomes variable and can no longer be forward-referenced. That's why you get the "out of scope" error when trying to access the symbol before the first definition happens.

You can see that this is the problem when you put additional condition around the problematic line:
Code:
if `name <> `structname name.__size = structname.__size end if

I would suggest to use ":=" instead of "=" to make sure that symbols can always be forward-referenced, but you still have to ensure that each of them is defined exactly once.
Post 03 Apr 2017, 12:44
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