You can't export a symbolic constant using global like you would do with
a variable, it doesn't have an address nor occupies space anywhere.

Global tells the assembler not to remove the symbol name from the
object-file symbol table, so the linker can use it later to fix-up
references to the symbol from other object-files.

Extern just tells the assembler that somewhere there is a symbol with a
given name that it can use and the linker will cope with later.

The more correct form is to define it in a file and include it where it
is needed, overkill or not.


Best regards,

Isaac


Em 12/3/2010 19:53, Brendan Gillatt escreveu:
> Hello list,
>
> I'm developing a multi-module MPASM project and have run into a bit of a
> problem.
>
> Say I have two modules, each requiring the use of a constant, 0xAA in
> this case. I could put
>
> |
> |        constant    testconst =3D 0xAA
> |
>
> or
>
> |
> |testconst    equ    0xAA
> |
>
> in both files but this is obviously not very elegant or easy to maintain.
>
> I have tried to define the constant--using both methods above--and using
> GLOBAL and EXTERN statements to "share" the constant between modules as I
> would with variable and code labels. This causes MPASM to throw:
>
> "Duplicate label ("testconst" or redefining symbol that cannot be
> redefined)"
>
> I could put the testconst in a .inc file and include in both modules, but
> this seems like overkill just for the odd constant.
>
> Is there a proper way to do this?
>
> Thanks,
> Brendan

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