gnupic: Trouble with macros conditionally generating code
Subject:
Re: Trouble with macros conditionally generating code
From:
Marco Pantaleoni ####@####.####
Date:
19 Nov 2004 08:32:07 +0000
Message-Id: <20041119083137.GA29386@lucifero>
On Fri, Nov 19, 2004 at 12:18:28AM -0800, Pete Elmore wrote:
> the rest come from the instruction itself. So, I thought that I could
> perform a simple test to see if we were crossing a page boundary, and if
> so, to just use bsf and bcf to set/clear the appropriate bits. I came
> up with the following:
>
> fcall macro label
I've tried the same approach, and came up with the macro:
fcall MACRO dest
LOCAL callsite = $
LOCAL curpage = (callsite / 0x0800)
LOCAL destpage = (dest / 0x0800)
IF (curpage == destpage)
call dest
ELSE
ERRORLEVEL -306
pagesel dest
call dest
ERRORLEVEL +306
ENDIF
ENDM
(we've even used the same name! :-)
>
> However, if I attempt to use the macro, I get errors like the following:
>
> menu.s:1:Error [116] Value of symbol "main_menu" differs on second pass
> ~ pass 1=1719, pass 2=1721
I *think* I could have an explanation, but I don't know how gpasm
works internally, so the following is only a guess.
That said, I think that the assembler on the first pass doesn't now some
of the addresses you are jumping into (at least not the ones for routines
not yet defined). So on the first pass the macro will generate a simple
call (when called from page 0), because the target address will be 0.
But on the second pass, for "far" targets, the macro is expanded in a
different way, so all subsequent labels are "shifted" in regard to the
first pass. Hence the warning.
Cheers,
Marco
--
========================================================================
Marco Pantaleoni ####@####.####
Padova, Italy
elastiC language developer http://www.elasticworld.org
