From: anakin AT pobox DOT com (Simon Tatham)
Newsgroups: comp.lang.asm.x86,alt.lang.asm,comp.os.msdos.djgpp
Subject: Re: NASM
Date: 1 Feb 1997 09:21:01 GMT
Organization: Trinity College, Cambridge
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Sugree Phatanapherom  <ioisgp AT std DOT cpc DOT ku DOT ac DOT th> wrote:
> 	times 512-$ db 0

That's what the $$ token is for.

In a generic relocated object file, that statement has very little
meaning, since `$' may end up anywhere at link time and the
assembler can't predict it; so in general, that statement is
incorrect. Therefore NASM flags the statement as incorrect in all
cases, and so it won't work even in the `bin' case with an explicit
ORG, when you might expect NASM to `know' where the segment begins.

The trouble is that it's only the `bin' output module that takes any
notice at all of the `org' directive: the main code in the assembler
doesn't. This could possibly be fixed, but huge hacks would be
required; and in any case, it still wouldn't work in the `.data' and
`.bss' segments.

The $$ token references the start of the given section, and so
that's the canonical one to use:

> buffer:
> 	times 512-$+buffer db 0

That's a way to get round it, but

        times 512-$+$$ db 0

will make absolutely sure, by definition, that you end up 512 bytes
from the start of your section.

Hope that helps,
-- 
<^ I /\/\ O /\/    Simon Tatham <sgt20 AT cam DOT ac DOT uk> <anakin AT pobox DOT com>
_> ------------      Trinity College, Cambridge, CB2 1TQ, England.