gnupic: Trouble with macros conditionally generating code
Subject:
Re: Trouble with macros conditionally generating code
From:
Craig Franklin ####@####.####
Date:
22 Nov 2004 16:26:26 +0000
Message-Id: <41A1BF6A.4070104@users.sourceforge.net>
Pete Elmore wrote:
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> In response to the request for a short, complete program that reproduces
> the problem I'm talking about:
>
> pete@bob:~$ cat t.s
> ~ processor 16f877
> if(main == 0)
> ~ nop
> endif
> main:
> end
> pete@bob:~$ gpasm t.s
> t.s:5:Error [116] Value of symbol "main" differs on second pass
> ~ pass 1=0, pass 2=1
>
> I've generalized this a bit; really it has nothing to do with macros.
> It's a problem with the preprocessor. To clarify, I don't have a
> problem with the fact that the assembler refuses to assemble the
> program; no assembler could assemble the above program. What I don't
> like is the error message.
All gpasm messages are roughly equivalent to the mpasm messages. In
this case they are very close. I agree that the message is a little
cryptic. This is mainly because it is a general purpose error that
handles more than just this case.
Adding a new type of error message is risky. It could cause some
existing code not to compile. Although the code is probably flawed,
there is a lot of flawed code that gpasm has to assemble. Not
assembling an existing project is a more critical problem than the
contents of an error message being cryptic.
Maybe as a compromise, I should generate a non-constant expression
warning on the IF expression and leave the error message as is. My only
concern is if it became a nuisance warning, everyone would ignore it.
Can anyone think of a legitimate case when a non-constant if expression
is required?
> This is how gas handles the same thing:
>
> pete@bob:~$ cat u.s
> .org 0
> .if (_start == 0)
> ~ nop
> .endif
> _start:
> pete@bob:~$ as u.s
> u.s: Assembler messages:
> u.s:2: Error: non-constant expression in ".if" statement
>
> Notice that with gas's error message, the problem is obvious.
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