Newsgroups: comp.lang.c
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Using a define that hasn't been #defined
Message-ID: <1990Oct3.180300.28041@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <5101@hsv3.UUCP>
Date: Wed, 3 Oct 90 18:03:00 GMT

In article <5101@hsv3.UUCP> jls@headland.UUCP (James Seidman) writes:
>Recently I've run into a couple of hard-to-track bugs because I have
>a section of conditionally compiled code using a symbol which hasn't
>been defined...
>Now, my question is how other people avoid these same kinds of idiotic
>mistakes?  Even if I put in "#if !defined(XYZZY)..." type things for
>every define, it still wouldn't catch all typos.  There should be some
>way to avoid this idiotic kind of error...

Two rules that can help with this and related problems are:

1. When enumerating values for a code, start at 1, not 0.

2. Make sure that if the user hasn't specified a choice (e.g. hasn't
	defined one of several symbols tested with #ifdef, or hasn't
	given a non-zero value to something tested with #if) that
	the result is a complaint, not a default choice.
-- 
Imagine life with OS/360 the standard  | Henry Spencer at U of Toronto Zoology
operating system.  Now think about X.  |  henry@zoo.toronto.edu   utzoo!henry