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From: Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Problem with Allegro and DzComm
Date: 1 Apr 2004 11:09:19 GMT
Organization: Aachen University of Technology (RWTH)
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Andris Pavenis <pavenis AT latnet DOT lv> wrote:

> It's in DZCOMM documentation (it was not read carefully enough):
> --------------------  fragment from documentation ----------
[...]

> include the allegro library. If you do so it is IMPERATIVE that you
> include allegro first (this how dzcomm knows where to link to):

>       #include <allegro.h>
>       #include <dzcomm.h>

This violates a number of sanity rules for #include file design.  As
in: it should always be irrelevant in which order you #include files,
and it should make no difference how often you #include each of them.
If DzComm needs special tricks to cohabitate with Allegro, fine, let
the user

	#define DZCOMM_USED_WITH_ALLEGRO 1

or whatever.  Relying on #include file ordering is way too fragile to
be a good solution.

>  If you have more than one C file in a project and you wish to
> access dzcomm from more than one of those files, you must put the
> following #define before all but one of the dzcomm includes:

>       #define DZCOMM_SECONDARY_INCLUDE
>       #include <dzcomm.h>

This is worse yet.  I consider an #include file that requires such
artistics to be used as pathecally ill-designed.  This file should
_always_ behave as if this #define had been set.

Whatever it exposes without that macro defined doesn't belong in a
public header file in the first place.  Such stuff belongs into one of
the .o files that form the actual library, not in the header.  If
at all, the #define should work the other way round, i.e. make it

	#define DZCOMM_EXPOSE_DEFINITIONS 1
	#include <dzcomm.h>

once, and plain

	#include <dzcomm.h>

in all other cases.

-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.