Including <stddef.h>

[sabbagh]

In article <71 at motto.UUCP> dave at motto.UUCP (dave brown) writes:
>I am writing a header file to be used by other programmers.  Within
>this file, one of the structures needs the type size_t.  This means
>that in order to compile properly, <stddef.h>, which defines size_t,
>must be included as well.  Since my header file will be used in
>programs I didn't write, I need to figure out how to make sure
><stddef.h> is included at the same time.
>
>Here are the ideas I have considered:
>
>1. Document the requirement 
> [stuff deleted]
>2. Include <stddef.h> at the top of my header

As far as I have seen, 1. is the usual approach.  If you want to
have <stddef.h> included in your own header file (as per 2.) the
best way to assure that it works is 

	1. Scan stddef.h for some symbol defined with an #define,
	   say, #define	FOO

	2. In your header, use the following:
		#ifndef FOO
		#include	<stddef.h>
		#endif
This will guarantee that your header file will always have the
stddef.h loaded, but it will cause problems for the user if
they try to #include <stddef.h> AFTER #including your header.

A third approach (if your are REALLY serious), is to copy those
parts of <stddef.h> into your own header file and #undef them when
your are done.  This resolves all the above problems, but gives
up something in portability.

Isn't C great?

Hadil G. Sabbagh
E-mail:		sabbagh at csd27.nyu.edu
Voice:		(212) 998-3285
Snail:		Courant Institute of Math. Sci.
		251 Mercer St.
		New York,NY 10012

186,282 miles per second -- it's not just a good idea, it's the law!