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From: nathan@elberton.inmos.co.uk (Nathan Sidwell)
Newsgroups: comp.lang.c
Subject: Re: How to force cpp to abort?
Message-ID: <9679@ganymede.inmos.co.uk>
Date: 17 Aug 90 09:12:17 GMT
References: <MIKEG.90Aug11180036@c3.c3.lanl.gov>
Sender: rob@inmos.co.uk
Reply-To: nathan@inmos.co.uk (Nathan Sidwell)
Distribution: comp
Organization: INMOS Limited, Bristol, UK.
Lines: 56

In article <MIKEG.90Aug11180036@c3.c3.lanl.gov> mikeg@c3.c3.lanl.gov (Michael P. Gerlek) writes:
>
>I'm writing some machine dependent code...
>
>#if defined(__convex__)
>	(do Convex stuff)
>#else
>#if defined(cray)
>	(do Cray stuff)
>#else
>#if defined(sun)
>	(do Sun stuff)
>#else
>	(oops)	/* force abort */
>#endif
>#endif
>#endif
>
>[how to tidily abort compile at oops]

You can use the #error preprocessor directive, viz

#error Machine type not supported

I would have emailed this, but it struck me that it also helps in another
thread about array initializing. When I define an initialized array in a
header file, and initialize it in the code file, the two must be kept in step.
Ie

"module.h"

#define DETECTORS 7
extern char *detectors[DETECTORS] ;

"module.c"

#if DETECTORS != 7
#error Module assumes DETECTORS == 7
#endif
extern char *detectors[DETECTORS] =
{
  "Photomultiplier",
  "Silicon",
  "Raman",
  "Detector 3",
  "Detector 4",
  "Detector 5",
  "Detector 6",
};

Much better than a comment telling me to keep them in step!


Nathan Sidwell, INMOS Ltd, UK         JANET:    nathan@uk.co.inmos
Generic disclaimer applies            UUCP:     ukc!inmos!nathan
My indicision is final (I think)      INTERNET: nathan@inmos.com