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From: gkt@iitmax.IIT.EDU (George Thiruvathukal)
Newsgroups: comp.lang.c
Subject: Re: Novice question.
Message-ID: <4524@iitmax.IIT.EDU>
Date: 15 Nov 90 05:45:09 GMT
References: <1990Oct31.014132.2400@agate.berkeley.edu> <336@brat.UUCP> <14624@neptune.inf.ethz.ch>
Organization: Illinois Institute of Technology, Chicago
Lines: 28

In article <14624@neptune.inf.ethz.ch>, mneerach@iiic.ethz.ch (Matthias Ulrich Neeracher) writes:
> "extern" essentially tells the compiler that this variable is defined 
> elsewhere.

It is truly unfortunate the "extern" keyword exists in C.  Let us examine the
following code fragment which allocates a vector of a size which is unknown
until function xyzpdq is encoded.

extern int TempCount;

void xyzpdq()
{
   void **temporaries = (void **)calloc(TempCount,sizeof(void *));

   /* code */

   free(temporaries);
}

/* resolution of TempCount in same compilation unit */
int TempCount = 5;

Although one might not opt to allocate temporary variables in exactly the above
fashion, it is easier than backpatching the code.  It manifests a usage of 
extern within the same compilation unit as the external reference.

George Thiruvathukal
gkt@iitmax.iit.edu