Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!udel!mmdf
From: lawsonse@vttcf.cc.vt.edu (Shannon Lawson)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Is this valid C?
Message-ID: <53200@nigel.ee.udel.edu>
Date: 10 May 91 12:58:51 GMT
Sender: mmdf@ee.udel.edu
Lines: 35

> 
> In article <616@lysator.liu.se> zap@lysator.liu.se (Zap Andersson) writes:
> >struct foop *p;
> > >struct foop { int a; char *b };
> > >main() { p->a = 39;  /* Will complier barf here? */ }
> > 
> > There will be a no barf since at the ->a, foop is no longer an incomplete
> > type.  It is not a problem.
>          ^^^^^^^^^^^^^^^^^^^
 
I disagree.  p is a pointer to foop, and has not been allocated a foop to which
it may point.  Depending on the compiler, p points to some random location, so
you are happily sticking the value 39 into some nebulous area.  Although your
syntax is correct (and the compiler may not gag), you should see a problem
at runtime when you try to reference p.
 
ALWAYS make sure your pointers point to something valid!
 
> 
> - Greg
> -- 
> 	 Comeau Computing, 91-34 120th Street, Richmond Hill, NY, 11418
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-- 
  Shannon Lawson                    ||  Virginia Polytechnic Institute 
  Graduate Student                  ||     & State University 
  Harry Lynde Bradley Department of ||
  Electrical Engineering            ||  E-Mail:  lawsons@csgrad.cs.vt.edu
 
  Disclaimer:  If I put my foot in my mouth, I can hardly hold someone else
  responsible, now can I?