Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!elroy.jpl.nasa.gov!jato!jdickson
From: jdickson@jato.jpl.nasa.gov (Jeff Dickson)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Is this valid C?
Message-ID: <1991May10.211545.14302@jato.jpl.nasa.gov>
Date: 10 May 91 21:15:45 GMT
References: <1991May5.222328.16225@csis.dit.csiro.au> <616@lysator.liu.se> <38542@ditka.Chicago.COM>
Reply-To: jdickson@jato.Jpl.Nasa.Gov (Jeff Dickson)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 32

In article <38542@ditka.Chicago.COM> comeau@csanta.attmail.com (Greg Comeau) writes:
>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.
>
>- Greg
>-- 
>	 Comeau Computing, 91-34 120th Street, Richmond Hill, NY, 11418
>                          Producers of Comeau C++ 2.1
>          Here:attmail.com!csanta!comeau / BIX:comeau / CIS:72331,3421
>                     Voice:718-945-0009 / Fax:718-441-2310

	Perhaps the compiler wouldn't barf, but the program would. 
"*p" is declared as a pointer to a structure of type "foop". Structure
"foop" is defined so the compiler would know at what offset each
member occurred at, but "*p" is not pointing to an allocated instance
of it. Now if you had:

		struct foop { int a; char *b } p;

	...then

		p.a = 39;

	...would be valid.


-jeff