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From: edw@ius1.cs.cmu.edu (Eddie Wyatt)
Newsgroups: comp.lang.c
Subject: Re: Arrays of Unknown Length in Structures (and sizeof)
Message-ID: <1044@ius1.cs.cmu.edu>
Date: Sun, 27-Sep-87 13:45:00 EDT
Article-I.D.: ius1.1044
Posted: Sun Sep 27 13:45:00 1987
Date-Received: Tue, 29-Sep-87 03:39:31 EDT
References: <243@mit-prep.ARPA>
Organization: Carnegie-Mellon University, CS/RI
Lines: 34

> 	struct  STRUCT_FOO
> 	{
> 	  int  one;
> 	  int  two;
> 	  int  open[];
> 	};
> 
> 	  foo_p = malloc(sizeof (struct STRUCT_FOO) + (7 * sizeof (int)));
> 
> 	  for (i = 0; i < 7; ++i)
> 	   foo_p->open[i] = i * 100;
> 
.......
> I've tried this on two systems:  VMS V4.5 running VAX C V2.3, and BSD 4.2
>  running "cc".  Both do what I want them to do, though "cc" gives a warning
>   message for line 6.
> 
.....
> As far as I'm concerned, if this isn't kosher, it should be!

   Let me give you a reason of why this should not be "kosher".

  	    I don't think it is  required in C that the fields in a structure
	    be phyically ordered in the same ordering they are declared.
	    Hence any of the 6 permutations of the fields you describe
	    are valid for phyical offset orderings (ie open could have
	    an offset of 0, two could have an offset of 0 and one could
	    have an offset of 0 + sizeof(int)).  This would wreak havoc!!

-- 

					Eddie Wyatt

e-mail: edw@ius1.cs.cmu.edu