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From: jym@mit-prep.UUCP
Newsgroups: comp.lang.c
Subject: Arrays of Unknown Length in Structures (and sizeof)
Message-ID: <243@mit-prep.ARPA>
Date: Tue, 22-Sep-87 14:13:39 EDT
Article-I.D.: mit-prep.243
Posted: Tue Sep 22 14:13:39 1987
Date-Received: Sat, 26-Sep-87 15:28:49 EDT
Organization: The MIT AI Lab, Cambridge, MA
Lines: 47

Consider the following:

	struct  STRUCT_FOO
	{
	  int  one;
	  int  two;
	  int  open[];
	};

	main()
	{
	  extern void  *malloc();

	  short int  i;
	
	  struct STRUCT_FOO  *foo_p;

	  printf("Size = %d\n",sizeof (struct STRUCT_FOO));

	  foo_p = malloc(sizeof (struct STRUCT_FOO) + (7 * sizeof (int)));

	  for (i = 0; i < 7; ++i)
	   foo_p->open[i] = i * 100;

	  for (i = 0; i < 7; ++i)
	   printf("open[%d] = %d\n",i,foo_p->open[i]);
	}

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.

My question:  is this kosher?  I've seen people do this by declaring the
 struct with an array of 1 element ("int  open[1];"), but this seems a bit
  kludgy to me.  Declaring it as an array of 0 elements ("int  open[0];")
   works with "cc" (albeit with two warning messages) but VAX C won't
    compile it at all.

As far as I'm concerned, if this isn't kosher, it should be!
 <_Jym_>
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