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From: lwm@bronze.ucs.indiana.edu (Larry Meehan)
Newsgroups: comp.sys.dec
Subject: Re: strcat(foo,NULL) core dumps on Ultrix
Keywords: null NULL
Message-ID: <1991Jun12.040043.24091@bronze.ucs.indiana.edu>
Date: 12 Jun 91 04:00:43 GMT
Article-I.D.: bronze.1991Jun12.040043.24091
References: <966@sdrc.COM>
Organization: Indiana University
Lines: 37

In <966@sdrc.COM> wggabb@sdrc.COM (Rob Gabbard) writes:

>A call to strcat with NULL as the second argument core dumps with a memory 
>fault on Ultrix.
...
>Actually, just coding strcat(foo,NULL) will dump.  Anyone run into this ?
>Am I doing a no-no here.

You must be on one of the MIPS-based DEC systems.  Due to a quirk of the VAX
port of ULTRIX, you can get by with what you are trying to do, but you are,
strictly speaking, doing a no-no.  The thing to remember is that NULL is not
the same thing as "", since strcat(foo,"") will work just fine.  This program
will fail too for *exactly* the same reason:
	main()
	{
		char *p, c;

		p = (char *) 0;
		c = *p;
	}
If you look in /usr/include/stdio.h, you will see that NULL is really just 0,
so our programs are trying to access location 0 which is legal on a VAX, but
not on the MIPS implementation of Ultrix.  A lot of "bug-free" code broke
when it was moved from VAX to non-VAX systems.  The little program above dumps
core on a MIPS CPU and runs without errors on a VAX.  The program is at fault,
not Ultrix.  Hope this helps.

-- 
	 Larry Meehan			University Computing Services
	 lwm@ucs.indiana.edu		Indiana University

	("Industry without art is brutality." -- Ananda Coomaraswamy)
-- 
	 Larry Meehan			University Computing Services
	 lwm@ucs.indiana.edu		Indiana University

	("Industry without art is brutality." -- Ananda Coomaraswamy)