Date: Tue, 16 Oct 2001 14:59:09 -0700 From: "Chad R. Larson" <chad@DCFinc.com> To: Dimitry Andric <dim@xs4all.nl> Cc: Nate Williams <nate@yogotech.com>, freebsd-stable@FreeBSD.ORG Subject: Re: setenv() cores with NULL value [was Re: Gdm proplem on 4.4] Message-ID: <20011016145909.B23454@freeway.dcfinc.com> In-Reply-To: <441356059.20011016201751@xs4all.nl>; from dim@xs4all.nl on Tue, Oct 16, 2001 at 08:17:51PM %2B0200 References: <200110160353.f9G3rO728525@harmony.village.org> <Pine.LNX.4.33.0110152249220.8479-100000@organ.cs.byu.edu> <20011016013834.E293@blossom.cjclark.org> <200110161002.f9GA2CA08544@shalimar.net.au> <15308.25432.608079.646993@nomad.yogotech.com> <441356059.20011016201751@xs4all.nl>
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On Tue, Oct 16, 2001 at 08:17:51PM +0200, Dimitry Andric wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 2001-10-16 at 18:42:00 Nate Williams wrote:
>
> NW> printf("%s", "");
> NW> printf("%s", NULL);
>
> NW> The first will work, the second will dump core.
>
> Nope, it will print the string "(null)", as you can see in
> /usr/src/lib/libc/stdio/vfprintf.c, around line 673:
>
> case 's':
> if ((cp = GETARG(char *)) == NULL)
> cp = "(null)";
>
> Almost any printf I've ever seen does the same.
Yes, but that is a function of printf(3), not of dereferencing NULL
pointers. Modify slightly:
/* dereference a null pointer */
#define NULL 0
main()
{
char *foo;
static int bar;
foo = "junk";
bar = *foo;
foo = NULL;
bar = *foo;
}
-crl
--
Chad R. Larson (CRL15) 602-953-1392 Brother, can you paradigm?
chad@dcfinc.com chad@larsons.org larson1@home.com
DCF, Inc. - 14623 North 49th Place, Scottsdale, Arizona 85254-2207
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