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From: "David Schwartz" <davids@webmaster.com>
To: "J. Dow" <jdow@earthlink.net>, <dank@alumni.caltech.edu>,
        <atmproj@yahoo.com>, <linux-kernel@vger.kernel.org>
Subject: RE: malloc(1/0) ??
Date: Mon, 6 Nov 2000 23:52:28 -0800
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> From: "Dan Kegel" <dank@alumni.caltech.edu>
> > atmproj@yahoo.com asked:
> > > [Why does this program not crash?]
> > >
> > > main()
> > > {
> > >    char *s;
> > >    s = (char*)malloc(0);
> > >    strcpy(s,"fffff");
> > >    printf("%s\n",s);
> > > }
> >
> > It doesn't crash because the standard malloc is
> > optimized for speed, not for finding bugs.
> >
> > Try linking it with a debugging malloc, e.g.
> >   cc bug.c -lefence
> > and watch it dump core.
>
> I'm not sure that is fully responsive, Dan. Why doesn't the
> strcpy throw a hissyfit and coredump?

	Why should it? Do you think that when you allocate memory, the chunk of
mappable memory you got always ends on the exact byte you asked it to? When
you invoke undefined behavior, anything can happen.

	DS

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