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From: "Lyle Coder" <x_coder@hotmail.com>
To: "David Schwartz" <davids@webmaster.com>,
        "RAJESH BALAN" <atmproj@yahoo.com>, <linux-kernel@vger.kernel.org>
In-Reply-To: <NCBBLIEPOCNJOAEKBEAKEEAJLMAA.davids@webmaster.com>
Subject: Re: malloc(1/0) ??
Date: Tue, 7 Nov 2000 00:09:09 -0800
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When a program does a malloc... the glibc gets atleast on page (brk)
[actually, glibs determins of it needs to brk more memory from the kernel...
because it maintains it;s own pool].. so if you malloc 4 byts, you can copy
to that pointer more than 4 bytes (upto a page size, ex 4K)... hope that
answers one of your questions... as far as why malloc(0) works... I dunno

Best Wishes,
Lyle
----- Original Message -----
From: "David Schwartz" <davids@webmaster.com>
To: "RAJESH BALAN" <atmproj@yahoo.com>; <linux-kernel@vger.kernel.org>
Sent: Monday, November 06, 2000 11:54 PM
Subject: RE: malloc(1/0) ??


> > hi,
> > why does this program works. when executed, it doesnt
> > give a segmentation fault. when the program requests
> > memory, is a standard chunk is allocated irrespective
> > of the what the user specifies. please explain.
> >
> > main()
> > {
> >    char *s;
> >    s = (char*)malloc(0);
> >    strcpy(s,"fffff");
> >    printf("%s\n",s);
> > }
> >
> > NOTE:
> >   i know its a 'C' problem. but i wanted to know how
> > this works
>
> The program does not work. A program works if it does what it's supposed
to
> do. If you want to argue that this program is supposed to print "ffffff"
> then explain to me why the 'malloc' contains a zero in parenthesis.
>
> The program can't possibly work because it invokes undefined behavior. It
> is impossible to determine what a program that invokes undefined behavior
is
> 'supposed to do'.
>
> DS
>
> -
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