Re: Return value of malloc(0)

On Fri, Jun 30, 2006 at 06:59:37AM +0200, Johannes Weiner wrote:
Hi,

On Thu, Jun 29, 2006 at 07:29:16PM +0200, Matthias Andree wrote:
No, sir. Operator precedence: assign first, and then compare, thus the
comparison will always be true (else you'd be comparing to undefined
values, which isn't any better). You might as well write:

foo = malloc(0);
/* make noise */

Ok, just for having it done:

if (foo == (foo = some_val))

.. would be right to check if foo stayed the same. No?

There is no way to see a 0x800 return from malloc(0) as "error".

So noone should actually use malloc(0) and check the size_t argument before
passing it, I guess.

But noone should dereference something beyound malloc'ed size.
The following code is broken no matter if x is 0 or anything else,
you always end up accessing data beyond allocated range:
foo = malloc(x);
foo[x] = bar;
It might be Ok not to check x when calling malloc, but is always
required to check if you access something outside the malloc'ed range
unless you can trust your size - in which case you wouldn't had
malloc'ed zero bytes anyway.

--
B.Walter http://www.bwct.de http://www.fizon.de
bernd@xxxxxxx info@xxxxxxx support@xxxxxxxx
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