From: Lucio De Re <lucio@proxima.alt.za>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] manual suggestions and upas/fs bug
Date: Tue, 17 Sep 2002 11:17:27 +0200 [thread overview]
Message-ID: <20020917111727.U6063@cackle.proxima.alt.za> (raw)
In-Reply-To: <3D8642ED.6BE57EE6@null.net>; from Douglas A. Gwyn on Tue, Sep 17, 2002 at 08:47:45AM +0000
On Tue, Sep 17, 2002 at 08:47:45AM +0000, Douglas A. Gwyn wrote:
> > > if(n==0){
> > > free(p);
> > > p = malloc(n);
> > > } else
> > > p = realloc(p, n);
>
> p = realloc(p,n) is almost always a mistake. If the allocation
> fails, the previous pointer value in p gets replaced by a null
> pointer value, so you lose the handle to the data that did not
> get extended (or, rarely, shrunk).
In other words,
if (n==0)
panic ("zero size");
p = realloc(p, n);
is closer to the intent here. Better still
char *p0 = realloc(p, n);
if (p0 == 0)
panic ("realloc failed");
p = p0;
would be a lot saner. I forget the semantics, but realloc(p, n) need
not return p even if the reallocation succeeds. What I don't know is
what happens to the space pointed to by p, I assume it's released.
++L
next prev parent reply other threads:[~2002-09-17 9:17 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-16 19:29 David Swasey
2002-09-17 1:58 ` Lyndon Nerenberg
2002-09-17 8:47 ` Douglas A. Gwyn
2002-09-17 9:17 ` Lucio De Re [this message]
2002-09-18 8:37 ` Douglas A. Gwyn
2002-09-17 4:34 David Swasey
2002-09-17 20:18 ` Lyndon Nerenberg
2002-09-17 4:58 Russ Cox
2002-09-17 13:28 Russ Cox
2002-09-17 23:05 Russ Cox
2002-09-18 2:06 ` Lyndon Nerenberg
2002-09-18 17:03 ` rob pike, esq.
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