From: Peter Stephenson <p.stephenson@samsung.com>
To: zsh workers <zsh-workers@zsh.org>
Subject: Re: Fishy code in sticky emulation?
Date: Mon, 05 Jan 2015 14:48:19 +0000 [thread overview]
Message-ID: <20150105144819.2f768fcb@pwslap01u.europe.root.pri> (raw)
In-Reply-To: <CAHYJk3SjCocOpnoS5K_N=J7CWKmVBTgrUtryLLf+cu6xLqxZ8w@mail.gmail.com>
On Mon, 5 Jan 2015 15:34:00 +0100
Mikael Magnusson <mikachu@gmail.com> wrote:
> I'm looking through Coverity issues (some patches to come later), and
> it flagged this in builtin.c that I can't quite say for sure if it's
> right or wrong about.
>
> int
> bin_emulate(UNUSED(char *nam), char **argv, Options ops, UNUSED(int func))
> {
> ...
> if (sticky->n_on_opts)
> on_ptr = sticky->on_opts =
> zhalloc(sticky->n_on_opts * sizeof(*sticky->on_opts));
> else
> on_ptr = NULL;
> if (sticky->n_off_opts)
> off_ptr = sticky->off_opts = zhalloc(sticky->n_off_opts *
> sizeof(*sticky->off_opts));
> else
> off_ptr = NULL;
> for (optnode = firstnode(optlist); optnode; incnode(optnode)) {
> /* Data is index into new_opts */
> char *optptr = (char *)getdata(optnode);
> int optno = optptr - new_opts;
> if (*optptr)
> *on_ptr++ = optno;
> else
> *off_ptr++ = optno;
> }
> ...
>
> In particular, on_ptr and off_ptr can be NULL, but unconditionally one
> of them is always incremented in the for loop, which isn't very well
> defined for a NULL pointer. Am I missing something, or are these
> n_*_opts simply never 0?
You missed out the previous loop which is exactly parallel to the second
one you quoted:
for (optnode = firstnode(optlist); optnode; incnode(optnode)) {
/* Data is index into new_opts */
char *optptr = (char *)getdata(optnode);
if (*optptr)
sticky->n_on_opts++;
else
sticky->n_off_opts++;
}
This means that in the second loop on_ptr must be non-NULL whenever
*optptr is non-NULL and off_ptr must be non-NULL whenever it's NULL.
However, it would be fine to make the test for the pointers more
explicit; it's not going to make any noticeable difference even if you
run emulate very frequently.
pws
next prev parent reply other threads:[~2015-01-05 14:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-05 14:34 Mikael Magnusson
2015-01-05 14:48 ` Peter Stephenson [this message]
2015-01-05 23:21 ` Mikael Magnusson
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