Re: [dev] [st] [PATCH 4/3] tresize: remove unnecessary if

From: Dimitris Papastamos <sin_AT_2f30.org>
Date: Tue, 14 Apr 2015 13:50:26 +0100

On Tue, Apr 14, 2015 at 01:43:56PM +0200, Silvan Jegen wrote:
> On Tue, Apr 14, 2015 at 12:55 PM, Gregor Best <gbe_AT_ring0.de> wrote:
> > The cause seems to be that for bot `term.line` and `term.alt` are NULL
> > at this point. While this does mean that even with a `len` parameter of
> > 0, the `dst` pointer gets touched, I don't think it's ever right to call
> > either `memcpy` or `memmove` with a NULL destination pointer.
>
> I just tested glibc's memmove. The results are:
>
> dst == NULL, n > 0: segfault
> src == NULL, n > 0: segfault
>
> if dst or src are NULL and n is 0 there is no segfault. Fascinating.

dst and src are required to be valid objects even if n is 0, otherwise
this is undefined behaviour.

The fact that it doesn't crash on this implementation doesn't mean
anything.
Received on Tue Apr 14 2015 - 14:50:26 CEST