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Message-ID: <20160112124855.GB13558@port70.net>
Date: Tue, 12 Jan 2016 13:48:55 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: Possible infinite loop in qsort()
* Alexander Cherepanov <ch3root@...nwall.com> [2016-01-12 15:25:57 +0300]:
> On 2016-01-10 14:38, Markus Wichmann wrote:
> >On Sat, Jan 09, 2016 at 11:05:16PM -0500, Rich Felker wrote:
> >>On Sat, Jan 09, 2016 at 10:07:19AM +0100, Felix Janda wrote:
> >>>musl enforces that object sizes should not be greater than PTRDIFF_MAX.
> >>>See for example the discussion at
> >>>
> >>>http://www.openwall.com/lists/musl/2013/06/27/7
> >>>
> >>>So there will not be objects of size 3GB with musl on x32. Since the
> >>>Leonardo numbers grow slower than 2^n in general no overflow should
> >>>happen if "size" is valid. Otherwise, UB was invoked.
> >>
> >
> >OK. Might want to make that assumption a bit more prominent, because
> >this is the first time I've ever heard about it, but OK, no objects >2GB
> >on 32-bit archs.
>
> Yeah, I don't see it in the doc. Did I miss it?
>
> If it neither works nor documented as a limit I'd call it a bug.
in musl things are documented in the git log for now, e.g.:
http://git.musl-libc.org/cgit/musl/commit/?id=3cd6f5229f079f892411e82fce3fe15c78eef4d8
i think if an implementation does not give this guarantee
that should be considered a bug.
(glibc does not guarantee this and indeed it is full of invalid
pointer arithmetics, but more importantly a huge number of
existing libraries depend on this)
> BTW the support in compilers for working with objects larger than half the
> address space is buggy -- see
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67999 . The same situation --
> it neither works nor documented. Somewhat puzzling...
yes, but it's not possible to support reasonably
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