Re: Possible infinite loop in qsort()

[Szabolcs Nagy <nsz@port70.net>]

* Alexander Cherepanov <ch3root@openwall.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