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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