From: Florian Weimer <fweimer@redhat.com>
To: Paul Eggert <eggert@cs.ucla.edu>, Joseph Myers <joseph@codesourcery.com>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH] Dynamic growable arrays for internal use
Date: Fri, 05 May 2017 15:23:00 -0000 [thread overview]
Message-ID: <2c8be504-90ad-6178-6698-fe61308af98c@redhat.com> (raw)
In-Reply-To: <75225ee3-2ae6-7a19-07be-e33818a43ac5@cs.ucla.edu>
On 05/05/2017 05:13 PM, Paul Eggert wrote:
> Florian Weimer wrote:
>> Does anyone have comments about the interface and implementation?
>
> It suffers from a common problem: it can allocate objects containing
> more than PTRDIFF_MAX bytes. Such objects do not work in C, because
> pointer subtraction has undefined behavior
Isn't this a non-sequitur? You can surely allocate such objects (on
some architectures, not all of course). You just have to be careful
with pointer differences. In particular, for an expression P[N] with P
a pointer type and N an integer type, N is *not* converted to ptrdiff_t.
I don't think the current implementation computes any pointer
differences, so it avoids this issue. Element counts are kept in size_t
variables.
Thanks,
Florian
next prev parent reply other threads:[~2017-05-05 15:23 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-22 15:46 Florian Weimer
2017-04-24 14:06 ` Joseph Myers
2017-05-05 11:48 ` Florian Weimer
2017-05-05 15:13 ` Paul Eggert
2017-05-05 15:23 ` Florian Weimer [this message]
2017-05-05 22:31 ` Paul Eggert
2017-05-20 2:01 ` Carlos O'Donell
2017-05-21 0:43 ` Paul Eggert
2017-06-01 16:13 ` Carlos O'Donell
2017-06-01 17:09 ` Jeff Law
2017-06-01 20:21 ` Florian Weimer
2017-06-01 21:13 ` Adhemerval Zanella
2017-06-01 18:08 ` Paul Eggert
2017-05-30 12:48 ` Florian Weimer
2017-06-02 7:37 ` Carlos O'Donell
2017-06-02 10:04 ` Florian Weimer
2017-06-06 15:30 ` Stefan Liebler
2017-06-06 15:46 ` H.J. Lu
2017-06-07 9:54 ` Florian Weimer
2017-06-07 9:41 ` Florian Weimer
2017-06-07 14:41 ` Stefan Liebler
2017-06-07 18:56 ` Florian Weimer
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