From: Gabriel Dos Reis <gdr@integrable-solutions.net>
To: Joe Buck <Joe.Buck@synopsys.com>
Cc: Florian Weimer <fw@deneb.enyo.de>,
Chris Lattner <clattner@apple.com>,
"Joseph S. Myers" <joseph@codesourcery.com>,
"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: operator new[] overflow (PR 19351)
Date: Thu, 02 Dec 2010 22:47:00 -0000 [thread overview]
Message-ID: <AANLkTikTyVP_HPHezd+ZuwXLnMyakSjNtsN=hh0UOc+s@mail.gmail.com> (raw)
In-Reply-To: <20101202202014.GI9549@synopsys.com>
On Thu, Dec 2, 2010 at 2:20 PM, Joe Buck <Joe.Buck@synopsys.com> wrote:
> On Wed, Dec 01, 2010 at 10:26:58PM -0800, Florian Weimer wrote:
>> * Chris Lattner:
>>
>> > On overflow it just forces the size passed in to operator new to
>> > -1ULL, which throws bad_alloc.
>>
>> This is also what my patch tries to implement.
>
> Yes, but Chris's code just checks the overflow of the multiply. Your
> patch achieves the same result in a more complex way, by
> computing the largest non-overflowing value of n in
>
> new T[n];
>
> and comparing n against that. Even though max_size_t/sizeof T is a
> compile-time constant, this is still more expensive.
I would expect max_size_t/sizeof(T) to be actually an integer
constant that n is compared against. I would be surprised
if that one-time comparison is noticeable in real applications that
new an array of objects.
>
>
next prev parent reply other threads:[~2010-12-02 22:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-30 21:34 Florian Weimer
2010-11-30 22:38 ` Joseph S. Myers
2010-11-30 22:56 ` Gabriel Dos Reis
[not found] ` <20101130231211.GI13905@synopsys.com>
2010-12-01 23:36 ` Chris Lattner
2010-12-02 2:51 ` Gabriel Dos Reis
2010-12-02 6:27 ` Florian Weimer
2010-12-02 20:20 ` Joe Buck
2010-12-02 22:47 ` Gabriel Dos Reis [this message]
2010-12-03 17:31 ` Joe Buck
2010-12-04 13:23 ` Florian Weimer
2010-12-04 16:09 ` Gabriel Dos Reis
2011-01-22 20:09 ` Florian Weimer
2010-12-05 7:56 ` Chris Lattner
2010-12-05 11:19 ` Richard Guenther
2010-12-05 17:49 ` Chris Lattner
2010-12-05 17:54 ` Chris Lattner
2010-12-05 20:52 ` Richard Guenther
2010-12-05 21:21 ` Joseph S. Myers
2010-12-05 21:44 ` Richard Guenther
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