From: Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>
To: jakub@redhat.com
Cc: libc-hacker@sources.redhat.com
Subject: Re: [PATCH] xdr_array and calloc security fix
Date: Fri, 02 Aug 2002 05:13:00 -0000 [thread overview]
Message-ID: <20020802121321.25638.qmail@md.dent.med.uni-muenchen.de> (raw)
In-Reply-To: <20020802140412.E20867@sunsite.ms.mff.cuni.cz> (message from Jakub Jelinek on Fri, 2 Aug 2002 14:04:12 +0200)
> Why not 2^32? size_t is unsigned.
Yes, however malloc can only handle chunks of a little less than 2^31
currently, so the _int_malloc later will fail anyway... But that is
ok, having a power of two as the compared value wins against this
micro-optimisation:
> So you mean something like:
> bytes = n * elem_size;
> if (__builtin_expect ((a | b) >= 65536, 0)) {
> if (bytes / elem_size != n) {
> MALLOC_FAILURE_ACTION;
> return 0;
> }
> }
Hey, nice, avoids the second comparision and ||. Looks like we have a
winner?
Regards,
Wolfram.
next prev parent reply other threads:[~2002-08-02 12:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-08-01 15:46 Jakub Jelinek
2002-08-02 0:20 ` Ulrich Drepper
2002-08-02 2:29 ` Wolfram Gloger
2002-08-02 2:43 ` Ulrich Drepper
2002-08-02 2:50 ` Ulrich Drepper
2002-08-02 2:56 ` Jakub Jelinek
2002-08-02 4:07 ` Andreas Schwab
2002-08-02 4:46 ` Jakub Jelinek
2002-08-02 4:57 ` Wolfram Gloger
2002-08-02 5:05 ` Jakub Jelinek
2002-08-02 5:13 ` Wolfram Gloger [this message]
2002-08-03 5:03 ` [PATCH] optimize calloc Jakub Jelinek
2002-08-03 12:02 ` Ulrich Drepper
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