Date: Mon, 5 May 2014 22:21:59 +0100 From: David Chisnall <theraven@FreeBSD.org> To: Pedro Giffuni <pfg@FreeBSD.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Andrey Chernov <ache@freebsd.org> Subject: Re: svn commit: r265367 - head/lib/libc/regex Message-ID: <3C7CFFB7-5C84-4AC1-9A81-C718D184E87B@FreeBSD.org> In-Reply-To: <5367EB54.1080109@FreeBSD.org> References: <201405051641.s45GfFje086423@svn.freebsd.org> <5367CD77.40909@freebsd.org> <B11B5B25-8E05-4225-93D5-3A607332F19A@FreeBSD.org> <5367EB54.1080109@FreeBSD.org>
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On 5 May 2014, at 20:49, Pedro Giffuni <pfg@FreeBSD.org> wrote: > Yes, but I reverted it because there are other ways to check for = overflows without the performance hit. Do we have a good reusable routine for doing this somewhere? Clang and = gcc both have some idiom recognisers that try to spot when people are = attempting to do this. Clang also has a builtin, which would be good to = use when available. Overflow checking is very cheap on modern CPUs = (add, branch on carry), so it would be nice if we could start looking = for this malloc() and realloc() pattern and replacing the multiply with = something that checks for the error. David
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