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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