Date: Tue, 31 May 2011 12:37:00 +0200 From: Dimitry Andric <dim@FreeBSD.org> To: Alexander Best <arundel@freebsd.org> Cc: Bruce Cran <bruce@cran.org.uk>, freebsd-hackers@FreeBSD.ORG, freebsd-toolchain@FreeBSD.ORG, Pan Tsu <inyaoo@gmail.com> Subject: Re: [rfc] a few kern.mk and bsd.sys.mk related changes Message-ID: <4DE4C4CC.4020905@FreeBSD.org> In-Reply-To: <20110531095742.GA99888@freebsd.org> References: <20110527115147.GA73802@freebsd.org> <3BF63174-1B29-4A4D-96DD-3ED65ED96EAC@bsdimp.com> <20110527181459.GA29908@freebsd.org> <20110527182906.GA31871@freebsd.org> <86oc2mlsey.fsf@gmail.com> <20110528182326.GA75447@freebsd.org> <20110528202619.GA27204@muon.cran.org.uk> <20110531095742.GA99888@freebsd.org>
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On 2011-05-31 11:57, Alexander Best wrote: ... >>> however i've often read messages - mostly by bruce evans - claiming that >>> anything greater than -O will in fact decrease a kernel's ability to be >>> debugged just as well as a kernel with -O. >> The critical option when -O2 is used is -fno-omit-frame-pointers, since removing >> frame pointers makes debugging impossible (on i386). With -O2 code is moved around and >> removed, so debugging is more difficult, but can still provide useful >> information. > any reason we cannot use -O2 -fno-omit-frame-pointers -fno-strict-aliasing as > standard COPTFLAGS with debugging enabled for *all* archs? Most likely, the performance gain from -O2 is rather small, except for special cases, but the pain during debugging is increased a great deal. Even if you add frame pointers, with -O2 large pieces of code can be transformed, variables or even entire functions can be completely eliminated, and so on, making debugging much more difficult.home | help
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