Date: Tue, 31 May 2011 12:37:00 +0200 From: Dimitry Andric <dim@FreeBSD.org> To: Alexander Best <arundel@freebsd.org> Cc: 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>
next in thread | previous in thread | raw e-mail | index | archive | help
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.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4DE4C4CC.4020905>