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Date: Tue, 31 May 2011 10:46:39 +0000
From: Alexander Best <arundel@freebsd.org>
To: Dimitry Andric <dim@FreeBSD.org>
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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
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On Tue May 31 11, Dimitry Andric wrote:
> 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.

*lol* we're moving in circles. so back to the beginning: why not use -O
for all archs, if debugging was enabled? for amd64 -O2 is always set, no
matter, if debugging is enabled or disabled.

cheers.
alex

-- 
a13x