[rfc] a few kern.mk and bsd.sys.mk related changes

Alexander Best arundel at freebsd.org
Sat May 28 18:36:23 UTC 2011


On Sat May 28 11, Alexander Best wrote:
> On Sat May 28 11, Pan Tsu wrote:
> > Alexander Best <arundel at freebsd.org> writes:
> > 
> > > On Fri May 27 11, Alexander Best wrote:
> > >> On Fri May 27 11, Warner Losh wrote:
> > >> > These look generally good.  Just one thing I had a question on:
> > >> > 
> > >> >  #
> > >> > +# Enable FreeBSD kernel-specific printf format specifiers. Also instruct gcc to
> > >> > +# enable some diagnostics, which make it easier to pinpoint tinderbox failures.
> > >> > +CFLAGS+=	-fformat-extensions -fdiagnostics-show-option
> > >> > +
> > >> > 
> > >> > Does this put sand in the gears of clang support?
> > >
> > > i've improved the above comment so as to note that clang won't be affected by
> > > -fdiagnostics-show-option. the new patch is available here:
> > >
> > > http://people.freebsd.org/~arundel/patches/kern.mk-bsy.sys.mk.patch
> > >
> > > another "issue" i've come across is the fact that on amd64, -O2 is always being
> > > set, no matter, if debugging is enabled or disabled. i think amd64 should also
> > > (just like all the other archs) be using -O, when debugging was enabled.
> > 
> > Any reason a kernel with symbols (DEBUG) *must* be pessimized to -O1 level?
> > Looking at r140606 it's not clear how symbols are related to a bump
> > from -O1 to -O2 for non-amd64 archs. And -RELEASE kernels since at least
> > 6.0R have `makeoptions DEBUG=-g' uncommented in GENERIC.
> 
> well i'm not an expert on this. but are we 100% sure that a kernel on amd64
> compiled with -O2 frename-registers can be debugged the same way as one with
> -O? if that is the case: sure...-O2 is fine. ;)
> 
> 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.

ok. so here are two seperate patches:

http://people.freebsd.org/~arundel/patches/kern.mk-bsd.sys.mk.patch

^^ this one will trigger -O on amd64, when debugging was enabled.

http://people.freebsd.org/~arundel/patches/kern.mk-bsd.sys.mk-O2.patch

^^ this one will leave the semantics as they are, so even when debugging was
enabled, -O2 gets set under amd64.

cheers.
alex

> 
> cheers.
> alex
> 
> > 
> > > changing this is quite easy. so if people think this is something worth
> > > changing i can integrate it into my existing patch.
> 
> -- 
> a13x

-- 
a13x


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