Re: [PATCH] Built kernel without -O2 option

[Michael Snyder]

AmÃrico Wang wrote:
> On Mon, Nov 29, 2010 at 11:12:16AM +0100, Mark Wielaard wrote:
> > On Mon, 2010-11-29 at 10:59 +0100, Andi Kleen wrote:
> > > Hui Zhu <teawater@xxxxxxxxx> writes:
> > >
> > > > Now, there are a lot of ways to debug the Linux kernel with GDB, like
> > > > qemu, kgtp or kgdb and so on.
> > > > But the developer more like add a printk. It have a lot of reason, a big one is:
> > > > (gdb) p ret
> > > > $3 = <value optimized out>
> > > > And the code execution order is not right.
> > > Really the right place to fix a lot of this would be gcc (and perhaps
> > > gdb). I suspect with some careful work the debugging experience
> > > for -O2 could be improved a lot.
> > > I also believe the latest gccs already have improvements in this area.
> > The VTA branch was merged for GCC 4.5
> > http://gcc.gnu.org/wiki/Var_Tracking_Assignments
> > Which helps a lot with generating dwarf for previously "optimized out"
> > values. There were also a couple of papers on generating even better
> > debuginfo at the recent GCC Summit: http://gcc.gnu.org/wiki/summit2010
> >
> > Jakub JelÃnek, Improving debug info for optimized away parameters
> > http://gcc.gnu.org/wiki/summit2010?action=AttachFile&do=get&target=jelinek.pdf
> > Alexandre Oliva, Consistent Views at Recommended Breakpoints
> > http://gcc.gnu.org/wiki/summit2010?action=AttachFile&do=get&target=oliva.pdf
>
> Cool! It would be much more convenient if this is solved by gcc.

Those features mentioned at the GCC summit are not real close to 
completion.  I wouldn't put off the discussion just because they're
(possibly) in the pipeline.

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