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Re: [PATCH] Built kernel without -O2 option

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 <> 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
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:

Jakub JelÃnek, Improving debug info for optimized away parameters
Alexandre Oliva, Consistent Views at Recommended Breakpoints

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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