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    SubjectRe: [PATCH] Built kernel without -O2 option
    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@gmail.com> 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 Jelínek, 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.
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