Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH] Built kernel without -O2 option | From | Mark Wielaard <> | Date | Mon, 29 Nov 2010 11:12:16 +0100 |
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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
Cheers,
Mark
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