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Date: Mon, 29 Nov 2010 10:59:40 +0100 From: Andi Kleen <andi@...stfloor.org> To: Hui Zhu <teawater@...il.com> Cc: linux-kernel@...r.kernel.org, gdb@...rceware.org, hellogcc@...elists.org Subject: Re: [PATCH] Built kernel without -O2 option Hui Zhu <teawater@...il.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. > > This is becuase the Kernel is bult with gcc -O2. Gcc will not > generate enough debug message with file with -O2. > So GDB cannot work very well with Linux kernel. > > So I make a patch that add a option in "Kernel hacking" called "Close > GCC optimization". It will make kernel be built without -O2. You need to at least keep aggressive inlining for header files, otherwise there will be too much code bloat and bad code. Like -O1 -finline-functions ? -Andi -- ak@...ux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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