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Re: PATCH: Turn on -fomit-frame-pointer by default for 32bit Linux/x86


On Wed, Aug 4, 2010 at 1:57 PM, David Daney <ddaney@caviumnetworks.com> wrote:
> On 08/04/2010 01:39 PM, Andi Kleen wrote:
>>
>> "H.J. Lu"<hjl.tools@gmail.com> ?writes:
>>
>>> I am not sure about single handler. For malloc, are you referring to
>>
>> In Linux the kernel provides unwind information for the signal
>> handler. I just tested it and it works here with a frame pointer
>> less 32bit executable using gdb.
>
> Not that I doubt your claim, but the ability of gdb to unwind signal frames
> is not proof of the existence of kernel unwind information.

The kernel VDSO page does in fact provide correct unwind info, but that
is completely irrelevant.

The issue here is not that the unwind info is missing; it's that glibc
backtrace() is not async-signal safe (which, given that it calls malloc
shouldn't be a big surprise :-).

Cheers,
-- 
Paul Pluzhnikov


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