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Re: [Libunwind-devel] FYI: new type of unwind info inaccuracy (x86-64, l
From: |
Lassi Tuura |
Subject: |
Re: [Libunwind-devel] FYI: new type of unwind info inaccuracy (x86-64, libm, rhel 6.x) |
Date: |
Thu, 5 May 2011 17:56:10 +0200 |
Hi,
>> While testing the new libunwind version we came across a new type of unwind
>> info inaccuracy on x86-64 RHEL6. See http://gcc.gnu.org/PR48597 for the
>> details.
>
> Looks like there is a gcc patch that fixes this now. But it'll be a
> while before distros package it. In the meanwhile libunwind will need
> to deal with these types of issues.
There now appears to be a patch for all of GCC 4.[456].x, so things look
positive.
My feeling is that libunwind currently deals with these adequately, at least on
x86-64. The omissions are not detectable in that unwind info is present and
correct - just missing some info.
x86-64 unw_step() loop will handle the problems by returning an error code - we
default to full paranoia memory checks, but it can be turned off if someone
builds on a platform not subject to the problems.
I don't feel we'd need additional options, for example for fast trace. Clients
can already choose full paranoia checks by using unw_step() loop, and adding
them to fast trace will turn it into slow trace :-) I think the fast trace is
reasonably useful as it is, as unfortunate as the crashes are.
Regards,
Lassi
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- Re: [Libunwind-devel] FYI: new type of unwind info inaccuracy (x86-64, libm, rhel 6.x),
Lassi Tuura <=