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Re: [commit 7.8] [patch+7.8] Fix 7.8 regression: resolve_dynamic_struct: Assertion `TYPE_NFIELDS (type) > 0' (PR 17642)
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Joel Brobecker <brobecker at adacore dot com>
- Cc: Jan Kratochvil <jan dot kratochvil at redhat dot com>, GDB <gdb-patches at sourceware dot org>
- Date: Mon, 15 Dec 2014 13:09:03 -0800
- Subject: Re: [commit 7.8] [patch+7.8] Fix 7.8 regression: resolve_dynamic_struct: Assertion `TYPE_NFIELDS (type) > 0' (PR 17642)
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- References: <20141125195444 dot GA3400 at host2 dot jankratochvil dot net> <20141213142351 dot GG5457 at adacore dot com> <20141215150609 dot GA4229 at adacore dot com> <20141215191244 dot GA23577 at host2 dot jankratochvil dot net> <CAMe9rOod8+arBG7T7FgoNpJmF5LhZ5kwqGfLDF-Wx6ESGH3Qog at mail dot gmail dot com> <20141215193658 dot GC5457 at adacore dot com> <CAMe9rOqefYPoN-qGpH-z2kiHpyB5q7_52YA1ibTTAGX4qeF2Qg at mail dot gmail dot com> <20141215204143 dot GD5457 at adacore dot com>
On Mon, Dec 15, 2014 at 12:41 PM, Joel Brobecker <brobecker@adacore.com> wrote:
>> > This is a fairly big patch...
>> > 1. How bad is performance without it?
>>
>> It was very bad, like > 100x slower.
>
> OK, but 100x slower than 1usec is still unnoticeable. When did you start
> noticing it, for what kind of program (size?), and what type of delay
> were you seeing? Also, is that a regression compared to 7.7? The idea
> is that, if it's just a second or two, or even ten, that's still quite
> bearable, and unless you are absolutely sure that your patch is safe,
> perhaps we should pass...
>
>> > 2. Can you find a binutils maintainer that will vouch that
>> > this patch is 100% safe?
>>
>> As the x86 binutils maintainer, do I count?
>
> Absolutely. I just need someone who knows the code well enough to
> be trusted with its maintainance to stand behind the code and
> confirm that it is considered safe. In this case, I need extra safe,
> considering the fact that this is a .2 release.
>
> I hope I've described my concerns well enough for you to make
> the decision. Now that I have explained my thought process, I feel
> you're more qualified to make an informed decision now. Your call.
>
> Please remember that, if you do push it to 7.8, you'll need a PR
> associated to is so you can document the fix in the release wiki
> page (see fixes in GDB 7.8.2):
> https://sourceware.org/gdb/wiki/GDB_7.8_Release
The bug was filed against bintuils:
https://sourceware.org/bugzilla/show_bug.cgi?id=17677
since the code in question is in bfd. But the actual bug is for GDB:
https://bugs.launchpad.net/ubuntu/+source/gdb/+bug/1388999
where the issues was observed. I will retest by my patch and
backport it to 7.8 branch.
Thanks.
--
H.J.