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Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Cary Coutant <ccoutant at gmail dot com>, Michael Matz <matz at suse dot de>, "Maciej W. Rozycki" <macro at imgtec dot com>, Alan Modra <amodra at gmail dot com>, Richard Biener <richard dot guenther at gmail dot com>, Joe Groff <jgroff at apple dot com>, Binutils <binutils at sourceware dot org>, GCC <gcc at gcc dot gnu dot org>
- Date: Mon, 25 Apr 2016 10:31:50 -0700
- Subject: Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
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On Mon, Apr 25, 2016 at 10:24 AM, Jeff Law <law@redhat.com> wrote:
> On 04/18/2016 11:55 AM, Cary Coutant wrote:
>>>>
>>>> That is why protected visibility is such a mess.
>>>
>>>
>>> Not mess, but it comes with certain limitations. And that's okay. It's
>>> intended as an optimization, and it should do that optimization if
>>> requested, and error out if it can't be done for whatever reason.
>>
>>
>> I completely agree.
>
> ISTM this ought to be the guiding principle here, with the additional caveat
> that if one of the limitations is tickled that we issue a good diagnostic.
>
> The current situation (gcc-5, gcc-6-rc) essentially de-optimizes protected
> systems in an attempt to work around the various limitations of protected
> symbols. Reverting that change is, IMHO, what needs to happen. My worry is
> that we're so damn late in the gcc-6 cycle that it may need to be deferred
> to 6.2 or beyond.
Please keep in mind that many limitations can only be detected at
link-time or run-time, which are yet to be implemented, not at
compile-time.
--
H.J.