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Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]

From: Jeff Law <law at redhat dot com>
To: Richard Biener <richard dot guenther at gmail dot com>, Alan Modra <amodra at gmail dot com>
Cc: "H.J. Lu" <hjl dot tools at gmail dot com>, Cary Coutant <ccoutant 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 11:35:46 -0600
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 04/19/2016 02:20 AM, Richard Biener wrote:

On Tue, Apr 19, 2016 at 7:08 AM, Alan Modra <amodra@gmail.com> wrote:

On Mon, Apr 18, 2016 at 07:59:50AM -0700, H.J. Lu wrote:

On Mon, Apr 18, 2016 at 7:49 AM, Alan Modra <amodra@gmail.com> wrote:

On Mon, Apr 18, 2016 at 11:01:48AM +0200, Richard Biener wrote:

To summarize: there is currently no testcase for a wrong-code issue
because there is no wrong-code issue.


I've added a testcase at
https://sourceware.org/bugzilla/show_bug.cgi?id=19965#c3
that shows the address problem (&x != x) with older gcc *or* older
glibc, and shows the program behaviour problem with current
binutils+gcc+glibc.


Thanks.

So with all this it sounds that current protected visibility is just broken
and we should forgo with it, making it equal to default visibility?

No, we revert to the gcc-4.9 behavior WRT protected visibility andensure that we're getting a proper diagnostic from the linker.

That direction is consistent with the intent of protected visibility,fixes the problem with preemption of protected symbols and gives us adiagnostic for the case that can't be reasonably handled.


Jeff

Follow-Ups:
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: Alan Modra

References:
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: Jeff Law
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: H.J. Lu
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: Richard Biener
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: Alan Modra
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: H.J. Lu
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: Alan Modra
- Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
  - From: Richard Biener

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