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

Jeff Law law@redhat.com
Mon Apr 25 17:35:00 GMT 2016 
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 and 
ensure 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 a 
diagnostic for the case that can't be reasonably handled.

Jeff
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