Re: [PATCH 4/4] Update tests for protected data and function symbols

[Florian Weimer <fweimer@redhat.com>]

* H. J. Lu:

> On Mon, Jun 21, 2021 at 12:19 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * H. J. Lu via Libc-alpha:
>>
>> > Protected data and function symbols don't work well without
>> > -fsingle-global-definition:
>> >
>> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=37611
>> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44166
>> >
>> > 1. Compile tst-protected1[ab].c and tst-protected1mod[ab].c with
>> > -fsingle-global-definition if possible so that GOT entries are used
>> > for undefined data accesses.
>> > 2. Add tests for protected function pointers.
>> > 3. Build tst-prelink.c without single global definition to keepp COPY
>> > relocation.
>>
>> I think these tests need to check that the statically linked bits from
>> GCC have been built with -fsingle-global-definition.  I don't think
>> that's guaranteed even if GCC supports -fsingle-global-definition.
>>
>> I think this shows the limitation of the single bit of markup: the
>> statically linked GCC bits are all hidden, so setting
>> GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION so is not correct as a
>> marker to *require* a single global definition, but neither is not
>> setting it because libgcc.a etc. should be *compatible* with
>> GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION.
>
> The output bit is ORed from all inputs.   When one input object file doesn't
> work with COPY relocation, the final output object is marked incompatible
> with COPY relocation even if some inputs do work with COPY relocation.

But for the main executable, it has to work the other way round.

Thanks,
Florian