[llvm-dev] [lld] elf linker creates undefined empty symbol

[Sean Silva via llvm-dev]

Rafael, did you ever get a chance to look at this?

-- Sean Silva

On Thu, Feb 23, 2017 at 1:14 AM, Sean Silva <chisophugis at gmail.com> wrote:

>
>
> On Wed, Feb 22, 2017 at 6:14 AM, Rafael Avila de Espindola <
> rafael.espindola at gmail.com> wrote:
>
>> Sean Silva <chisophugis at gmail.com> writes:
>> >> When __libc_start_main is hidden, it doesn't end up in the dynamic
>> symbol
>> >> table and so we use the default DynsymIndex of 0.
>> >>
>> >
>> >
>> > I think BFD is doing the right thing. The `extern_weak hidden` is
>> resolved
>> > to null since by virtue of being hidden it doesn't refer to the
>> function in
>> > libc.so (and there is no definition in the executable). For some reason,
>> > LLD thinks that it needs to resolve __libc_start_main dynamically and
>> > things go horribly wrong. Rafael, what do you think?
>>
>> If it is hidden it should really not end up in the dynamic symbol
>> table. I will try to take a look at your reproducible latter in the day.
>>
>
>
> FWIW, gold issues an error:
>
> /usr/bin/ld.gold: error: hidden symbol '__libc_start_main' is not defined
> locally
> /usr/bin/ld.gold: error: hidden symbol '__libc_start_main' is not defined
> locally
>
> In theory `extern_weak hidden` could still fail to have a local definition
> and then it would resolve to 0 due to being weak, which is what BFD does.
> But `extern_weak hidden` is still pretty questionable. E.g. in the original
> case that Carlo ran into, this was not the expected behavior (and this
> error may have saved him some time actually).
>
> -- Sean Silva
>
>
>>
>> Cheers,
>> Rafael
>>
>
>
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