[LLVMdev] Some thought on handling ELF shared libraries in lld

[Dave Bozier]

> It is technically possible. But we have to find the total symbols
> early (symbol resolution) and so we would need to do an early scan of
> another table just to find that number.

That shouldn't be too expensive. I would expect roughly as many
dynamic relocations as there are symbols as they will mostly just be
patching PLT/GOT entries for them.

You could also make it easier by creating a new tag defining the size
of the symbol table. That would at least allow shared libraries
produced by lld to be able to easily parse the dynamic symbol table.

Is statically linking against shared libraries that have been stripped
of their section header tables something that is likely to be
requested?



On Tue, Jul 21, 2015 at 3:30 PM, Rafael Espíndola
<rafael.espindola at gmail.com> wrote:
> On 21 July 2015 at 09:34, Dave Bozier <seifsta at gmail.com> wrote:
>> Sounds reasonable. The sstrip tool that performs stripping of the
>> section header does state that this makes shared libraries unsuitable
>> for static linking. From the documentation:
>>
>>> A shared-object library stripped in this fashion will still be usable by the dynamic linker, but not by the static linker.
>>
>> That said, it should be technically possible to statically link a
>> shared library with no section header table if we chose to support
>> that use case. Can't you use the symbol indices of dynamic relocations
>> to achieve this instead of counting the number of symbols?
>
> It is technically possible. But we have to find the total symbols
> early (symbol resolution) and so we would need to do an early scan of
> another table just to find that number.
>
> Cheers,
> Rafael