Re: [RFC] elf: Implement filtering of symbols historically defined in libpthread

[Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>]

* H. J. Lu:

> On Tue, May 4, 2021 at 5:27 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * H. J. Lu:
>>
>> >> The patch attempts to detect old main programs by looking for the
>> >> GLIBC_2.34 symbol version.  Since we added __libc_start_main@@GLIBC_2.34
>> >> (which is called from our version of _start), all standard main programs
>> >> linked with glibc 2.34 or later will have this symbol version.
>>
>> > Can we invent a symbol or version to detect the older binaries?
>> > If not, can GNU property, ABI note, .... help here?
>>
>> I think we have all we need due to __libc_start_main@@GLIBC_2.34.  It
>> was an unrelated change, but it helps here as well.
>
> So your patch isn't required?  Can you add some tests to verify it?

No, the patch uses the absence of GLIBC_2.34 for detecting old binaries.

We cannot use symbol versions in other ways because one key
characteristic of weak references and underlinking is the lack of
version information on the symbol itself.

Thanks,
Florian