Undefined use of weak symbols in gnulib

[Florian Weimer]

* Bruno Haible:

> Florian Weimer wrote on 2021-04-28:
>> However, you should really remove those weak symbol
>> hacks.  They won't have any effect for glibc 2.34
>
> I'm trying to do this now. But what is the right condition?
>
> 1) I understand that it's only for glibc >= 2.34 on Linux (NPTL),
>    right? Not on Hurd (HTL)?

Yes, Hurd hasn't been integrated.

> 2) /usr/include/gnu/lib-names.h still defines LIBPTHREAD_SO.
>    How about not defining LIBPTHREAD_SO, since linking with it is supposed
>    to be a no-op in these newer glibc versions?

I'm not sure if this is the right way, given that the file still exists
for all currently supported targets.

An alternative would be to add a macro to <pthread.h>, such as
PTHREAD_IN_LIBC.

Thanks,
Florian