Re: MIPSEL GLIBC sem_init() not shared

[Florian Weimer <fweimer@redhat.com>]

* Alessandro Carminati via Libc-help:

> But looking at the liba.so dependencies, I've been surprised by the
> fact that the library depends only on the main libc library
> (libc.so.6) and has no dependency on libpthread.so.0 where the actual
> sem_* symbols are implemented.
>
> $ /lib/ld-2.31.so --list /usr/lib/liba.so
>         linux-vdso.so.1 (0x7ffaa000)
>         libc.so.6 => /lib/libc.so.6 (0x77ddc000)
>         /lib/ld-2.31.so (0x77f8a000)
>
> I guess this might be related to my problem, but I have no clue how to
> link these two facts. How the liba.so could be compiled and linked
> using symbols its dependencies do not provide?

This is called underlinking.  It produces invalid objects.

> How to force the GNU linker to link against sem_init@@GLIBC_2.2
> instead of sem_init@GLIBC_2.0?

Just link with -lpthread, it will add the symbol version and call the
right function.

We are working on changes to glibc that makes it much less likely that
such underlink can happen, so hopefully such difficult-to-debug problems
will become a non-issue at some point in the future.

Thanks,
Florian