How does versioning work (was: Bug mixing old sem_wait and new pthread_cond_broadcast)

[Erland Lewin]

I wrote:
> 
> |> Hello,
> |>
> |> I think there is a bug in linuxthreads, when the same thread uses
> |> pthread calls from both the old calls and new calls (for instance, when
> |> one library was made with an older glibc).
 
Andreas Schwab replied:
> You can't do that.  If you compile an application you must make sure all
> dependent libraries were compiled against the same version of glibc.  We
> only guarantee run time compatibility, but not link time compatibility.

Thanks for the clarification. Perhaps this should be pointed out in the
documentation (or did I miss it?).
  Wow. So that means, for instance, that I have to recompile X-windows
and all dependent libraries on my system if I want to program graphical
applications? That really makes upgrading glibc an enormous task. 

But ok. I'm now trying to recompile all relevant libraries on my system,
but I find it difficult to understand how the versioning works.
  For example, I tried to recompile a new version of glib (from gtk)
from scratch.
  However, when I do (on the newly compiled libglib):

> ldd -v /usr/lib/libglib-1.2.so.0.0.9
        libc.so.6 => /lib/libc.so.6 (0x40033000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x2aaaa000)

        Version information:
        /usr/lib/libglib-1.2.so.0.0.9:
                libc.so.6 (GLIBC_2.1.2) => /lib/libc.so.6
                libc.so.6 (GLIBC_2.0) => /lib/libc.so.6
        /lib/libc.so.6:
                ld-linux.so.2 (GLIBC_2.1.1) => /lib/ld-linux.so.2
                ld-linux.so.2 (GLIBC_2.1) => /lib/ld-linux.so.2
                ld-linux.so.2 (GLIBC_2.2) => /lib/ld-linux.so.2
                ld-linux.so.2 (GLIBC_2.0) => /lib/ld-linux.so.2

I was expecting to see libc.so.6 (GLIBC_2.2) under the version
information for libglib-1.2.so.0.0.9. How should this look?
  Is there any documentation on how the output from ldd -v should be
interpreted?
  Why is it not there?
  Is the library not linked against the latest GLIBC?
  Why are two versions of libc.so.6 listed under libglib-1.2.so.0.0.9? 
  How does the system determine which versions are required for a given
library?
  Can I get the linker to warn if inconsistent glibc versions are used
in a binary/shared library?

  Thankful for any enlightenments you can offer,

    Erland