How to get top-level library installed in lib/gcc-lib/...?

[Joe Buck]

>  > You've just made programs which use libstdc++ (any C++ program) rely
>  > on being able to find libsubdir/libstdc++.so at runtime.  ANd if your
>  > sysadmin updates compilers and wipes out the old version, then your
>  > programs will be unable to find the right libstdc++.so and will not
>  > run.
> 
> I even agree with this. But, imagine the other way round: You've just
> installed a new snapshot, which simply overwrites any existing egcs
> release's or other snapshot's libs; unfortunately, the new lib's
> interfaces have changed :-( What gives? The programs won't start,
> either, or even worse, they'll start but won't work as they should.

This is not a problem in practice.  When building a snapshot, you choose a
value for --prefix (or accept the default, /usr/local).  This can be set
to anything; this suffices to make sure that libraries from the snapshot
don't override your release's libs or a previous snapshot's libs.

It's a very bad idea to put shared libraries in libsubdir.