Re: -rpath with libtool and Debian Linux

[Richard Braakman <dark@xs4all.nl>]

Alexandre Oliva wrote:
> ld.so is trying to outsmart everybody, but it is not smart enough to
> do it.  When you moved libc5-compatible libraries from /usr/lib to
> /usr/lib/libc5, you established a rule that, if any program was linked 
> with libc5, it should look for libraries in /usr/lib/libc5 first,
> right?  Then why doesn't ld.so follow this rule, by replacing /usr/lib 
> with /usr/lib/libc5 when it finds this directory in the rpath too?

No, that's not how it works.  To the best of my understanding, it works
by adding a "libc5 or libc6" field to its cache.  When it looks for
a cached library, and it finds two entries, it picks the one with the
correct libc.  It always searches all of its directories.

It allows -rpath and LD_LIBRARY_PATH to override this behaviour.
I think that that is correct -- these _are_ overrides.  They're
to be used when the default behaviour gets things wrong.

I think the dynamic linker could be further changed to always ignore a
library that would introduce a mixed libc5/libc6 linkage.  That would
give the correct behaviour even with these overrides.

However, that only solves the _previous_ problem, not any future ones.
A general solution would require that "soname" be split into a library
name and a major version, so that the dynamic linker can detect
incompatible versions of the same library.  That would be a major change.

Richard Braakman