rtld enhancement to add osversion sub-directory search

[Brooks Davis]

On Thu, Feb 12, 2009 at 07:19:35PM -0500, David Schultz wrote:
> On Thu, Feb 12, 2009, Doug Ambrisko wrote:
> > Kostik Belousov writes:
> > | There is a popular feature, unfortunately, not supported by FreeBSD
> > | ld.so, called Dynamic String Tokens, see
> > | http://docs.sun.com/app/docs/doc/817-1984/appendixc-4?l=en&a=view
> > | 
> > | I have almost abandoned patch that adds support for $ORIGIN, $OSREL,
> > | $OSNAME, and $PLATFORM. Quite amazingly, it merged with today CURRENT
> > | without serious conflicts.
> > | http://people.freebsd.org/~kib/misc/rtld_locks.4.patch
> > 
> > That is an interesting feature, however, it almost seems backwards for
> > me if I understand it correctly.  I need old binaries to find the library 
> > it was built with and not new ones based on the base OS.  The plus that 
> > I see with their feature is for a library that has been optimized for a 
> > specific type of CPU etc.
> 
> The Solaris rtld features are very useful when you want to
> export a volume with a bunch of apps over NFS, and the clients are
> running different releases or different architectures. It can
> probably also solve your problem if you bother to place different
> library versions in different directories and set your library
> path appropriately.
> 
> As you mention, it's also useful for optimization; people who
> install binary releases don't need to tolerate libraries that have
> been compiled to run on an 80486 DX.

In principle this would allow numeric libraries like ATLAS to be
compiled for all the microarchitectures on a heterogeneous cluster.
That could have a major impact on some applications.

-- Brooks
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