cross version development

[Gail Bowman]

I've never done it on linux, but I did do this on VMS.  What we did
was to run the latest versions of an OS, but for each OS version (as we 
upgraded) we made a directory for the system libraries (shared 
libraries) that we linked against.
You can get this list be looking at the map files.  Then
when we built the product we redirected the build (LD_LIBRARY_PATH) to
link against these older libraries first.  Voila - we developed on the 
latest OS, but
built against the older OS.   We did eventually test on earlier 
versions before
shipping, but we never had a problem due to this.

As release engineer it was my job to keep track of the library 
dependencies.
If a new dependency appeared, then I would determine whether or not that
library existed in the oldest OS version we intended to support and 
what the version was.
If it didn't then I'd talk to the developer and development manager to 
understand the
impact of this.   So I would keep something like the output from the 
ldd command
under source code control and regenerate it as part of the build.

Hope this helps,
Gail