thanks mark,

> At present the optimisation flags such as -O3 only need to be
> specified when compilation (rather than linking) is occurring.  So if
> your link command only lists previously-compiled files, there is no
> need to specify such options.

my question was more: let's say i want the best possible performance.
can i make sure that the precompiled library i am linking with is using
-O3 ? does that make sense?