Dumb linker/loader question

[walt]

Context:  I told Joerg I would work on a port override for the
ksysguard component of  kdebase3.  As expected, I'm running up
against my own ignorance of how the dynamic library system works.

I've modified the C code in ksysguard to use kinfo.h instead of
dkstat.h (per Joerg's instructions).  The modified code compiles
and installs without error.

What mystifies me is that the installed program is *not* linked
against the necessary libkinfo.so.  The reason is no mystery:
I never modified any Makefile or linker flags which would do
the necessary linking.

The mystery (to me, at least) is why the whole build completes
*without* libkinfo (???)

I'm clearly lacking some basic understanding of how this whole
thing works.  How can code that uses the header files from a
library compile *and* link successfully without that library?

(Assume I know nothing, which seems to be the case :o)

Thanks!