How do I clean up "might not be defined" wrnings?

[Eric S. Raymond]

I've started a significant refactoring and simplification of the VC
code. This has involved moving functions to different files, which
is causing "functions might not be defined" warnings.

What is the approved way to prevent these or clean them up?
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>

In recent years it has been suggested that the Second Amendment
protects the "collective" right of states to maintain militias, while
it does not protect the right of "the people" to keep and bear arms.
If anyone entertained this notion in the period during which the
Constitution and the Bill of Rights were debated and ratified, it
remains one of the most closely guarded secrets of the eighteenth
century, for no known writing surviving from the period between 1787
and 1791 states such a thesis.
        -- Stephen P. Halbrook, "That Every Man Be Armed", 1984