fine a flag in any source-code file in your executable.
Only define a flag once!  If you want to access a flag in more than
one source file, DEFINE it in one file, and <A
HREF="#declare">DECLARE</A> it in the others.  Even better, DEFINE it
in <code>foo.cc</code> and DECLARE it in <code>foo.h</code>; then
everyone who <code>#includes foo.h</code> can use the flag.</p>

<p>
Defining flags in libraries rather than in main() is powerful, but
does have some costs. One is that a library might not have a good
def