example

int
#ifdef HAVE_FEATURE
thing(int args)
#else
other_thing(int args)
#endif
{
    do_things();

#ifdef HAVE_FEATURE
    do_feature_things();
#else
    do_workaround_things();
#endif

    do_more_things();
    return whatever;
}

int main() {
#ifdef HAVE_FEATURE
    thing(7);
#else
    other_thing(7);
#endif

    return 0;
}