When --enable-debug (CWDEBUG_DEBUG) is enabled, this turns on a lot of extra debugging output concerning the internal state of libcwd, and when --enable-alloc (CWDEBUG_ALLOC) is enabled, about internal allocations of libcwd. This will not be usefull to you unless you manage to let the program coredump even before it reaches main().
Never, unless you are a developer of libcwd.
This is disabled by default. Use configure –enable-debug-output to enable it.