You need only check function returns for errors that set run-time errors. All development errors are reported to you automatically when using the development libraries and the VCS error reporting system. Coding an explicit check to detect this type of error is not necessary. When using the VCS error reporting system, any error detected by wn_dn() will be automatically reported to you.
An error check is made on wn_up() because wn_up() allocates memory and will fail if there is insufficient memory. This is a runtime error.
