Memory management routines are provided for runtime consistency on operating systems with shared libraries and multiple runtimes.
One problem with just printing the error code to the user is that frequently the context behind the error has been lost. For example if KIM is trying to obtain credentials via referrals, it may fail partway through the process. In this case the error code will be KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN, which maps to "Client not found in Kerberos database". Unfortunately this error isn't terribly helpful because it doesn't tell the user whether they typoed their principal name or if referrals failed.
To avoid this problem, KIM maintains an explanatory string for the last error seen in each thread calling into KIM. If a caller wishes to display an error to the user, immediately after getting the error the caller should call kim_string_create_for_last_error() to obtain a copy of the descriptive error message.
See KIM String Reference Documentation for information on specific APIs.