The macros GSS_CALLING_ERROR(), GSS_ROUTINE_ERROR() and GSS_SUPPLEMENTARY_INFO() are provided, each of which takes a GSS status code and removes all but the relevant field. For example, the value obtained by applying GSS_ROUTINE_ERROR() to a status code removes the calling errors and supplementary information fields, leaving only the routine errors field. The values delivered by these macros can be directly compared with a GSS_S_xxx symbol of the appropriate type. The macro GSS_ERROR() is also provided, which when applied to a GSS–API status code returns a non-zero value if the status code indicated a calling or routine error, and a zero value otherwise. All macros defined by the GSS-API evaluate their argument(s) exactly once.