sasl_errstring man page
sasl_errstring — Translate a SASL return code to a human-readable form
#include <sasl/sasl.h> const char * sasl_errstring(int saslerr, const char * langlist, const char ** outlang);
sasl_usererr is called to convert a SASL return code (an integer) into a human readable string. At this time the only language available is american english written by programmers (aka gobbledygook). Note that a server should call sasl_usererr on a return code first if the string is going to be sent to the client.
saslerr specifies the error number to convert.
langlist is currently unused; Use NULL.
outlang specifies the desired RFC 1766 language for output. NULL defaults to "en-us," currently the only supported language.
It should be noted that this function is not the recommended means of extracting error code information from SASL, instead application should use sasl_errdetail(3), which contains this information (and more)
Returns the string. If langlist is NULL, US-ASCII is used.
sasl(3), sasl_errdetail(3), sasl_errors(3)