@subheading idna_strerror
@anchor{idna_strerror}
@deftypefun {const char *} {idna_strerror} (Idna_rc @var{rc})
@var{rc}: an @code{Idna_rc}  return code.

Convert a return code integer to a text string.  This string can be
used to output a diagnostic message to the user.

@strong{IDNA_SUCCESS:} Successful operation.  This value is guaranteed to
always be zero, the remaining ones are only guaranteed to hold
non-zero values, for logical comparison purposes.

@strong{IDNA_STRINGPREP_ERROR:} Error during string preparation.

@strong{IDNA_PUNYCODE_ERROR:} Error during punycode operation.

@strong{IDNA_CONTAINS_NON_LDH:} For IDNA_USE_STD3_ASCII_RULES, indicate that
the string contains non-LDH ASCII characters.

@strong{IDNA_CONTAINS_MINUS:} For IDNA_USE_STD3_ASCII_RULES, indicate that
the string contains a leading or trailing hyphen-minus (U+002D).

@strong{IDNA_INVALID_LENGTH:} The final output string is not within the
(inclusive) range 1 to 63 characters.

@strong{IDNA_NO_ACE_PREFIX:} The string does not contain the ACE prefix
(for ToUnicode).

@strong{IDNA_ROUNDTRIP_VERIFY_ERROR:} The ToASCII operation on output
string does not equal the input.

@strong{IDNA_CONTAINS_ACE_PREFIX:} The input contains the ACE prefix (for
ToASCII).

@strong{IDNA_ICONV_ERROR:} Character encoding conversion error.

@strong{IDNA_MALLOC_ERROR:} Could not allocate buffer (this is typically a
fatal error).

@strong{IDNA_DLOPEN_ERROR:} Could not dlopen the libcidn DSO (only used
internally in libc).

Return value: Returns a pointer to a statically allocated string
containing a description of the error with the return code  @code{rc} .
@end deftypefun

