Convert a return code integer to a text string. This string can be
used to output a diagnostic message to the user.
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.
IDNA_STRINGPREP_ERROR
Error during string preparation.
IDNA_PUNYCODE_ERROR
Error during punycode operation.
IDNA_CONTAINS_NON_LDH
For IDNA_USE_STD3_ASCII_RULES, indicate that
the string contains non-LDH ASCII characters.
IDNA_CONTAINS_MINUS
For IDNA_USE_STD3_ASCII_RULES, indicate that
the string contains a leading or trailing hyphen-minus (U+002D).
IDNA_INVALID_LENGTH
The final output string is not within the
(inclusive) range 1 to 63 characters.
IDNA_NO_ACE_PREFIX
The string does not contain the ACE prefix
(for ToUnicode).
IDNA_ROUNDTRIP_VERIFY_ERROR
The ToASCII operation on output
string does not equal the input.
IDNA_CONTAINS_ACE_PREFIX
The input contains the ACE prefix (for
ToASCII).
IDNA_ICONV_ERROR
Could not convert string in locale encoding.
IDNA_MALLOC_ERROR
Could not allocate buffer (this is typically a
fatal error).
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 rc.
