pg_do_encoding_conversion glitch

I have a question about the result contract of pg_do_encoding_conversion().
It can receive non null-terminated string because its arguments are
a char array and a byte length.
And it only returns a string, so the string should be null-terminated.

However, if conversions are not required, the function returns
the input string itself even though it might be not null-terminated.

I checked usages of pg_do_encoding_conversion() and xml_parse()
could cause troubles. Is it a bug? needed to be fixed?

---- [utils/mb/mbutils.c]
unsigned char *
pg_do_encoding_conversion(unsigned char *src, int len,
int src_encoding, int dest_encoding)
{
...
if (src_encoding == dest_encoding)
return src;
----

---- [utils/adt/xml.c]
static xmlDocPtr
xml_parse(text *data, XmlOptionType xmloption_arg, bool preserve_whitespace,
xmlChar * encoding)
{
...
len = VARSIZE(data) - VARHDRSZ; /* will be useful later */
string = xml_text2xmlChar(data);

utf8string = pg_do_encoding_conversion(string,
len,
encoding ?
xmlChar_to_encoding(encoding) :
[It could be UTF8 to UTF8] --> GetDatabaseEncoding(),
PG_UTF8);
----

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center