BUG #14984: function "heap_tuple_from_minimal_tuple" lost HeapTupleHeader->t_len value

The following bug has been logged on the website:

Bug reference: 14984
Logged by: bucoo hsiao
Email address: bucoo(at)sohu(dot)com
PostgreSQL version: 10.1
Operating system: all
Description:

HeapTuple
heap_tuple_from_minimal_tuple(MinimalTuple mtup)
{
HeapTuple result;
uint32 len = mtup->t_len + MINIMAL_TUPLE_OFFSET;

result = (HeapTuple) palloc(HEAPTUPLESIZE + len);
result->t_len = len;
ItemPointerSetInvalid(&(result->t_self));
result->t_tableOid = InvalidOid;
result->t_data = (HeapTupleHeader) ((char *) result + HEAPTUPLESIZE);
memcpy((char *) result->t_data + MINIMAL_TUPLE_OFFSET, mtup,
mtup->t_len);
memset(result->t_data, 0, offsetof(HeapTupleHeaderData, t_infomask2));
/* when memset return, result->t_data->t_len value lost
should append code:
HeapTupleHeaderSetDatumLength(result->t_data, len);
*/
return result;
}