[Discuss-gnuradio] What value is in in[noutput_items+1]?

[Ghost Op]

I was looking back over the Quadrature Demod code and I happened to
notice something unusual.  The call to the Volk multiply conjugate
routine appears to use in[noutput_items+1] on the last calculation.

Here's the call:
volk_32fc_x2_multiply_conjugate_32fc(&tmp[0], &in[1], &in[0], noutput_items);

It obviously works correctly, and the buffer's bigger than
noutput_items so it doesn't seem to cause a memory access issue.

So my question is: when volk uses the memory at in[noutput_items+1]
what value is it using?  Is it using a zeroed byte, something from a
history buffer, or whatever happened to be there?

Would anyone have any insight?

Thanks!