substr() - copying or not copying, that is here the question.

In the context   p=index(substr(t,s),r)
it would not be necessary to copy the substr(t,s),
the index() function could operate on the original
using some access "descriptor" (say, a pointer and
a length) in read-only mode.

Will (GNU) Awk do a copy of the data value or does
it use a read-only descriptor access to the already
existing substring of variable "t"?

Currently I'm playing with some huge data and copies
of MB sized data is costly (if it's repeatedly done
with various substr() subscripts).

Janis