dynamic array output by .C

Greetings,

I am building a stochastic simulation model in a C++ shared library
for R. My model will generate a random number of new observations and
also delete some old observations, however, the numbers cannot be
predicted before the computation engine runs. For simplicity, I am
trying to control my programming at the second stage (pure C++ for R).
It seems .C accepts fixed size of arrays as input (also ouput), can I
modify size of array for deleting old and adding new observations in
.C?
Thanks in advance.

I am Tib, not Rob.