prod and F90 product

Hi,
I'm having strange differences between the R function prod ad the F90 function product.
Processing the same vector C (see attachment). I get 2 different results:
prod(C) = 1.069678e-307
testProduct(C) = 0

where testProd is the following wrapping function:

testProd <- function(x) {
   return(.Fortran('testProd', as.double(x), as.double(0), as.double(0), as.integer(length(x))))
}

subroutine testProd(x, p, q,  n)
   implicit none
   integer, intent (in) :: n
   double precision, intent (in) :: x(n)
   double precision, intent (out) :: p
   double precision, intent (out) :: q
   integer :: i

   p = product(x)
   q=1
   do i = 1, n
       q = q*x(i)
   end do
end subroutine testProd

I check the lowest possible number and seems to be the same for both R and F90.
Can anyone help me understanding this behaviour?
Thank you in advance
Regards,
Filippo

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