If the parameter is passed by reference (e.g., Pascal
parameters), then the symbol descriptor is ‘v’ if it is in the
argument list, or ‘a’ if it in a register. Other than the fact
that these contain the address of the parameter rather than the
parameter itself, they are identical to ‘p’ and ‘R’,
respectively. I believe ‘a’ is an AIX invention; ‘v’ is
supported by all stabs-using systems as far as I know.