Are there versions of parent.frame or sys.calls or other general context functions that can be called directly from C code invoked by .Call? Looking around the Rinternals.h, etc, I can't seem to find anything of the sort. The best I can come up with is something like:
my_fun <- function(x) {
.Call(my_fun_C, substitute(x), parent.frame(), sys.calls())
}
but ideally I'd prefer to avoid the R calls to substitute, parent.frame, etc. and do those directly from C. Why? Each of those function calls adds 300ns to the evaluation of my_fun, and while that isn't exactly going to kill me, I'd like to know if there is a way to avoid it or if I'm stuck with the above.
There is this tantalizing tidbit of code from main/context.c in the function do_sys:
RCNTXT *cptr;
cptr = R_GlobalContext;
t = cptr->sysparent;
but RCNTXT is defined in includes/Defn.h, and Defn.h looks to be an internal non-exported header.
