1(stack grows down, the usual case) or
-1(stack grows up).
sizewill be returned as
NA, and stack-checking is not performed.
The information on the stack base address is thought to be accurate on
Windows, Linux (using
glibc), OS X and FreeBSD but a heuristic
is used on other platforms. Because this might be slightly
inaccurate, the current usage could be estimated as negative. (The
heuristic is not used on embedded uses of R on platforms where the
stack base information is not thought to be accurate.)
The evaluation depth is the number of nested R expressions
currently under evaluation: this has a limit controlled by