Returns the size of the current stack.
The current size of the stack, in 32 bit words (in 32-bit implementations) or 64-bit words (in 64-bit implementations).
In LispWorks 4.4 and previous on Windows and Linux platforms,
was not implemented. This is fixed in LispWorks 5.0 and later.
(current-stack-length) => 16000
LispWorks User Guide and Reference Manual - 21 Dec 2011