The function foreign-array-dimensions
takes a FLI array, a pointer to a FLI array or the name of a FLI array type as its argument and returns a list containing the dimensions of the array.
In the following example an instance of a 3 by 4 array is created, and these dimensions are returned using the foreign-array-dimensions
function.
(setq array1 (fli:allocate-foreign-object
:type '(:c-array :int 3 4)))
(fli:foreign-array-dimensions array1)
LispWorks Foreign Language Interface User Guide and Reference Manual - 29 Sep 2017