here is the way CvMemStorage is defined typedef struct CvMemStorage {     int signature;     CvMemBlock* bottom;           /* First allocated block.                   */     CvMemBlock* top;              /* Current memory block - top of the stack. */     struct  CvMemStorage* parent; /* We get new blocks from parent as needed. */     int block_size;               /* Block size.                              */     int free_space;               /* Remaining free space in current block.   */ } CvMemStorage; bu i get unknown CFFI type: (:STRUCT CV-MEM-STORAGE).    [Condition of type SIMPLE-ERROR] when i wrap like this....i know lisp is known for recursion how do i bypass this (defcstruct cv-mem-storage     (signature :int)     (bottom (:pointer (:struct cv-mem-block)))     (top (:pointer (:struct cv-mem-block)))     (parent (:pointer (:struct cv-mem-storage)))     (block-size :int)     (free-space :int))