(defun get-cols-example ()
  (let* ((matrix (create-mat 5 7 +8uc1+))
     (submat (foreign-alloc `(:struct cv-mat)
                :initial-contents '())))
   (get-cols matrix submat 0 3)
    (foreign-free submat)))

when i run the above code with the (get-cols matrix submat 0 3) line commented or without foreign-free  it runs fine but as it is above i get below error

 Error in `/usr/bin/sbcl': free(): invalid next size (fast): 0x00007fffd4000c60 ***

in inferior lisp followed by many lines of code las below. All the fuinctions in the defun above are neccessary to reproduce issue:

======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x80996)[0x7ffff7154996]
[0x100681f7b8]
======= Memory map: ========
00400000-00435000 r-xp 00000000 08:03 135423                             /usr/bin/sbcl
00635000-00636000 r-xp 00035000 08:03 135423                             /usr/bin/sbcl
00636000-00648000 rwxp 00036000 08:03 135423                             /usr/bin/sbcl

I dont have any foreign-free functions in my  wrappers and the functions involved GET-COLS and CREATE-MAT  are wrappers for OpenCV's cvGetCols and cvCreateMat...the wrappers are below for debugging purpose

;; CvMat* cvGetCols(const CvArr* arr, CvMat* submat, int start_col, int end_col)
(defcfun ("cvGetCols" get-cols) (:pointer (:struct cv-mat))
  "Returns array column span."
  (arr cv-arr)
  (submat (:pointer (:struct cv-mat)))
  (start-col :int)
  (end-col :int))

;; CvMat* cvCreateMat(int rows, int cols, int type)
(defcfun ("cvCreateMat" create-mat) (:pointer (:struct cv-mat))
  (rows :int)
  (cols :int)
  (type :int))

any way i can help debug this i will and any guidance on this issue is much appreciated =)