I'm using (with-thickness (5) to draw some lines, and when I compile the code (in emacs slime with C-c C-k) I get a bunch of messages that look like: ; ==> ; (SB-ALIEN-INTERNALS:%SAP-ALIEN ALIEN ; '#<SB-ALIEN-INTERNALS:ALIEN-RECORD-TYPE (STRUCT ; CL-GD::GD-IMAGE ; (CL-GD::PIXELS ; #) ; (CL-GD::SX ; #) ; (CL-GD::SY ; #) ; (CL-GD::COLORS-TOTAL ; #) ; (CL-GD::RED ..))>) ; ; note: unable to ; optimize ; because: ; could not optimize away %SAP-ALIEN: forced to do runtime ; allocation of alien-value structure ; compilation unit finished What the heck does this mean? Here's the code that causes the pain: ; This section draws the map. (require "cl-gd") (cl-gd:with-image* (*pngwidth* *pngheight*) (cl-gd:allocate-color 190 190 190) (let ((red (cl-gd:allocate-color 163 83 84)) (green (cl-gd:allocate-color 104 156 84)) (yellow (cl-gd:allocate-color 236 236 236)) (black (cl-gd:allocate-color 0 0 0))) ;; Draw all towns. (dolist (town *towns*) (cl-gd:draw-filled-circle (mapdim (getf town :lat) *pngwidth*) (mapdim (getf town :long) *pngheight*) 20 :color black) ;; Draw roads between neighboring towns. (cl-gd:with-thickness (5) (dolist (neighbor (getf town :neighbors)) (cl-gd:draw-line (mapdim (getf town :lat) *pngwidth*) (mapdim (getf town :long) *pngheight*) (mapdim (getf (town-lookup neighbor *towns*) :lat) *pngwidth*) (mapdim (getf (town-lookup neighbor *towns*) :long) *pngheight*) :color black)))) ;; Draw start town as green circle. (cl-gd:draw-filled-circle (mapdim (getf *start-town* :lat) *pngwidth*) (mapdim (getf *start-town* :long) *pngheight*) 15 :color green) ;; Fill in evaluation function's choices. (dolist (town *path*) (cl-gd:draw-filled-circle (mapdim (getf town :lat) *pngwidth*) (mapdim (getf town :long) *pngheight*) 15 :color yellow)) ;; Draw goal town as red circle. (cl-gd:draw-filled-circle (mapdim (getf *goal-town* :lat) *pngwidth*) (mapdim (getf *goal-town* :long) *pngheight*) 15 :color red)) (cl-gd:write-image-to-file "/var/www/website/draw1.png" :compression-level 6 :if-exists :supersede)) Thanks for the help.