Pardon the question concerning lispbuilder-sdl in this list, but I have a feeling more developers here use lispbuilder-sdl and cl-openl in combination and I may have a better chance of having this question answered. The set-gl-attribute command in lispbuilder-sdl breaks when using SBCL in Windows 7 or OS X. This command is most often used to set doublebuffer mode; as shown below; (sdl:set-gl-attribute :SDL-GL-DOUBLEBUFFER 1) Is there a way to set the OpenGL attributes using cl-opengl, and if there is, does this work on Windows 7 and OS X? I'm trying to determine if this is a lispbuilder-sdl problem, a SDL problem, or a CFFI problem In SBCL: * (sdl:with-init () (sdl:set-gl-attribute :sdl-gl-doublebuffer 1)) debugger invoked on a SIMPLE-ERROR: EXCEPTION_ACCESS_VIOLATION Type HELP for debugger help, or (SB-EXT:QUIT) to exit from SBCL. restarts (invokable by number or by possibly-abbreviated name): 0: [ABORT] Exit debugger, returning to top level. ("bogus stack frame") And in OS X; CORRUPTION WARNING in SBCL pid 69894(tid 2693764352): Memory fault at 17c (pc=0x8654d, sp=0x11ffa80) The integrity of this image is possibly compromised. Continuing with fingers crossed. debugger invoked on a SB-SYS:MEMORY-FAULT-ERROR in thread #<THREAD "initial thread" RUNNING {119BEB99}>: Unhandled memory fault at #x17C. Thanks, - Luke