Not sure whether this is a bug, or I don't have a required library set up. Whenever I try to do (with-image-from file (img "/my/image/path.jpg") (image-size img)) I get an UNDEFINED-ALIEN-FUNCTION-ERROR trace follows Attempt to call an undefined alien function. [Condition of type SB-KERNEL::UNDEFINED-ALIEN-FUNCTION-ERROR] Restarts: 0: [RETRY] Retry SLIME REPL evaluation request. 1: [*ABORT] Return to SLIME's top level. 2: [TERMINATE-THREAD] Terminate this thread (#<THREAD "repl-thread" RUNNING {10032E9BA1}>) Backtrace: 0: (SB-KERNEL::UNDEFINED-ALIEN-FUNCTION-ERROR) 1: ("foreign function: #x422520") 2: (GD-IMAGE-CREATE-FROM-JPEG-FILE "/my/image.path.jpg" #<SB-ALIEN-INTERNALS:ALIEN-VALUE :SAP #X7FFFF37AFFF0 :TYPE (* (SB-ALIEN:SIGNED 32))>) 3: (CREATE-IMAGE-FROM-FILE #<unavailable argument> NIL) 4: ((LAMBDA ())) 5: (SB-INT:SIMPLE-EVAL-IN-LEXENV ..) 6: (SWANK::EVAL-REGION "(with-image-from-file (img \"/my/image.path.jpg\")\n (image-size img))\n") 7: ((LAMBDA ())) 8: (SWANK::TRACK-PACKAGE #<CLOSURE (LAMBDA #) {1004B732C9}>) 9: (SWANK::CALL-WITH-RETRY-RESTART "Retry SLIME REPL evaluation request." #<CLOSURE (LAMBDA #) {1004B731E9}>) 10: (SWANK::CALL-WITH-BUFFER-SYNTAX NIL #<CLOSURE (LAMBDA #) {1004B731B9}>) 11: (SWANK::REPL-EVAL "(with-image-from-file (img \"/my/image.path.jpg\")\n (image-size img))\n") 12: (SB-INT:SIMPLE-EVAL-IN-LEXENV (SWANK:LISTENER-EVAL "(with-image-from-file (img \"/my/image.path.jpg\")\n (image-size img))\n") #<NULL-LEXENV>) 13: (SWANK::EVAL-FOR-EMACS (SWANK:LISTENER-EVAL "(with-image-from-file (img \"/my/image.path.jpg\")\n (image-size img))\n") "CL-GD" 172) 14: (SWANK::PROCESS-REQUESTS NIL) 15: ((LAMBDA ())) 16: ((LAMBDA ())) 17: (SWANK-BACKEND::CALL-WITH-BREAK-HOOK #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA #) {10032F3139}>) 18: ((FLET SWANK-BACKEND:CALL-WITH-DEBUGGER-HOOK) #<FUNCTION SWANK:SWANK-DEBUGGER-HOOK> #<CLOSURE (LAMBDA #) {10032F3139}>) 19: (SWANK::CALL-WITH-BINDINGS ((*STANDARD-OUTPUT* . #) (*STANDARD-INPUT* . #) (*TRACE-OUTPUT* . #) (*ERROR-OUTPUT* . #) (*DEBUG-IO* . #) (*QUERY-IO* . #) ...) #<CLOSURE (LAMBDA #) {10032F3159}>) 20: (SWANK::HANDLE-REQUESTS #<SWANK::CONNECTION {1002E87B91}> NIL) 21: (SWANK::CALL-WITH-BINDINGS NIL #<CLOSURE (LAMBDA #) {10032F30F9}>) 22: ((FLET #:WITHOUT-INTERRUPTS-BODY-[BLOCK369]374)) 23: ((FLET SB-THREAD::WITH-MUTEX-THUNK)) 24: ((FLET #:WITHOUT-INTERRUPTS-BODY-[CALL-WITH-MUTEX]300)) 25: (SB-THREAD::CALL-WITH-MUTEX ..) 26: (SB-THREAD::INITIAL-THREAD-FUNCTION) 27: ("foreign function: #x422520") 28: ("foreign function: #x419227") I've tried it running SBCL 1.0.40 from the Debian repos, as well as 1.0.52 from the official SBCL site. I'm using the copy of cl-gb from the latest quicklisp release, and I've tried it on both a 32 bit and 64 bit system (the included stack trace is from the 64-bit SBCL 1.0.40). Any ideas?