[Sbcl-help] Need help with with-alien

[Richard R. <rr...@ms...>]

Could someone please explain?

* (defvar z 12)

Z
* (with-alien((buf (array unsigned-char z))) buf)

debugger invoked on a SIMPLE-ERROR in thread
#<THREAD "initial thread" {A91C3A9}>:
   The first dimension is not a non-negative fixnum or NIL: Z

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.

(SB-ALIEN::ALIEN-ARRAY-TYPE-TRANSLATOR (ARRAY UNSIGNED-CHAR Z) 
#<NULL-LEXENV>)
0]


Why an I not able to use a variable here?

Thanks
Richard