[cells-devel] Cells: Why am I put in the debugger here ?

[Kenneth Tilton]

Frank Goenninger wrote:
> Hi !
> 
> I have:
> 
> (defmd color ()
>   red
>   green
>   blue
>   alpha
>   foreign-object
> 
>   :md-name (gensym "CELLO-COLOR-")
>   :red     (c-in 0)
>   :green   (c-in 0)
>   :blue    (c-in 0)
>   :alpha   (c-in 0)
>   :foreign-object (c? (progn
>                         (when (and (^foreign-object)

use .cache to get the current value of the same cell a rule mediates. 
going through the normal slot accessor establishes a dependency of the 
cell on itself. Not good. Leads specifically to....


>                                    (not (null-pointer-p 
> (^foreign-object))))
>                           (foreign-free (^foreign-object)))
>                         (let ((fo (foreign-alloc :float :count 4)))
>                           (when (not (null-pointer-p fo))
>                             (progn
>                                (setf (mem-aref fo :float 0)
>                                     (/ (^red) 255.00000000000f0))
>                                (setf (mem-aref fo :float 1)
>                                      (/ (^green) 255.0000000000f0))
>                                (setf (mem-aref fo :float 2)
>                                      (/ (^blue) 255.0000000000f0))
>                                (setf (mem-aref fo :float 3)
>                                      (/ (^alpha) 255.0000000000f0))))))))
> 
> So far so good. Compiling this works ok. Now I do:
> 
> CL-USER> (make-instance 'cnx::color :red 255 :green 128 :blue 0 :alpha 0)
> 
> A NEW CELLS::C-DEPENDENT struct @ #x10c95502 = <...>
>    0 Class --------> #<STRUCTURE-CLASS CELLS::C-DEPENDENT>
>    1 MODEL --------> CELLO-COLOR-12992
>    2 SLOT-NAME ----> The symbol CNX::FOREIGN-OBJECT
>    3 VALUE --------> The symbol NIL
>    4 INPUTP -------> The symbol NIL
>    5 SYNAPTIC -----> The symbol NIL
>    6 CALLER-STORE -> (NIL), a proper list with 1 element
>    7 STATE --------> The symbol :AWAKE
>    8 VALUE-STATE --> The symbol :UNEVALUATED
>    9 PULSE --------> fixnum 0 [#x00000000]
>   10 PULSE-LAST-CHANGED -> fixnum 0 [#x00000000]
>   11 PULSE-OBSERVED -> fixnum 0 [#x00000000]
>   12 LAZY ---------> The symbol NIL
>   13 OPTIMIZE -----> The symbol T
>   14 DEBUG --------> The symbol NIL
>   15 MD-INFO ------> The symbol NIL
>   16 CODE ---------> ((PROGN ...)), a proper list with 1 element
>   17 RULE ---------> #<Function (:INTERNAL
>                                  (MOP:CLASS-DEFAULT-INITARGS
>                                   CNX::COLOR
>                                   :FOREIGN-OBJECT)
>                                  0)
>                        @ #x10cb44ca>
>   18 USEDS --------> The symbol NIL
>   19 USAGE --------> A simple-bit-vector (16) #*0000000000000000
> [Current process: new-repl-thread]
> [1i] CL-USER(1):
> 
> The only way out is a :reset - not good. What I am doing wrong ? (This 
> is on AllegroCL 8.1).

Actually, the above does not show a problem. "Only way out" of what? 
Possibly just printing the thing, since without *print-circle* set you 
will get into an infinite recursion when the cell lists its dependencies 
which include itself.

hth, kt