I'm getting an error when loading a function that contains an atomic operation. As a simple example, the file test.lisp contains:
(defparameter *count* 0)
(defun test ()
(sb-ext:atomic-incf *count*))
which generates the following error:
* (load "d:\\test.lisp")
; file: d:/test.lisp
; in: DEFUN TEST
; (ATOMIC-INCF *COUNT*)
;
; caught ERROR:
; during macroexpansion of (ATOMIC-INCF *COUNT*). Use *BREAK-ON-SIGNALS* to
; intercept.
;
; Invalid first argument to ATOMIC-INCF: *COUNT*
;
; compilation unit finished
; caught 1 ERROR condition
T
*
Why is *count* invalid?
From the docstring:
PLACE must access one of the following:
- a DEFSTRUCT slot with declared type (UNSIGNED-BYTE 64)
or AREF of a (SIMPLE-ARRAY (UNSIGNED-BYTE 64) (*))
The type SB-EXT:WORD can be used for these purposes.
- CAR or CDR (respectively FIRST or REST) of a CONS.
- a variable defined using DEFGLOBAL with a proclaimed type of FIXNUM.
Macroexpansion is performed on PLACE before expanding ATOMIC-INCF.
I suspect these are in place to avoid runtime checks when doing compare-and-swap.