4 files changed, 18 insertions, 20 deletions

diff --git a/Lisp/class-definition.lisp b/Lisp/class-definition.lisp
index 118e76a..28e97dd 100644
--- a/Lisp/class-definition.lisp
+++ b/Lisp/class-definition.lisp
@@ -149,9 +149,10 @@
                                          (effective-slot-definition
                                           foreign-effective-slot-definition))
   (with-slots (foreign-name foreign-type) effective-slot-definition
-    (cffi:convert-from-foreign
-     (%objcl-slot-value (pointer-to instance) foreign-name)
-     (typespec->c-type foreign-type))))
+    ;; FIXME: Do proper value conversion here (like LOW-LEVEL-INVOKE).
+    (cffi:with-foreign-object (return-value-cell (typespec->c-type foreign-type))
+      (%objcl-get-slot-value (pointer-to instance) foreign-name return-value-cell)
+      (mem-ref return-value-cell (typespec->c-type foreign-type)))))
 
 
 (defmethod (setf c2mop:slot-value-using-class) (value
diff --git a/Lisp/libobjcl.lisp b/Lisp/libobjcl.lisp
index da85f31..727bfc5 100644
--- a/Lisp/libobjcl.lisp
+++ b/Lisp/libobjcl.lisp
@@ -104,9 +104,10 @@
   (slot-name :string)
   (value :pointer)) ; void
 
-(defcfun ("objcl_slot_value" %objcl-slot-value) :pointer
+(defcfun ("objcl_get_slot_value" %objcl-get-slot-value) :void
   (obj :pointer) ; id
-  (slot-name :string))
+  (slot-name :string)
+  (value-out :pointer))
 
 (defcfun ("objcl_class_direct_slots" %objcl-class-direct-slots) :pointer
   (class :pointer) ; Class
@@ -849,14 +850,6 @@ separating parts by hyphens works nicely in all of the `:INVERT`,
 
 
 ;;;; (@* "Slot access")
-(defun objcl-set-slot-value (instance slot-name value)
-  ;; FIXME
-  (error "To be done."))
-
-(defun objcl-slot-value (instance slot-name)
-  ;; FIXME
-  (error "To be done."))
-
 (defun objcl-slot-type (slot)
   (%objcl-slot-type slot))
 
diff --git a/Objective-C/libobjcl.h b/Objective-C/libobjcl.h
index 4b26fae..758c831 100644
--- a/Objective-C/libobjcl.h
+++ b/Objective-C/libobjcl.h
@@ -139,8 +139,8 @@ objcl_alignof_type (const char *typespec);
 void
 objcl_set_slot_value (id obj, const char *ivar_name, void *value);
 
-void *
-objcl_slot_value (id obj, const char *ivar_name);
+void
+objcl_get_slot_value (id obj, const char *ivar_name, void *value_out);
 
 /* The following function returns a freshly consed array that the caller
    must deallocate. */
diff --git a/Objective-C/libobjcl.m b/Objective-C/libobjcl.m
index cd35b86..d02e58b 100644
--- a/Objective-C/libobjcl.m
+++ b/Objective-C/libobjcl.m
@@ -487,15 +487,19 @@ objcl_set_slot_value (id obj, const char *ivar_name, void *value)
 }
 
 
-void *
-objcl_slot_value (id obj, const char *ivar_name)
+void
+objcl_get_slot_value (id obj, const char *ivar_name, void *value_out)
 {
-  void *value;
   /* Caching Ivars may be useful here.  Using those instead of strings
      is claimed to be faster. */
+
   /* For the GNU runtime, this function is defined in objc-runtime-gnu.m. */
-  object_getInstanceVariable (obj, ivar_name, &value);
-  return value;
+
+  /* NOTE: Contrary to what the official Objective-C runtime docs claim,
+     value_out is actually a (void *) rather than a (void **).
+     Likewise, the result that is copied to value_out is the slot value
+     itself, not a pointer to it. */
+  object_getInstanceVariable (obj, ivar_name, value_out);
 }