-(defconstant +size-of-short+ 2)
-(defconstant +size-of-int+ 4)
-(defconstant +size-of-long+ 4)
-(defconstant +size-of-pointer+ 4)
-(defconstant +size-of-float+ 4)
-(defconstant +size-of-double+ 8)
+(defconstant +size-of-short+
+ #+sbcl (sb-sizeof 'sb-alien:short)
+ #-sbcl 2)
+(defconstant +size-of-int+
+ #+sbcl (sb-sizeof 'sb-alien:int)
+ #-sbcl 4)
+(defconstant +size-of-long+
+ #+sbcl (sb-sizeof 'sb-alien:long)
+ #-sbcl 4)
+(defconstant +size-of-pointer+
+ #+sbcl (sb-sizeof 'sb-alien:system-area-pointer)
+ #-sbcl 4)
+(defconstant +size-of-float+
+ #+sbcl (sb-sizeof 'sb-alien:float)
+ #-sbcl 4)
+(defconstant +size-of-double+
+ #+sbcl (sb-sizeof 'sb-alien:double)
+ #-sbcl 8)
+