Re: [Swarm-Modelling] conformsTo: with Collections

[Paul Johnson]

glen e. p. ropella wrote:
> Gary Polhill wrote:
>   
> > I get a bus error in Swarm 2.2 (from CVS on 12 June 2006) when asking a
> > List if it follows the Collections protocol. In Swarm 2.1.1 it complains
> > that I've sent the request to nil! See attached perl script and
> > Makefile.
> >
> > (e.g. test_protocol.pl List Collections; ./conforms -> Bus Error;
> > test_protocol.pl Array Collections -> "Array var conforms to Collection
> > protocol")
> >     
>
> This is a address@hidden question, by the way.
>
> Marcus recently configured Swarm so that it disallowed messages to nil.
>
> All you need to do is test to see if the receiver is nil and if it is,
> don't send it a message.
>
>   
Gary was referring to the CVS as of June 12, 2006, and so I don't think 
the message to nil would crash Swarm.  Hence, there's a good chance the 
bus error is caused by sending a message to nil, that does not cause an 
error/warning, and then something is empty and fails to respond to an 
instruction.  In particular, I expect lispArchiver is not created, and 
the bus error happens when you tell a nill object to get some data.  We 
had problems with the gcc in FC5 that cause that kind of trouble.

The Swarm-2.1 stops because it did have the "message to nil" warning in 
place, and I liked it that way.  The newest Swarm is that way again.
pj

--
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504                              
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66044-3177           FAX: (785) 864-5700