Re: [Swarm-Support] arborgamesII test fail on Fedora 5

[Bill Northcott]

On 30/01/2007, at 3:15 AM, Paul Johnson wrote:

> > worked fine. When I ran arborgames, I got following messages.
> > << In Batch mode >>
> > Nil receiver for step
> > Arboted
> Yes, it is due to new tightness in gcc checking for messages to nil.

Just to avoid confusion, this is nothing to do with gcc old or new.

The Objective-C language specification allows messages to nil and  
does not regard them as errors.  Indeed it is a widely used technique  
in GUI programming.

However, in Swarm models, a message to nil is generally an error.  So  
in the Swarm runtime they are treated as errors.  This behaviour  
varies between versions of Swarm and my change in the future.  The  
moral is that if it matters that the object you are messaging exists,  
you need to check that it does in the way Paul suggested.

Bill Northcott