Re: Project Center segfault and nil objects

[Richard Frith-Macdonald]

On 2005-06-24 07:10:57 +0100 Duncan Anker <danker@server101.com> wrote:

> I was of the belief that it is legal to send messages to nil in Objective 
> C, 
> and nothing would happen. This is supposed to be one of the benefits of it 
> after all, not having to check every object before sending a message. 

That is correct ... however, it's really only true for methods which return 
objects (in practice, also for pointers and scalar return types).  If the 
compiler expects the method to return a structure or floating point number, 
there are different conventions for how the return value is handled, and 
this can cause problems when the message to nil tries to return nil.

> Given 
> that assumption is true then, is it possible that nil has a different value 
> between the Project Center support libraries and the Objective C runtime?

No ... I don't see how that could be.

I think you probably need to compile everything with debug enabled, and run 
under gdb to catch exactly what is happening and how it gets to that point, 
as I've not seen a problem with return type of a message to nil causing a 
crash in objc_msg_lookup, and it's not clear how it could.