Re: Crash when creating instance of class

FROM : Scott Stevenson
DATE : Tue Nov 23 19:57:03 2004

On Nov 23, 2004, at 9:35 AM, Jason Bell wrote:

> AIPerson *person;
> person = [[AIPerson alloc] init];
>
> Pretty simple, right?  We all do it millions of times.  Well, the
> second line produces a crash log with this:
>
> Exception:  EXC_BAD_ACCESS (0x0001)
> Codes:      KERN_PROTECTION_FAILURE (0x0002) at 0x00000010
>
> Thread 0 Crashed:
> 0  libobjc.A.dylib               0x9083293c class_initialize + 0x9c
> 1  libobjc.A.dylib               0x9083294c class_initialize + 0xac
> 2  libobjc.A.dylib               0x90831524
> _class_lookupMethodAndLoadCache + 0x84
> 3  libobjc.A.dylib               0x90831298 objc_msgSend + 0xb8
> ......
>
> It doesn't even get to the init method.  I don't have my own
> +(void)initialize method and if I add one, it doesn't get run either. 
> I've tried a clean-rebuild and even deleting the entire build folder. 
> Since I get no compile-time errors or warnings and this log is all I
> have to go on, I'm at a bit of a loss.


This is a somewhat unorthodox approach, but you could try something
like:

   id person = (id)malloc ( sizeof(id) );
   id alias = person;

   NSLog(@"crashed yet? part 1");
   alias->isa = AIPerson;

   NSLog(@"crashed yet? part 2");
   [alias init];


Or something like that. From what I remember, the "alias" somehow
circumvents the protected status of the isa member. I'm also not 100%
sure the third line is correct.

If I'm missing something obvious, I'll blame it on the fact that the
coffee hasn't fully entered my system yet.


    - Scott

--
http://treehouseideas.com/
http://theobroma.treehouseideas.com/ [blog]