Class clusters: MacOSX/GNUstep differences?

[Ronan Collobert]

Hello,

  I have to implement a true subclass of the NSArray class. My code works
well under MacOS X, but does a "seg fault" under GNUstep.

After looking at the code of NSArray.m and GSArray.m, I found that in
GNUstep, if we want to implement a subclass of NSArray we have to derive
not only the standard two primitives count: and objectAtIndex:
but also

- (id) initWithObjects: (id*)objects count: (unsigned)count;

Indeed, in NSArray.m, the init method is implemented as
- (id) init
{
  return [self initWithObjects: (id*)0 count: 0];
}

and initWithObjects: as
- (id) initWithObjects: (id*)objects count: (unsigned)count
{
  [self subclassResponsibility: _cmd];
  return nil;
}

I understand that if we define initWithObjects: in a subclass, then it's
cool because all other init methods of NSArray will work well in the
subclass. However, we are *forced* to declare this method in the
subclasses with GNUstep, which is not (to my opinion) what is specified in
the Cocoa framework. Here is a cut and paste of a discussion on class
clusters by apple:
(see
http://developer.apple.com/documentation/Cocoa/Conceptual/Foundation/Concepts/ClassClusters.html)

"Your subclass should declare its own init... [...] It should not
rely on any of those that it inherits. To maintain its link in the
initialization chain, it should invoke its superclass's designated
initializer within its own designated initializer method. Within a class
cluster, the designated initializer of the abstract superclass is always
init"

Note that in the NextStep3.3 specifications, there is exactly the same
text.
(see
http://www.channelu.com/NeXT/NeXTStep/3.3/nd/Foundation/IntroFoundation.htmld/index.html)

And I never saw in the Apple/NextStep documentation that initWithObjects:
has to be considered as a primitive method.

Maybe the OpenStep specifications are different, but the document provided
on www.gnustep.org seems not to talk about this particular point.

Anyways, it is quite annoying, because I cannot have the full
compatibility between MacOS X and GNUstep. Even if I declare this
initWithObjects: method in my code, in MacOS X I should have a line
such as
[super init]
according to what apple says, which will cause an infinite loop under
GNUstep.

Maybe this has been already discussed in the past, but I didn't find
anything in the mailing list archives. Any comments on this?

Thanks,
Ronan.