Re: ABI Compatibility (was Re: Installation woes for the average user...)

[David Chisnall]

On 11 Mar 2009, at 08:26, Yavor Doganov wrote:

> Glib/GTK+ have a stable API/ABI throughout the whole lifetime of the
> GNOME 2 platform

It is very easy to have a stable ABI for a procedural API because  
there is no notion of subclassing.  Even with GObject this is not  
really a problem, as it doesn't really present an OO model.

The GNUstep ABI changes are USUALLY only a problem when an application  
has subclasses of that class that changed.  Some classes are  
subclassed more often than others.  A change to the ivar layout of  
NSObject would break everything, but this never happens (NSObject has  
no ivars, and never will).  A change to something like NSView would  
break a lot of things, but there are still a lot of applications with  
no custom NSView subclasses.

> Of course, API/ABI stability is a big promise, and personally I don't
> think it's worth the trouble for GNUstep at this point.  It would be  
> good
> enough to break the ABI *only* when necessary.


I'd agree with this.  At the very least, I'd hope that people would  
post a mail to gnustep-dev BEFORE breaking the ABI and not commit  
until there had been some discussion of whether it really is a  
problem.  Committing to trunk and reverting if enough people complain  
is not really a good approach.

David