On Oct 18, 2008, at 1:36 AM, Steve Cronin wrote:

...(bug fixes) which are only enabled for binaries linked against the 10.5 SDK. This is both a good and bad thing. It means your program works consistently on Tiger and Leopard, which makes testing easier. But it might behave consistently incorrectly due to the bugs. Check the various Leopard release notes for specifics.
I'm afraid I don't understand this comment.
What do you mean "..behave consistently incorrectly due to the bugs.."?

I mean that, where there's a bug, an application linked against the 10.4 SDK will continue to get the buggy behavior from the framework, even when running on Leopard. Consistency. Whatever workaround you have for the bug will continue to work correctly on Leopard.

If you link against the 10.5 SDK, then the application will get one kind of behavior when running on Tiger and get a different behavior when running on Leopard. Inconsistency. Any workaround for the Tiger bug may cause trouble when running on Leopard, but failure to work around the bug will cause trouble when running on Tiger. You have to write your code with this in mind, and you have to test both possibilities.

Can you refer me to a specific item you might be thinking of here?

Well, any of the bugs fixes listed in the release notes which note that the new behavior only occurs for applications linked against 10.5. For example, in the AppKit release notes, see the item titled "KeyValueObserving notifications for IBOutlets during Nib loading". Consider how easy it would be to unwittingly code an application that relies either on the old behavior which would break with the new behavior, or vice versa.


So in sum, I think what you are saying is:
Stick w/ 10.4 SDK as the safest path.
However there might be bug fixes which you could benefit from by using the 10.5 SDK. To determine whether or not you actually do benefit from 10.5 means you have to learn more about it by reading the Release Notes.
Does that sound right?

Yup.


So based on this reading of your comments and a few minutes with the XCode documentation I scan the AppKit Release Notes for Leopard and find the following: NSCompoundPredicateFor applications linked on Mac OS X 10.5 "Leopard" or later, initializing an NSCompoundPredicate now copies the subpredicates array rather than retaining it. Applications linked on Mac OS X 10.4 "Tiger" continue to only retain the subpredicates array for binary compatibility.

Well this appears germane to my application as I do use compound predicates. Judging by the scope the Release Notes and the speed with which I could locate even one germane issue I am convinced that my original instinct to use the 10.5 SDK because the code base is better IS correct.

But I am puzzled by your "good and bad thing" comment...

Well, consider this: if the bug fix were purely good, why would Apple maintain backward compatibility for apps which are linked against the 10.4 SDK?

And remember, if you link against the 10.5 SDK but support deployment on 10.4, then you still have to cope with the case where NSCompoundPredicate merely retains rather than copying its subpredicates array, because that's what will happen when it's run on 10.4. So, your code has to be safe under both behaviors rather than just having one behavior to worry about.

Cheers,
Ken

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