Interesting difference in memory management of MacOS Foundation and GNUstep

[Mathias Bauer]

Hi dear list members,

I have ported most parts of the CocoaHTTPServer from Robbie Hanson 
including GCDAsyncSocket to Linux and found an interesting difference in 
memory management.

Here's the dealloc function of GCDAsyncSocket:

> - (void)dealloc
> {
>         LogInfo(@"%@ - %@ (start)", THIS_METHOD, self);
>         
>         if (dispatch_get_specific(IsOnSocketQueueOrTargetQueueKey))
>         {
>                 [self closeWithError:nil];
>         }
>         else
>         {
>                 dispatch_sync(socketQueue, ^{
>                         [self closeWithError:nil];
>                 });
>         }

This method crashes on Linux when the dealloc function in not called in 
the socket or target queue as the block that calls closeWithError is 
executed in this case. Catching "self" in it increments and after block 
execution decrements the retain count of "self". Doing this in a dealloc 
method of course leads into disaster.

But the same code does not crash on MacOS or iOS, even if the block 
containing closwWithError is executed.

I don't understand that, but maybe somebody knowing the differences 
better than I can explain that.

Best regards,
Mathias