Cocoa Gotcha: NSApplicationMain never returns

There is an old feature of Cocoa, not well documented, that bit me 
recently:

When you create a new project, Apple gives you a main() that looks like 
this:
-----------------
#im****t <Cocoa/Cocoa.h>

int main(int argc, const char *argv[]){
  return NSApplicationMain(argc, argv);
}
-----------------


I'm often tempted to add a little code here, like so:
(toy example)


-----------------
int main(int argc, const char *argv[]){
  NSLog(@[EMAIL PROTECTED]
"now %@[EMAIL PROTECTED]
", [NSDate date]);
  return NSApplicationMain(argc, argv);
}
-----------------

But that puts a message on the console:

-----------------
.... *** _NSAutoreleaseNoPool(): Object 0x3042d0 of class NSCFDate 
autoreleased with no pool in place - just leaking
-----------------

So I make the obvious fix to make the message go away and get:

-----------------
int main(int argc, const char *argv[]){
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  NSLog(@[EMAIL PROTECTED]
"now %@[EMAIL PROTECTED]
", [NSDate date]);
  int retVal = NSApplicationMain(argc, argv);
  [pool release];
  return retVal;
}
-----------------

But, a quick test shows that "now", below, is never executed.
-----------------
int main(int argc, const char *argv[]){
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  NSLog(@[EMAIL PROTECTED]
"then %@[EMAIL PROTECTED]
", [NSDate date]);
  int retVal = NSApplicationMain(argc, argv);
  NSLog(@[EMAIL PROTECTED]
"now %@[EMAIL PROTECTED]
", [NSDate date]);
  [pool release];
  return retVal;
}
-----------------


So what's going on here? Well, if you set a breakpoint on exit(), and 
just quit the program you'll see that the Quit menu command calls 

[NSApplication terminate: ... ];

which in turn calls exit(). If you quit the program by logging out, the 
Finder sends your program a "quit" appleEvent, you'll still go through 
exit().

I was surprised by this behavior, since MFC, Powerplant, and Carbon all 
normally cleanly terminate the runloop and return all the way out.

So how do we fix this?

1.) You can't. There are operations you might desperately want to do 
after the user signals he wants to quit, but if the user does a force 
quit, or if the machine crashes, those operations aren't going to happen.

2.) Rather than putting code in main(), you can put it in an 
+(void)initialize; method of some class. Of course, you can't control 
the order that initialize;s get called. If you need a guarantee that you 
are run first, you are back to putting code in main() or a more 
complicated solution.

3.) You can use atexit() to register a function handler that will be 
called from a normal exit().

BUT: NSApplicationMain() does clean up ALL the autorelease pools before 
calling exit(), including the one we made before we called 
NSApplicationMain().

So the finished code is the rather peculiar looking:

-----------------
static void Finish(void) {
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  NSLog(@[EMAIL PROTECTED]
"now %@[EMAIL PROTECTED]
", [NSDate date]);
  [pool release];
}

int main(int argc, const char *argv[]){
  [[NSAutoreleasePool alloc] init];
  atexit(Finish);
  NSLog(@[EMAIL PROTECTED]
"then %@[EMAIL PROTECTED]
", [NSDate date]);
  return NSApplicationMain(argc, argv);
}
-----------------


I suppose the moral of the story is: don't try to do things in main in a 
Cocoa program.