下面外国友人给出了一定的结果：
Consider the following main() method which you’ll find in most iPhone applications:
- int main(int argc, char *argv[])
- {
- NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
- int retVal = UIApplicationMain(argc, argv, nil, nil);
- [pool release];
- return retVal;
- }
You might assume (as I did) that when an iPhone application ends, the above call to UIApplicationMain() will return and the rest of main() will run, eventually returning an integer. That assumption would be incorrect, however.
UIApplicationMain() never actually gets a chance to finish, nor do any of the statements that follow it have a chance to execute. When an iPhone OS application is closed (e.g., the user pushes the home button) the application is given a few seconds to run its
-applicationWillTerminate method and then it calls the exit() system function. This makes sense, if you think about it: it’s more efficient to just stop the program and let the operating system free up all of its memory at once instead of running several individual
-dealloc statements. Dump the whole trash bin instead of picking stuff out one-by-one, so to speak.
However, when I noticed this several months ago (while trying to run some logging and shut-down statements in main) I was very confused; the official Apple documentation for the UIApplicationMain() function said zilch about
UIApplicationMain() never returning. In fact, while all the iPhone documentation obviously encouraged putting shutdown code inside the standard -applicationWillTerminate method, it said nothing about the fact that it’s essentially pointless to write any code
after your call to UIApplicationMain() (aside from the return statement, necessary to keep the compiler happy).
After some collective head-scratching on developer forums someone observed that the documentation for NSApplicationMain()–the AppKit/Cocoa counterpart to UIApplicationMain()–did describe
the exit(0) behavior. This prompted me to fill out a quick bug
report requesting that Apple update thedocumentation.
Fast-forward to today, when I randomly came across that documentation and noticed that it has been updated and my bug was closed. Who knows if I’m actually the one responsible for instigating the correction, but I’ll tell myself that I am.
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好吧，我承认这是个BUG，下面有读者给出了一个方法：
Nevertheless, there are situations when it returns. For example, if you are raising an exception in applicationDidFinishLaunching and
intercepting it in main you are reaching this point. Of course it’s non-standard way to run,
but it may be considered in development as test-case in order to carefully log what happens.
int main(int argc, char *argv[])
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
int retVal = -1;
@try
{
retVal = UIApplicationMain(argc, argv, nil, nil);
}
@catch(NSException* ex)
{
NSLog(@”Application terminates unexpectedly. The reason is ‘ %@ ‘.”, ex.reason);
}
[pool release];
return retVal;
}
PS：这个也许就是Apple尽力弱化mian函数的作用的实际反应吧...