Is an autorelease pool necessary if I'm not creating autoreleased objects?

Question

I mean, if I were absolutely certain I wasn't creating any autoreleased objects, then of course it wouldn't. My real concern is if there's anything else under the hood I don't understand. I have a background thread that calls a function. Must I always create an autorelease pool anyway?

- (void)someFuncOnABackgroundThread
{
    //don't seem to need this. no leaks found
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    //do something that doesn't create any objects, or only use alloc/init/release

    NSString* str = [[NSString alloc] init];
    [str release];
    [pool drain];
}

Answer 1

ultimately, it depends on the interfaces you're using in the implementation.

example 1

if you're interacting with Foundation or other objc types, you should. without question.

to answer specific to the example you've posted: definitely create one in this case -- NSString apis should assume an autorelease pool is in place.

example 2

if you're dealing entirely with apis in libc, there is no need.

bottom line

• it can take a lot of time to understand where it's necessary (or not).

• implementations can change, and they could introduce autoreleased objects.

• you should guarantee a leak is never introduced, especially for such a simple reason.

• it's a simple problem to overcome: if in doubt, create one.

Answer 2

Yep! You have to. You might be calling a function that's internally using autorelease pools, so you never really know if you're using or not any autorelease.

Good luck!