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iosobjective-cxcodememory-leaksreachability

Apple's reachability memory leak


I use apple's Reachabiliry class in my non-arc project. And when I run it with instruments to find memory leaks, it referes to Reachability method. Here is the problem:

+ (instancetype)reachabilityWithAddress:(const struct sockaddr_in *)hostAddress;
{
    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr *)hostAddress);

    WReachability* returnValue = NULL;

    if (reachability != NULL)
    {
        returnValue = [[self alloc] init];
        if (returnValue != NULL)
        {
            returnValue->reachabilityRef = reachability;
            returnValue->localWiFiRef = NO;
        }
    }
    return returnValue;
}

The leaked objects are reachability and returnValue. I understand that SCNetworkReachabilityCreateWithAddress creates a new instance and I must CFRelease it, but it happens right in dealloc!

- (void)dealloc
{
    [self stopNotifier];
    if (reachabilityRef != NULL)
    {
        CFRelease(reachabilityRef);
    }
    [super dealloc];
}

So what can I do to avoid memory leak here?

UPD: Maybe the problem is in how reachability get called? I use this method:

+ (instancetype)reachabilityForInternetConnection;
{
    struct sockaddr_in zeroAddress;
    bzero(&zeroAddress, sizeof(zeroAddress));
    zeroAddress.sin_len = sizeof(zeroAddress);
    zeroAddress.sin_family = AF_INET;

    return [self reachabilityWithAddress:&zeroAddress];
}

Then I called Reachability like this:

[[Reachability reachabilityForInternetConnection] startNotifier];

And don't assign it to any object, just use this line. I've tried to change this calls to something like:

Reachability *reachability = [[Reachability reachabilityForInternetConnection] autorelease];
[reachability startNotifier];

But after this analyzer told me "too many autorelease".


Solution

  • If returnValue equals to NULL reachability object is leaked, you should release it in this case. Also by Cocoa naming convention (https://developer.apple.com/library/ios/documentation/cocoa/conceptual/MemoryMgmt/Articles/mmRules.html#//apple_ref/doc/uid/20000994-SW1) you must return autoreleased object:

    + (instancetype)reachabilityWithAddress:
    {
        ...
         returnValue = [[[self alloc] init] autorelease];
    

    Or rename the method to start for example from new: newReachabilityWithAddress or something like this if you don't want to return an autoreleased object.

    Try to run static analyser in Xcode, it can help to spot the problems.