[jira] [Created] (CB-2395) iOS: Timing issue in user-agent lock mechanism (memory leaking)

["Christoph Jerolimov (JIRA)" <ji...@apache.org>]

Christoph Jerolimov created CB-2395:
---------------------------------------

             Summary: iOS: Timing issue in user-agent lock mechanism (memory leaking)
                 Key: CB-2395
                 URL: https://issues.apache.org/jira/browse/CB-2395
             Project: Apache Cordova
          Issue Type: Bug
          Components: iOS
    Affects Versions: 2.4.0
            Reporter: Christoph Jerolimov
            Assignee: Shazron Abdullah


If found a obj-c reference counting problem with Cordova 2.4.

Analysing the retain/release calls of CDVViewController i found the following problem. If you just want fix this i added a recommendation at the! ;-)

 
*Retain:* When the view was displayed they load the request in a c-block (simplified source here!). This callback-code needs the CDVViewController itself:

{code}
- (void)viewDidLoad {
    ...
    [CDVUserAgentUtil acquireLock:^(NSInteger lockToken) {
        _userAgentLockToken = lockToken;
        [CDVUserAgentUtil setUserAgent:self.userAgent lockToken:lockToken];
        NSURLRequest* appReq = [NSURLRequest requestWithURL:appURL ....;
        [self.webView loadRequest:appReq];
    }];
}
{code}


*Release:* To release the block (and so the CDVViewController) it's required to call the the {{acquireLock}} associated {{releaseLock}} method. This was called in the delegate methods of the webview.

{code}
- (void)webViewDidFinishLoad:(UIWebView*)theWebView   AND
- (void)webView:(UIWebView*)webView didFailLoadWithError:(NSError*)error

    ...
    if (_userAgentLockToken != 0) {
        [CDVUserAgentUtil releaseLock:_userAgentLockToken];
        _userAgentLockToken = 0;
    }
{code}


*But:* If the webview.delegate was set to nil before the response was received the {{releaseLock}} was never called!


*To fix this* please add these lines at least two the {{dealloc}} method!

For iOS 5.x it makes also sense to add this to the {{viewDidUnload}} method where the webView.delegate was also removed. Otherwise remove this deprecated method completly. Feel also free to externalize the then 3 or 4 calls to CDVUserAgentUtil to a small privat method.

{code}
    if (_userAgentLockToken != 0) {
        [CDVUserAgentUtil releaseLock:_userAgentLockToken];
        _userAgentLockToken = 0;
    }
{code}


Thank you and best regards,

Christoph

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