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From "Shazron Abdullah (Resolved) (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CB-401) Crash on iOS when taking multiple pictures
Date Fri, 06 Apr 2012 19:33:23 GMT

     [ https://issues.apache.org/jira/browse/CB-401?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Shazron Abdullah resolved CB-401.
---------------------------------

    Resolution: Duplicate

This is incorrect. Autoreleasing it there is correct. Let me explain.

self.pickerController = [[[CameraPicker alloc] init] autorelease];

After this, the retain count is 1. If you removed the autorelease, the retain count is 2,
which is incorrect, and the Static Analyzer will back me up on this. The property is a retain
property. 

You would be correct if we are dealing with naked ivars, but these are synthesized properties
that are retained - @synthesize is just syntactic sugar, this is how it works internally:
http://stackoverflow.com/questions/5350563/what-equivalent-code-is-synthesized-for-a-declared-property

Also, if it's nil, setting it to nil again will not send the release message on it again,
so it's safe (again, a retained synthesized property thing, see above link).

The actual problem has been found in CB-391. Closing as a dupe of CB-391.
                
> Crash on iOS when taking multiple pictures
> ------------------------------------------
>
>                 Key: CB-401
>                 URL: https://issues.apache.org/jira/browse/CB-401
>             Project: Apache Callback
>          Issue Type: Bug
>          Components: iOS
>    Affects Versions: 1.4.0
>         Environment: 1.4.1, 1.5.0 on iOS
> Crash on iPad (third generation)
>            Reporter: Marc Rhodes
>            Assignee: Shazron Abdullah
>            Priority: Critical
>
> We have an app that allows the user to take four pictures. It had been working fine but
we started seeing crashes when we tested on a new iPad (third generation).
> We have eliminated the crash in our application by making the following change to the
PhongeGap/Cordova code. I tested with PhoneGap 1.4.1. I'm currently upgrading to Cordova 1.5.0
but a review of {{Camera.m}}/{{CDVCamera.m}} shows only the name changes.
> Line numbers below correspond to {{CDVCamera.m}}.
> In {{CDVCamera.m}}, we found the following code around line 67:
> {code}
> if (self.pickerController == nil) 
> {
>     self.pickerController = [[[CameraPicker alloc] init] autorelease];
> }
> {code}
> We removed the autorelease message:
> {code}
> if (self.pickerController == nil) 
> {
>     self.pickerController = [[CameraPicker alloc] init];
> }
> {code}
> Our reason for doing this is that we found that {{self.pickerController}} appears to
be released in all the right places:
> * at line 220 in {{imagePickerController:didFinishPickingMediaWithInfo:}}
> {code}
> 		self.pickerController = nil;
> {code}
> * at line 251 in {{imagePickerControllerDidCancel:}}
> {code}
> 		self.pickerController = nil;
> {code}
> * at line 399 in {{dealloc}}:
> {code}
> 		self.pickerController = nil;
> {code}
> This last one may not always be necessary but should be okay since the previous releases
set the instance variable to {{nil}}. And, of course, since pickerController is a property,
setting it to {{nil}} serves to release it.
> I think both autoreleasing and explicitly releasing an object is not following the memory
management rules. Apple says:
> * [https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmRules.html]
> * Memory Management Policy
> 	** Basic Memory Management Rules
> 		*** You relinquish ownership of an object by sending it a release message or an autorelease
message.
> My thought (confirmed with an instructor at [Big Nerd Ranch|http://www.bignerdranch.com/])
is that "or" is the key word in this statement and removing the extra autorelease could certainly
prevent zombie crashes that only occur in certain circumstances.
> This issue seems like a duplicate of [CB-264|https://issues.apache.org/jira/browse/CB-264]
but since that one is resolved as "won't fix," I have submitted this new issue containing
a possible solution.

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