Debug objc_msgSend crash I cant reproduce

Question

I've had some crash reports from bugsense for my iOS app I'm not able to reproduce and so not to debug. It happens more than 200 times a day so I guess it's quite serious.

I've read something about NSZombie but I'm not able to reproduce the crash so I guess it's useless. Here is a crash report:

SIGSEGV
0 libobjc.A.dylib 0x3aa515b0 objc_msgSend + 15
1 UIKit 0x34d493df + 294
2 UIKit 0x34cae469 + 52
3 QuartzCore 0x34926099 + 160
4 QuartzCore 0x34925ff1 + 64
5 IOMobileFramebuffer 0x36ba1fd7 + 154
6 IOKit 0x33920449 IODispatchCalloutFromCFMessage + 192
7 CoreFoundation 0x32d035db + 118
8 CoreFoundation 0x32d0e173 + 34
9 CoreFoundation 0x32d0e117 + 138
10 CoreFoundation 0x32d0cf99 + 1384
11 CoreFoundation 0x32c7febd CFRunLoopRunSpecific + 356
12 CoreFoundation 0x32c7fd49 CFRunLoopRunInMode + 104
13 GraphicsServices 0x368562eb GSEventRunModal + 74
14 UIKit 0x34b95301 UIApplicationMain + 1120
15 My Bet main (main.m:16) Live 0x000705e7 0x6d000 + 13799

On some similar threads they believe the problem can be in UIAlertView, so here is an example on how I use them: in file.h

UIAlertView *alertView;

in file.m

-(void)wait{
UIActivityIndicatorView * activityView = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
activityView.frame = CGRectMake(121.0f, 50.0f, 37.0f, 37.0f);
[activityView startAnimating];
alertView = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Searching...", @"") message:nil delegate:nil cancelButtonTitle:nil otherButtonTitles:nil];
[alertView addSubview:activityView];
[alertView show];
[NSThread detachNewThreadSelector:@selector(function) toTarget:self withObject:nil];
}
-(void)function{
// Do some web request
[alertView dismissWithClickedButtonIndex:0 animated:NO];
if(response == nil){
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Timeout", @"") message:NSLocalizedString(@"Connection timeout", @"") delegate:nil cancelButtonTitle:NSLocalizedString(@"Close", @"") otherButtonTitles:nil ];
    [alert show];
}
}

Any hint on how I can procede to solve this? Thanks

Answer 1

Possibly the crash is due to dismissing and showing the UIAlertView from other thread.

Never do UI tasks in other threads. UI tasks should be done in Main Thread.

Change function like:

-(void)function
{
 // Do some web request

 dispatch_async(dispatch_get_main_queue(), ^{
    [alertView dismissWithClickedButtonIndex:0 animated:NO];
    if(response == nil)
    {
       UIAlertView *alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Timeout", @"") message:NSLocalizedString(@"Connection timeout", @"") delegate:nil cancelButtonTitle:NSLocalizedString(@"Close", @"") otherButtonTitles:nil ];
    [alert show];
    }
  });
}