UITableView section index related crashes under iOS 7

Question

I have a simple section index for a table view that appears fine for the first time but then crashes if certain kinds of interaction happens that force a redraw of the section index, either by:

1. Pushing a view controller by tapping on one of the cells
2. Tapping on the search bar in the header of the table view or by making it first responder in other ways
3. Going to an info screen and then coming back to the view controller with that table view.

If I comment out the section index (by returning nil in sectionIndexTitlesForTableView instead of the "[self.collation sectionIndexTitles]"), it works just fine.

It ONLY happens under iOS 7 (since the betas and it's not fixed in the 7.0.1 release) and I always get the following stack trace related to CoreText / animations / transitions:

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x000001f0
Triggered by Thread:  0

Thread 0 Crashed:
0   CoreText                        0x31403312 TComponentFont::GetMinSideBearing(CGAffineTransform const&, bool) const + 10
1   CoreText                        0x313f3ada TRun::GetLeftHangersGlyphCountAndWidth(long, unsigned long, TCharStream const&) const + 322
2   CoreText                        0x313f394c TLine::GetLeftHangersGlyphCountAndWidth(unsigned long const*) const + 148
3   CoreText                        0x314025d8 TLine::GetBounds(unsigned long) const + 496
4   CoreText                        0x314023ca CTLineGetBoundsWithOptions + 10
5   UIKit                           0x333641f6 -[UITableViewIndex _cacheAndMeasureTitles] + 758
6   UIKit                           0x33364b8e -[UITableViewIndex sizeThatFits:] + 198
7   UIKit                           0x332f0d62 -[UITableView _updateIndexFrameSuppressingChangeNotification:] + 546
8   UIKit                           0x332f6fe0 -[UITableView setContentInset:] + 268
9   UIKit                           0x332cbaf8 -[UIViewController _setNavigationControllerContentInsetAdjustment:] + 436
10  UIKit                           0x332e432e -[UINavigationController navigationTransitionView:didEndTransition:fromView:toView:] + 458
11  UIKit                           0x333af438 __49-[UINavigationController _startCustomTransition:]_block_invoke + 156
12  UIKit                           0x333340b0 -[_UIViewControllerTransitionContext completeTransition:] + 72
13  UIKit                           0x333f4402 __53-[_UINavigationParallaxTransition animateTransition:]_block_invoke105 + 450
14  UIKit                           0x332557c6 -[UIViewAnimationBlockDelegate _didEndBlockAnimation:finished:context:] + 282
15  UIKit                           0x33255412 -[UIViewAnimationState sendDelegateAnimationDidStop:finished:] + 174
16  UIKit                           0x3325532a -[UIViewAnimationState animationDidStop:finished:] + 66
17  QuartzCore                      0x32eadd94 CA::Layer::run_animation_callbacks(void*) + 228
18  libdispatch.dylib               0x3b21cd64 _dispatch_client_callout + 20
19  libdispatch.dylib               0x3b2237bc _dispatch_main_queue_callback_4CF$VARIANT$mp + 264
20  CoreFoundation                  0x30d1480c __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 4
21  CoreFoundation                  0x30d130e0 __CFRunLoopRun + 1296
22  CoreFoundation                  0x30c7dcd2 CFRunLoopRunSpecific + 518
23  CoreFoundation                  0x30c7dab6 CFRunLoopRunInMode + 102
24  GraphicsServices                0x356c32d6 GSEventRunModal + 134
25  UIKit                           0x3328211c UIApplicationMain + 1132

I've pretty much ruled out it's memory-related because it happens with an empty table as well as 6000 cells.

This is the code for the section index:

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section 
{
    // Don't show section titles when a search is in progress
    if (isFilterInProgress && [self.searchDisplayController isActive]) {
        return nil;
    }

    return  [[self.collation sectionIndexTitles] objectAtIndex:section];
}


- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView 
{
    if(tableView == self.resultsTable){

        // Don't show section titles when a search is in progress
        if (isFilterInProgress && [self.searchDisplayController isActive]) {
            return nil;
        }

        // Don't show section titles when there are filtered results
        if ([self.filteredListContent count] > 0)
            return nil;

        // iOS7 temporary fix for crashes (ICM-9)
        if(SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"7.0")){

            // Crashes under iOS 7 when displayed for a second time!
            return [self.collation sectionIndexTitles];
            //return nil;

        }else{

            return [self.collation sectionIndexTitles];  

        }

    }else return nil;
}


- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index 
{

    // Return correct section
    if(tableView == self.resultsTable){
        return [self.collation sectionForSectionIndexTitleAtIndex:index];
    }else{
        return 0;
    }   
}

Is anyone else having similar issues or any other related to section indices? I knew there were some layouting issues with the table view section index together with delete buttons on editing cells but I'm not sure if those have been fixed either. I suspect it's just a bug in iOS 7?

Answer 1

I have been experiencing this exact issue. I solved this after days of frustration by using a 3rd party section index view and not using the native sectionIndexTitlesForTableView. Check out CMIndexBar. Super easy, got it up an running in about 5 minutes. Easily customizable. This is what I will be using until Apple addresses this bug and I highly recommend it if you are experiencing this crash.

Answer 2

The issue seemed to have to do with a reloadData call being attempted from a background thread on a background thread, in my case. I guess the data in the view was inconsistent with the index or something like that.

Weird how it manifests itself in the form seen in the CoreText library (as seen in the stack trace above) and on iOS 7 only.

When dispatching the call on the main queue to reload the table view's data, reloading performance improved and I could use the section index again. I haven't had that crash since.

See if doing that fixes it for you.