是什么导致SIGBUS

Question

我们得到一个SIGBUS (BUS_ADRALN)，它指向这个线程。是什么导致了这个错误?第68行是NSString *dateString = [dateFormat stringFromDate:currentTimestamp];或[dateFormat释放];

NSDate *currentTimestamp = self.timestamp;
if (!currentTimestamp)
    return nil; // sanity check 
[currentTimestamp retain];
NSDateComponents *otherDay = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:currentTimestamp];
NSDateComponents *today = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:[NSDate date]];
NSDateComponents *yesterday = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:[[NSDate date] addTimeInterval: -24 * 60 * 60]];
if ([today day] == [otherDay day] &&
    [today month] == [otherDay month] &&
    [today year] == [otherDay year]) {
    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"h:mm a"];
    NSString *dateString = [dateFormat stringFromDate:currentTimestamp];
    [dateFormat release];
    [currentTimestamp release];
    return [NSString stringWithFormat:@"Today %@", dateString];
}
else if ([yesterday day] == [otherDay day] &&
         [yesterday month] == [otherDay month] &&
         [yesterday year] == [otherDay year]) {
    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"h:mm a"];
    NSString *dateString = [dateFormat stringFromDate:currentTimestamp];
    [dateFormat release];
    [currentTimestamp release];
    return [NSString stringWithFormat:@"Yesterday %@", dateString];
}
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"MM/dd/yyyy h:mm a"];
// below is line 68
NSString *dateString = [dateFormat stringFromDate:currentTimestamp];
[dateFormat release];
[currentTimestamp release];
return dateString;
0   CoreFoundation                      0x33474894 CFDateFormatterCreateStringWithAbsoluteTime + 60
1   CoreFoundation                      0x33474817 CFDateFormatterCreateStringWithDate + 31
2   Foundation                          0x326c4ad7 -[NSDateFormatter stringForObjectValue:] + 91
3   Foundation                          0x326c4a75 -[NSDateFormatter stringFromDate:] + 21
4   MyApp                              0x000a81dc -[Message getFormattedTimestamp] (Message.m:68)
5   MyApp                              0x0007b7a4 -[ConversationView newBubble:withFrame:] (ConversationView.m:452)
6   MyApp                              0x0007b2fc -[ConversationView tableView:heightForRowAtIndexPath:] (ConversationView.m:520)
7   UIKit                               0x31bb3b09 -[UISectionRowData refreshWithSection:tableView:tableViewRowData:] + 2173
8   UIKit                               0x31bb3225 -[UITableViewRowData numberOfRows] + 73
9   UIKit                               0x31bb2c73 -[UITableView noteNumberOfRowsChanged] + 83
10  UIKit                               0x31bb27f7 -[UITableView reloadData] + 583
11  MyApp                              0x0007cccc -[ConversationView reloadAndMoveToEnd:] (ConversationView.m:147)
12  MyApp                              0x0007cc6c -[ConversationView managedObjectContext:fetchCompletedForRequest:withResults:error:] (ConversationView.m:153)
13  MyApp                              0x00197670 -[IZManagedObjectContext backgroundFetchOperation:completedWithIDs:error:] (IZManagedObjectContext.m:150)
14  MyApp                              0x001970b0 -[IZBackgroundFetchOperation fetchRequestDidCompleteWithUserInfo:] (IZBackgroundFetchOperation.m:108)
15  CoreFoundation                      0x3347df03 -[NSObject(NSObject) performSelector:withObject:] + 23
16  Foundation                          0x327237a9 __NSThreadPerformPerform + 269
17  CoreFoundation                      0x334e7a79 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 13
18  CoreFoundation                      0x334e975f __CFRunLoopDoSources0 + 383
19  CoreFoundation                      0x334ea4eb __CFRunLoopRun + 231
20  CoreFoundation                      0x3347aec3 CFRunLoopRunSpecific + 231
21  CoreFoundation                      0x3347adcb CFRunLoopRunInMode + 59
22  GraphicsServices                    0x311a541f GSEventRunModal + 115
23  GraphicsServices                    0x311a54cb GSEventRun + 63
24  UIKit                               0x31b90d69 -[UIApplication _run] + 405
25  UIKit                               0x31b8e807 UIApplicationMain + 671
26  MyApp                              0x0009b578 main (main.m:5)

Answer 1

上面的代码很好，因为我们最终为它编写了一个单元测试。原来是记忆问题。奇怪的是它总是指向这条线。