Question

我正在调查我的应用程序的Crashlytics控制台中报告的频繁崩溃。

我拥有的众多示例之一有以下崩溃的线程堆栈跟踪：

#11. Crashed: com.apple.root.default-qos
0  libobjc.A.dylib                0x22f3fa86 objc_msgSend + 5
1  Foundation                     0x23ee3005 -[NSString caseInsensitiveCompare:] + 28
2  Foundation                     0x23ed10bd _NSCompareObject + 28
3  Foundation                     0x23ed109d _NSSortFunctionOne + 120
4  CoreFoundation                 0x2373e6a3 __CFSimpleMergeSort + 114
5  CoreFoundation                 0x2373e6c5 __CFSimpleMergeSort + 148
6  CoreFoundation                 0x2373e6d9 __CFSimpleMergeSort + 168
7  CoreFoundation                 0x2373e6c5 __CFSimpleMergeSort + 148
8  CoreFoundation                 0x2373e6d9 __CFSimpleMergeSort + 168
9  CoreFoundation                 0x2368ac35 CFSortIndexes + 404
10 CoreFoundation                 0x2368c241 CFMergeSortArray + 176
11 Foundation                     0x23ed0a9d _sortedObjectsUsingDescriptors + 456
12 Foundation                     0x23f9c9fb -[NSSet(NSKeyValueSorting) sortedArrayUsingDescriptors:] + 510
13 MyApp                          0x6d431 __24-[MyApp refresh]_block_invoke (MyApp.m:247)
14 CoreFoundation                 0x23769499 __NSArrayEnumerate + 372
15 CoreFoundation                 0x236e6c3b -[NSArray enumerateObjectsWithOptions:usingBlock:] + 62
16 MyApp                          0x6d17d -[MyApp refresh] (MyApp.m:263)
17 MyApp                          0xa97eb __52-[MyAppRequest updateAfterNotification:]_block_invoke (MyAppRequest.m:1175)
18 libdispatch.dylib              0x23307cbf _dispatch_call_block_and_release + 10
19 libdispatch.dylib              0x233136a1 _dispatch_root_queue_drain + 1572
20 libdispatch.dylib              0x2331307b _dispatch_worker_thread3 + 94
21 libsystem_pthread.dylib        0x234a6e0d _pthread_wqthread + 1024
22 libsystem_pthread.dylib        0x234a69fc start_wqthread + 8

崩溃的其他实例发生在相同的应用代码中（在refresh类的MyApp方法中），但在CoreFoundation sortedArrayUsingDescriptors方法逻辑的不同部分。例如，另一个崩溃示例stacktrace具有：

0  libobjc.A.dylib                0x1823cdb90 objc_msgSend + 16
1  CoreFoundation                 0x182c42738 CFStringCompareWithOptionsAndLocale + 232
2  Foundation                     0x183644840 _NSCompareObject + 64
3  CoreFoundation                 0x182d150f4 __CFSimpleMergeSort + 196
4  CoreFoundation                 0x182d15124 __CFSimpleMergeSort + 244
5  CoreFoundation                 0x182d15124 __CFSimpleMergeSort + 244
6  CoreFoundation                 0x182d15124 __CFSimpleMergeSort + 244
7  CoreFoundation                 0x182d1513c __CFSimpleMergeSort + 268
8  CoreFoundation                 0x182d15124 __CFSimpleMergeSort + 244
9  CoreFoundation                 0x182d15124 __CFSimpleMergeSort + 244
10 CoreFoundation                 0x182d15124 __CFSimpleMergeSort + 244
11 CoreFoundation                 0x182c3b738 CFSortIndexes + 472
12 CoreFoundation                 0x182c3cf58 CFMergeSortArray + 220
13 Foundation                     0x1836440f8 _sortedObjectsUsingDescriptors + 564
14 Foundation                     0x183725120 -[NSSet(NSKeyValueSorting) sortedArrayUsingDescriptors:] + 564
15 MyApp                          0x10006f264 __24-[MyApp refresh]_block_invoke (MyApp.m:247)

刷新时的应用代码是：

- (void)refresh {
    NSArray *products = [self getProducts];
    NSMutableArray *validProducts = [NSMutableArray array];
    [products enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        Product *prod = obj;

        // Convert to internal native format (MyAppProduct) for business reasons...
        MyAppProduct *myAppProd = [[MyAppProduct alloc] init];
        myAppProd.ID = prod.id;
        myAppProd.name = prod.name;

        NSArray *subProds = [prod.subProds sortedArrayUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"subProds" ascending:NO]]];
        NSMutableArray *validSubProds = [NSMutableArray array];
        [subProds enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
            SubProd *subProd = obj;

            // Convert to internal native format (MyAppSubProduct) for business reasons...
            MyAppSubProduct *myAppSubProd = [[MyAppSubProduct alloc] initWithSubProd:subProd];
            [validSubProds addObject:myAppSubProd];
        }];
        myAppProd.subProds = validSubProds;
        myAppProd.count = [product.count integerValue];

        // Add to array
        [validProducts addObject:myAppProd];
    }];

    // Apply array to self
    _products = validProducts
}

其中getProducts是：

- (NSArray*)getProducts {
    NSFetchRequest *productFetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Products"];

    // Filter
    NSMutableArray *productsPredicates = [NSMutableArray array];
    [productsPredicates addObject:[NSPredicate predicateWithFormat:@"life_uid == %@", req.lifeUid]];
    [productsPredicates addObject:[NSPredicate predicateWithFormat:@"hidden == %@", @NO]];
    [productFetchRequest setPredicate:[NSCompoundPredicate andPredicateWithSubpredicates:productsPredicates]];

    // Sort
    NSSortDescriptor *sortProductsByName = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];
    [productFetchRequest setSortDescriptors:@[sortProductsByName]];

    [productFetchRequest setReturnsObjectsAsFaults:NO];
    [productFetchRequest setRelationshipKeyPathsForPrefetching:@[@"subprods", @"subprods.special"]];

    NSManagedObjectContext *moc = [MyAppCoreDataController sharedController].mainManagedObjectContext;
    NSError *error = nil;
    NSArray *products = [moc executeFetchRequest:productFetchRequest error:&error];
    if (error) {
        NSLog(@"Error fetching products %@", error);
    }
    return products;
}

正在调用刷新：

- (void)updateAfterNotification:(NSNotification *)notification {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [[MyApp instance] refresh];
    });
}

Answer 1

很可能是因为您没有正确处理Core Data并发。使用NSPrivateQueueConcurrencyType或NSMainQueueConcurrencyType创建托管对象上下文时，必须将所有Core Data访问权限置于对performBlock或performBlockAndWait的调用中。这包括提取以及访问已获取对象的属性值。

您正在使用dispatch_async，这不是使用Core Data处理并发的正确方法。您应该切换为使用performBlock或performBlockAndWait。

libobjc.A.dylib objc_msgSend在后台线程中使用核心数据时发生崩溃

1 个答案: