[CFNumber release]: 发送给已释放实例的消息

Question

[CFNumber release]: 发送给已释放实例的消息

iphoneioscore-datacrashautomatic-ref-counting

5

以下代码在我从历史核心数据对象中记录/请求值时返回以下错误：

-[CFNumber release]: message sent to deallocated instance 0x17ea2a90

我最初认为问题出在其他地方，花费无数个小时进行调试，但没有成功。经过进一步测试，我已经确定将崩溃点定位到从历史核心数据对象请求特定值上。有人能看出来对象值被释放的原因吗？

    [[DocumentHandler sharedDocumentHandler] performWithDocument:^(UIManagedDocument *document) {

    if(!self.document) {
        self.document = document;
    }

    __block NSString *identifier = [[NSUserDefaults standardUserDefaults] objectForKey:kUserDefaultsUserIdentifier];

    [self.document.managedObjectContext performBlock:^{

        // Create history object
        History *history      = [NSEntityDescription insertNewObjectForEntityForName:@"History"
                                                              inManagedObjectContext:self.document.managedObjectContext];
        history.identifier    = identifier;
        history.followers     = [NSNumber numberWithInteger:53];
        history.following     = [NSNumber numberWithInteger:53];
        history.newFollowers  = [NSNumber numberWithInteger:53];
        history.unfollowers   = [NSNumber numberWithInteger:53];
        history.fans          = [NSNumber numberWithInteger:53];
        history.mutualFriends = [NSNumber numberWithInteger:53];
        history.nonFollowers  = [NSNumber numberWithInteger:53];

        [self.document saveToURL:self.document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:^(BOOL success) {

            // Fetch previous records
            NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"History"];
            request.predicate
            = [NSPredicate predicateWithFormat:@"identifier == %@", identifier];

            NSError *error = nil;

            NSArray *records = [self.document.managedObjectContext executeFetchRequest:request error:&error];

            [records enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
                NSLog(@"%@", [(History *)obj newFollowers]); // Crash takes place here
            }];

        }];

    }];

}];

启用异常断点后的更多日志：

    (lldb) bt
* thread #1: tid = 0x28b70, 0x3b5787fa libobjc.A.dylib`objc_release + 10, queue = 'com.apple.main-thread, stop reason = EXC_BAD_ACCESS (code=1, address=0x10)
    frame #0: 0x3b5787fa libobjc.A.dylib`objc_release + 10
    frame #1: 0x3b578022 libobjc.A.dylib`(anonymous namespace)::AutoreleasePoolPage::pop(void*) + 358
    frame #2: 0x311b4298 CoreFoundation`_CFAutoreleasePoolPop + 16
    frame #3: 0x3127533e CoreFoundation`__NSArrayEnumerate + 614
    frame #4: 0x31216012 CoreFoundation`-[NSArray enumerateObjectsWithOptions:usingBlock:] + 62
    frame #5: 0x000eae26 Twitter Followers`__71-[MainViewController updateCurrentRecordAndTableHeaderForUpdateAction:]_block_invoke_2(.block_descriptor=0x15e58080, success='\x01') + 678 at MainViewController.m:671
    frame #6: 0x3ba65bea libdispatch.dylib`_dispatch_barrier_sync_f_slow_invoke + 66
    frame #7: 0x3ba600ee libdispatch.dylib`_dispatch_client_callout + 22
    frame #8: 0x3ba629a8 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 268
    frame #9: 0x3124b5b8 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 8
    frame #10: 0x31249e84 CoreFoundation`__CFRunLoopRun + 1308
    frame #11: 0x311b4540 CoreFoundation`CFRunLoopRunSpecific + 524
    frame #12: 0x311b4322 CoreFoundation`CFRunLoopRunInMode + 106
    frame #13: 0x35eeb2ea GraphicsServices`GSEventRunModal + 138
    frame #14: 0x33a6b1e4 UIKit`UIApplicationMain + 1136

- morcutt

异常发生在哪一行？你能提供一个堆栈回溯吗？ - Martin R

它发生在[records enumerateObjectsUsingBlock...]期间。我只是添加了进一步的日志。这些日志带有异常断点。 - morcutt

我也遇到了这个错误，但显然原因不同（没有以“new”开头的属性）。是否有可能使用其地址获取有关已释放对象的更多信息？ - Symmetric

1

@Symmetric - 我知道这是一个非常古老的评论，但为了未来读者的利益，我建议您查看https://dev59.com/sWYq5IYBdhLWcg3w5kpm#14105056中讨论的“记录引用计数”功能。这在跟踪每个强引用的建立（即引用计数增加+1）和释放（即引用计数减少-1）的位置方面非常有价值。 - Rob

当我将字段类型从int更改为NSNumber *，但忘记将属性从assign更改为strong时，我遇到了这个错误。最奇怪的是，在iPhone 6 / 6s上一切正常，但在iPhone 5 / 5s上崩溃了。 - Bohdan Savych

1个回答

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可以查看英文原文，
原文链接

- Rob · Accepted Answer

根据过渡到自动引用计数（ARC）发布说明：

To allow interoperation with manual retain-release code, ARC imposes a constraint on method naming:
You cannot give an accessor a name that begins with new. This in turn means that you can’t, for example, declare a property whose name begins with new unless you specify a different getter:
    // Won't work:
    @property NSString *newTitle;

    // Works:
    @property (getter=theNewTitle) NSString *newTitle;

归根结底，以new开头的方法被认为返回一个由ARC负责管理和释放的对象（但这里并非如此）。我建议您只需更改属性，使其不以new开头，以避免任何混淆。