ios - EXC_BAD_ACCESS KERN_INVALID_ADDRESS 但内存未被删除

Question

我在发布的应用程序中偶尔会发生崩溃，并且从崩溃报告中知道它发生的行和崩溃类型 - EXC_BAD_ACCESS (SIGSEGV) KERN_INVALID_ADDRESS - 但我不知道内存如何变得无效，因为生命周期被引用的对象的生命周期是应用程序的生命周期，除非应用程序终止，否则不会被删除。因此，如果崩溃不是由于访问已删除的内存(因为该内存未被删除)导致的，那么在这种特定情况下，EXC_BAD_ACCESS 还会有哪些其他原因？

代码如下:

 @interface Model()
 @property (strong, nonatomic)   NSMutableDictionary*  cityAndStateDictionary;
 @end


- (NSString*) findAddress: (NSString*) key
{
    if (key == nil)
    {
        return nil;
    }
    NSString* cityAndState = (self.cityAndStateDictionary)[key]; // Crash here
}



@implementation Model
- (id) init
{
    self = [super init];
    if (self)
    {
        dispatch_async(modelQueue(), ^{
            [self readCityAndStateData];
        });
    }
}


- (void) readCityAndStateData
{
    NSBundle* bundle = [NSBundle bundleForClass:[Model class]];
    NSString *filePath = [bundle pathForResource:@"CityState" ofType:@"json"];
    NSData *data = [NSData dataWithContentsOfFile:filePath];
    NSError* __autoreleasing  nserror;
    NSDictionary* jsonParser = [NSJSONSerialization JSONObjectWithData: data
                                                               options: NSJSONReadingAllowFragments
                                                                 error: &nserror];
    if (nserror == nil)
    {
        self.cityAndStateDictionary = [[NSMutableDictionary alloc] init];
        for (NSDictionary *item in jsonParser)
        {
            // create value object
            (self.cityAndStateDictionary)[key] = value;
        }
    }
}

readCityAndStateData()正在线程中创建和填充，如果 findAddress()在完成之前被调用，那么 cityAndStateDictionary 将为 nil，因此对 (self.cityAndStateDictionary)[key] 的调用在 findAddress 中只是零。cityAndStateDictionary对象不会在任何地方被删除，因此崩溃不应该是由于访问已删除的内存。

崩溃的原因是什么？

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x000000010624ae60
Termination Signal: Segmentation fault: 11
Termination Reason: Namespace SIGNAL, Code 0xb
Terminating Process: exc handler [0]
Triggered by Thread:  0

Thread 0 name:
Thread 0 Crashed:
0   CoreFoundation                  0x000000018356446c -[__NSDictionaryM objectForKey:] + 108 (NSDictionary.m:543)
1   CoreFoundation                  0x0000000183564450 -[__NSDictionaryM objectForKey:] + 80 (NSDictionary.m:538)
2   Name Of May App                 0x0000000100021f38 -[Model findAddress:] + 268 (Model.m:590)
3   Name Of May App                 0x00000001000beb78 _TTSf4g_n_n___TFC14Caller_Name_ID28BlockedNumbersViewController17formatBlockedCellfT6callerCS_6Caller3rowSi_CS_11BlockedCell + 1688 (BlockedNumbersViewController.swift:395)
4   Name Of May App                 0x00000001000bf1b0 _TTSf4g_g_n___TFC14Caller_Name_ID28BlockedNumbersViewController9tableViewfTCSo11UITableView12cellForRowAtV10Foundation9IndexPath_CSo15UITableViewCell + 528 (BlockedNumbersViewController.swift:0)
5   Name Of May App                 0x00000001000ba01c _TToFC14Caller_Name_ID28BlockedNumbersViewController9tableViewfTCSo11UITableView12cellForRowAtV10Foundation9IndexPath_CSo15UITableViewCell + 76 (BlockedNumbersViewController.swift:0)
6   UIKit                           0x0000000189af5aa8 -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 688 (UITableView.m:10803)
7   UIKit                           0x0000000189af5cc0 -[UITableView _createPreparedCellForGlobalRow:willDisplay:] + 80 (UITableView.m:10848)
8   UIKit                           0x0000000189ae33c4 -[UITableView _updateVisibleCellsNow:isRecursive:] + 2152 (UITableView.m:2273)
9   UIKit                           0x0000000189afacb0 -[UITableView _performWithCachedTraitCollection:] + 120 (UITableView.m:12556)
10  UIKit                           0x0000000189893774 -[UITableView layoutSubviews] + 176 (UITableView.m:7390)
11  UIKit                           0x00000001897adf98 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1200 (UIView.m:14232)
12  QuartzCore                      0x000000018699e274 -[CALayer layoutSublayers] + 148 (CALayer.mm:8937)
13  QuartzCore                      0x0000000186992de8 CA::Layer::layout_if_needed(CA::Transaction*) + 292 (CALayer.mm:8817)
14  QuartzCore                      0x0000000186992ca8 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 32 (CALayer.mm:2345)
15  QuartzCore                      0x000000018690e34c CA::Context::commit_transaction(CA::Transaction*) + 252 (CAContextInternal.mm:1689)
16  QuartzCore                      0x00000001869353ac CA::Transaction::commit() + 504 (CATransactionInternal.mm:420)
17  QuartzCore                      0x0000000186935e78 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 120 (CATransactionInternal.mm:793)
18  CoreFoundation                  0x000000018362c9a8 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32 (CFRunLoop.c:1802)
19  CoreFoundation                  0x000000018362a630 __CFRunLoopDoObservers + 372 (CFRunLoop.c:1898)
20  CoreFoundation                  0x000000018362aa7c __CFRunLoopRun + 956 (CFRunLoop.c:2849)
21  CoreFoundation                  0x000000018355ada4 CFRunLoopRunSpecific + 424 (CFRunLoop.c:3113)
22  GraphicsServices                0x0000000184fc5074 GSEventRunModal + 100 (GSEvent.c:2245)
23  UIKit                           0x0000000189815f74 UIApplicationMain + 208 (UIApplication.m:4089)
24  Name Of May App                 0x000000010003a8b4 main + 56 (Database.swift:17)
25  libdyld.dylib                   0x000000018256959c start + 4

Answer 1

可变字典不是线程安全的。

您需要确保字典只能从单个线程访问。

请注意 init 中的 dispatch_async 不是问题。但在这种情况下不太可能有必要。您是否测量了 readCityAndStates 方法的执行时间以确定它是否真的是性能问题？同样，不应将该静态资源存储为 JSON，而应将其存储为二进制格式。这将大大加快解析速度，更重要的是，还能缩减应用程序包的大小。