iOS 严重问题解释（crash）

问题1：Exception Type: 00000020 Exception Codes: 0x000000008badf00d Exception Note: SIMULATED (this is NOT a crash)  Application Specific Information:com.wwc.test1 failed to scene-create after 19.94s (launch took 0.06s of total time limit 20.00s)

解答：app如果在20s内没有启动，系统的时间狗就会将程序杀死。也就会说应用启动超时。（注意：程序在真机调试的时候超时，时间狗是不起作用的）

问题2：Exception Type:  00000020 Exception Codes: 0x000000008badf00d Exception Note:  SIMULATED (this is NOT a crash) Highlighted by Thread:  11 Application Specific Information:
<BKNewProcess: 0x12f623190; com.sina.weibo; pid: 10924; hostpid: -1> has active assertions beyond permitted time:
{(
    <BKProcessAssertion: 0x12f653f20> id: 10924-F212D20C-B907-46DA-88BB-23E9BF606091 name: Called by UIKit, from <redacted> process: <BKNewProcess: 0x12f623190; com.sina.weibo; pid: 10924; hostpid: -1> permittedBackgroundDuration: 180.000000 reason: finishTask owner pid:10924 preventSuspend  preventIdleSleep  preventSuspendOnSleep
)}

解答：The result is that when we go into the background, the watchdog process sees that the app is behaving badly and kills it summarily.（程序退出到后台后，在某一时刻被时间狗杀死）

问题3：Exception Type:  EXC_RESOURCE Exception Subtype: WAKEUPS Exception Message: (Limit 150/sec) Observed 435/sec over 300 secs Exception Note:  NON-FATAL CONDITION (this is NOT a crash)

解答：Background threads in iOS 8 have a hard limit on how many times you can run a sleep/wake cycle on each thread per second, and having a high count here is usually an indication that something is wrong / inefficient in your thread management.（后台线程的睡眠唤起次数是有限制的 150次）

问题4：EXC_BAD_ACCESS一般是内存管理引起的，且在控制台不会输出错误信息（因为访问的内部不确定从什么时候已被损坏），在手动管理内存的情况先可能经常见到；在ARC下出现的概率降低，但是有时也会出现。（访问损坏的内存地址），有时候报错EXC_BAD_ACCESS（SIGSEGV），SIGSEGV是当一个进程执行了一个无效的内存引用

解答：1.设置NSZombie（僵尸对象）调试程序     2.对程序做Analyze分析

问题5：SIGABRT 当异常终止一个进程。中止当前进程，返回一个错误代码。该函数产生SIGABRT信号并发送给自己。实际就是系统发现操作异常，调用发送SIGABRT（abort()函数）信号，杀死进程。

解答：这种异常，系统会知道程序在什么地方有不合法的操作，会在控制台输出异常信息。例如：向一个对象发送它无法识别的消息。

-(BOOL) respondsToSelector:(SEL)aSelector {
    printf("SELECTOR: %s\n", [NSStringFromSelector(aSelector) UTF8String]);
    return [super respondsToSelector:aSelector];
}