message from debugger: terminated due to signal 13
https://blog.csdn.net/jia12216/article/details/50844013
https://forums.developer.apple.com/message/358350#358350
https://forums.developer.apple.com/message/358276#358276
分析：
记不清楚了，好像是替换了uilabel的layer层，或者是给uiview添加了Gradient类型
报错如下：
[CAGradientLayer _clearContents]: unrecognized selector sent to instance 0x2815c31a0
| CoreFoundation | ___exceptionPreprocess + 232 |
| 1 libobjc.A.dylib | objc_exception_throw + 60 |
| 2 CoreFoundation | -[NSOrderedSet initWithSet:copyItems:] |
| 3 CoreFoundation | ____forwarding___ + 1412 |
| 4 CoreFoundation | _CF_forwarding_prep_0 + 96 |
| 5 UIKitCore | -[UILabel _startMarquee] + 3332 |
| 6 libdispatch.dylib | __dispatch_call_block_and_release + 32 |
| 7 libdispatch.dylib | __dispatch_client_callout + 20 |
| 8 libdispatch.dylib | _dispatch_main_queue_callback_4CF + 1012 |
| 9 CoreFoundation | ___CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 16 |
| 10 CoreFoundation | ___CFRunLoopRun + 1888 |
| 11 CoreFoundation | CFRunLoopRunSpecific + 452 |
| 12 GraphicsServices | GSEventRunModal + 108 |
| 13 UIKitCore | UIApplicationMain + 216 |
| 14 金囿 | main (main.m:14)
|
| 15 libdyld.dylib | _start + 4 |
来源：oschina
链接：https://my.oschina.net/KeepDoing/blog/3785374