没有断点调试不会崩溃，一旦启用断点，XCode会调试到该行代码，然后立即崩溃。它在线程22崩溃如下：
Thread 22 Crashed:: <DBGLLDBSessionThread (pid=838)> Dispatch queue: DVTInvalidationPreventionQueue
0 com.apple.LLDB.framework 0x0000000118e3d986 clang::ASTContext::getFunctionType(clang::QualType, llvm::ArrayRef<clang::QualType>, clang::FunctionProtoType::ExtProtoInfo const&) const + 294
1 com.apple.LLDB.framework 0x000000011a139964 lldb_private::ClangASTContext::CreateFunctionType(clang::ASTContext*, lldb_private::CompilerType const&, lldb_private::CompilerType const*, unsigned int, bool, unsigned int) + 542
2 com.apple.LLDB.framework 0x0000000119fb290a DWARFASTParserClang::ParseTypeFromDWARF(lldb_private::SymbolContext const&, DWARFDIE const&, lldb_private::Log*, bool*) + 9830
3 com.apple.LLDB.framework 0x000000011a120e68 SymbolFileDWARF::ParseType(lldb_private::SymbolContext const&, DWARFDIE const&, bool*) + 184
4 com.apple.LLDB.framework 0x000000011a11b108 SymbolFileDWARF::GetTypeForDIE(DWARFDIE const&, bool) + 368
5 com.apple.LLDB.framework 0x000000011a11ab21 SymbolFileDWARF::ResolveType(DWARFDIE const&, bool, bool) + 129
6 com.apple.LLDB.framework 0x0000000119fb7ff9 DWARFASTParserClang::CompleteTypeFromDWARF(DWARFDIE const&, lldb_private::Type*, lldb_private::CompilerType&) + 1165
7 com.apple.LLDB.framework 0x000000011a11aedc SymbolFileDWARF::CompleteType(lldb_private::CompilerType&) + 628
8 com.apple.LLDB.framework 0x000000011a1a59cb lldb_private::Type::ResolveClangType(lldb_private::Type::ResolveStateTag) + 1483
9 com.apple.LLDB.framework 0x000000011a1a5c74 lldb_private::Type::GetFullCompilerType() + 26
10 com.apple.LLDB.framework 0x000000011a0007da lldb_private::ValueObject::MaybeCalculateCompleteType() + 352
11 com.apple.LLDB.framework 0x000000011a000568 lldb_private::ValueObject::GetCompilerType() + 18
12 com.apple.LLDB.framework 0x000000011a1c680a lldb_private::Process::IsPossibleDynamicValue(lldb_private::ValueObject&) + 64
13 com.apple.LLDB.framework 0x000000011a005bca lldb_private::ValueObject::CalculateDynamicValue(lldb::DynamicValueType) + 90
14 com.apple.LLDB.framework 0x000000011a005c6f lldb_private::ValueObject::GetDynamicValue(lldb::DynamicValueType) + 65
15 com.apple.LLDB.framework 0x0000000117ff51dd ValueImpl::GetSP(lldb_private::ProcessRunLock::ProcessRunLocker&, lldb_private::Mutex::Locker&, lldb_private::Error&) + 243
16 com.apple.LLDB.framework 0x0000000117fef90a lldb::SBValue::GetSP(ValueLocker&) const + 58
17 com.apple.LLDB.framework 0x0000000117fef9f9 lldb::SBValue::GetName() + 41
18 com.apple.dt.dbg.DebuggerLLDB 0x0000000117f3ad75 -[DBGLLDBDataValue initWithLLDBValueObject:forStackFrame:withParent:updateSummary:] + 234
19 com.apple.dt.dbg.DebuggerLLDB 0x0000000117f3ac29 -[DBGLLDBDataValue initWithLLDBValueObject:forStackFrame:withParent:] + 92
20 com.apple.dt.dbg.DebuggerLLDB 0x0000000117f38370 -[DBGLLDBStackFrame _findSymbolWithName:symbolKind:atLocation:] + 1070
21 com.apple.dt.dbg.DebuggerLLDB 0x0000000117f38748 __93-[DBGLLDBStackFrame requestDataValueForSymbol:symbolKind:atLocation:onQueue:withResultBlock:]_block_invoke + 60
22 com.apple.dt.DVTFoundation 0x000000010d08dfb4 ___DVTPreventInvalidationForObjectAllowingRecursiveCallsDuringBlock_block_invoke_2 + 49
23 libdispatch.dylib 0x00007fff8491b40b _dispatch_client_callout + 8
24 libdispatch.dylib 0x00007fff8492c5a4 _dispatch_sync_f_invoke + 56
25 com.apple.dt.DVTFoundation 0x000000010d08df54 ___DVTPreventInvalidationForObjectAllowingRecursiveCallsDuringBlock_block_invoke + 150
26 libdispatch.dylib 0x00007fff8491b40b _dispatch_client_callout + 8
27 libdispatch.dylib 0x00007fff8492c5a4 _dispatch_sync_f_invoke + 56
28 com.apple.dt.DVTFoundation 0x000000010d08dda3 _DVTPreventInvalidationForObjectAllowingRecursiveCallsDuringBlock + 383
29 com.apple.dt.DVTFoundation 0x000000010d08e10d _DVTPreventInvalidationAllowingRecursiveCallsDuringBlock + 35
30 com.apple.dt.dbg.DebuggerLLDB 0x0000000117f37b80 __45-[DBGLLDBStackFrame _addSessionThreadAction:]_block_invoke + 108
31 com.apple.dt.dbg.DebuggerLLDB 0x0000000117f50755 -[DBGLLDBSession handleNextActionWithState:withRunPending:] + 457
32 com.apple.dt.dbg.DebuggerLLDB 0x0000000117f4aca5 DBGLLDBSessionThread(void*) + 2089
33 libsystem_pthread.dylib 0x00007fff8dc4599d _pthread_body + 131
34 libsystem_pthread.dylib 0x00007fff8dc4591a _pthread_start + 168
35 libsystem_pthread.dylib 0x00007fff8dc43351 thread_start + 13
Thread 22 crashed with X86 Thread State (64-bit):