title: Xcode encountered an internal logic error
body: <p>Need help
  I get the following error when i try to change anything in buildsetting section in Xcode 4.Once i change the value immediately i get the error as follows and xcode crashes. </p>
  
  <blockquote>
    <p>Xcode encountered an internal logic error. Choose "Continue" to  continue running Xcode in an inconsistent state.  Choose "Crash" to halt  Xcode and file a bug with Crash Reporter. Choosing "Crash" will result  in the loss of all unsaved data.**</p>
  </blockquote>
  
  <p>The log says as follows</p>
  
  <pre><code>Process:         Xcode [13518]
  Path:            /Developer/Applications/Xcode.app/Contents/MacOS/Xcode
  Identifier:      com.apple.dt.Xcode
  Version:         4.0.2 (99)
  Build Info:      IDEApplication-990000~53
  Code Type:       X86-64 (Native)
  Parent Process:  launchd [103]
  
  Date/Time:       2011-07-10 18:14:39.963 +0530
  OS Version:      Mac OS X 10.6.6 (10D573)
  Report Version:  6
  
  Interval Since Last Report:          6925 sec
  Crashes Since Last Report:           3
  Per-App Interval Since Last Report:  913 sec
  Per-App Crashes Since Last Report:   3
  Anonymous UUID:                      860BC8C7-2425-44F4-87CA-B9680C691297
  
  Exception Type:  EXC_CRASH (SIGABRT)
  Exception Codes: 0x0000000000000000, 0x0000000000000000
  Crashed Thread:  0  Dispatch queue: com.apple.main-thread
  
  Application Specific Information:
  ProductBuildVersion: 4A2002a
  UNCAUGHT EXCEPTION (NSInvalidArgumentException): *** -[NSCFSet removeObject:]: attempt to remove nil
  UserInfo: (null)
  Hints: None
  Backtrace:
    0  0x00007fff85188d06 __exceptionPreprocess (in CoreFoundation)
    1  0x00007fff83e300f3 objc_exception_throw (in libobjc.A.dylib)
    2  0x00007fff85188b47 +[NSException raise:format:arguments:] (in CoreFoundation)
    3  0x00007fff85188ad4 +[NSException raise:format:] (in CoreFoundation)
    4  0x00007fff8272342b -[NSCFSet removeObject:] (in Foundation)
    5  0x000000010002ee1b -[DVTModelObjectGraph didDeleteModelObject:] (in DVTFoundation)
    6  0x0000000100516b97 -[IDEFileReference _invalidateStartingWith:changeBlock:] (in IDEFoundation)
    7  0x00000001005167f5 -[IDEFileReference _invalidateResolvedFilePath] (in IDEFoundation)
    8  0x00007fff8273965b __NSThreadPerformPerform (in Foundation)
    9  0x00007fff85125f21 __CFRunLoopDoSources0 (in CoreFoundation)
   10  0x00007fff85124119 __CFRunLoopRun (in CoreFoundation)
   11  0x00007fff851238df CFRunLoopRunSpecific (in CoreFoundation)
   12  0x00007fff83234ada RunCurrentEventLoopInMode (in HIToolbox)
   13  0x00007fff8323483d ReceiveNextEventCommon (in HIToolbox)
   14  0x00007fff83234798 BlockUntilNextEventMatchingListInMode (in HIToolbox)
   15  0x00007fff800a4a2a _DPSNextEvent (in AppKit)
   16  0x00007fff800a4379 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] (in AppKit)
   17  0x00007fff8006a05b -[NSApplication run] (in AppKit)
   18  0x00007fff80062d7c NSApplicationMain (in AppKit)
   19  0x0000000100000eec
  
  abort() called
  objc[13518]: garbage collection is ON
  
  Thread 0 Crashed:  Dispatch queue: com.apple.main-thread
  0   libSystem.B.dylib               0x00007fff824a3886 __kill + 10
  1   libSystem.B.dylib               0x00007fff82543eae abort + 83
  2   com.apple.dt.IDEKit             0x0000000100949290 +[IDEAssertionHandler _handleAssertionWithLogString:] + 343
  3   com.apple.dt.IDEKit             0x0000000100949de3 -[IDEAssertionHandler handleUncaughtException:] + 563
  4   com.apple.AppKit                0x00007fff8006a15b -[NSApplication run] + 651
  5   com.apple.AppKit                0x00007fff80062d7c NSApplicationMain + 364
  6   com.apple.dt.Xcode              0x0000000100000eec 0x100000000 + 3820
  
  Thread 1:  Dispatch queue: com.apple.libdispatch-manager
  0   libSystem.B.dylib               0x00007fff8249a996 select$DARWIN_EXTSN$NOCANCEL + 10
  1   libSystem.B.dylib               0x00007fff824704a7 _dispatch_mgr_invoke + 388
  2   libSystem.B.dylib               0x00007fff82470094 _dispatch_queue_invoke + 185
  3   libSystem.B.dylib               0x00007fff8246fbbe _dispatch_worker_thread2 + 252
  4   libSystem.B.dylib               0x00007fff8246f4e8 _pthread_wqthread + 353
  5   libSystem.B.dylib               0x00007fff8246f385 start_wqthread + 13
  
  Thread 2:
  0   libSystem.B.dylib               0x00007fff8245575a mach_msg_trap + 10
  1   libSystem.B.dylib               0x00007fff82455dcd mach_msg + 59
  2   com.apple.CoreFoundation        0x00007fff85124452 __CFRunLoopRun + 1698
  3   com.apple.CoreFoundation        0x00007fff851238df CFRunLoopRunSpecific + 575
  4   com.apple.DTDeviceKit           0x0000000114016598 -[DTDKRemoteDeviceDataListener listenerThreadImplementation] + 314
  5   com.apple.Foundation            0x00007fff82721ead __NSThread__main__ + 1429
  6   libSystem.B.dylib               0x00007fff8248e8b6 _pthread_start + 331
  7   libSystem.B.dylib               0x00007fff8248e769 thread_start + 13
  
  Thread 3:
  0   libSystem.B.dylib               0x00007fff82499286 select$DARWIN_EXTSN + 10
  1   com.apple.CoreFoundation        0x00007fff85145ef2 __CFSocketManager + 818
  2   libSystem.B.dylib               0x00007fff8248e8b6 _pthread_start + 331
  3   libSystem.B.dylib               0x00007fff8248e769 thread_start + 13
  
  Thread 4:
  0   libSystem.B.dylib               0x00007fff82490316 __semwait_signal + 10
  1   libSystem.B.dylib               0x00007fff82494131 _pthread_cond_wait + 1286
  2   com.apple.Xcode.DevToolsCore    0x00000001151d9f04 -[XCInvocationQueue _processInvocationsInThreadSlotNumber:] + 330
  3   com.apple.Foundation            0x00007fff82721ead __NSThread__main__ + 1429
  4   libSystem.B.dylib               0x00007fff8248e8b6 _pthread_start + 331
  5   libSystem.B.dylib               0x00007fff8248e769 thread_start + 13
  
  Thread 5:
  0   libSystem.B.dylib               0x00007fff82490316 __semwait_signal + 10
  1   libSystem.B.dylib               0x00007fff82494131 _pthread_cond_wait + 1286
  2   com.apple.CoreVideo             0x00007fff824048ba CVDisplayLink::runIOThread() + 804
  3   com.apple.CoreVideo             0x00007fff8240455b startIOThread(void*) + 139
  4   libSystem.B.dylib               0x00007fff8248e8b6 _pthread_start + 331
  5   libSystem.B.dylib               0x00007fff8248e769 thread_start + 13
  
  Thread 6:
  0   libSystem.B.dylib               0x00007fff8246f30a __workq_kernreturn + 10
  1   libSystem.B.dylib               0x00007fff8246f71c _pthread_wqthread + 917
  2   libSystem.B.dylib               0x00007fff8246f385 start_wqthread + 13
  
  Thread 7:
  0   libSystem.B.dylib               0x00007fff8246f30a __workq_kernreturn + 10
  
  1   libSystem.B.dylib               0x00007fff8246f71c _pthread_wqthread + 917
  2   libSystem.B.dylib               0x00007fff8246f385 start_wqthread + 13
  
  Thread 8:
  0   libSystem.B.dylib               0x00007fff8246f30a __workq_kernreturn + 10
  1   libSystem.B.dylib               0x00007fff8246f71c _pthread_wqthread + 917
  2   libSystem.B.dylib               0x00007fff8246f385 start_wqthread + 13
  
  Thread 9:  Dispatch queue: com.apple.root.default-priority
  0   libSystem.B.dylib               0x00007fff82455796 semaphore_wait_trap + 10
  1   libSystem.B.dylib               0x00007fff824919b5 _dispatch_semaphore_wait_slow + 211
  2   libSystem.B.dylib               0x00007fff824917e9 _dispatch_barrier_sync_f_slow + 134
  3   com.apple.dt.IDEFoundation      0x00000001005ffd82 -[IDEIndexableMainThreadProxy indexableFiles] + 132
  4   com.apple.dt.IDEFoundation      0x0000000100555ca3 -[IDEIndex _purgeStaleData] + 471
  5   com.apple.dt.IDEFoundation      0x00000001005553c3 __36-[IDEIndex _finishIndexingWorkspace]_block_invoke_0 + 198
  6   com.apple.Foundation            0x00007fff8274b081 -[__NSOperationInternal start] + 681
  7   com.apple.Foundation            0x00007fff8274ad37 ____startOperations_block_invoke_2 + 99
  8   libSystem.B.dylib               0x00007fff82491610 _dispatch_call_block_and_release + 15
  9   libSystem.B.dylib               0x00007fff8246fbb1 _dispatch_worker_thread2 + 239
  10  libSystem.B.dylib               0x00007fff8246f4e8 _pthread_wqthread + 353
  11  libSystem.B.dylib               0x00007fff8246f385 start_wqthread + 13
  
  Thread 10:
  0   libSystem.B.dylib               0x00007fff8246f30a __workq_kernreturn + 10
  1   libSystem.B.dylib               0x00007fff8246f71c _pthread_wqthread + 917
  2   libSystem.B.dylib               0x00007fff8246f385 start_wqthread + 13
  
  Thread 11:
  0   libSystem.B.dylib               0x00007fff8245575a mach_msg_trap + 10
  1   libSystem.B.dylib               0x00007fff82455dcd mach_msg + 59
  2   com.apple.CoreFoundation        0x00007fff85124452 __CFRunLoopRun + 1698
  3   com.apple.CoreFoundation        0x00007fff851238df CFRunLoopRunSpecific + 575
  4   com.apple.DebugSymbols          0x00007fff854939dc SpotlightQueryThread(void*) + 380
  5   libSystem.B.dylib               0x00007fff8248e8b6 _pthread_start + 331
  6   libSystem.B.dylib               0x00007fff8248e769 thread_start + 13
  
  Thread 0 crashed with X86 Thread State (64-bit):
    rax: 0x0000000000000000  rbx: 0x00007fff5fbffa08  rcx: 0x00007fff5fbff9a8  rdx: 0x0000000000000000
    rdi: 0x00000000000034ce  rsi: 0x0000000000000006  rbp: 0x00007fff5fbff9c0  rsp: 0x00007fff5fbff9a8
     r8: 0x0000000000000000   r9: 0x000000011c9c44e0  r10: 0x00007fff8249f8ca  r11: 0x0000000000000202
    r12: 0x00007fff70509258  r13: 0x00000002062d89c0  r14: 0x0000000201f95260  r15: 0x00000001001505e0
    rip: 0x00007fff824a3886  rfl: 0x0000000000000202  cr2: 0x0000000005ba9000
  </code></pre>