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copied!<p>What you're seeing is an unfortunate quirk of AppKit and UIKit. Both iOS and OS X have an exception handler in <code>CFRunLoop</code> that traps all uncaught exceptions. On OS X, the handler displays the exception to the user with a dialog box, but on iOS, the handler simply rethrows the exception.</p> <p>Objective-C exceptions, as implemented by <code>NSException</code>, save their backtraces within the exception object right before the actual "throw" happens, as part of <code>[NSException init]</code> (or a similar initializer method). Unfortunately, C++ exceptions don't do the same. Normally, a C++ exception has a backtrace because the runtime library detects that there's no <code>catch</code> and immediately calls <code>std::terminate</code>, which in turn calls <code>abort()</code>, leaving the entire call stack intact, like so:</p> <pre><code>Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 libsystem_kernel.dylib 0x00007fff93ef8d46 __kill + 10 1 libsystem_c.dylib 0x00007fff89968df0 abort + 177 2 libc++abi.dylib 0x00007fff8beb5a17 abort_message + 257 3 libc++abi.dylib 0x00007fff8beb33c6 default_terminate() + 28 4 libobjc.A.dylib 0x00007fff8a196887 _objc_terminate() + 111 5 libc++abi.dylib 0x00007fff8beb33f5 safe_handler_caller(void (*)()) + 8 6 libc++abi.dylib 0x00007fff8beb3450 std::terminate() + 16 7 libc++abi.dylib 0x00007fff8beb45b7 __cxa_throw + 111 8 test 0x0000000102999f3b main + 75 9 libdyld.dylib 0x00007fff8e4ab7e1 start + 1 </code></pre> <p>However, when the run loop exception handler traps the exception, execution resumes normally within the <code>catch</code> block. The original backtrace is therefore lost. The rethrow subsequently calls <code>std::terminate</code>, but at this point, the call stack reflects the run loop exception handler.</p> <p>To get a backtrace from a C++ exception in this circumstance, you have to throw an exception object which mimics <code>NSException</code> and reads the call stack as part of its constructor, and make sure that all exceptions thrown in your code do the same. <code>std::exception</code> doesn't do this, and it's not at all likely that any third-party code you're using will either.</p> <p>File a bug with Apple asking them to remove the <code>CFRunLoop</code> exception handler, or at least provide an API for shutting it off. There is no API, not even an SPI, for doing this right now.</p>

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