Created attachment 13673 [details]
Test Case

Found in this desk case:

https://kb.xamarin.com/agent/case/226313

This simple example will crash when you try to call CreateTestClassWithCallBack2.

A test case (with a simple C# console application) is attached. I can also reproduce the issue in a XM Unified Mobile application.

While trivial, the source code for the native library can be found on the desk case. (32-bit binary included in test case attached). 

I have Mono 4.2.1 (explicit/804ddbc) installed.

Stack Trace:

(lldb) command source -s 0 '/tmp/mono-gdb-commands.LKzwZ3'
Executing commands in '/tmp/mono-gdb-commands.LKzwZ3'.
(lldb) process attach --pid 89097
Process 89097 stopped
* thread #1: tid = 0x10aeef, 0x97204e16 libsystem_kernel.dylib`__wait4 + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
    frame #0: 0x97204e16 libsystem_kernel.dylib`__wait4 + 10
libsystem_kernel.dylib`__wait4:
->  0x97204e16 <+10>: jae    0x97204e26                ; <+26>
    0x97204e18 <+12>: calll  0x97204e1d                ; <+17>
    0x97204e1d <+17>: popl   %edx
    0x97204e1e <+18>: movl   0x9aea207(%edx), %edx

Executable module set to "/Library/Frameworks/Mono.framework/Versions/4.2.1/bin/mono".
Architecture set to: i386-apple-macosx.
(lldb) thread list
Process 89097 stopped
* thread #1: tid = 0x10aeef, 0x97204e16 libsystem_kernel.dylib`__wait4 + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  thread #2: tid = 0x10aef0, 0x97204512 libsystem_kernel.dylib`__psynch_cvwait + 10
  thread #3: tid = 0x10aef2, 0x971fea0a libsystem_kernel.dylib`semaphore_wait_trap + 10
  thread #4: tid = 0x10aef3, 0x972058ce libsystem_kernel.dylib`kevent64 + 10, queue = 'com.apple.libdispatch-manager'
  thread #5: tid = 0x10aef4, 0x9720476e libsystem_kernel.dylib`__recvfrom + 10
(lldb) thread backtrace all
* thread #1: tid = 0x10aeef, 0x97204e16 libsystem_kernel.dylib`__wait4 + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x97204e16 libsystem_kernel.dylib`__wait4 + 10
    frame #1: 0x950c7b19 libsystem_c.dylib`waitpid$UNIX2003 + 48
    frame #2: 0x001b939d mono`mono_handle_native_sigsegv(signal=6, ctx=0xbff0630c, info=0xbff062cc) + 541 at mini-exceptions.c:2193 [opt]
    frame #3: 0x002098e1 mono`sigabrt_signal_handler(_dummy=<unavailable>, _info=<unavailable>, context=<unavailable>) + 129 at mini-posix.c:208 [opt]

  thread #2: tid = 0x10aef0, 0x97204512 libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #0: 0x97204512 libsystem_kernel.dylib`__psynch_cvwait + 10
    frame #1: 0x94c54163 libsystem_pthread.dylib`_pthread_cond_wait + 726
    frame #2: 0x94c57528 libsystem_pthread.dylib`pthread_cond_wait$UNIX2003 + 71
    frame #3: 0x0032c852 mono`thread_func(thread_data=0x00000000) + 466 at sgen-thread-pool.c:118 [opt]
    frame #4: 0x94c53c25 libsystem_pthread.dylib`_pthread_body + 138
    frame #5: 0x94c53b9b libsystem_pthread.dylib`_pthread_start + 162
    frame #6: 0x94c50e32 libsystem_pthread.dylib`thread_start + 34

  thread #3: tid = 0x10aef2, 0x971fea0a libsystem_kernel.dylib`semaphore_wait_trap + 10
    frame #0: 0x971fea0a libsystem_kernel.dylib`semaphore_wait_trap + 10
    frame #1: 0x0034f34a mono`mono_sem_wait(sem=0x0042f08c, alertable=1) + 26 at mono-semaphore.c:109 [opt]
    frame #2: 0x002cc44e mono`finalizer_thread(unused=0x00000000) + 158 at gc.c:1096 [opt]
    frame #3: 0x002a666c mono`start_wrapper [inlined] start_wrapper_internal + 463 at threads.c:723 [opt]
    frame #4: 0x002a649d mono`start_wrapper(data=<unavailable>) + 29 at threads.c:770 [opt]
    frame #5: 0x00356ee0 mono`inner_start_thread(arg=<unavailable>) + 240 at mono-threads-posix.c:97 [opt]
    frame #6: 0x94c53c25 libsystem_pthread.dylib`_pthread_body + 138
    frame #7: 0x94c53b9b libsystem_pthread.dylib`_pthread_start + 162
    frame #8: 0x94c50e32 libsystem_pthread.dylib`thread_start + 34

  thread #4: tid = 0x10aef3, 0x972058ce libsystem_kernel.dylib`kevent64 + 10, queue = 'com.apple.libdispatch-manager'
    frame #0: 0x972058ce libsystem_kernel.dylib`kevent64 + 10
    frame #1: 0x92839ce3 libdispatch.dylib`_dispatch_mgr_invoke + 245
    frame #2: 0x928398c6 libdispatch.dylib`_dispatch_mgr_thread + 52

  thread #5: tid = 0x10aef4, 0x9720476e libsystem_kernel.dylib`__recvfrom + 10
    frame #0: 0x9720476e libsystem_kernel.dylib`__recvfrom + 10
    frame #1: 0x950c7d26 libsystem_c.dylib`recv$UNIX2003 + 55
    frame #2: 0x001edc38 mono`socket_transport_recv(buf=<unavailable>, len=<unavailable>) + 168 at debugger-agent.c:1130 [opt]
    frame #3: 0x001dee27 mono`debugger_thread [inlined] transport_recv(len=11) + 35 at debugger-agent.c:1515 [opt]
    frame #4: 0x001dee04 mono`debugger_thread(arg=0x00000000) + 1572 at debugger-agent.c:9563 [opt]
    frame #5: 0x00356ee0 mono`inner_start_thread(arg=<unavailable>) + 240 at mono-threads-posix.c:97 [opt]
    frame #6: 0x94c53c25 libsystem_pthread.dylib`_pthread_body + 138
    frame #7: 0x94c53b9b libsystem_pthread.dylib`_pthread_start + 162
    frame #8: 0x94c50e32 libsystem_pthread.dylib`thread_start + 34
(lldb) detach

=================================================================
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.
=================================================================

(lldb) quit
Process 89097 detached
Abort trap: 6