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xpc_abort(3)             BSD Library Functions Manual             xpc_abort(3)

NAME
     xpc_abort -- conditions which cause XPC to abort

DESCRIPTION
     The XPC API will aggressively defend itself against perceived misuse. Wherever XPC can definitively
     detect misuse of its APIs or data corruption, it will abort. For example, if the retain count of an
     object underflows by calling xpc_release(3) on it too many times, XPC will abort the process.

     Many frameworks opt to keep the program limping along in such a state (and will perhaps print a warning
     message to the system log), but aborting upon detection provides unmistakable warning that there is a
     bug present in the application which should be fixed before shipping.

     When XPC aborts a process, it will place information about the condition which triggered the abort in
     the Application Specific Information section of the crash report. The message will be human-readable,
     prefixed with "XPC API Misuse:", and the crash report will indicate the stack trace which caused the
     abort.

     XPC will also abort if it detects unrecoverable data corruption in its internal state. The messages for
     these conditions will be prefixd with "Bug in libxpc:".  If you come across such a crash, please file a
     bug and include the generated crash log, system log and steps to reproduce (if there are any identifi-able identifiable
     able steps).

     Currently, the manner in which XPC aborts the process will result in termination due to SIGILL (illegal
     instruction). The exact signal raised may change from release to release (or platform to platform). But
     on OS X Lion, SIGILL may be used as a hint that the process was terminated intentionally.

DEBUGGING
     When debugging in Xcode or at the gdb command prompt, the debugger acts as the exception handler for
     the process being debugged. As a result, if the process is aborted by XPC, no crash report will be gen-erated, generated,
     erated, and thus it may not be obvious why the program was terminated.

     As mentioned before, SIGILL is an indication that the process was terminated intentionally. If you
     observe the last frame in the crashing stack to be _xpc_api_misuse(), you may use the
     xpc_debugger_api_misuse_info() API from within the debugger to obtain a human-readable string describ-ing describing
     ing why the process was aborted. For example:

           Program received signal EXC_BAD_INSTRUCTION, Illegal instruction/operand.
           0x000000010012b25e in _xpc_api_misuse ()
           (gdb) p (char *)xpc_debugger_api_misuse_info()
           $1 = 0x7fff5fbff908 "XPC API Misuse: Over-release of object."
           (gdb)

     This message indicates that xpc_release(3) was called too many times on an object.

     IMPORTANT: The xpc_debugger_api_misuse_info() API can ONLY be called from within a debugger. It is not
     meant to be called directly from the program. Do not call it directly from your code, and do not rely
     on the address of the result for any reason.

SEE ALSO
     xpc(3), xpc_object(3), xpc_objects(3)

Darwin                           1 July, 2011                           Darwin