visualstudio_py_debugger.py 文件源码

def trace_func(self, frame, event, arg):
        # If we're so far into process shutdown that sys is already gone, just stop tracing.
        if sys is None:
            return None
        elif self.is_sending:
            # https://pytools.codeplex.com/workitem/1864 
            # we're currently doing I/O w/ the socket, we don't want to deliver
            # any breakpoints or async breaks because we'll deadlock.  Continue
            # to return the trace function so all of our frames remain
            # balanced.  A better way to deal with this might be to do
            # sys.settrace(None) when we take the send lock, but that's much
            # more difficult because our send context manager is used both
            # inside and outside of the trace function, and so is used when
            # tracing is enabled and disabled, and so it's very easy to get our
            # current frame tracking to be thrown off...
            return self.trace_func

        try:
            # if should_debug_code(frame.f_code) is not true during attach
            # the current frame is None and a pop_frame will cause an exception and 
            # break the debugger
            if self.cur_frame is None:
                # happens during attach, we need frame for blocking
                self.push_frame(frame)
            if self.stepping == STEPPING_BREAK and should_debug_code(frame.f_code):
                if self.detach:
                    if stackless is not None:
                        stackless.set_schedule_callback(None)
                        stackless.tasklet.__call__ = self.__oldstacklesscall__
                    sys.settrace(None)
                    return None

                self.async_break()

            return self._events[event](frame, arg)
        except (StackOverflowException, KeyboardInterrupt):
            # stack overflow, disable tracing
            return self.trace_func