Python sys.settrace() Examples

def test_call_tracing(self):
        def f(i):
            return i * 2
        def g():
            pass

        # outside of a traceback
        self.assertEqual(10, sys.call_tracing(f, (5, )))

        # inside of a traceback
        log = []
        def thandler(frm, evt, pl):
            if evt == 'call':
                log.append(frm.f_code.co_name)
                if log[-1] == 'g':
                    sys.call_tracing(f, (5, ))
            return thandler

        sys.settrace(thandler)
        g()
        sys.settrace(None)

        self.assertEqual(log, ['g', 'f']) 

def no_tracing(func):
    """Decorator to temporarily turn off tracing for the duration of a test."""
    if not hasattr(sys, 'gettrace'):
        return func
    else:
        def wrapper(*args, **kwargs):
            original_trace = sys.gettrace()
            try:
                sys.settrace(None)
                return func(*args, **kwargs)
            finally:
                sys.settrace(original_trace)
        wrapper.__name__ = func.__name__
        return wrapper


# Return True if opcode code appears in the pickle, else False. 

def set_trace(self, frame=None):
        """Starts debugging from 'frame'"""
        if frame is None:
            frame = sys._getframe().f_back  # Skip set_trace method

        if sys.version_info[0] == 2:
            stopOnHandleLine = self._dbgClient.handleLine.func_code
        else:
            stopOnHandleLine = self._dbgClient.handleLine.__code__

        frame.f_trace = self.trace_dispatch
        while frame.f_back is not None:
            # stop at erics debugger frame or a threading bootstrap
            if frame.f_back.f_code == stopOnHandleLine:
                frame.f_trace = self.trace_dispatch
                break

            frame = frame.f_back

        self.stop_everywhere = True
        sys.settrace(self.trace_dispatch)
        sys.setprofile(self._dbgClient.callTraceEnabled) 

def test_cp30130(self):
        def f(frame, event, arg):
            if event == 'exception':
                    global ex
                    ex = arg
            return f

        sys.settrace(f)

        def g():
            raise Exception()

        try:
            g()
        except:
            pass

        exc_type = ex[0]
        exc_value = ex[1]
        tb_value = ex[2]

        import traceback
        self.assertTrue(''.join(traceback.format_exception(exc_type, exc_value, tb_value)).find('line') != -1)

        sys.settrace(None) 

def runeval(self, expr, globals=None, locals=None):
        if globals is None:
            import __main__
            globals = __main__.__dict__
        if locals is None:
            locals = globals
        self.reset()
        sys.settrace(self.trace_dispatch)
        if not isinstance(expr, types.CodeType):
            expr = expr+'\n'
        try:
            return eval(expr, globals, locals)
        except BdbQuit:
            pass
        finally:
            self.quitting = 1
            sys.settrace(None) 

def run(self, cmd, globals=None, locals=None):
        if globals is None:
            import __main__
            globals = __main__.__dict__
        if locals is None:
            locals = globals
        self.reset()
        sys.settrace(self.trace_dispatch)
        if not isinstance(cmd, types.CodeType):
            cmd = cmd+'\n'
        try:
            exec cmd in globals, locals
        except BdbQuit:
            pass
        finally:
            self.quitting = 1
            sys.settrace(None) 

def restore_settrace(monkeypatch):
    """(Re)store sys.gettrace after test run.

    This is required to re-enable coverage tracking.
    """
    assert sys.gettrace() is _orig_trace

    orig_settrace = sys.settrace

    # Wrap sys.settrace to restore original tracing function (coverage)
    # with `sys.settrace(None)`.
    def settrace(func):
        if func is None:
            orig_settrace(_orig_trace)
        else:
            orig_settrace(func)
    monkeypatch.setattr("sys.settrace", settrace)

    yield

    newtrace = sys.gettrace()
    if newtrace is not _orig_trace:
        sys.settrace(_orig_trace)
        assert newtrace is None 

def updateSysTrace(self):
        ## Install or uninstall  sys.settrace handler 
        
        if not self.ui.catchNextExceptionBtn.isChecked() and not self.ui.catchAllExceptionsBtn.isChecked():
            if sys.gettrace() == self.systrace:
                sys.settrace(None)
            return
        
        if self.ui.onlyUncaughtCheck.isChecked():
            if sys.gettrace() == self.systrace:
                sys.settrace(None)
        else:
            if sys.gettrace() is not None and sys.gettrace() != self.systrace:
                self.ui.onlyUncaughtCheck.setChecked(False)
                raise Exception("sys.settrace is in use; cannot monitor for caught exceptions.")
            else:
                sys.settrace(self.systrace) 

def test_jump_to_firstlineno(self):
        # This tests that PDB can jump back to the first line in a
        # file.  See issue #1689458.  It can only be triggered in a
        # function call if the function is defined on a single line.
        code = compile("""
# Comments don't count.
output.append(2)  # firstlineno is here.
output.append(3)
output.append(4)
""", "<fake module>", "exec")
        class fake_function:
            func_code = code
        tracer = JumpTracer(fake_function, 2, 0)
        sys.settrace(tracer.trace)
        namespace = {"output": []}
        exec code in namespace
        sys.settrace(None)
        self.compare_jump_output([2, 3, 2, 3, 4], namespace["output"]) 

def test_trash_stack(self):
        def f():
            for i in range(5):
                print i  # line tracing will raise an exception at this line

        def g(frame, why, extra):
            if (why == 'line' and
                frame.f_lineno == f.func_code.co_firstlineno + 2):
                raise RuntimeError, "i am crashing"
            return g

        sys.settrace(g)
        try:
            f()
        except RuntimeError:
            # the test is really that this doesn't segfault:
            import gc
            gc.collect()
        else:
            self.fail("exception not propagated")


# 'Jump' tests: assigning to frame.f_lineno within a trace function
# moves the execution position - it's how debuggers implement a Jump
# command (aka. "Set next statement"). 

def run_test_for_event(self, event):
        """Tests that an exception raised in response to the given event is
        handled OK."""
        self.raiseOnEvent = event
        try:
            for i in xrange(sys.getrecursionlimit() + 1):
                sys.settrace(self.trace)
                try:
                    self.f()
                except ValueError:
                    pass
                else:
                    self.fail("exception not raised!")
        except RuntimeError:
            self.fail("recursion counter not reset")

    # Test the handling of exceptions raised by each kind of trace event. 

def run(self, cmd, globals=None, locals=None):
        if globals is None:
            import __main__
            globals = __main__.__dict__
        if locals is None:
            locals = globals
        self.reset()
        sys.settrace(self.trace_dispatch)
        if not isinstance(cmd, types.CodeType):
            cmd = cmd+'\n'
        try:
            exec cmd in globals, locals
        except BdbQuit:
            pass
        finally:
            self.quitting = 1
            sys.settrace(None) 

def testInteractionWithTraceFunc(self):

        import sys
        def tracer(a,b,c):
            return tracer

        def adaptgetter(name, klass, getter):
            kind, des = getter
            if kind == 1:       # AV happens when stepping from this line to next
                if des == "":
                    des = "_%s__%s" % (klass.__name__, name)
                return lambda obj: getattr(obj, des)

        class TestClass:
            pass

        sys.settrace(tracer)
        adaptgetter("foo", TestClass, (1, ""))
        sys.settrace(None)

        self.assertRaises(TypeError, sys.settrace) 

def testLocalsClass_WithTrace(self):
        # Issue23728: after the trace function returns, the locals()
        # dictionary is used to update all variables, this used to
        # include free variables. But in class statements, free
        # variables are not inserted...
        import sys
        sys.settrace(lambda a,b,c:None)
        try:
            x = 12

            class C:
                def f(self):
                    return x

            self.assertEqual(x, 12) # Used to raise UnboundLocalError
        finally:
            sys.settrace(None) 

def set_trace(self):
		# Start debugging from _2_ levels up!
		try:
			1 + ''
		except:
			frame = sys.exc_info()[2].tb_frame.f_back.f_back
		self.reset()
		self.userbotframe = None
		while frame:
			# scriptutils.py creates a local variable with name
			# '_debugger_stop_frame_', and we dont go past it
			# (everything above this is Pythonwin framework code)
			if "_debugger_stop_frame_" in frame.f_locals:
				self.userbotframe = frame
				break

			frame.f_trace = self.trace_dispatch
			self.botframe = frame
			frame = frame.f_back
		self.set_step()
		sys.settrace(self.trace_dispatch) 

def dispatch_call(self, frame, arg):
        traceenter("dispatch_call",_dumpf(frame))
        frame.f_locals['__axstack_address__'] = axdebug.GetStackAddress()
        if frame is self.botframe:
            trace("dispatch_call is self.botframe - returning tracer")
            return self.trace_dispatch
        # Not our bottom frame.  If we have a document for it,
        # then trace it, otherwise run at full speed.
        if self.codeContainerProvider.FromFileName(frame.f_code.co_filename) is None:
            trace("dispatch_call has no document for", _dumpf(frame), "- skipping trace!")
##                      sys.settrace(None)
            return None
        return self.trace_dispatch

#               rc =  bdb.Bdb.dispatch_call(self, frame, arg)
#               trace("dispatch_call", _dumpf(frame),"returned",rc)
#               return rc 

def post_mortem(t=None):
	if t is None:
		t = sys.exc_info()[2] # Will be valid if we are called from an except handler.
	if t is None:
		try:
			t = sys.last_traceback
		except AttributeError:
			print "No traceback can be found from which to perform post-mortem debugging!"
			print "No debugging can continue"
			return
	p = _GetCurrentDebugger()
	if p.frameShutdown: return # App closing
	# No idea why I need to settrace to None - it should have been reset by now?
	sys.settrace(None)
	p.reset()
	while t.tb_next != None: t = t.tb_next
	p.bAtPostMortem = 1
	p.prep_run(None)
	try:
		p.interaction(t.tb_frame, t)
	finally:
		t = None
		p.bAtPostMortem = 0
		p.done_run() 

def test_no_jump_without_trace_function(self):
        # Must set sys.settrace(None) in setUp(), else condition is not
        # triggered.
        no_jump_without_trace_function() 

def _settrace_and_return(tracefunc):
    sys.settrace(tracefunc)
    sys._getframe().f_back.f_trace = tracefunc 

def test_cp24381(self):
        import sys
        orig_sys_trace_func = sys.gettrace()
        def f(*args):
            global CP24381_MESSAGES
            CP24381_MESSAGES += args[1:]
            return f

        cp24381_file_name = "cp24381.py"
        cp24381_contents  = """
print 'a'
print 'b'
print 'c'

def f():
    print 'hi'

f()
"""

        try:
            self.write_to_file(cp24381_file_name, cp24381_contents)
            sys.settrace(f)
            with path_modifier('.'):
                import cp24381
        finally:
            sys.settrace(orig_sys_trace_func)
            os.unlink(cp24381_file_name)

        self.assertEqual(CP24381_MESSAGES,
                ['call', None, 'line', None, 'line', None, 'line', None, 'line',
                None, 'line', None, 'call', None, 'line', None, 'return', None,
                'return', None]) 

def __enter__(self, context=0):
        if not self.config.enabled:
            return

        calling_frame = sys._getframe(context + 1)
        if not self._is_internal_frame(calling_frame):
            calling_frame.f_trace = self.trace
            self.target_frames.add(calling_frame)
            self.config.last_frame = calling_frame
            self.trace(calling_frame, 'enter', None)

        stack = thread_global.__dict__.setdefault('original_trace_functions', [])
        stack.append(sys.gettrace())
        sys.settrace(self.trace) 

def test_frame_tstate_tracing(self):
        # Issue #14432: Crash when a generator is created in a C thread that is
        # destroyed while the generator is still used. The issue was that a
        # generator contains a frame, and the frame kept a reference to the
        # Python state of the destroyed C thread. The crash occurs when a trace
        # function is setup.

        def noop_trace(frame, event, arg):
            # no operation
            return noop_trace

        def generator():
            while 1:
                yield "generator"

        def callback():
            if callback.gen is None:
                callback.gen = generator()
            return next(callback.gen)
        callback.gen = None

        old_trace = sys.gettrace()
        sys.settrace(noop_trace)
        try:
            # Install a trace function
            threading.settrace(noop_trace)

            # Create a generator in a C thread which exits after the call
            _testcapi.call_in_temporary_c_thread(callback)

            # Call the generator in a different Python thread, check that the
            # generator didn't keep a reference to the destroyed thread state
            for test in range(3):
                # The trace function is still called here
                callback()
        finally:
            sys.settrace(old_trace) 

def test_finalize_with_trace(self):
        # Issue1733757
        # Avoid a deadlock when sys.settrace steps into threading._shutdown
        p = subprocess.Popen([sys.executable, "-c", """if 1:
            import sys, threading

            # A deadlock-killer, to prevent the
            # testsuite to hang forever
            def killer():
                import os, time
                time.sleep(2)
                print 'program blocked; aborting'
                os._exit(2)
            t = threading.Thread(target=killer)
            t.daemon = True
            t.start()

            # This is the trace function
            def func(frame, event, arg):
                threading.current_thread()
                return func

            sys.settrace(func)
            """],
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE)
        self.addCleanup(p.stdout.close)
        self.addCleanup(p.stderr.close)
        stdout, stderr = p.communicate()
        rc = p.returncode
        self.assertFalse(rc == 2, "interpreted was blocked")
        self.assertTrue(rc == 0,
                        "Unexpected error: " + repr(stderr)) 

def set_continue(self):
        # Calling set_continue unconditionally would break unit test
        # coverage reporting, as Bdb.set_continue calls sys.settrace(None).
        if self.__debugger_used:
            pdb.Pdb.set_continue(self) 

def do_debug(self, arg):
        sys.settrace(None)
        globals = self.curframe.f_globals
        locals = self.curframe_locals
        p = Pdb(self.completekey, self.stdin, self.stdout)
        p.prompt = "(%s) " % self.prompt.strip()
        print >>self.stdout, "ENTERING RECURSIVE DEBUGGER"
        sys.call_tracing(p.run, (arg, globals, locals))
        print >>self.stdout, "LEAVING RECURSIVE DEBUGGER"
        sys.settrace(self.trace_dispatch)
        self.lastcmd = p.lastcmd 

def __exit__(self, exc_type, exc_value, exc_traceback, context=0):
        if not self.config.enabled:
            return

        stack = thread_global.original_trace_functions
        sys.settrace(stack.pop())
        calling_frame = sys._getframe(context + 1)
        self.trace(calling_frame, 'exit', None)
        self.target_frames.discard(calling_frame)
        self.frame_infos.pop(calling_frame, None) 

def run(self, cmd,globals=None, locals=None, start_stepping = 1):
		if type(cmd) not in [types.StringType, types.CodeType]:
			raise TypeError("Only strings can be run")
		self.last_cmd_debugged = cmd
		if start_stepping:
			self.isInitialBreakpoint = 0
		else:
			self.isInitialBreakpoint = 1
		try:
			if globals is None:
				import __main__
				globals = __main__.__dict__
			if locals is None:
				locals = globals
			self.reset()
			self.prep_run(cmd)
			sys.settrace(self.trace_dispatch)
			if type(cmd) != types.CodeType:
				cmd = cmd+'\n'
			try:
				try:
					if start_stepping: self.skipBotFrame = SKIP_STEP
					else: self.skipBotFrame = SKIP_RUN
					if sys.version_info > (2,2):
						exec cmd in globals, locals
					else:
						_doexec(cmd, globals, locals)
				except bdb.BdbQuit:
					pass
			finally:
				self.skipBotFrame = SKIP_NONE
				self.quitting = 1
				sys.settrace(None)

		finally:
			self.done_run(cmd) 

def set_continue(self):
        # Calling set_continue unconditionally would break unit test 
        # coverage reporting, as Bdb.set_continue calls sys.settrace(None).
        if self.__debugger_used:
            _orp.set_continue(self) 

def set_quit(self):
        self.stopframe = self.botframe
        self.returnframe = None
        self.quitting = 1
        sys.settrace(None)

    # Derived classes and clients can call the following methods
    # to manipulate breakpoints.  These methods return an
    # error message is something went wrong, None if all is well.
    # Set_break prints out the breakpoint line and file:lineno.
    # Call self.get_*break*() to see the breakpoints or better
    # for bp in Breakpoint.bpbynumber: if bp: bp.bpprint(). 

def restore_sys_gettrace(self, trace_fxn):
        sys.settrace(trace_fxn)