fork(1) download 
  1. import inspect
  2. import types
  3. import ctypes
  4. import sys
  5. import traceback
  6.  
  7.  
  8. frameobject_fields = [
  9. 	# PyObject_VAR_HEAD
  10. 	("ob_refcnt", ctypes.c_int64),
  11. 	("ob_type", ctypes.py_object),
  12. 	("ob_size", ctypes.c_ssize_t),
  13. 	# struct _frame *f_back;      /* previous frame, or NULL */
  14. 	("f_back", ctypes.c_void_p),
  15. 	# PyCodeObject *f_code;       /* code segment */
  16. 	("f_code", ctypes.c_void_p),
  17. 	# PyObject *f_builtins;       /* builtin symbol table (PyDictObject) */
  18. 	("f_builtins", ctypes.py_object),
  19. 	# PyObject *f_globals;        /* global symbol table (PyDictObject) */
  20. 	("f_globals", ctypes.py_object),
  21. 	####
  22. 	("f_locals", ctypes.py_object),
  23. 	("f_valuestack", ctypes.POINTER(ctypes.py_object)),
  24. 	("f_stacktop", ctypes.POINTER(ctypes.py_object)),
  25. 	("f_trace", ctypes.py_object),
  26. 	("f_exc_type", ctypes.py_object),
  27. 	("f_exc_value", ctypes.py_object),
  28. 	("f_exc_traceback", ctypes.py_object),
  29. 	("f_tstate", ctypes.c_void_p),
  30. 	("f_lasti", ctypes.c_int),
  31. ]
  32. if hasattr(sys, "getobjects"):
  33. 	# This python was compiled with debugging enabled.
  34. 	frameobject_fields = [
  35. 		("_ob_next", ctypes.c_void_p),
  36. 		("_ob_prev", ctypes.c_void_p),
  37. 	] + frameobject_fields
  38. class PyFrameObject(ctypes.Structure):
  39. 	_fields_ = frameobject_fields
  40.  
  41.  
  42. class Continuation:
  43. 	def __init__(self, frame):
  44. 		self.frame = frame
  45. 		self.lasti = frame.f_lasti
  46. 		self.lastis = []
  47.  
  48. 		frame = frame.f_back
  49. 		while frame is not None:
  50. 			self.lastis.append(frame.f_lasti)
  51. 			frame = frame.f_back
  52.  
  53. 	def __call__(self):
  54. 		print('\nbefore')
  55. 		traceback.print_stack()
  56.  
  57. 		cur_frame = PyFrameObject.from_address(id(inspect.currentframe()))
  58. 		PyFrameObject.from_address(cur_frame.f_back).ob_refcnt -= 1
  59. 		cur_frame.f_back = id(self.frame)
  60. 		PyFrameObject.from_address(id(self.frame)).ob_refcnt += 1
  61.  
  62. 		frame = self.frame
  63. 		_frame = PyFrameObject.from_address(id(frame))
  64. 		_frame.f_lasti = self.lasti + 4
  65.  
  66. 		frame = frame.f_back
  67. 		for lasti in self.lastis:
  68. 			if len(frame.f_code.co_code) != frame.f_lasti + 2:
  69. 				break
  70. 			_frame = PyFrameObject.from_address(id(frame))
  71. 			_frame.f_lasti = lasti + 4
  72. 			frame = frame.f_back
  73.  
  74. 		print('\nafter')
  75. 		traceback.print_stack()
  76.  
  77.  
  78. def callcc(f):
  79. 	f(Continuation(inspect.currentframe().f_back))
  80.  
  81.  
  82. cc = None
  83.  
  84.  
  85. def func():
  86. 	bar = 0
  87. 	print("This should show only once")
  88. 	def save_cont(k):
  89. 		global cc
  90. 		cc = k
  91. 	callcc(save_cont)
  92. 	print(bar)
  93. 	bar += 1
  94.  
  95.  
  96. def g():
  97. 	func()
  98. 	print("This should show multiple times")
  99.  
  100. sys.stderr = sys.stdout
  101. g()
  102. cc()
Success #stdin #stdout 0.02s 33448KB
comments (?)
stdin 
Standard input is empty
stdout 
This should show only once
0
This should show multiple times

before
  File "./prog.py", line 102, in <module>
  File "./prog.py", line 55, in __call__

after
  File "./prog.py", line 102, in <module>
  File "./prog.py", line 98, in g
  File "./prog.py", line 92, in func
  File "./prog.py", line 75, in __call__
https://ideone.com/kGchEm
language:
Python 3 (python  3.9.5)
created:
6 years ago
visibility:
secret

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