Ctrl-C crashes Python after importing scipy.stats

Question

I\'m running 64-bit Python 2.7.3 on Win7 64-bit. I can reliably crash the Python interpreter by doing this:

>>> from scipy import stats
>>>         


        

Answer 1

Here's a variation on your posted solution that may work. Maybe there's a better way to solve this problem -- or maybe even avoid it all together by setting an environment variable that tells the DLL to skip installing a handler. Hopefully this helps until you find a better way.

Both the time module (lines 868-876) and _multiprocessing module (lines 312-321) call SetConsoleCtrlHandler. In the case of the time module, its console control handler sets a Windows event, hInterruptEvent. For the main thread, time.sleep waits on this event via WaitForSingleObject(hInterruptEvent, ul_millis), where ul_millis is the number of milliseconds to sleep unless interrupted by Ctrl+C. Since the handler that you've installed returns True, the time module's handler never gets called to set hInterruptEvent, which means sleep cannot be interrupted.

I tried using imp.init_builtin('time') to reinitialize the time module, but apparently SetConsoleCtrlHandler ignores the 2nd call. It seems the handler has to be removed and then reinserted. Unfortunately, the time module doesn't export a function for that. So, as a kludge, just make sure you import the time module after you install your handler. Since importing scipy also imports time, you need to pre-load libifcoremd.dll using ctypes to get the handlers in the right order. Finally, add a call to thread.interrupt_main to make sure Python's SIGINT handler gets called^[1].

For example:

import os
import imp
import ctypes
import thread
import win32api

# Load the DLL manually to ensure its handler gets
# set before our handler.
basepath = imp.find_module('numpy')[1]
ctypes.CDLL(os.path.join(basepath, 'core', 'libmmd.dll'))
ctypes.CDLL(os.path.join(basepath, 'core', 'libifcoremd.dll'))

# Now set our handler for CTRL_C_EVENT. Other control event 
# types will chain to the next handler.
def handler(dwCtrlType, hook_sigint=thread.interrupt_main):
    if dwCtrlType == 0: # CTRL_C_EVENT
        hook_sigint()
        return 1 # don't chain to the next handler
    return 0 # chain to the next handler

win32api.SetConsoleCtrlHandler(handler, 1)

>>> import time
>>> from scipy import stats
>>> time.sleep(10)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyboardInterrupt

---

[1] interrupt_main calls PyErr_SetInterrupt. This trips Handlers[SIGINT] and calls Py_AddPendingCall to add checksignals_witharg. In turn this calls PyErr_CheckSignals. Since Handlers[SIGINT] is tripped, this calls Handlers[SIGINT].func. Finally, if func is signal.default_int_handler, you'll get a KeyboardInterrupt exception.