ERROR: test_issue9324 (test.test_signal.WindowsSignalTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_signal.py", line 213, in test_issue9324
    signal.signal(sig, signal.signal(sig, handler))
TypeError: signal handler must be signal.SIG_IGN, signal.SIG_DFL, or a callable object

Related issue: #9324 (closed 3 years ago).

This error is reproducible by simply passing '-j' to regrtest on any Windows build so it is not Win64-specific.

It seems that when run in a subprocess, certain signals have C handlers that cause the return value of getsignal() to return None which, of course, is not a valid handler for signal().

The C-level handlers seem to be coming from faulthandler so I am unsure if it is wise to replace those signal handlers within the test.  Attached is a patch which only resets signal handlers for those without a C-level handler.

Is it possible this is indicating a real bug with faulthandler on Windows? Why are we returning None from signal.getsignal?

It do not think that it is a just a Windows issue wrt faulthandler. It is that there are no similar tests for signals on other platforms.

getsignal() needs to return *something* for the value of a handler which is not SIG_DFL or SIG_IGN.

Added nosy list from issue 18523

I checked the getsignal docs, and indeed None is the expected return value for "signal handler exists, but was not installed from Python". That's accurate given the way faulthandler works:

On Linux (Python 3.3.0):

$ python3 -c "import signal; print(signal.getsignal(signal.SIGSEGV))"
0
$ python3 -X faulthandler -c "import signal; print(signal.getsignal(signal.SIGSEGV))"
None

So Jeremy's patch looks correct to me - when faulthandler is enabled, we need to skip over the signals that have those handlers attached.

New changeset b7834800562f by Nick Coghlan in branch '3.3':
Close #18396: fix spurious test_signal failure on Windows
http://hg.python.org/cpython/rev/b7834800562f

New changeset 6fc71ed6a910 by Nick Coghlan in branch 'default':
Merge #18396 from 3.3
http://hg.python.org/cpython/rev/6fc71ed6a910

I added one slight tweak to Jeremy's patch - an assertion to ensure that test loop is checking at least some* signals, even when faulthandler is enabled.