[Scons-users] Crash in signal handling in Jobs.py

[Brian Quistorff]

Hi Bill,

Yes, that's the situation.

Thanks, Brian



On Wed, Oct 6, 2021 at 9:31 PM Bill Deegan <bill at baddogconsulting.com>
wrote:

> I see this
> "None means that the previous signal handler was not installed from
> Python."
>
> In the docs https://docs.python.org/3/library/signal.html#signal.getsignal
> -Bill
>
> On Wed, Oct 6, 2021 at 6:29 PM Bill Deegan <bill at baddogconsulting.com>
> wrote:
>
>> Brian,
>>
>> O.k. so if I understand correctly you have a signal handler registerer
>> outside SCons (in C code for example), and when this is the case python's
>> signal.signal() will return None?
>> And then when SCons tries to reset it back to it's original setting
>> attempts to set it to None and that causes Python to crash?
>>
>> -Bill
>> SCons Co-Manager
>>
>> On Wed, Oct 6, 2021 at 5:10 PM Brian Quistorff <brian at quistorff.com>
>> wrote:
>>
>>> Hello,
>>>
>>> Thanks all for the wonderful tool.
>>>
>>> My scons crashes in situations where there is a signal handler
>>> registered from "outside Python" (the phrase used in the Python docs for
>>> signal.signal). This happens for me when I run scons from inside Stata (a
>>> stats program), which embeds Python, and sets up a signal handler. I think
>>> this could also happen if one runs scons from a Python environment where a
>>> compiled plugin registered a signal handler. I tracked the problem to
>>> Jobs.py, where _setup_sig_handler() retrieves the previous signal handler
>>> (signal.signal() returns None in this case) and then in
>>> _reset_sig_handler() it tries to the set the signal handler to this
>>> previous (None) value. None is not allowed and this causes a crash.
>>>
>>> I've coded up a patch that resets the signal handler to signal.SIG_DFL
>>> (the default handler) when the previous one was None and warns the user
>>> that this is happening. I'm looking for feedback, to see if this is an
>>> acceptable fix, and if/how I should proceed on GitHub.
>>>
>>> Thanks,
>>> Brian
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>>> Scons-users at scons.org
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>>>
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