[issue13285] signal module ignores external signal changes

Jeroen Demeyer added the comment: For reference, the sources for my implementation: https://github.com/sagemath/cysignals/blob/master/src/cysignals/pysignals.pyx -- ___ Python tracker

[issue13285] signal module ignores external signal changes

Jeroen Demeyer added the comment: > In Jeroen's API, I can see what the Python-level signal handler is, but > there's no way to find out whether that signal handler is actually in use or > not. I added support for that in the latest cysignals release. Now you can do >>> import signal >>>

[issue13285] signal module ignores external signal changes

Nathaniel Smith added the comment: Here's another case where this bug bites us: https://github.com/python-trio/trio/issues/673 At startup, Trio checks if SIGINT is currently being handled by Python's default SIGINT handler, and if so it substitutes its own SIGINT handler (which works just

[issue13285] signal module ignores external signal changes

Jeroen Demeyer added the comment: I have a preliminary implementation (in the cysignals package) at https://github.com/sagemath/cysignals/pull/53 -- ___ Python tracker

[issue13285] signal module ignores external signal changes

Jeroen Demeyer added the comment: Ping? I'll try to implement this in cysignals (which is more difficult than doing it in CPython because I cannot access all internals of the Python signal module). -- ___ Python tracker

[issue13285] signal module ignores external signal changes

Jeroen Demeyer added the comment: Here is a proposal for an API: * getsignal: return the Python-level signal handler (this is an existing function) * setsignal: set the Python-level signal handler (but not the OS-level signal handler) * getossignal: get the OS-level signal handler as opaque

[issue13285] signal module ignores external signal changes

Thomas Kluyver added the comment: I pitched both the opaque handle and the context manager to python-ideas, but didn't get any responses, positive or negative. -- ___ Python tracker

[issue13285] signal module ignores external signal changes

Jeroen Demeyer added the comment: Let me add that this "low-level opaque object" would be rather easy to implement on POSIX systems (I have no clue about other systems such as Windows). I could implement it, but it would be good to have some pre-approval from Python devs that it's a good idea

[issue13285] signal module ignores external signal changes

R. David Murray added the comment: IMO the signal handler context manager would be useful (I have existing code where I wrote one that didn't quite work right :). I suggest you propose this on python-ideas. -- nosy: +r.david.murray ___ Python

[issue13285] signal module ignores external signal changes

Thomas Kluyver added the comment: I'd like to make the case for a fix in the code again. Our use case is, I believe, the same as Vilya's. We want to temporarily set a signal handler from Python and then restore the previous handler. This is fairly straightforward for Python handler functions,

[issue13285] signal module ignores external signal changes

Changes by Robert Cope : -- nosy: +rpcope1 ___ Python tracker ___ ___ Python-bugs-list

[issue13285] signal module ignores external signal changes

STINNER Victor added the comment: If anyone wants to work on this issue, I suggest to requalify it as a documentation issue. Just explain the behaviour and don't try to implement complex workaround. -- ___ Python tracker

[issue13285] signal module ignores external signal changes

Martin Panter added the comment: Also, the documentation currently suggests it returns None in these cases, but it actually returns SIG_DFL in at least one case (noticed in Issue 23735). FWIW Vilya’s opaque object sounds fairly sensible to me. Yes, it is ugly, but one does not look at Unix

[issue13285] signal module ignores external signal changes

Changes by Antoine Pitrou pit...@free.fr: -- nosy: +pitrou ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13285 ___ ___ Python-bugs-list mailing

[issue13285] signal module ignores external signal changes

Vilya Harvey vilya.har...@gmail.com added the comment: Petri: yes, that what I was suggesting. Charles-François: I'm certainly open to alternatives. Unless I've overlooked something though, the problem is that no workaround is possible at the moment. BTW this came up in the context of a

[issue13285] signal module ignores external signal changes

Petri Lehtinen pe...@digip.org added the comment: Could it return an opaque wrapper object, rather than just the raw address? Something like: Are you suggesting that it would return either a Python function object or a wrapper object? -- ___

[issue13285] signal module ignores external signal changes

Charles-François Natali neolo...@free.fr added the comment: Could it return an opaque wrapper object, rather than just the raw address? Something like: Are you suggesting that it would return either a Python function object or a wrapper object? I think it would be an ugly kludge. I don't

[issue13285] signal module ignores external signal changes

Changes by Petri Lehtinen pe...@digip.org: -- nosy: +petri.lehtinen ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13285 ___ ___ Python-bugs-list

[issue13285] signal module ignores external signal changes

Changes by Vilya Harvey vilya.har...@gmail.com: -- title: signal module in ignores external signal changes - signal module ignores external signal changes ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13285

[issue13285] signal module ignores external signal changes

Charles-François Natali neolo...@free.fr added the comment: So it's impossible to reliably save and restore signal handlers through python when they can also be changed outside the python interpreter. signal.getsignal() or signal.signal() return the current/previous handler as a Python

[issue13285] signal module ignores external signal changes

Changes by STINNER Victor victor.stin...@haypocalc.com: -- nosy: +haypo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13285 ___ ___

[issue13285] signal module ignores external signal changes

Vilya Harvey vilya.har...@gmail.com added the comment: Could it return an opaque wrapper object, rather than just the raw address? Something like: typedef struct _PyNativeSignalHandler { PyObject_HEAD sighandler_t handler_func; } PyNativeSignalHandler; where the type object doesn't expose

[issue13285] signal module ignores external signal changes

Changes by Florent Xicluna florent.xicl...@gmail.com: -- components: +Library (Lib) nosy: +flox versions: +Python 3.3 -Python 2.6, Python 3.1 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13285