On Tue, Sep 25, 2018 at 1:10 AM Erik Bray <erik.m.bray@gmail.com> wrote:
On Fri, Sep 21, 2018 at 12:58 AM Chris Angelico <rosuav@gmail.com> wrote:
On Fri, Sep 21, 2018 at 8:52 AM Kyle Lahnakoski <klahnakoski@mozilla.com> wrote:
Since the java.lang.Thread.stop() "debacle", it has been obvious that stopping code to run other code has been dangerous. KeyboardInterrupt (any interrupt really) is dangerous. Now, we can probably code a solution, but how about we remove the danger:
I suggest we remove interrupts from Python, and make them act more like java.lang.Thread.interrupt(); setting a thread local bit to indicate an interrupt has occurred. Then we can write explicit code to check for that bit, and raise an exception in a safe place if we wish. This can be done with Python code, or convenient places in Python's C source itself. I imagine it would be easier to whitelist where interrupts can raise exceptions, rather than blacklisting where they should not.
The time machine strikes again!
https://docs.python.org/3/c-api/exceptions.html#signal-handling
Although my original post did not explicitly mention PyErr_CheckSignals() and friends, it had already taken that into account and it is not a silver bullet, at least w.r.t. the exact issue I raised, which had to do with the behavior of context managers versus the
setup() try: do_thing() finally: cleanup()
pattern, and the question of how signals are handled between Python interpreter opcodes. There is a still-open bug on the issue tracker discussing the exact issue in greater details: https://bugs.python.org/issue29988
To be fair, your post not only didn't mention CheckSignals, but it almost perfectly described its behaviour. So I stand by my response. :) I don't think the system needs to be replaced; it ought to be possible to resolve the context manager issue without tossing out the existing code. ChrisA