Enable the -Xrs flag when starting the JVM to allow signals to be propagated

Enable the -Xrs flag when starting the JVM to allow signals to be propagated fully back to Python and on to other systems such as Qt.

This was removed recently in !69 (comment 4313762) (but was limited to JPype <1). @isinkare has an example that demonstrates its use in newer JPype versions (please leave a comment here with the code to reproduce).

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• 591828c7 - Enable the -Xrs flag when starting the JVM to allow signals to be propagated...

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import sys
import jpype
from PyQt5.QtWidgets import QApplication, QToolButton
import signal; signal.signal(signal.SIGINT, signal.SIG_DFL)

app = QApplication(sys.argv)
jpype.startJVM()
btn = QToolButton()
btn.show()
sys.exit(app.exec_())

Ctrl+C here produces an output:

QObject::~QObject: Timers cannot be stopped from another thread

Replacing jpype.startJVM() with jpype.startJVM('-Xrs') makes the warning disappear.

This warning is particularly visible when using QToolButton, that reimplements QObject.timerEvent(). More info in ACCPY-760.

Thanks Ivan. Can you also check what the interrupt kwarg does with/without the -Xrs flag (https://jpype.readthedocs.io/en/latest/api.html#jpype.startJVM)

From what I understand, interrupt keyword is enabled by default when running a python file, and is disabled in interactive shell. This results in Ctrl+C terminating the process when running from file, and having no effect when running in interactive shell (presumably because application is still being in the Qt event loop, and SIGINT handler is undone, or is not getting called). Generally, setting it explicitly to True has no effect compared to omitting it, when running a Python file. One interesting thing, is that -Xrs seems to override it, e.g. jpype.startJVM('-Xrs', interrupt=False) will allow to still exit cleanly on Ctrl+C.

Great, thank you. I'll get the test passing and we can merge this.

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• 0b3b2382 - Enable the -Xrs flag when starting the JVM to allow signals to be propagated...

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enabled an automatic merge when the pipeline for 0b3b2382 succeeds

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• 1e43ddb1 - Move the minimum JPype1 version up to 1.1.

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• 0c58a8d9 - Move the minimum JPype1 version up to 1.1.

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Another example script, which doesn't involve Qt:

from time import sleep
import signal
from jpype import *

startJVM(
    getDefaultJVMPath(),
    #'-Xrs',
)

def handler(signum, frame):
    raise KeyboardInterrupt()

#the overloaded signal handling has to be here to make KeyboardInterrupt work again
#please comment out to check how the script dies without doing any clean-up
#signal.signal(signal.SIGINT, handler)

try:
    while True:
        print(".", end="", flush=True)
        sleep(1)
except (BaseException, KeyboardInterrupt) as e:
    print(e, type(e))
finally:
    print("This should be always executed", flush=True)

merged

mentioned in commit ff3a6b5c