[New-bugs-announce] [issue30589] With forkserver, Process.exitcode does not get signal number

[Antoine Pitrou]

New submission from Antoine Pitrou:

The documentation for multiprocessing.exitcode says:
"""
    The child’s exit code. This will be None if the process has not yet terminated. A negative value -N indicates that the child was terminated by signal N.
"""

This is true for the "fork" method, but not "forkserver" where a child terminated by a signal will get an exitcode of 255.  This is because forkserver relies on the child writing its own exit code in a pipe, which obviously doesn't work if it was killed (255 is simply a fallback value).

See forkserver's Popen.poll():

    def poll(self, flag=os.WNOHANG):
        if self.returncode is None:
            from multiprocessing.connection import wait
            timeout = 0 if flag == os.WNOHANG else None
            if not wait([self.sentinel], timeout):
                return None
            try:
                self.returncode = forkserver.read_unsigned(self.sentinel)
            except (OSError, EOFError):
                # The process ended abnormally perhaps because of a signal
                self.returncode = 255
        return self.returncode

----------
components: Library (Lib)
messages: 295343
nosy: davin, pitrou, sbt
priority: normal
severity: normal
status: open
title: With forkserver, Process.exitcode does not get signal number
type: behavior
versions: Python 3.5, Python 3.6, Python 3.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30589>
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