[New-bugs-announce] [issue29096] Signal Handlers reliably cause UnboundLocalErrors

Ted Meyer report at bugs.python.org
Wed Dec 28 15:38:35 EST 2016


New submission from Ted Meyer:

Using this simple snippit of code:
import signal



import signal

def sig_hdlr(signum, frame):
    raise ValueError()

def faulty():
    local_var = ""
    signal.signal(signal.SIGALRM, sig_hdlr)
    signal.alarm(1)
    try:
        while True:
            local_var += "!"
    except ValueError:
        print (local_val)

faulty()



I can reliably get a crash:
tmathmeyer at tmathmeyer-linuxstation:~$ python --version
Python 2.7.6
tmathmeyer at tmathmeyer-linuxstation:~$ python pybug.py 
Traceback (most recent call last):
  File "pybug.py", line 16, in <module>
    faulty()
  File "pybug.py", line 14, in faulty
    print local_val
NameError: global name 'local_val' is not defined

tmathmeyer at tmathmeyer-linuxstation:~$ python3.4 pybug.py 
Traceback (most recent call last):
  File "pybug.py", line 12, in faulty
    local_var += "!"
  File "pybug.py", line 4, in sig_hdlr
    raise ValueError()
ValueError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "pybug.py", line 16, in <module>
    faulty()
  File "pybug.py", line 14, in faulty
    print (local_val)
NameError: name 'local_val' is not defined


I can repro this on 2.7.6 and 3.4, but do not have other versions to test on.

----------
messages: 284196
nosy: Ted Meyer
priority: normal
severity: normal
status: open
title: Signal Handlers reliably cause UnboundLocalErrors
versions: Python 2.7, Python 3.3, Python 3.4

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29096>
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