signal.signal should check tripped signals

[jdemeyer]

BPO	30057
Nosy	@pitrou, @jdemeyer
PRs	bpo-30057: Fix potential missed signal in signal.signal(). #4258 [3.6] bpo-30057: Fix potential missed signal in signal.signal(). (GH-4258) #4261 [2.7] bpo-30057: Fix potential missed signal in signal.signal(). (GH-4258) #4263
Files	fix30057-py2.patch: Patch for Python 2 fix30057-py3.patch: Patch for Python 3

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2017-11-03.19:36:58.774>
created_at = <Date 2017-04-12.15:52:29.807>
labels = ['interpreter-core', '3.7']
title = 'signal.signal should check tripped signals'
updated_at = <Date 2017-11-03.19:36:58.773>
user = 'https://github.com/jdemeyer'

bugs.python.org fields:

activity = <Date 2017-11-03.19:36:58.773>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2017-11-03.19:36:58.774>
closer = 'pitrou'
components = ['Interpreter Core']
creation = <Date 2017-04-12.15:52:29.807>
creator = 'jdemeyer'
dependencies = []
files = ['46801', '46802']
hgrepos = []
issue_num = 30057
keywords = ['patch']
message_count = 5.0
messages = ['291561', '305494', '305497', '305499', '305501']
nosy_count = 2.0
nosy_names = ['pitrou', 'jdemeyer']
pr_nums = ['4258', '4261', '4263']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue30057'
versions = ['Python 2.7', 'Python 3.6', 'Python 3.7']

[jdemeyer]

There is a race condition in calling signal.signal() if the signal arrives while (or right before) signal.signal() is being executed: the function signal.signal(sig, action) marks the signal "sig" as not tripped. Because of this, signals can get lost. Instead, it would be better to call PyErr_CheckSignals() to check for pending signals.

[pitrou]

Thanks for the report! I will push your patch soon.

[pitrou]

New changeset f6f90ff by Antoine Pitrou in branch 'master':
bpo-30057: Fix potential missed signal in signal.signal(). (bpo-4258)
f6f90ff

[pitrou]

New changeset ea80ae0 by Antoine Pitrou (Miss Islington (bot)) in branch '3.6':
bpo-30057: Fix potential missed signal in signal.signal(). (GH-4258) (bpo-4261)
ea80ae0

[pitrou]

New changeset c713837 by Antoine Pitrou in branch '2.7':
[2.7] bpo-30057: Fix potential missed signal in signal.signal(). (GH-4258) (bpo-4263)
c713837