Source: diffoscope
Severity: minor
Tags: patch
diffoscope sets the timezone to UTC to ensure that timezones are consistent
from diff output tools. However, it does not call tzset after it does this.
Because of this, C code running in the same process may continue to see and
use the user's original timezone. In particular, the python-magic module
that wraps libmagic is susceptible to this.
I believe this is the source of test_gzip.metadata test failures that have
been reported in, e.g., #817193. Test failures look inconsistent because
you'll only see it if (a) you're using the python-magic wrapper module, and
(b) your current timezone does not align with UTC.
A patch is attached.
-- System Information:
Debian Release: 8.6
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 4.9.0-rc6+ (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL
set to en_US.utf8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
>From de145d41ed76e57dcae8dbfc1c7404171ac9c2d8 Mon Sep 17 00:00:00 2001
From: Brett Smith <brettcsm...@brettcsmith.org>
Date: Thu, 15 Dec 2016 12:14:42 -0500
Subject: [PATCH] diffoscope: set_locale calls tzset.
This is necessary to update timezone information for C code we've pulled in
that might've already called it. In particular, the python-magic libmagic
wrapper can be affected by this, and print out gzip mtimes in the user's
timezone.
Accordingly, we call set_locale as a test fixture in test_gzip to make sure
things are set up correctly for the metadata difference tests.
---
diffoscope/__init__.py | 2 ++
tests/comparators/test_gzip.py | 2 +-
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/diffoscope/__init__.py b/diffoscope/__init__.py
index b1bb1d4..827445f 100644
--- a/diffoscope/__init__.py
+++ b/diffoscope/__init__.py
@@ -23,6 +23,7 @@ import logging
import platform
import tempfile
import functools
+import time
from distutils.spawn import find_executable
@@ -90,6 +91,7 @@ def set_locale():
os.environ[var] = 'C'
os.environ['LC_CTYPE'] = 'C.UTF-8'
os.environ['TZ'] = 'UTC'
+ time.tzset()
temp_files = []
diff --git a/tests/comparators/test_gzip.py b/tests/comparators/test_gzip.py
index a448820..6481ef6 100644
--- a/tests/comparators/test_gzip.py
+++ b/tests/comparators/test_gzip.py
@@ -25,7 +25,7 @@ from diffoscope.comparators import specialize
from diffoscope.comparators.gzip import GzipFile
from diffoscope.comparators.binary import FilesystemFile, NonExistingFile
-from utils import data, load_fixture
+from utils import data, load_fixture, set_locale
TEST_FILE1_PATH = data('test1.gz')
TEST_FILE2_PATH = data('test2.gz')
--
2.1.4
